The Role of Yeasts and Lactic Acid Bacteria on the Metabolism of Organic Acids during Winemaking

Proanthocyanidins and volatile aroma of cranberry juice are modulated by its microbiota and processing environment

The quality and sensory attributes of juices are influenced by their natural microbiota and the microorganisms found on filtration membranes. This study aimed to assess the influence of natural microbiota and specific contaminants, including Candida krusei, Rhodotorula mucilaginosa, Debaryomyces prosopidis, Ralstonia insidiosa, and Lactiplantibacillus paraplantarum, isolated from cranberry juice and its associated industrial filtration membranes, on the characteristics of cranberry juice. Their growth kinetics and impacts on total phenols, total anthocyanins, total proanthocyanins, total organic acids, pH, titratable acidity, and volatile compounds were assessed. During the 42 h fermentation period, Candida krusei and Ralstonia insidiosa exhibited significant growth, increasing by 1-log and 3-log, respectively. The natural microbiota led to a 7% and 6% reduction in anthocyanins and proanthocyanidins, while Candida krusei and Rhodotorula mucilaginosa caused losses of 10% and 7% in proanthocyanidins, respectively. Organic acid content remained stable, except for an 8% decrease caused by Ralstonia insidiosa. Volatile compounds underwent significant increases, particularly in green (703%), winey (100%), mushroom (306%), and fusel (2678%) notes. These findings underscore the rapid impact of microorganisms from natural microbiota and filtration membranes on cranberry juice characteristics, highlighting the importance for beverage industries to prioritize customer safety and satisfaction.

Insight into the growth and metabolic characteristics of indigenous commercial S. cerevisiae NX11424 at high and low levels of yeast assimilable nitrogen based on metabolomic approach

Yeast assimilable nitrogen (YAN) is one of the important factors affecting yeast growth and metabolism. However, the nitrogen requirement of indigenous commercial S. cerevisiae NX11424 is unclear. In this study, metabolomics was used to analyze the metabolite profiles of the yeast strain NX11424 under high (433 mg/L) and low (55 mg/L) YAN concentrations. It was found that yeast biomass exhibited different trends under different YAN conditions and was generally positively correlated with the initial YAN concentration, while changes of key biomarkers of yeast strain NX11424 at different stages of fermentation showed a similar trend under high and low YAN concentrations. The YAN concentration affected the metabolite levels of the yeast strain NX11424, which resulted in the significant difference in the levels of pyruvic acid, α-oxoglutarate, palmitoleic acid, proline, butane-2,3-diol, citrulline, ornithine, galactinol, citramalic acid, tryptophan, alanine, phosphate and phenylethanol, mainly involving pathways such as central carbon metabolism, amino acid metabolism, fatty acid metabolism, purine metabolism, and energy metabolism. Yeast strain NX11424 could utilize proline to produce protein under a low YAN level. The intracellular level of citrulline and ornithine under high YAN concentration was higher than that under low YAN level. Yeast strain NX11424 is more suitable for fermentation at lower YAN level. The results obtained here will help to rational utilize of YAN by S. cerevisiae NX11424, and is conducive to precise control of the alcohol fermentation and improve wine quality.

The insights into sour flavor and organic acids in alcoholic beverages

Alcoholic beverages have developed unique flavors over millennia, with sourness playing a vital role in their sensory perception and quality. Organic acids, as crucial flavor compounds, significantly impact flavor. This paper reviews the sensory attribute of sour flavor and key organic acids in alcoholic beverages. Regarding sour flavor, research methods include both static and dynamic sensory approaches and summarize the interaction of sour flavor with aroma, taste, and mouthfeel. In addition, this review focuses on identifying key organic acids, including sample extraction, chromatography, olfactometry/taste, and mass spectrometry. The key organic acids in alcoholic beverages, such as wine, Baijiu, beer, and Huangjiu, and their primary regulatory methods are discussed. Finally, future avenues for the exploration of sour flavor and organic acids by coupling machine learning, database, sensory interactions and electroencephalography are suggested. This systematic review aims to enhance understanding and serve as a reference for further in-depth studies on alcoholic beverages.

Geographical characterization of wines from seven regions of China by chemical composition combined with chemometrics: Quality characteristics of Chinese 'Marselan' wines

This study investigated the basic and functional compositions, volatile compounds, intelligent sensory characteristics and antioxidant capacity of the commercial 'Marselan' wines from seven Chinese regions. The Nei Mongol wines featured high total reducing sugar, fructose, ammonia nitrogen, 17 monomeric phenolic acids contents and elevated antioxidant capacity. Malic acid was the only organic acid that significantly different in all seven regions. Malvidin-3-O-glucoside and trans-peonidin-3-O-(6-O-p-coumaryl)-glucoside showed the highest and lowest contents. A total of 102 volatiles was detected and Hebei wines had the most (91). Hexanoic acid and β-damascenone were considered to have high potential sensory effects (OAV ≥ 1) as compounds detected in all regions. Floral, sweet, and fruity were the most important aroma series. E-eye analysis revealed the colors of the samples tended to yellowish with aging. PCA and OPLS-DA based on the basic wine composition, monomeric organic acids and anthocyanins allowed achieving a discrimination of the seven regions, respectively.

Enhancing the flavour quality of Laiyang pear wine by screening sorbitol-utilizing yeasts and co-fermentation strategies

This study took a novel approach to address the dual challenges of enhancing the ethanol content and aroma complexity in Laiyang pear wine. It focused on sorbitol as a pivotal element in the strategic selection of yeasts with specific sorbitol-utilization capabilities and their application in co-fermentation strategies. We selected two Saccharomyces cerevisiae strains (coded as Sc1, Sc2), two Metschnikowia pulcherrima (coded as Mp1, Mp2), and one Pichia terricola (coded as Tp) due to their efficacy as starter cultures. Notably, the Sc2 strain, alone or with Mp2, significantly increased the ethanol content (30% and 16%). Mixed Saccharomyces cerevisiae and Pichia terricola fermentation improved the ester profiles and beta-damascenone levels (maximum of 150%), while Metschnikowia pulcherrima addition enriched the phenethyl alcohol content (maximum of 330%), diversifying the aroma. This study investigated the efficacy of strategic yeast selection based on sorbitol utilization and co-fermentation methods in enhancing Laiyang pear wine quality and aroma.

Inoculation of Zaopei with biofortification: Inducing variation in community structure and improving flavor compounds in Nongxiangxing baijiu

The deterioration of the quality of raw liquor caused by the low content of ethyl hexanoate in Nongxiangxing baijiu has become a pervasive problem in the baijiu industry. Therefore, this study attempted to increase the synthesis of ethyl hexanoate by microorganisms with high esterase activity to increase Zaopei fermentation. The results showed that biofortification was a feasible and important way to improve the quality of the raw liquor and increase the ethyl hexanoate content. Adding Bacillus subtilis, Staphylococcus epidermidis, and Millerozyma farinosa for biofortified fermentation disturbed the microbial community structure of Zaopei and increased the abundance of Wickerhamomyces, Saccharomyces, and Thermoascus. The contents of ethyl hexanoate, ethyl valerate, ethyl caprylate, and ethyl heptanoate also increased noticeably in baijiu. The results of E-nose and sensory analysis tested and verified that the baijiu in the fortified group had better flavor characteristics.

Dynamic changes of microbiota and metabolite of traditional Hainan dregs vinegar during fermentation based on metagenomics and metabolomics

Hainan dregs vinegar (HNDV) is a traditional fermented food in China that is renowned for its unique flavor. HNDV is one of the most popular vinegars in Southeast Asia. However, research on the microorganisms and characteristic metabolites specific to HNDV is lacking. This study investigated the changes in microbial succession, volatile flavor compounds and characteristic non-volatile flavor compounds during HNDV fermentation based on metagenomics and metabolomics. The predominant microbial genera were Lactococcus, Limosilactobacillus, Lactiplantibacillus, and Saccharomyces. Unlike traditional vinegar, l-lactic acid was identified as the primary organic acid in HNDV. Noteworthy flavor compounds specific to HNDV included 3-methylthiopropanol and dl-phenylalanine. Significant associations were observed between six predominant microorganisms and six characteristic volatile flavor compounds, as well as seven characteristic non-volatile flavor compounds. The present results contribute to the development of starter cultures and the enhancement of HNDV quality.

Improving Muscat Hamburg Wine Quality with Innovative Fermentation Strategies Using Schizosaccharomyces pombe Derived from Fermented Grains of Sauce-Flavor Baijiu

This study investigates innovative approaches to improve the quality and aroma characteristics of Muscat Hamburg wine production by substituting the conventional Saccharomyces cerevisiae yeast with an efficient fermentation strain of Schizosaccharomyces pombe. The typical use of S. cerevisiae in Muscat Hamburg wine often leads to uniformity and prolonged processing times, requiring subsequent malolactic fermentation to degrade excessive malic acid. The study advocates for the replacement of S. cerevisiae with a specific S. pombe strain, Sp-410, isolated from the fermented grains of sauce-flavor Baijiu, a Chinese spirit. Muscat Hamburg wine fermented with the S. pombe strain demonstrates decreased malic acid levels, offering a potential alternative to malolactic fermentation. However, exclusive S. pombe fermentation may result in an overproduction of acetic acid metabolites, leading to a monotonous taste. In response, the study proposes a mixed fermentation approach, combining the S. pombe strain with a Saccharomyces uvarum strain and a non-Saccharomyces yeast, Torulaspora delbrueckii. The optimized mixed fermentation strategies (M:SP+TD and M60SP+TD) involve specific proportions and intervals of inoculation, aiming to enhance the quality and aroma complexity of Muscat Hamburg wine. In conclusion, this research contributes to advancing the production of high-quality Muscat Hamburg wines, utilizing S. pombe as the primary yeast strain and implementing mixed fermentation methodologies.

Application of Strain Selection Technology in Alcoholic Beverages: A Review

The diversity of alcohol beverage microorganisms is of great significance for improving the brewing process and the quality of alcohol beverage products. During the process of making alcoholic beverages, a group of microorganisms, represented by yeast and lactic acid bacteria, conducts fermentation. These microorganisms have complex synergistic or competitive relationships, and the participation of different microorganisms has a major impact on the fermentation process and the flavor and aroma of the product. Strain selection is one of the key steps. Utilizing scientific breeding technology, the relationship between strains can be managed, the composition of the alcoholic beverage microbial community can be improved, and the quality and flavor of the alcoholic beverage products can be increased. Currently, research on the microbial diversity of alcohol beverages has received extensive attention. However, the selection technology for dominant bacteria in alcohol beverages has not yet been systematically summarized. To breed better-quality alcohol beverage strains and improve the quality and characteristics of wine, this paper introduces the microbial diversity characteristics of the world's three major brewing alcohols: beer, wine, and yellow wine, as well as the breeding technologies of related strains. The application of culture selection technology in the study of microbial diversity of brewed wine was reviewed and analyzed. The strain selection technology and alcohol beverage process should be combined to explore the potential application of a diverse array of alcohol beverage strains, thereby boosting the quality and flavor of the alcohol beverage and driving the sustainable development of the alcoholic beverage industry.

Comparison of the sugar and organic acid components of seventeen table grape varieties produced in Ankara (Türkiye): a study over two consecutive seasons

Sugars and organic acids not only have a significant impact on taste balance and sensory acceptance by consumers but also play a crucial role in the chemical equilibrium of grape juices and wines. Therefore, this study aimed to quantify the content and composition of sugars and organic acids in 17 grape varieties over two consecutive years using high-performance liquid chromatography. The variability in all the parameters studied was strongly influenced by both the grape cultivars and specific years (p ≤ 0.05). In grape berries, the primary sugars identified were fructose and glucose, which ranged from 6.50 to 11.10 g/L and from 5.83 to 12.12 g/L, respectively, over the two years. However, sucrose was not detected in any of the grape varieties examined. For the two respective years, the highest titratable acidity (TA) was found in Tekirdağ Çekirdeksizi (TeCe) (0.89 and 0.90 g/L), while the lowest was detected in Victoria (Vi) (0.48 and 0.51 g/L). Total soluble solids (TSS) peaked in Horoz Karası (HoKA) (21.90 °Brix), whereas it reached its lowest point in Big Perlon (BiPe) (14.1 °Brix). The tartaric acid content in the grape berries, ranging from 1.48 to 10.33 g/L for the two years, exhibited similar characteristics to malic acid, which ranged from 1.09 to 9.62 g/L and from 1.03 to 9.68 g/L for the two respective years. The succinic, malic, tartaric, citric, and oxalic acid contents were notably higher in the Kyoho (Ky) variety than in the other varieties. When examining the dendrogram of the contents of organic acid and sugar for similarities, it was evident that 16 out of the 17 grape varieties had a high degree of similarity, except for Alphonse Lavallée (AlLa) and HoKa. The similarity levels among the varieties ranged from 99.49% to 72.36%. The highest similarity (99.49%) was observed between the AlLa and Barış (Ba) varieties. The lowest similarity was observed among the AlLa, HoKa, and Ky varieties. In summary, this study underscores that certain table grape varieties grown in Ankara exhibit significant variations in valuable organic acids and sugars, which are associated with potential health benefits when considering human consumption.

Insights into the mechanisms driving microbial community succession during pepper fermentation: Roles of microbial interactions and endogenous environmental changes

Elucidating the driving mechanism of microbial community succession during pepper fermentation contributes to establishing efficient fermentation regulation strategies. This study utilized three-generation high-throughput sequencing technology, microbial co-occurrence network analysis, and random forest analysis to reveal microbial community succession processes and driving mechanisms during pepper fermentation. The results showed that more positive correlations than negative correlations were observed among microorganisms, with positive correlation proportions of 60 %, 51.03 %, and 71.43 % between bacteria and bacteria, fungi and fungi, and bacteria and fungi in sipingtou peppers, and 69.23 %, 54.93 %, and 79.44 % in zhudachang peppers, respectively. Microbial interactions, mainly among Weissella hellenica, Lactobacillus plantarum, Hanseniaspora opuntiae, and Kazachstania humillis, could drive bacterial and fungal community succession. Notably, the bacterial community successions during the fermentation of two peppers were similar, showing the transition from Leuconostoc pseudomesenteroides, Lactococcus lactis, Weissella ghanensis to Weissella hellenica and Lactobacillus plantarum. However, the fungal community successions in the two fermented peppers differed significantly, and the differential biomarkers were Dipodascus geotrichum and Kazachstania humillis. Differences in autochthonous microbial composition and inherent constituents brought by pepper varieties resulted in different endogenous environmental changes, mainly in fructose, malic acid, and citric acid. Furthermore, endogenous environmental factors could also drive microbial community succession, with succinic acid, lactic acid, and malic acid being the main potential drivers of bacterial community succession, whereas fructose, glucose, and succinic acid were the main drivers of fungal community succession. These results will provide insights into controlling fermentation processes by raw material combinations, optimization of environmental parameters, and microbial interactions.

Quality improvement of soybean meal by yeast fermentation based on the degradation of anti-nutritional factors and accumulation of beneficial metabolites

BACKGROUND

Soybean meal (SBM) is the main protein source for animal diets but its anti-nutritional constituents affect animal growth and immunity. The yeast culture of soybean meal (SBM-YC) that fermented with yeast and hydrolyzed by protease simultaneously could reduce anti-nutritional factors effectively and accumulate beneficial metabolites.

RESULTS

The crude protein and acid-soluble protein content of SBM-YC reached 542.5 g kg-1 and 117.2 g kg-1 , respectively, and the essential amino acid content increased by 17.9%. Raffinose and stachyose decreased over 95.0%, and the organic acid content such as acetic acid, butyric acid, citric acid, lactic acid, succinic acid, and propionic acid produced by fermentation reached 6.1, 3.8, 3.6, 2.5, 1.2, and 0.4 g kg-1 , respectively. As biomarkers of yeast culture, nucleosides and their precursors reached 1.7 g kg-1 ; in particular, the inosine content increased from 0 to 0.3 g kg-1 . The total antioxidant capacity, 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid (ABTS) free radical activity, metal chelating ability, and 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging ability were increased by 50.3%, 46.1%, 43.9%, and 20.6%, respectively.

CONCLUSION

This study established a diversified evaluation index, which could lay the foundations for the production and quality control of SBM-YC in the future. © 2023 Society of Chemical Industry.

Mixed biofilm formation by Oenococcus oeni and Saccharomyces cerevisiae: A new strategy for the wine fermentation process

Bacterial biofilms have attracted much attention in the food industry since this phenotype increases microbial resistance to environmental stresses. In wine-making, the biofilm produced by Oenococcus oeni is able to persist in this harsh environment and perform malolactic fermentations. Certain viticultural practices are interested in the simultaneous triggering of alcoholic fermentation by yeasts of the species Saccharomyces cerevisiae and malolactic fermentation by lactic acid bacteria. As yet, no data is available on the ability of these micro-organisms to produce mixed biofilms and promote fermentations. Here, the ability of S. cerevisiae and O. oeni to form mixed biofilms on different surfaces found in vinification was observed and analyzed using scanning electron microscopy experiments. Then, following co-inoculation with biofilm or planktonic cells microvinifications were carried out to demonstrate that the mixed biofilms developed on oak allow the efficient completion of fermentations because of their high resistance to stress. Finally, comparisons of the different metabolic profiles obtained by LC-MS were made to assess the impact of the mode of life of biofilms on wine composition.

UHPLC-QTOF-MS-based untargeted metabolomic authentication of Chinese red wines according to their grape varieties

Wine is a very popular alcoholic drink owing to its health benefits of antioxidant effects. However, profits-driven frauds of wine especially false declarations of variety frequently occurred in markets. In this work, an UHPLC-QTOF-MS-based untargeted metabolomics method was developed for metabolite profiling of 119 bottles of Chinese red wines from four varieties (Cabernet Sauvignon, Merlot, Cabernet Gernischt, and Pinot Noir). The metabolites of red wines from different varieties were assessed using orthogonal partial least-squares discriminant analysis (OPLS-DA) and analyzed using KEGG metabolic pathway analysis. Results showed that the differential compounds among different varieties of red wines are mainly flavonoids, phenols, indoles and amino acids. The KEGG metabolic pathway analysis showed that indoles metabolism and flavonoids metabolism are closely related to wine varieties. Based on the differential compounds, OPLS-DA models could identify external validation wine samples with a total correct rate of 90.9 % in positive ionization mode and 100 % in negative ionization mode. This study indicated that the developed untargeted metabolomics method based on UHPLC-QTOF-MS is a potential tool to identify the varieties of Chinese red wines.

Unraveling the role of intra-cellular metabolites in the lactic acid production by novel Bacillus amyloliquefaciens using sugarcane molasses as a substratum

Lactic acid is a versatile, multi-functional organic monomer in various industries, creating worldwide demand. High titer lactic acid production was achieved by novel Bacillus amyloliquefaciens J2V2AA through sugarcane molasses fermentation up to 178 mg mL-1. A metabolomics approach such as combined GC-MS and LC-MS was applied to elucidate the involvement of key metabolites in lactic acid production. The results revealed the participation of 58 known intra-cellular metabolites at various pathways in lactic acid production. Twenty-eight highly up-regulated and down-regulated metabolites were analyzed, and a schematic diagram of a possible lactic acid production pathway was proposed. The produced lactic acid was analyzed through FTIR, UV-Spectrum, and HPLC analysis.

Simultaneous Analysis of Organic Acids, Glycerol and Phenolic Acids in Wines Using Gas Chromatography-Mass Spectrometry

Fermented beverages, particularly wines, exhibit variable concentrations of organic and phenolic acids, posing challenges in their accurate determination. Traditionally, enzymatic methods or chromatographic analyses, mainly high-performance liquid chromatography (HPLC), have been employed to quantify these compounds individually in the grape must or wine. However, chromatographic analyses face limitations due to the high sugar content in the grape must. Meanwhile, phenolic acids, found in higher quantities in red wines than in white wines, are typically analyzed using HPLC. This study presents a novel method for the quantification of organic acids (OAs), glycerol, and phenolic acids in grape musts and wines. The approach involves liquid-liquid extraction with ethyl acetate, followed by sample derivatization and analysis using gas chromatography-mass spectrometry (GC-MS) in selected ion monitoring (SIM) detection mode. The results indicated successful detection and quantification of all analyzed compounds without the need for sample dilution. However, our results showed that the method of adding external standards was more suitable for quantifying wine compounds, owing to the matrix effect. Furthermore, this method is promising for quantifying other metabolites present in wines, depending on their extractability with ethyl acetate. Fermented beverages, particularly wines, exhibit variable concentrations of organic and phenolic acids, posing challenges in their accurate determination. Traditionally, enzymatic methods or chromatographic analyses, mainly high-performance liquid chromatography (HPLC), have been employed to quantify these compounds individually in the grape must or wine. The approach of this proposed method involves (i) methoximation of wine compounds in a basic medium, (ii) acidification with HCl, (iii) liquid-liquid extraction with ethyl acetate, and (iv) silyl derivatization to analyze samples with gas chromatography-mass spectrometry (GC-MS) in ion monitoring detection mode (SIM). The results indicated successful detection and quantification of all analyzed compounds without the need for sample dilution. However, our results showed that the method of adding external standards was more suitable for quantifying wine compounds, owing to the matrix effect. Furthermore, this method is promising for quantifying other metabolites present in wines, depending on their extractability with ethyl acetate. In other words, the proposed method may be suitable for profiling (targeted) or fingerprinting (untargeted) strategies to quantify wine metabolites or to classify wines according to the type of winemaking process, grape, or fermentation.

Potential of Cheese-Associated Lactic Acid Bacteria to Metabolize Citrate and Produce Organic Acids and Acetoin

Lactic acid bacteria (LAB) are pivotal in shaping the technological, sensory, and safety aspects of dairy products. The evaluation of proteolytic activity, citrate utilization, milk pH reduction, and the production of organic compounds, acetoin, and diacetyl by cheese associated LAB strains was carried out, followed by Principal Component Analysis (PCA). Citrate utilization was observed in all Leuconostoc (Le.) mesenteroides, Le. citreum, Lactococcus (Lc.) lactis, Lc. garvieae, and Limosilactobacillus (Lm.) fermentum strains, and in some Lacticaseibacillus (Lact.) casei strains. Most strains exhibited proteolytic activity, reduced pH, and generated organic compounds. Multivariate PCA revealed Le. mesenteroides as a prolific producer of acetic, lactic, formic, and pyruvic acids and acetoin at 30 °C. Enterococcus sp. was distinguished from Lact. casei based on acetic, formic, and pyruvic acid production, while Lact. casei primarily produced lactic acid at 37 °C. At 42 °C, Lactobacillus (L.) helveticus and some L. delbrueckii subsp. bulgaricus strains excelled in acetoin production, whereas L. delbrueckii subsp. bulgaricus and Streptococcus (S.) thermophilus strains primarily produced lactic acid. Lm. fermentum stood out with its production of acetic, formic, and pyruvic acids. Overall, cheese-associated LAB strains exhibited diverse metabolic capabilities which contribute to desirable aroma, flavor, and safety of dairy products.

Evaluation of homemade fermented pickle juice as a marinade: Effects on the microstructure, microbiological, physicochemical, textural properties, and sensory attributes of beef strip loin steaks

The current study aimed to characterize homemade fermented pickle juice and evaluate its efficacy as a marinade on physicochemical, microbiological, textural properties, microstructure, and sensory attributes of the strip loins. Organic acids, phenolics, flavonoids, volatiles, total phenolic content (TPC), and in-vitro antioxidant capacity (ABTS and FRAP) analyses were carried out. Furthermore, minimum inhibitory concentration (MIC), and the diameter of inhibition zones of the pickle juice were determined against Escherichia coli O157:H7, Salmonella Typhimurium, S. enteritidis, and Listeria monocytogenes. The strip loins were marinated with five different concentrations (10%, 25%, 50%, 75%, and 100%) of pickle juice at 4 °C for 24 h. A total of 4 organic acids, 23 phenolic and flavonoid compounds, and 69 volatiles were identified in the pickle juice. The TPC, ABTS, and FRAP values of the pickle juice were found to be 184.24 ± 33.28 GAE/L, 44.48 ± 0.41 mg TEAC/L, and 2.79 ± 0.01 mM FE/L, respectively. The MIC and inhibition zones were recorded between 7.81 and 12.50% and 8.25-13.80 mm against pathogenic bacteria, respectively. The textural properties of the strip loins marinated with 100% pickle were improved compared to the control (P < 0.05). Moreover, this concentration decreased the number of pathogens in strip loins, ranging between 1.07 and 2.77 log10 CFU/g (P < 0.05). Regarding sensory attributes, the strip loins marinated with 50% and 100% pickle juice had higher scores compared to the non-marinated samples. The results of this study indicated that pickle juice can be evaluated as a marinade to improve the microbiological quality and textural properties of strip loins.

Natural versus conventional production of Spanish white wines: an exploratory study

BACKGROUND

Natural wine (NW) lacks an official or agreed definition, but it can be generally described as a wine produced with organic or biodynamic grapes with minimal intervention in the cellar, and with minimal or no use of oenological additives. The present study aimed to test the hypotheses that self-defined NWs differ from conventional wines (CW) in their chemical composition and main sensory characteristics. The levels of conventional oenological parameters, turbidity, biogenic amines, ochratoxin A, ethyl carbamate, sulphites, chlorides, some metals, major, trace and Strecker aldehyde volatile compounds were determined in 28 wines, including natural and conventional Spanish commercial white wines. Wines were also sensory described following a labelled free sorting task.

RESULTS

NWs presented higher pH, volatile acidity (VA) and turbidity values, and a more intense yellow colour, whereas they have a lower malic acid content compared to theor conventional counterparts. NWs presented lower levels of total sulphur dioxide but significantly higher levels of biogenic amine putrescine, although both compounds are within the legal limits in all cases. None of the dimensions of the similarity space discriminated NWs from CWs. However, 70% of the NWs were grouped on the basis of various aromatic defects related to their higher content in 4-ethylphenols and VA. The remaining 30% were not differentiated from their conventional counterparts.

CONCLUSION

It could be confirmed that NW can be globally differentiated from CW with respect to to their chemical and their sensory profiles, whereas the content in toxicants was not significantly different, with the exception of total sulphur dioxide and putrescine levels. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Effect of high-voltage electrospray on the inactivation, induced damage and growth of microorganisms and flavour components of honey raspberry wine

Electrospray (ES) is a new non-thermal processing technology for pasteurising liquid foods. This study aimed to investigate the effects of ES on the cell structure and function of Saccharomyces cerevisiae, Escherichia coli and Staphylococcus aureus and then compare the effects of ES and heat treatment (HT) on microbial inactivation and flavour composition in honey raspberry wine. First, we found that the inactivation effect of ES treatment on the three microorganisms was significantly influenced by the voltage intensity. The degree of damage to the cellular structures and functions of the three microorganisms increased with increasing voltage. Second, the environment in which the microorganisms were present significantly influenced the ES pasteurisation effect. Pasteurisation by ES was better when the three microorganisms were in honey raspberry wine than in saline. Finally, the total number of colonies in honey raspberry wine was reduced from 4.50 to 2.03 log colony forming units/mL after ES treatment, and the wine had good stability during storage (84 days at 4 °C). In the honey raspberry wine, the contents of the main flavour substances (ketones and esters) did not change significantly after ES treatment, but HT decreased the content of esters and ketones by 13.5 % and 75.4 %, respectively.

Sequential culture with aroma-producing yeast strains to improve the quality of Kyoho wine

Despite many non-Saccharomyces yeasts being considered spoilage microorganisms, they can increase aroma and flavor diversity in alcoholic beverages. The purpose of this study was to investigate nontraditional inoculation strategies using aroma-producing yeast strains for Kyoho wine fermentation, followed by an instrumental analysis and sensory evaluation. The winemaking process was carried out using Saccharomyces cerevisiae Gr112, Hanseniaspora uvarum Pi235, and Pichia kluyveri Pe114. Multiple inoculation strategies were explored. In instrumental analysis results, mixed culture could promote the formation of esters (5.9-folds) and glycerol (1.3-folds) and reduce the content of ethanol (-0.5% [v/v]) in wine. The sensory analysis results suggested that the three yeast strains sequential inoculation treatment was associated with the aroma attributes "floral," "red fruity," and "tropical fruity." Co-cultivation contributed to an increase in complexity and aromatic intensity, with the three-strain inoculation treatment presenting a more distinctive appearance. PRACTICAL APPLICATION: The inoculation of S. cerevisiae improved the accumulation of volatile acids and esters by inhibiting the growth of non-Saccharomyces yeast strains. Inoculation of H. uvarum and P. kluyveri would effectively solve the defect of excessive content of higher alcohols in wines produced by S. cerevisiae. The suitable inoculation strategy between non-Saccharomyces yeasts could improve the overall quality of Kyoho wine whose starter might be widely used in fermentation industry.

Non-Lactic Probiotic Beverage Enriched with Microencapsulated Red Propolis: Microorganism Viability, Physicochemical Characteristics, and Sensory Perception

This work aimed to develop a non-dairy functional beverage fermented with probiotic strains and fortified with Brazilian red propolis (microencapsulated and extracted). The non-dairy matrix consisted of oats (75 g), sunflower seeds (175 g), and almonds (75 g). It was fermented by a starter co-culture composed of Lactiplantibacillus plantarum CCMA 0743 and Debaryomyces hansenii CCMA 176. Scanning electron microscopy analysis was initially performed to verify the integrity of the microcapsules. The viability of the microorganisms after fermentation and storage, chemical composition (high performance liquid chromatography (HPLC) and gas chromatography coupled to mass spectrometry (GC-MS) analyses), rheology, antioxidant activity, and sensory profile of the beverages were determined. After fermentation and storage, the starter cultures were well adapted to the substrate, reducing the pH (6.50 to 4) and cell count above 7.0 log CFU/mL. Lactic acid was the main organic acid produced during fermentation and storage. In addition, 39 volatile compounds were detected by gas chromatography coupled to mass spectrometry (GC-MS), including acids, alcohols, aldehydes, alkanes, alkenes, esters, ethers, phenols, terpenes, and others. The addition of propolis extract increased the antioxidant and phenolic activity and the presence of volatile esters but reduced the beverage’s acceptability. The addition of microencapsulated propolis was more associated with the presence of higher alcohols and had similar acceptance to the control beverage. The combination of a non-dairy substrate, a starter co-culture, and the addition of propolis led to the development of a probiotic beverage with great potential for health benefits.

Thiamine and Biotin: Relevance in the Production of Volatile and Non-Volatile Compounds during Saccharomyces cerevisiae Alcoholic Fermentation in Synthetic Grape Must

Vitamins are major cofactors to numerous key metabolic pathways in enological yeasts, and both thiamine and biotin, notably, are believed to be essential to yeast fermentation and growth, respectively. In order to further assess and clarify their role in winemaking, and in the resulting wine, alcoholic fermentations of a commercial Saccharomyces cerevisiae active dried yeast were conducted in synthetic media containing various concentrations of both vitamins. Growth and fermentation kinetics were monitored and proved the essential character of biotin in yeast growth, and of thiamine in fermentation. The synthetic wine volatile compounds were quantified, and notable influences of both vitamins appeared, through a striking positive effect of thiamine on the production of higher alcohols, and of biotin on fatty acids. Beyond the evidence of this influence on fermentations and on the production of volatiles, this work proves, for the first time, the impact held by vitamins on wine yeasts' exometabolome, investigated through an untargeted metabolomic analysis. This highlighted chemical differences in the composition of synthetic wines through a notably marked influence of thiamine on 46 named S. cerevisiae metabolic pathways, and especially in amino acid-associated metabolic pathways. This provides, overall, the first evidence of the impact held by both vitamins on the wine.

Unravelling metabolic cross-feeding in a yeast-bacteria community using 13 C-based proteomics

Cross-feeding is fundamental to the diversity and function of microbial communities. However, identification of cross-fed metabolites is often challenging due to the universality of metabolic and biosynthetic intermediates. Here, we use ¹³ C isotope tracing in peptides to elucidate cross-fed metabolites in co-cultures of Saccharomyces cerevisiae and Lactococcus lactis. The community was grown on lactose as the main carbon source with either glucose or galactose fraction of the molecule labelled with ¹³ C. Data analysis allowing for the possible mass-shifts yielded hundreds of peptides for which we could assign both species identity and labelling degree. The labelling pattern showed that the yeast utilized galactose and, to a lesser extent, lactic acid shared by L. lactis as carbon sources. While the yeast provided essential amino acids to the bacterium as expected, the data also uncovered a complex pattern of amino acid exchange. The identity of the cross-fed metabolites was further supported by metabolite labelling in the co-culture supernatant, and by diminished fitness of a galactose-negative yeast mutant in the community. Together, our results demonstrate the utility of ¹³ C-based proteomics for uncovering microbial interactions.

Investigating the mechanism of the flavor formation in Sichuan sun vinegar based on flavor-orientation and metagenomics

Fermentation and aging are the key stages of flavor formation in Sichuan sun vinegar (SSV), but the generation mechanisms of the flavor produced by these processes are unknown. However, complex microbial metabolism is critical to the flavor development of SSV. In this study, we analyzed the key flavor compounds present in SSV. Combined with odor activity value (OAV), the main aroma components of SSV were screened, and the relationship between microorganisms and key flavor formation was predicted using metagenomic sequencing technology. The results revealed 38 key flavor compounds in SSV. Lactobacillus, Weissella, Acetobacter, Lichtheimia, Pediococcus, Oenococcus, Brettanomyces, Kazachstania, Pichia, Xanthomonas, Lenconostoc are widely involved in the production of key flavor compounds such as 2,3-butanediol, 2-Furanmethanol, phenylethanol, 3-(Methylthio)-1-propanol, acetic acid, lactic acid, butyric acid, isovaleric acid and other organic acids. Among them, Lichtheimia and Lactobacillus are important genera for the degradation of starch, arabinoxylan and cellulose. The acetaldehyde,4-ethyl-2-methoxy-phenol and 2-methoxy-4-methyl-phenol production pathway may be related to Lactobacillus, Acetobacter and Brettanomyces. This study provides a new understanding of the key flavor-formation stage and flavor compound generation mechanism of SSV and provides a reference for the screening and isolation of functional strains and the reconstruction of microbial communities.

The Metabolite Profiling and Microbial Community Dynamics during Pineapple By-Product Fermentation Using Co-Inoculation of Lactic Acid Bacteria and Yeast

Value-added utilization of pineapple waste is very import for the food industry and environmental protection. In this study, whey protein (2.6%, w/w) was added to pineapple waste in order to make up for the protein deficiency of the raw material and give the final products better flavor characteristics. Autochthonous Lactococcus lactis LA5 and Hanseniaspora opuntiae SA2 were used for the co-inoculation of pineapple by-products; during fermentation, the metabolite profiling and microbial community dynamics were investigated. Results showed that the contents of organic acids, total FAAs, total phenolic compounds and flavonoids significantly increased with fermentation, and 152 kinds of peptides were identified in the final products. Relevant analyses demonstrated that dominant strains including Lactococcus lactis, Hanseniaspora and Saccharomyces not only significantly promoted the accumulation of organic acids, total phenols and other active substances, but also inhibited the growth of pathogenic bacteria and further influenced the fermentation process of pineapple waste.

Aroma profiles of sweet cherry juice fermented by different lactic acid bacteria determined through integrated analysis of electronic nose and gas chromatography-ion mobility spectrometry

Sweet cherries are popular among consumers, with a recent explosion in sweet cherry production in China. However, the fragility of these fruits poses a challenge for expanding production and transport. With the aim of expanding the product categories of sweet cherries that can bypass these challenges, in this study, we prepared sweet cherry juice fermented by three different lactic acid bacteria (LAB; Lactobacillus acidophilus, Lactobacillus plantarum, and Lactobacillus rhamnosus GG), and evaluated the growth, physiochemical, and aroma characteristics. All three strains exhibited excellent growth potential in the sweet cherry juice; however, Lactobacillus acidophilus and Lactobacillus plantarum demonstrated more robust acid production capacity and higher microbial viability than Lactobacillus rhamnosus GG. Lactic acid was the primary fermentation product, and malic acid was significantly metabolized by LAB, indicating a transition in microbial metabolism from using carbohydrates to organic acids. The aroma profile was identified through integrated analysis of electronic nose (E-nose) and headspace gas chromatography-ion mobility spectrometry (HS-GC-IMS) data. A total of 50 volatile compounds characterized the aromatic profiles of the fermented juices by HS-GC-IMS. The flavor of sweet cherry juice changed after LAB fermentation and the fruity odor decreased overall. Lactobacillus acidophilus and Lactobacillus plantarum significantly increased 2-heptanone, ethyl acetate, and acetone contents, bringing about a creamy and rummy-like favor, whereas Lactobacillus rhamnosus GG significantly increased 2-heptanone, 3-hydroxybutan-2-one, and 2-pentanone contents, generating cheesy and buttery-like odors. Principal component analysis of GC-IMS data and linear discriminant analysis of E-nose results could effectively differentiate non-fermented sweet cherry juice and the sweet cherry juice separately inoculated with different LAB strains. Furthermore, there was a high correlation between the E-nose and GC-IMS results, providing a theoretical basis to identify different sweet cherry juice formulations and appropriate starter culture selection for fermentation. This study enables more extensive utilization of sweet cherry in the food industry and helps to improve the flavor of sweet cherry products.

First report on metagenomics and their predictive functional analysis of fermented bamboo shoot food of Tripura, North East India

Moiya pansung, mileye amileye, moiya koshak, and midukeye are naturally fermented bamboo shoot foods of Tripura. The present study aimed to reveal the whole microbial community structure of naturally fermented moiya pangsung, mileye amileye, moiya koshak, and midukeye along with the prediction of microbial functional profiles by shotgun metagenomic sequence analysis. The metataxonomic profile of moiya pangsung, mileye amileye, moiya koshak, and midukeye samples showed different domains, viz., bacteria (97.70%) followed by the virus (0.76%), unclassified (0.09%), eukaryotes (1.46%) and archaea (0.05%). Overall, 49 phyla, 409 families, 841 genera, and 1,799 species were found in all the fermented bamboo shoot samples collected from different places of Tripura. Firmicutes was the most abundant phylum (89.28%) followed by Proteobacteria (5.13%), Bacteroidetes (4.38%), Actinobacteria (1.02%), and Fusobacteria (0.17%). Lactiplantibacillus plantarum was the most abundant species in moiya pangsung, mileye amileye, moiya koshak, and midukeye followed by Lactococcus lactis, Levilactobacillus brevis, Leuconostoc mesenteroides, Weissella paramesenteroides, Leuconostoc kimchii, Pediococcus pentosaceus, Leuconostoc gasicomitatum, and Lacticaseibacillus casei. A few phyla of fungus were found, viz., Ascomycota, Basidiomycota, and Glomeromycota, where Ascomycota was present in high abundance. Functional analysis of moiya pangsung, mileye amileye, moiya koshak, and midukeye metagenome revealed the genes for the synthesis and metabolism of a wide range of bioactive compounds including, various essential amino acids, and conjugated amino acids. The abundance profile and predictive analysis of fermented bamboo shoots revealed a huge plethora of essential microorganisms and KEGG analysis revealed genes for amino acid metabolism, pectin degradation, lipid metabolism, and many other essential pathways that can be essential for the improvement of nutritional and sensory qualities of the fermented bamboo shoot products.

Influence of Green Tea Added to Cherry Wine on Phenolic Content, Antioxidant Activity and Alpha-Glucosidase Inhibition during an In Vitro Gastrointestinal Digestion

Cherries are a good source of bioactive compounds, with high antioxidant activity as well as nutritional and therapeutic importance. In this study, cherry wines enriched with green tea infusion (mild and concentrated) were produced, and their biological properties were evaluated. During winemaking, the main vinification parameters (alcohol, reducing sugars, acidity, total polyphenol content) as well biological activity (antioxidant activity, alpha-glucosidase inhibition potential) were determined. An in vitro digestion process was also performed to evaluate the impact of the gastrointestinal environment on the biological stability of the wines, and to analyze the interactions of wine-intestinal microflora. The addition of green tea to the cherry wine significantly increased the total polyphenol content (up to 2.73 g GAE/L) and antioxidant activity (up to 22.07 mM TE/L), compared with the control wine. However, after in vitro digestion, a reduction in total polyphenols (53–64%) and antioxidant activity (38–45%) were noted. Wines fortified with green tea expressed a stronger inhibition effect on intestinal microflora growth, of which E. coli were the most sensitive microorganisms. The tea-derived bioactive compounds significantly increased the potential of alpha-glucosidase inhibition. The proposed wines could be a good alternative type of wine, with an increased polyphenol content and the potential to control the insulin response supporting therapy for diabetes.

Effect of Commercial Yeast Starter Cultures on Cabernet Sauvignon Wine Aroma Compounds and Microbiota

Commercial Saccharomyces cerevisiae plays an important role in the traditional winemaking industry. In this study, the correlation of microbial community and aroma compound in the process of alcohol fermentation of Cabernet Sauvignon by four different commercial starters was investigated. The results showed that there was no significant difference in the fermentation parameters of the four starters, but there were differences in microbial diversity among the different starters. The wine samples fermented by CEC01 had higher microbial abundance. GC-MS detected a total of 58 aromatic compounds from the fermentation process by the experimental yeasts. There were 25 compounds in the F6d variant, which was higher than in other samples. The PCA score plot showed that 796 and F15 yeast-fermented wines had similar aromatic characteristic compositions. According to partial least squares (PLS, VIP > 1.0) analysis and Spearman’s correlation analysis, 11, 8, 8 and 10 microbial genera were identified as core microorganisms in the fermentation of 796, CEC01, CECA and F15 starter, respectively. Among them, Leuconostoc, Lactobacillus, Sphingomonas and Pseudomonas played an important role in the formation of aroma compounds such as Ethyl caprylate, Ethyl caprate and Ethyl-9-decenoate. These results can help us to have a better understanding of the effects of microorganisms on wine aroma and provide a theoretical basis for improving the flavor quality of Cabernet Sauvignon wine.

Evaluation of Malolactic Starters in White and Rosé Winemaking of Moschofilero Wines

The aim of the present study was to induce malolactic fermentation (MLF) after alcoholic fermentation (AF) of must of the Moschofilero cultivar, the only ‘gris’ native grape variety that is cultivated in Greece. For this purpose, Oenococcus oeni strains Viniflora® CH16, Viniflora® Oenos and Viniflora® CiNe were inoculated after the completion of AF driven by the Saccharomyces cerevisiae strain UCLM S325. Growth of the aforementioned starter cultures was assessed during fermentation by classical microbiological techniques, and verification of their dominance was performed by (GTG)5 fingerprinting. Assessment of standard enological parameters and colorimetric analysis were performed by established approaches. Identification and quantification of organic acids, ethanol and glycerol was performed by high performance liquid chromatography (HPLC), while the solid-phase microextraction method (SPME), coupled with gas chromatography/mass spectrometry (GC/MS), was employed for the identification and quantification of volatile compounds. Finally, sensory analysis took place according to ISO 13299:2016. The suitability of the starter cultures employed to drive AF and MLF was exhibited; AF and MLF of the white and rosé wines were completed after 15 days. Upon completion of AF, substantial differences were observed in the chemical characteristics of the white and rosé wines, which were also reflected in the balance descriptor. MLF also resulted in significant changes. In all cases total acidity decreased and volatile acidity and pH value increased, while the vanilla and butter descriptors increased. Interestingly, the color intensity of the rosé wines also increased. A series of strain-dependent changes in the chemical composition and sensory analysis of both white and rosé wines was also observed.

Starmerella bacillaris Strains Used in Sequential Alcoholic Fermentation with Saccharomyces cerevisiae Improves Protein Stability in White Wines

Haze can appear in white wines as a result of the denaturation and subsequent aggregation of grape pathogenesis-related (PR) proteins. Yeast cell-wall polysaccharides, particularly mannoproteins, represent a promising strategy to reduce the incidence of this phenomenon. The aim of this study was to evaluate the effects of 13 Starmerella bacillaris strains, in sequential fermentation with Saccharomyces cerevisiae, on wine protein stability of three white wines (Sauvignon blanc, Pinot grigio, and Manzoni bianco). The resulting wines were characterized in terms of their chemical composition, content of PR proteins and polysaccharides, and heat stability. In addition, the mannoprotein fraction was purified from six wines, five produced with S. bacillaris and one with S. cerevisiae EC1118 used as control. Generally, wines produced with S. bacillaris strains were more heat-stable, despite generally containing higher amounts of PR proteins. The increased heat stability of Starmerella wines was attributed to the stabilizing effect resulting from their higher concentrations of both total polysaccharides and mannoprotein fractions. In particular, for the most heat unstable wine (Manzoni bianco), the low MW mannoprotein fraction resulted to be the most involved in wine stability. The ability to produce wines with different heat stability was demonstrated to be strain-dependent and was more evident in the most unstable wines. By reducing fining waste, the use of S. bacillaris as an enological starter can be proposed as a new tool to manage wine protein stability for a more sustainable winemaking.

Functional Verification of the Citrate Transporter Gene in a Wine Lactic Acid Bacterium, Lactiplantibacillus plantarum

Organic acid metabolism by lactic acid bacteria plays a significant role in improving wine quality. During this process, the uptake of extracellular organic acids by the transporters is the first rate-limiting step. However, up to now, there is very little published research on the functional verification of organic acid transporter genes in wine lactic acid bacteria. In this study, a predicted citrate transporter gene JKL54_04345 (citP) by protein homology analysis was knocked out using a CRISPR/Cas9-based gene-editing system, and then complemented using the modified pMG36e vectors in a major wine lactic acid bacterium, Lactiplantibacillus plantarum XJ25, to verify its function in citrate metabolism for the first time. The results showed that the gene knockout mutant XJ25-ΔcitP lost the ability to utilize citric acid, while the gene complement mutant XJ25-ΔcitP-pMG36ek11-citP fully recovered the ability of citric acid utilization. Meanwhile, citP knockout and complement barely affected the utilization of l-malic acid. These indicated that citP in L. plantarum functioned as a citrate transporter and was the only gene responsible for citrate transporter. In addition, two modified plasmid vectors used for gene supplement in L. plantarum showed distinct transcription efficiency. The transcription efficiency of citP in XJ25-ΔcitP-pMG36ek11-citP mutant was 4.01 times higher than that in XJ25-ΔcitP-pMG36ek-citP mutant, and the utilization rate of citric acid in the former was 3.95 times higher than that in the latter, indicating that pMG36ek11 can be used as a high-level expression vector in lactic acid bacteria.

The Use of γ-Aminobutyric Acid-Producing Saccharomyces cerevisiae SC125 for Functional Fermented Beverage Production from Apple Juice

The development of functional fermented beverages enriched with γ-aminobutyric acid (GABA) has been pursued because of the health benefits of GABA; however, few studies have described GABA production by yeast. Therefore, this study aimed to produce fermented apple beverages enriched with GABA produced by Saccharomyces cerevisiae SC125. Golden Delicious apples were fermented by S. cerevisiae SC125 to produce a novel functional beverage; commercial yeast was used as the control. The GABA, organic acid, and volatile compound content during the fermentation process was investigated by high-performance liquid chromatography and headspace solid-phase microextraction/gas chromatography-mass spectrometry. A yield of 898.35 ± 10.10 mg/L GABA was achieved by the efficient bioconversion of L-monosodium glutamate. Notably, the S. cerevisiae SC125-fermented beverage produced several unique volatile compounds, such as esters, alcohols, 6-decenoic acid, and 3-hydroxy−2-butanone, and showed significantly enhanced contents of organic acids, including malic acids, citric acid, and quinic acid. Sensory analysis demonstrated that the S. cerevisiae SC125-fermented apple beverage had improved aroma, flavor, and overall acceptability. In conclusion, a fermented functional apple beverage containing GABA was efficiently produced using S. cerevisiae SC125.

Application of Chitosan-Lignosulfonate Composite Coating Film in Grape Preservation and Study on the Difference in Metabolites in Fruit Wine

In order to solve the global problem of fruit rotting due to microbial infection and water loss after harvest, which leads to a large amount of food waste, this experiment uses degradable biological composite coating to prolong the preservation period of grapes. Chitosan (CH) and Lignosulfonate (LS) were used as Bio-based film materials, CH films, 1% CH/LS films and 2% CH/LS biomass composite films were synthesized by the classical casting method and applied to grape preservation packaging. Its preservation effect was tested by grape spoilage rate, water loss rate, hardness, soluble solids, titratable acid, and compared with plastic packaging material PE film. At the same time, 1H NMR technology combined with pattern recognition analysis (PCA) and partial least squares discriminant analysis (PLS-DA) was used to determine the nuclear magnetic resonance (NMR) of Cabernet Sauvignon, Chardonnay and Italian Riesling wines from the eastern foothills of Helan Mountain to explore the differences in metabolites of wine. The results of preservation showed that the grapes quality of CH films and 2% CH/LS coating package is better than the control group, the decay rates decreased from 37.71% to 21.63% and 18.36%, respectively, the hardness increased from 6.83 to 10.4 and 12.78 and the soluble solids increased from 2.1 in the control group to 3.0 and 3.2. In terms of wine metabolites, there are similar types of metabolites between cabernet Sauvignon dry red wine and Chardonnay and Italian Riesling dry white wine, but there are significant differences in content. The study found that 2% CH/LS coating package could not only reduce the spoilage rate of grapes, inhibit the consumption of soluble solids and titratable acids, but also effectively extend the shelf life of grapes by 6 days.

Technological Improvements on FML in the Chianti Classico Wine Production: Co-Inoculation or Sequential Inoculation?

Winemaking variables and techniques are known to affect the composition of wines. To obtain a rapid and safe fermentation course, with a reduced risk of proliferation of unwanted microbial species, frequent recourse is made to the use of selected microorganisms, which can greatly simplify the complex management of the fermentation process. In particular, selected strains of lactic acid bacteria are used, which are much more sensitive than yeasts to the operating conditions of the medium. In this regard, the overall aim of this research was to verify whether the early inoculation of homolactic acid bacteria for hexoses (Lactobacillus plantarum) carried out after 24 h, compared with that of saccharomycetes operating alcoholic fermentation, could be advantageous compared with a traditional innoculation with a different heterolactic bacterial strain for hexoses (Oenococcus oeni) operated at the end of alcoholic fermentation. The grape variety chosen was Sangiovese, the protagonist of Tuscan oenology. The evaluation focused on different aspects such as the management of winery operations, and the quality and longevity of the product; was carried out in all phases of winemaking; and analysed both from a chemical and sensory point of view.

New Isolated Autochthonous Strains of S. cerevisiae for Fermentation of Two Grape Varieties Grown in Poland

Many commercial strains of the Saccharomyces cerevisiae species are used around the world in the wine industry, while the use of native yeast strains is highly recommended for their role in shaping specific, terroir-associated wine characteristics. In recent years, in Poland, an increase in the number of registered vineyards has been observed, and Polish wines are becoming more recognizable among consumers. In the fermentation process, apart from ethyl alcohol, numerous microbial metabolites are formed. These compounds shape the wine bouquet or become precursors for the creation of new products that affect the sensory characteristics and quality of the wine. The aim of this work was to study the effect of the grapevine varieties and newly isolated native S. cerevisiae yeast strains on the content of selected wine fermentation metabolites. Two vine varieties—Regent and Seyval blanc were used. A total of 16 different yeast strains of the S. cerevisiae species were used for fermentation: nine newly isolated from vine fruit and seven commercial cultures. The obtained wines differed in terms of the content of analyzed oenological characteristics and the differences depended both on the raw material (vine variety) as well as the source of isolation and origin of the yeast strain used (commercial vs. native). Generally, red wines characterized a higher content of tested analytes than white wines, regardless of the yeast strain used. The red wines are produced with the use of native yeast strains characterized by higher content of amyl alcohols and esters.

Enhancing Ethanol Tolerance via the Mutational Breeding of Pichia terricola H5 to Improve the Flavor Profiles of Wine

Although using non-Saccharomyces yeasts during alcoholic fermentation can improve the wine aroma, most of them are not ethanol tolerant; therefore, in 2017, this study screened 85 non-Saccharomyces yeasts isolated and identified from 24 vineyards in seven Chinese wine-producing regions, obtaining Pichia terricola strain H5, which displayed 8% ethanol tolerance. Strain H5 was subjected to ultraviolet (UV) irradiation and diethyl sulfate (DES) mutagenesis treatment to obtain mutant strains with different fermentation characteristics from the parental H5. Compared with strain H5, the UV-irradiated strains, UV5 and UV8, showed significantly higher ethanol tolerance and fermentation capacity. Modified aroma profiles were also evident in the fermentation samples exposed to the mutants. Increased ethyl caprate, ethyl caprylate, and ethyl dodecanoate content were apparent in the UV5 samples, providing the wine with a distinctly floral, fruity, and spicy profile. Fermentation with strain UV8 produced a high ethyl acetate concentration, causing the wine to present a highly unpleasant odor. To a certain extent, UV irradiation improved the ethanol tolerance and fermentation ability of strain H5, changing the wine aroma profile. This study provides a theoretical basis for the industrial application of non-Saccharomyces yeasts that can improve wine flavor.

Oenological Characterization of Native Hanseniaspora uvarum Strains

The utilization of native yeast strains associated with a distinct terroir for autochthonous grape types represents a novel trend in winemaking, contributing to the production of unique wines with regional character. Hence, this study aimed to isolate native strains of the yeast H. uvarum from the surface of various fruits and to characterize its fermentation capability in Prokupac grape must. Out of 31 yeasts, 8 isolates were identified as H. uvarum. The isolates were able to grow at low (4 °C) temperatures, SO2 concentrations up to 300 ppm and ethanol concentrations up to 5%. Additionally, they provided a good profile of organic acids during the microvinification of sterile grape must. Although the content of acetic acid (0.54–0.63 g/L) was relatively high, the sniffing test proved that the yeast isolates developed a pleasant aroma characterized as fruity. All H. uvarum isolates produced twice the concentration of glycerol compared to commercial wine yeast Saccharomyces cerevisiae, contributing to the fullness and sweetness of the wine. The results for pure and sequential fermentation protocols confirmed that the selected S-2 isolate has good oenological characteristics, the capability to reduce the ethanol content (up to 1% v/v) and a potential to give a distinctive note to Prokupac-grape wines.

Use of Non-Saccharomyces Yeast Co-Fermentation with Saccharomyces cerevisiae to Improve the Polyphenol and Volatile Aroma Compound Contents in Nanfeng Tangerine Wines

This study attempted to improve the polyphenol and volatile aroma compound contents in Nanfeng tangerine wines using non-Saccharomyces yeast and Saccharomyces cerevisiae. The effects of fermentation with pure cultures of Candida ethanolica, Hanseniaspora guilliermondii and Hanseniaspora thailandica, as well as in sequential and mixed inoculations (1:1 or 1:100 ratio) with S. cerevisiae in Nanfeng tangerine wines were evaluated. C. ethanolica was found to produce the most polyphenols (138.78 mg/L) during pure fermentation, while H. guilliermondii produced the most volatile aroma compounds (442.34 mg/L). The polyphenol content produced during sequential fermentation with S. cerevisiae and H. guilliermondii (140.24 mg/L) or C. ethanolica (140.21 mg/L) was significantly higher than other co-fermentations. Meanwhile, the volatile aroma compounds were found to be more abundant in S. cerevisiae/H. guilliermondii mixed fermentation (1:1 ratio) (588.35 mg/L) or S. cerevisiae/H. guilliermondii sequential fermentation (549.31 mg/L). Thus, S. cerevisiae/H. guilliermondii sequential fermentation could considerably boost the polyphenol and volatile aroma component contents in Nanfeng tangerine wines. The findings of this study can be used to drive strategies to increase the polyphenol content and sensory quality of tangerine wines and provide a reference for selecting the co-fermentation styles for non-Saccharomyces yeast and S. cerevisiae in fruit wine fermentation.

Effects of sequential inoculation of Lachancea thermotolerans and Oenococcus oeni on chemical composition of spent coffee grounds hydrolysates

Spent coffee grounds (SCG) disposal is an environmental problem. These residues from coffee brewing and instant coffee production have potential to produce novel alcoholic beverages. SCG valorization through sequential alcoholic and malolactic fermentation was investigated using a yeast, Lachancea thermotolerans Concerto and a lactic acid bacterium (LAB), Oenococcus oeni Lalvin 31 in this study. Our results showed that sequential inoculation prevented early death of yeast confronted when simultaneous inoculation was adopted, allowing for growth and persistence of both yeast and LAB till the end of fermentation. Adequate ethanol production (4.91 ± 0.13 %, v/v) with low residual sugar content was also attained. In addition, relatively lower levels of acetic, lactic, and succinic acids were produced by sequential inoculation than that of simultaneous inoculation. Furthermore, SCG hydrolysates fermented via sequential inoculation had the widest variety of volatiles (e.g. esters and ketones). Overall, our results indicated that sequential inoculation of L. thermotolerans and O. oeni in SCG hydrolysates might be a way to develop novel beverages with pleasant flavor profiles.

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L. thermotolerans and O. oeni were used in spent coffee grounds (SCG) hydrolysates fermentation.

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Sequential inoculation of O. oeni prevented early yeast cell death.

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Sequential inoculation produced desired content of ethanol.

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Sequential inoculation generated and/or retained the widest variety of volatiles.

Apple Pomace as a Sustainable Substrate in Sourdough Fermentation

Innovations range from food production, land use, and emissions all the way to improved diets and waste management. Global apple production has amounted to over 87 million tons/year, while 18% are processed, resulting in 20-35% (apple fruit fresh weight) apple pomace (AP). Using modern AP management, integrated knowledge in innovative fermentation demonstrates opportunities for reducing environmental pollution and integration into a circular economy. With this association in view, integrating AP flour during sourdough fermentation increases the nutritional value, highlighting a new approach that could guide innovative fermented foods. In this study, the wheat flour (WF) and AP flour were mixed at different ratios, hydrated with water (1:1 w/v), and fermented using a selective culture of Fructilactobacillus florum DSM 22689 and baker's yeast (single and co-culture). Sourdough fermentation was monitored and analyzed for 72 h. Results suggested that AP may be an important source of organic acids and fermentable sugars that increase nutritional sourdough value. AP flour addition in WF had a positive effect, especially in fermentations with 95% WF and 5% AP, mainly in co-culture fermentation.