Selection of non-Saccharomyces yeasts for orange wine fermentation based on their enological traits and volatile compounds formation

Evaluation of the effect of Torulaspora delbrueckii on important volatile compounds in navel orange original brandy using E-nose combined with HS-SPME-GC-MS

Simultaneous inoculation of non-Saccharomyces cerevisiae during the alcoholic fermentation process has been found to be an effective strategy for enhancing wine flavor. This study aimed to investigate the effect of Torulaspora delbrueckii NCUF305.2 on the flavor of navel orange original brandy (NOOB) using E-nose combined with HS-SPME-GC-MS. The results showed a significant increase (p < 0.05) in the sensitivity of NOOB to W5C, W3C, W1S, and W3S sensors by mixed fermentation (MF). Esters in NOOB increased by 4.13%, while higher alcohols increased by 21.93% (p < 0.001), terpenes and others increased by 52.07% and 40.99% (p < 0.01), respectively. Notably, several important volatile compounds with relative odor activity values above 10 showed an increase. Sensory analysis revealed that a more pronounced citrus-like flavor and higher overall appearance scores were found in MF than in pure fermentation (PF). These findings offer valuable theoretical guidance for enhancing the quality of fruit brandies.

Molecular decoding a meat-like aroma generated from Laetiporus sulphureus-mediated fermentation of onion (Allium cepa L.)

The organoleptic properties of plant-based meat alternatives do not meet consumer expectations due to the lack of characteristic flavors resembling meat. To address this challenge, a fermentation system utilizing Laetiporussulphureus was developed to generate a meat-like and fatty flavor from a vegetable source, onion. By means of multiple stir bar sorptive extraction and gas chromatography-mass spectrometry-olfactometry, an unsaturated aldehyde, (E,Z)-2,4-decadienal, which imparts a tallow-like and fatty odor, and a sulfurous compound benzothiazole, with a broth-like odor were identified, which well contributed to the characteristic odor of the supernatant. (E,Z)-2,4-Decadienal as the most important odorant (odor activity value = 206) was biosynthesized by transformation of linoleic acid with L.sulphureus, as revealed by isotopic tracing experiments. For the first time in Basidiomycota, the biogenetic pathway of (E,Z)-2,4-decadienal from linoleic acid was proposed.

Kinetic Evaluation of the Production of Mead from a Non-Saccharomyces Strain

There is a growing market for craft beverages with unique flavors. This study aimed to obtain a palate-pleasing mead derived from Pichia kudriavzevii 4A as a monoculture. Different culture media were evaluated to compare the fermentation kinetics and final products. The crucial factors in the medium were ~200 mg L-1 of yeast assimilable nitrogen and a pH of 3.5-5.0. A panel of judges favored the mead derived from Pichia kudriavzevii 4A (fermented in a medium with honey initially at 23 °Bx) over a commercial sample produced from Saccharomyces cerevisiae, considering its appearance, fruity and floral flavors (provided by esters, aldehydes, and higher alcohols), and balance between sweetness (given by the 82.91 g L-1 of residual sugars) and alcohol. The present mead had an 8.57% v/v ethanol concentration, was elaborated in 28 days, and reached a maximum biomass growth (2.40 g L-1) on the same fermentation day (6) that the minimum level of pH was reached. The biomass growth yield peaked at 24 and 48 h (~0.049 g g-1), while the ethanol yield peaked at 24 h (1.525 ± 0.332 g g-1), in both cases declining thereafter. The Gompertz model adequately describes the kinetics of sugar consumption and the generation of yeast biomass and ethanol. Pathogenic microorganisms, methanol, lead, and arsenic were absent in the mead. Thus, Pichia kudriavzevii 4A produced a safe and quality mead with probable consumer acceptance.

Volatilomics of Fruit Wines

Volatilomics is a scientific field concerned with the evaluation of volatile compounds in the food matrix and methods for their identification. This review discusses the main groups of compounds that shape the aroma of wines, their origin, precursors, and selected metabolic pathways. The paper classifies fruit wines into several categories, including ciders and apple wines, cherry wines, plum wines, berry wines, citrus wines, and exotic wines. The following article discusses the characteristics of volatiles that shape the aroma of each group of wine and the concentrations at which they occur. It also discusses how the strain and species of yeast and lactic acid bacteria can influence the aroma of fruit wines. The article also covers techniques for evaluating the volatile compound profile of fruit wines, including modern analytical techniques.

Temporal Profile of the Microbial Community and Volatile Compounds in the Third-Round Fermentation of Sauce-Flavor baijiu in the Beijing Region

Sauce-flavor baijiu produced in the Beijing and Guizhou regions has regional characteristic flavors, but the differences in flavor compounds and reasons for their formation remain unclear. The sauce-flavor baijiu brewing process involves several rounds of fermentation. In this study, we investigated the temporal distribution of microbial communities and flavor substances during the third round of sauce-flavor baijiu fermentation in the Beijing region, and we then compared and analyzed the differences of flavor substances and microorganisms in the fermented grains of sauce-flavor baijiu in the Beijing and Guizhou regions. It was found that 10 bacterial genera and 10 fungal genera were dominant in the fermented grains. The acidity of the fermented grains had a significant driving effect on the microbial community succession. A total of 81 volatile compounds were identified and quantified in the fermented grains, of which esters and alcohols were relatively abundant. The differences in 30 microbial community compositions and their resulting differences in terms of the fermentation parameters of fermented grains are responsible for the differences in the profiles of flavor compounds between sauce-flavor baijiu produced in the Beijing and Guizhou regions.

Exploring future applications of the apiculate yeast Hanseniaspora

As a metaphor, lemons get a bad rap; however the proverb 'if life gives you lemons, make lemonade' is often used in a motivational context. The same could be said of Hanseniaspora in winemaking. Despite its predominance in vineyards and grape must, this lemon-shaped yeast is underappreciated in terms of its contribution to the overall sensory profile of fine wine. Species belonging to this apiculate yeast are known for being common isolates not just on grape berries, but on many other fruits. They play a critical role in the early stages of a fermentation and can influence the quality of the final product. Their deliberate addition within mixed-culture fermentations shows promise in adding to the complexity of a wine and thus provide sensorial benefits. Hanseniaspora species are also key participants in the fermentations of a variety of other foodstuffs ranging from chocolate to apple cider. Outside of their role in fermentation, Hanseniaspora species have attractive biotechnological possibilities as revealed through studies on biocontrol potential, use as a whole-cell biocatalyst and important interactions with Drosophila flies. The growing amount of 'omics data on Hanseniaspora is revealing interesting features of the genus that sets it apart from the other Ascomycetes. This review collates the fields of research conducted on this apiculate yeast genus.

Identification of dominant functional microbes that contribute to the characteristic aroma of Msalais, traditional wine fermented from boiled local grape juice in China

Msalais is a traditional wine produced from naturally fermented boiled local grape juice in China. It has characteristic dried fruit and caramel odors, mainly attributed to aromatic compounds, such as furaneol and 5-methylfurfural. However, it is unclear how microbes involved in the natural fermentation of Msalais contribute to this characteristic aroma. Here, we analyzed the Msalais-fermenting microbes and aromatic compounds formed during natural Msalais fermentation by using high-throughput sequencing and gas chromatography-mass spectrometry, respectively. The analysis revealed that Saccharomyces cerevisiae, Kazachstania humilis, Lactobacillus plantarum, and Lactobacillus farraginis are the dominant and key functional species that produce high amounts of furaneol and 5-methylfurfural during Msalais fermentation. Of these, K. humilis and L. farraginis are rarely detected during regular wine fermentation. The identified functional species could be used to control typical aromatic characteristics of Msalais.

Correlation Analysis of Microbial Community Changes and Physicochemical Characteristics in Aged Vinegar Brewing

This study aimed to explore key physicochemical characteristics and evolutionary patterns of microbial community structure during the fermentation of aged vinegar. The correlation between microorganisms and physicochemical characteristics during fermentation was examined. The results revealed significant differences in genera at different stages of fermentation. The dominant bacteria in R1 were Bacillus, Lactobacillus, Aspergillus, and Issatchenkia. During the R2 fermentation stage, Lactobacillus, Acetobacter, and Saccharomyces exhibited an upward trend and finally became the dominant bacteria. Aspergillus was the main bacterial genus at the end of overall fermentation. The correlation analysis showed that the bacterial genera significantly positively and negatively correlated with reducing sugars and amino acid nitrogen were the same in Cuqu. Similarly, the bacterial genera significantly positively and negatively correlated with pH and saccharification power were the same. pH, reducing sugar, and saccharification ability were mainly positively correlated with bacterial genera during fermentation. Further, studies found that the overall correlation between fungal communities and physicochemical characteristics was weaker than the correlation with bacteria during fermentation.

Effect of commercial yeasts (Saccharomyces cerevisiae) on fermentation metabolites, phenolic compounds, and bioaccessibility of Brazilian fermented oranges

Brazil is the largest producer of oranges worldwide, as well as one of the largest producers of orange juice. Alcoholic fermented beverages have been considered a marketable alternative for oranges. In this study, four S. cerevisiae commercial yeasts were evaluated for metabolites generated during orange juice (cv. 'Pêra D9') fermentation. Alcohols, sugars, and organic acids were evaluated by HPLC-DAD-RID during fermentation, and phenolic compounds were analyzed in fermented orange. Orange juice and fermented oranges were also subjected to digestion simulations. The yeasts presented an adequate fermentation activity, based on sugar consumption, and high ethanol (>10.5%) and glycerol (4.8-5.5 g/L) contents. The yeast strains T-58 and US-05 produced high levels of lactic acid. Phenolic compounds and antioxidant activity did not differ amongst yeasts, presenting hesperidin levels between 115 and 127 mg/L, respectively. The fermented orange showed a >70% bioaccessibility, compared to juice, especially for catechin, epigallocatechin-gallate, procyanidin-B2, rutin, and procyanidin-B1.

PCR-based gene targeting in Hanseniaspora uvarum

Lack of gene-function analyses tools limits studying the biology of Hanseniaspora uvarum, one of the most abundant yeasts on grapes and in must. We investigated a rapid PCR-based gene targeting approach for one-step gene replacement in this diploid yeast. To this end, we generated and validated two synthetic antibiotic resistance genes, pFA-hygXL and pFA-clnXL, providing resistance against hygromycin and nourseothricin, respectively, for use with H. uvarum. Addition of short flanking-homology regions of 56-80 bp to these selection markers via PCR was sufficient to promote gene targeting. We report here the deletion of the H. uvarum LEU2 and LYS2 genes with these marker genes via two rounds of consecutive transformations, each resulting in the generation of auxotrophic strains (leu2/leu2; lys2/lys2). The hereby constructed leucine auxotrophic leu2/leu2 strain was subsequently complemented in a targeted manner, thereby further validating this approach. PCR-based gene targeting in H. uvarum was less efficient than in Saccharomyces cerevisiae. However, this approach, combined with the availability of two marker genes, provides essential tools for directed gene manipulations in H. uvarum.

Chemical and Sensory Characteristics of Fruit Juice and Fruit Fermented Beverages and Their Consumer Acceptance

Recent social, economic, and technological evolutions have impacted consumption habits. The new consumer is more rational, more connected and demanding with products, more concerned with the management of the family budget, with the health, origin, and sustainability of food. The food industry over the last few years has shown remarkable technological and scientific evolution, with an impact on the development and innovation of new products using non-thermal processing. Non-thermal processing technologies involve methods by which fruit juices receive microbiological inactivation and enzymatic denaturation with or without the direct application of low heat, thereby lessening the adverse effects on the nutritional, bioactive, and flavor compounds of the treated fruit juices, extending their shelf-life. The recognition of the nutritional and protective values of fruit juices and fermented fruit beverages is evident and is attributed to the presence of different bioactive compounds, protecting against chronic and metabolic diseases. Fermentation maintains the fruit's safety, nutrition, and shelf life and the development of new products. This review aims to summarize the chemical and sensory characteristics of fruit juices and fermented fruit drinks, the fermentation process, its benefits, and its effects.

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.

Cocoa bean turning as a method for redirecting the aroma compound profile in artisanal cocoa fermentation

Two artisanal fermentation processes for Criollo cocoa beans with different turning start times (24 h and 48 h) were studied. The aromatic profile of cocoa turned every 24 h (B1) displayed volatile compounds associated with fermented, bready, and fruity aromas. When cocoa beans were fermented with a different turning technique with a start time of 48 h (B2), they provided volatile compounds mainly associated with descriptors of floral, woody, sweet, fruity and chocolate aromas. The turning start time of 48 h stimulated a microbial profile dominated by yeast such as Hanseniaspora opuntiae, Pichia manshurica, and Meyerozyma carpophila, favoring the production of several key aroma markers associated with cocoa bean fermentation quality, such as phenylethyl acetate, 2-phenylacetaldehyde, 3-methylbutanal, 2-phenylethyl alcohol, 2,3-butanedione, 3-methylbutanoic acid, and 2-methylpropanoic acid, while an immediate turning start time (24 h) favored an aerobic environment that stimulated the rapid growth of Acetobacter pasteurianus, Bacillus subtilis and a higher biodiversity of lactic acid bacteria (LAB) (e.g., Lactobacillus plantarum and Pediococcus acidilactici), which increased the production of ethyl acetate and 3-hydroxy-2-butanone. Volatile compound generation and microbial populations were evaluated and analyzed by multivariate analysis (principal component analysis and partial least squares discriminant analysis) to find correlations and significant differences. This study shows that the method of turning Criollo cacao beans can lead to the formation of desirable aromatic compounds.

Microbial Community Succession and Its Environment Driving Factors During Initial Fermentation of Maotai-Flavor Baijiu

The microbial composition and environmental factors can take a great influence on community succession during the solid-state fermentation (SSF) of Maotai-flavor Baijiu. In this paper, high-throughput sequencing was used to reveal the dominant microorganisms and the evolution process of microbial community structure in the initial fermentation of Maotai-flavor Baijiu. The correlation analysis was carried out for the relationship between physicochemical factors and fermented microbes. The results showed that microorganisms were obviously enriched and the diversity of bacteria and fungi showed a downward trend during the heap fermentation process of Maotai-flavor Baijiu. However, the diversity of fungi in the pit fermentation process increased. Generally, Lactobacillus, Pichia, and Saccharomyces were the dominant microorganisms in the initial fermentation of Maotai-flavor Baijiu. According to the redundancy analysis, we found that reducing sugar was the key driving factor for microbial succession in the heap fermentation, while acidity, alcohol, and temperature were the main driving forces in pit fermentation. This study revealed the microbial succession and its related environmental factors in the initial fermentation of Maotai-flavor Baijiu, which will enrich our knowledge of the mechanism of solid-state liquor fermentation.

Secondary Aroma: Influence of Wine Microorganisms in Their Aroma Profile

Aroma profile is one of the main features for the acceptance of wine. Yeasts and bacteria are the responsible organisms to carry out both, alcoholic and malolactic fermentation. Alcoholic fermentation is in turn, responsible for transforming grape juice into wine and providing secondary aromas. Secondary aroma can be influenced by different factors; however, the influence of the microorganisms is one of the main agents affecting final wine aroma profile. Saccharomyces cerevisiae has historically been the most used yeast for winemaking process for its specific characteristics: high fermentative metabolism and kinetics, low acetic acid production, resistance to high levels of sugar, ethanol, sulfur dioxide and also, the production of pleasant aromatic compounds. Nevertheless, in the last years, the use of non-saccharomyces yeasts has been progressively growing according to their capacity to enhance aroma complexity and interact with S. cerevisiae, especially in mixed cultures. Hence, this review article is aimed at associating the main secondary aroma compounds present in wine with the microorganisms involved in the spontaneous and guided fermentations, as well as an approach to the strain variability of species, the genetic modifications that can occur and their relevance to wine aroma construction.

The Sensory Quality Improvement of Citrus Wine through Co-Fermentations with Selected Non-Saccharomyces Yeast Strains and Saccharomyces cerevisiae

Co-fermentation of selected non-Saccharomyces yeast strain with Saccharomyces cerevisiae is regarded as a promising approach to improve the sensory quality of fruit wine. To evaluate the effects of co-fermentations between the selected non-Saccharomyces yeast strains (Hanseniaspora opuntiae, Hanseniaspora uvarum and Torulaspora delbrueckii) and S. cerevisiae on the sensory quality of citrus wine, the fermentation processes, the chemical compositions, and the sensory evaluations of citrus wines were analyzed. Compared with those of S. cerevisiae fermentation, co-fermentations produced high sensory qualities, and S. cerevisiae/H. opuntiae co-fermentation had the best sensory quality followed by Sc-Hu and Sc-Td co-fermentations. Additionally, all the co-fermentations had a lower amount of ethanol and total acidity, higher pH value, and higher content of volatile aroma compounds, especially the content of higher alcohol and ester compounds, than those of S. cerevisiae fermentation. Therefore, co-fermentations of the non-Saccharomyces yeast strains and S. cerevisiae could be employed to improve the sensory quality of citrus wines. These results would provide not only methods to improve the sensory quality of citrus wine, but also a valuable reference for the selection of non-Saccharomyces yeast strains for fruit wine fermentation.