Characterization of volatile aroma compounds in litchi (Heiye) wine and distilled spirit

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.

Effects of Loquat Juice Addition on Sensory Characteristics and Volatile Organic Compounds of Loquat Beer

Beer, as an ancient and widely consumed alcoholic beverage, holds a rich cultural heritage and history. In recent years, fruit beer has gained significant attention as a distinct beer type produced by incorporating fruit juice into traditional beer ingredients. This study employed headspace solid-phase microextraction-gas chromatography-mass spectrometry techniques, redundancy analysis, and orthogonal projections to latent structures discriminant analysis to analyze the sensory evaluation, physicochemical properties, organic acids, and volatile organic compounds (VOCs) of loquat beer with different proportions of loquat juice. The results shown that the addition of an appropriate amount of loquat juice (40%) enhanced the overall sensory quality of the beer; as the proportion of loquat juice increased, the contents of malic acid and tartaric acid significantly increased (p < 0.05). A total of 100 VOCs were identified, among which 23 key VOCs (VIP > 1, p < 0.05) represented the most important characteristic flavor components in loquat beer based on their odor activity value (OAV). This study holds significant importance for the value-added processing and economic development of loquat.

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.

Exploring the regulated effects of solid-state fortified Jiuqu and liquid-state fortified agent on Chinese Baijiu brewing

Zaopei is the direct source of Chinese liquor (Baijiu). Adding functional strains to Zaopei is a potential strategy to regulate Baijiu brewing, mainly including the two ways of solid-state fortified Jiuqu (SFJ) and liquid-state fortified agent (LFA). Here, to explore their regulated details, the response patterns of Zaopei microecosystem and the changes in the product features were comprehensively investigated. The results showed that SFJ more positively changed the physicochemical properties of Zaopei and improved its ester content, from 978.57 mg/kg to 1078.63 mg/kg over the fermentation of 30 days, while LFA decreased the content of esters, alcohols, and acids. Microbial analysis revealed that SFJ significantly increased Saccharomycopsis and Aspergillus from the start of fermentation and induced a positive interaction cluster driven by the added functional Paenibacillus, while LFA exhibited a community structure near that of the original microecosystem and led to a simpler network with the reduced microbial nodes and correlations. Metabolism analysis found that both SFJ and LFA weakened the flavor-producing metabolism by suppressing some key enzyme pathways, such as EC 3.2.1.51, EC 4.2.1.47, EC 1.1.1.27, EC 1.1.1.22, EC 1.5.1.10, EC 1.14.11.12. As a result, SFJ improved the raw liquor yield by 28.5 % and endowed the final product with a more fragrant aroma, mainly through ethyl (E)-cinnamate, ethyl isovalerate, ethyl phenacetate with the higher odor activity values, while LFA promoted the yield by 13.2 % and resulted in a purer and less intense aroma through the aroma-active β-damascenone, ethyl heptoate, ethyl phenacetate. These results facilitated the regulated mechanism of SFJ and LFA on Baijiu brewing and indicated that the used functional strains in this study could be applicated in SFJ way for the further industrial-scale application.

Process Optimization for Production of Persimmon Wine with Lower Methanol

Persimmon wine has various nutritional elements and high commercial potential. However, the high content of methanol, which is derived from the fruit's pectin, always hinders persimmon wine production. To reduce the methanol level in the wine, the effects of persimmon cultivar, starter, pectinase, and pretreatment methods were investigated via single-factor and orthogonal experiments. The persimmon cultivar 'MaoKui' was finally used throughout the study owing to its lowest pectin concentration (24.5 g/kg). The best treatment conditions against the persimmon pulp were pectinase (0.04 g/kg) at 30 °C for 4 h, then boiled at 115 °C for 15 min before fermentation started. The optimized fermentation conditions for wine production were pectinase (0.03 g/kg), 250 mg/kg starter (BO213 and SPARK with equal amounts), at 28 °C for 6 d. The obtained wine had 77.7 mg/L methanol and a 68.4% raw juice yield. The fruit wine had 111.4 mg/L methanol and a 90.6 sensory evaluation score. Forty-nine volatile aromas were identified. Ethyl acetate content was the highest, followed by 3-methyl-1-butanol, 2,3-butanediol, and lactate ethyl ester. The persimmon wine had a unique style with transparent color, elegant aroma, and pure taste.

Separation techniques for manufacturing fruit spirits: From traditional distillation to advanced pervaporation process

Separation process is one of the key processes in the production of fruit spirits, including the traditional distillation method and the new pervaporation membrane method. The separation process significantly determines the constituents and proportions of compounds in the fruit spirit, which has a significant impact on the spirit quality and consumer acceptance. Therefore, it is important and complex to reveal the changing rules of chemical substances and the principles behind them during the separation process of fruit spirits. This review summarized the traditional separation methods commonly used in fruit spirits, covering the types, principles, and corresponding equipment of distillation methods, focused on the enrichment or removal of aroma compounds and harmful factors in fruit spirits by distillation methods, and tried to explain the mechanism behind it. It also proposed a new separation technology for the production of fruit spirits, pervaporation membrane technology, summarized its working principle, operation, working parameters, and application in the production of fruit spirits, and outlined the impact of the separation method on the production of fruit spirits based on existing research, focusing on the separation of flavor compounds, sensory qualities, and hazard factors in fruit spirits, along with a preliminary comparison with distillation. Finally, according to the current researches of the separation methods and the development requirement of the separation process of fruit spirits, the prospect of corresponding research is put forward, in order to propose new ideas and development directions for the research in this field.

Application of Cyclocarya paliurus-Kiwifruit Composite Fermented to Enhance Antioxidant Capacity, Flavor, and Sensory Characteristics of Kiwi Wine

A new fermentation method for kiwi wine was explored by developing the well-known medicinal and edible plant Cyclocarya paliurus (C. paliurus) to create more value with undersized kiwifruits. In this study, the changes in bioactive substances during the C. paliurus-kiwi winemaking process were analyzed on the basis of response surface optimization results, and the antioxidant capacity, aromatic compounds, and sensory quality of the C. paliurus-kiwi composite wine with kiwi wine and two commercial kiwi wines were compared. The results showed that DPPH radical, OH- radical, and ABTS+ scavenging rates remained at over 60.0%, 90.0%, and 70.0% in C. paliurus-kiwi wine, respectively. The total flavonoid content (TFC) and total polyphenol content (TPC) of C. paliurus-kiwi wine were significantly higher than those of the other three kiwi wines. C. paliurus-kiwi wine received the highest score and detected 43 volatile compounds. Ethyl hexanoate, which showed stronger fruity and sweet aromas, was one of the main aroma components of C. paliurus-kiwi wine and different from commercial wines. This wine has a good flavor with a natural and quality feeling of C. paliurus-kiwifruit extract, low-cost processing, and great market potential.

Alcoholic Fermentation as a Source of Congeners in Fruit Spirits

Fermentation is a crucial process in the production of alcoholic beverages such as spirits, which produces a number of volatile compounds due to the metabolic activities of yeast. These volatile compounds, together with the volatile components of the raw materials and the volatile compounds produced during the distillation and aging process, play a crucial role in determining the final flavor and aroma of spirits. In this manuscript, we provide a comprehensive overview of yeast fermentation and the volatile compounds produced during alcoholic fermentation. We will establish a link between the microbiome and volatile compounds during alcoholic fermentation and describe the various factors that influence volatile compound production, including yeast strain, temperature, pH, and nutrient availability. We will also discuss the effects of these volatile compounds on the sensory properties of spirits and describe the major aroma compounds in these alcoholic beverages.

Gamma-Aminobutyric Acid-Producing Levilactobacillus brevis Strains as Probiotics in Litchi Juice Fermentation

Levilactobacillus brevis strains can be isolated from traditional Chinese pickles and used as the starter cultures to improve the nutritional profiles of fermented juices. Three L. brevis strains (LBG-29, LBG-24, LBD−14) that produce high levels of gamma-aminobutyric acid (GABA; >300 mg/L) were isolated from traditional Chinese pickles. The strains showed tolerance to low pH and high bile salts and exhibited safety in vitro. Litchi juice was fermented using each strain at 37 °C for 48 h. The litchi juice was determined to be a good substrate for fermentation as the process enhanced its functional profile. Overall, cell vitality increased (above 8.7 log10 CFU/mL), the antioxidant activities of 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ferric ion-reducing antioxidant power (FRAP) were significantly increased, and the antioxidant capacity of the 2,2′-amino-di(3-ethyl-benzothiazoline sulphonic acid-6)ammonium salt (ABTS) was decreased. There was also a significant increase in the GABA and acetic acid content after LBG-29 and LBG-24 fermentation. It was thus determined that the LBG-29 and LBG-24 strains could be used to improve beverage functionality and aid in the development of new products. This is the first report of litchi fermentation using L. brevis as a starter culture. Further research is required to elucidate the functional benefits for the human body and the nutritional and functional properties during its shelf life.

Elucidating the effects of Lactobacillus plantarum fermentation on the aroma profiles of pasteurized litchi juice using multi-scale molecular sensory science

Three Lactobacillus Plantarum (LP), namely LP28, LP226 and LPC2W, were employed to investigate the effect on the aroma profiles of pasteurized litchi juice using E-nose, GC-IMS, GC-MS, and sensory evaluation. The E-nose results showed that pasteurization weakened the flavor profile of litchi juice, while LP fermentation effectively promoted flavor formation. The GC-MS analysis demonstrated that pasteurization significantly reduced the content of alcohols (28.51%), especially geraniol and citronellol, which give litchi juices a fruity and floral aroma. Different LP fermentation enhances the characteristic aroma and produces some new compounds that give it a strong fruity and citrus-like aroma. Moreover, 37 aroma-active compounds (OAV>1) indicated that the linalool (OAV 7504) was the highest, followed by (Z)-rose oxide (OAV 4265), 1-octen-3-ol (OAV 1055) and geraniol (OAV 764), which jointly form the main characteristic flavor. More esters were identified by GC-IMS, indicating the advantage of the combined approach for a better understanding of the impact of pasteurization and fermentation on the litchi juice. The sensory evaluation confirmed that the aroma attributes of fruity, citrus-like, floral, sweet and litchi-like were stronger for the samples fermented by LP28 than those for the other samples. The combination strategy used in this study would facilitate the awareness of litchi juice aroma and broaden our insight into the deep processing of litchi.

Linalool attenuated ischemic injury in PC12 cells through inhibition of caspase-3 and caspase-9 during apoptosis

Numerous studies have indicated the pharmacological properties of linalool, a volatile terpene alcohol found in many flowers and spice plants, including anti-nociceptive, anti-inflammatory, and neuroprotective activities. The aim of this study was to explore the mechanisms of neuroprotection provided by (±) linalool and its enantiomer, (R)-(-) linalool against oxygen, and glucose deprivation/reoxygenation (OGD/R) in PC12 cells. PC12 cells were treated with (±) linalool and (R)-(-) linalool before exposure to OGD/R condition. Cell viability, reactive oxygen species (ROS) production, malondialdehyde (MDA) level, DNA damage, and the levels of proteins related to apoptosis were evaluated using MTT, comet assay, and western blot analysis, respectively. IC50 values for the PC12 cells incubated with (±) linalool and (R)-(-) linalool were 2700 and 2600 μM after 14 h, as well as 5440 and 3040 μM after 18 h, respectively. Survival of the ischemic cells pre-incubated with (±) linalool and (R)-(-) linalool (100 μM of both) increased compared to the cells subjected to the OGD/R alone (p < .001). ROS and MDA formation were also decreased following incubation with (±) linalool and (R)-(-) linalool compared to the OGD/R group (p < .01). In the same way, pre-treatment with (±) linalool and (R)-(-) linalool significantly reduced OGD/R-induced DNA injury compared to that seen in OGD/R group (p < .001). (±) Linalool and (R)-(-) linalool also restored Bax/Bcl-2 ratio and cleaved caspase-3 and caspase-9 (p < .001, p < .01) following ischemic injury. The neuroprotective effect of linalool against ischemic insult might be mediated by alleviation of oxidative stress and apoptosis.

Effect of Starters on Quality Characteristics of Hongsuantang, a Chinese Traditional Sour Soup

Hongsuantang (HST) is a traditional Chinese and famous sour soup. However, the quality of naturally fermented HST is not controllable. We investigated the effects of different lactic acid bacteria starters on HST acid production, color, antioxidant capacity, total phenols, total carotenoids, organic acids, volatile substances, and sensory properties to determine the most suitable strain for HST production. The results showed that among the seven lactic acid bacteria strains used to inoculate fermented HST, Lactiplantibacillus plantarum SQ-4 exhibited the most excellent fermentation characteristics. SQ-4 rapidly reduced the HST’s pH by 0.77. It significantly increased the HST’s color, organic acids, total phenols, carotenoids, lycopene, and free radical scavenging ability. Lactiplantibacillus plantarum SQ-4 was an excellent starter for preparing HST with good acid production capacity, moderate sourness and spiciness, and good sensory and other characteristics. Each starter produces its distinct flavor components. α-Pinene, myrcene, α-copaene, and guaiol were vital aroma compounds in HST fermentation by the starter. This study laid a foundation for selecting HST starters and potential industrial production.

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.