Purple sweet potato (PSP) is a rich source of anthocyanins and other bioactive compounds, yet its use as a value-added bakery ingredient remains underdeveloped. PSP syrup was fermented with Lactobacillus bulgaricus, Lactobacillus plantarum and Lactobacillus rhamnosus in this work, the physicochemical changes, anthocyanin remodeling, and bioactivity were characterized, and then the fermented syrups were subsequently incorporated into frozen bread to evaluate their effects on dough properties, bread quality, and storage stability. Results showed that lactobacillus fermentation rapidly acidified PSP syrup (pH 6.8 to 3.5–4.2), reduced sugars and free amino acids, increased organic acids, and promoted strain-dependent exopolysaccharide production. Rather than simply increasing total polyphenol content, lactobacillus fermentation selectively remodeled anthocyanin composition, with total anthocyanins still increased by 11.00–13.00%. The greatest biofunctional enhancement was observed in L. plantarum-fermented syrup, where ABTS+ IC₅₀ decreased from 0.61 to 0.45 mg/mL and α-amylase inhibition increased from 32.4% to 59.2%. A different pattern emerged in bread systems, where L. bulgaricus-fermented syrup gave the best overall baking performance. At 5% addition, this treatment produced the highest loaf specific volume (5.3 mL/g), improved dough handling, and reduced the crumb compactness associated with unfermented PSP syrup. This advantage extended into frozen storage, where the bread retained higher moisture, lower hardness, lower retrogradation enthalpy, and better-preserved crumb microstructure over 40 d. The strain delivering the strongest biofunctional enhancement was therefore not the one giving the best breadmaking performance. L. bulgaricus fermentation emerged as the most effective route for developing PSP syrup into a functional ingredient for frozen bakery products.

Extended wine storage often leads to a reduction in volatile compounds, diminishing the fruity aroma. Yeast mannoproteins (MPs) have been identified as a mitigating factor against this effect, although the mechanisms involved remain poorly understood. This study examines the impact of MPs from Pichia strains, noting differences in chemical composition and structure, on the volatility of wine fruity esters. Gas chromatography, high-performance liquid chromatography, and Fourier transform infrared spectroscopy were used to analyze MPs from Saccharomyces cerevisiae SC-19 (MP-SC), Pichia fermentans Z9Y-3 (MP-PF), and Pichia kluyveri MP-PK. The influence of MPs on wine ester volatility was further explored through headspace solid-phase microextraction and gas chromatographic-mass spectrometry, alongside thermodynamic assessments. The findings revealed that mannose predominates in the monosaccharide composition of MPs, with MP-SC presenting the highest mannose levels. MP-PF and MP-PK, however, exhibited higher protein concentrations and significantly more hydrophilic amino acids, contributing to a 3-6-fold reduction in ester volatility compared with MP-SC, likely due to enhanced van der Waals forces and hydrogen bonding.

This study extensively characterized yeast polysaccharides (YPs) from Pichia fermentans (PF) and Pichia kluyveri (PK), with a specific focus on their structural attributes and their interaction with wine fruity esters in a model wine system. By finely tuning enzymatic reactions based on temperature, pH, and enzyme dosage, an optimal YP yield of 77.37% was achieved, with a specific mass ratio of cellulase, pectinase, and protease set at 3:5:2. There were four YP fractions (YPPF-W, YPPF-N, YPPK-W, and YPPK-N) isolated from the two yeasts. YPPF-N and YPPK-N were identified as glucans based on monosaccharide analysis and Fourier-transform infrared spectroscopy analysis. "Specific degradation-methylation-nuclear magnetic" elucidated YPPF-W's backbone structure as 1,3-linked α-l-Man and 1,6-linked α-d-Glc residues, while YPPK-W displayed a backbone structure of 1,3-linked α-Man residues, indicative of a mannoprotein nature. Isothermal titration calorimetry revealed spontaneous interactions between YPPK-W/YPPF-W and fruity esters across temperatures (25-45 °C), with the strongest interaction observed at 30 °C. However, distinct esters exhibited varying interactions with YPPK-W and YPPF-W, attributed to differences in molecular weights and hydrophobic characteristics. While shedding light on these intricate interactions, further experimental data is essential for a comprehensive understanding of yeast polysaccharides' or mannoproteins' impact on fruity esters. This research significantly contributes to advancing our knowledge of yeast polysaccharides' role in shaping the nuanced sensory attributes of wine.

【Objective】The aim of this study was to investigate the apparent matrix effect of yeast polysaccharide (YP) from S. cerevisiae on the hydrolysis of fruity ester, and to explore the potential application of yeast polysaccharide in stabilizing wine aroma profile and expand shelf life of product.【Method】YP was extracted from S. cerevisiae by hot water extraction and alkali methods, and the basic components of YP were analyzed by ultraviolet spectrophotometer (UV), gas chromatography (GC) and high- performance liquid chromatography (HPLC). The model wine containing the conventional concentration of fruity esters was prepared and treated with YP, and the concentration of YP was set in the range of 0-2.0 g·L-1. The effect of YP on the volatility of fruity esters was analyzed by the static headspace method. Next, the model wines with different treatments were stored at 4℃ for 6 months, and the content of fruity esters in model wine was regularly monitored. Finally, sensory analysis was used to evaluate the aroma notes of model wine stored 6-months.【Result】Instrumental analysis showed that the total polysaccharide content of YP was (72.61±3.29)%, and the protein contents accounts for (11.20±0.02)%. The main monosaccharide composition of YP was mannose and glucose, and their molar ratio was 1.790:1. The high molecular weight components of YP are 18, 163 and 21 819 kD, and the low molecular weight components are 576 Da. Static headspace analysis indicated that YP treatment could reduce the volatility of acetate esters in model wine, especially 0.8 g∙L-1. While YP treatment could increase the volatility of ethyl esters. Data of regular sampling found that the hydrolysis rate of ethyl esters was significantly higher than that of acetate esters during 6 months storage. Compared with the control, 0.4-0.8 g∙L-1 YP slowed down the hydrolysis of acetate esters and ethyl esters by 10%-40% and 3.7%-26.7%, respectively. Sensory analysis showed that model wine added with YP showed higher MF% of temperate sour and sweet fruity, and preserved fruit and floral aroma notes of wine samples compared with the control.【Conclusion】From the study of model wine system, it was concluded that adding 0.4-0.8 g∙L-1 YP during wine storage slowed down the hydrolysis of fruity esters, stabilized wine fruity aroma profile, and showed potential application value for prolonging wine shelf life.

Carotenoids and their cleavage products (norisoprenoids) have excellent functional properties with diverse applications in foods, medicaments, cosmetics, etc. Carotenoids can be oxidatively cleaved through nonspecific reactions or by carotenoid cleavage oxygenases (CCOs), the product of which could further modify food flavor. This review provides comprehensive information on both carotenoid synthesis and cleavage processes with emphasis on enzyme characterization and biosynthetic pathway optimization. The use of interdisciplinary approaches of bioengineering and computer-aided experimental technology for key enzyme modification and systematic pathway design is beneficial to monitor metabolic pathways and assess pathway bottlenecks, which could efficiently lead to accumulation of carotenoids in microorganisms. The identification of CCOs spatial structures isolated from different species has made a significant contribution to the current state of knowledge. Current trends in carotenoid-related flavor modification are also discussed. In particular, we propose the carotenoid-synthesizing yeast Rhodotorula spp. for the production of food bioactive compounds. Understanding the behavior underlying the formation of norisoprenoids from carotenoids using interdisciplinary approaches may point toward other areas of investigation that could lead to better exploiting the potential use of autochthonous yeast in flavor enhancement.

Synthetic grape juice was fermented with Pichia fermentans Z9Y-3 and Pichia kluyveri PK-19, along with S. cerevisiae of different antagonistic abilities, to investigate their impact on aroma stability. During 12-month storage, wine was stored for 2 months with lees and for 10 months without lees. Levels of fruity esters and polysaccharides were monitored using gas chromatography (GC)-mass spectrometry and GC-flame ionization detector, respectively, and wine aroma attributes were quantified by trained panelists. Results showed that co-fermentation elevated fruity ester content during fermentation and retarded fruity ester hydrolysis during storage, which increased the intensity of fruity traits, especially in the highly antagonistic group. Spent yeast from co-fermentation released more polysaccharides, which was predominantly composed of 50 % glucose, 30 % galacturonic acid, and 20 % mannose. During storage, the polysaccharide content decreased until it reached equilibrium at 6 months. Pearson analysis revealed that polysaccharide content correlated positively with fruity ester content and profile.

研究优选胶红酵母与酿酒酵母不同混合发酵方案对季风性气候区干红葡萄酒的香气质量、多酚及颜色的影响,优化增香酿造技术方案.实验以陕西合阳梅鹿辄葡萄为试材,设计2种菌株不同比例同时接种和顺序接种策略酿造干红葡萄酒.酿造完成后,对葡萄酒样品的香气成分进行顶空固相微萃取结合气相色谱-质谱联用法定性定量分析,香气特征通过感官量化品评法描述,采用光谱法量化分析酒样的13个颜色与多酚相关指标.结果表明,高比例同时接种显著增加了品种香气成分的含量,尤其是C6化合物和硫醇,而顺序接种更利于释放萜烯类和β-大马酮香气成分;发酵香气中高级醇、C6～C12脂肪酸及其酯类的含量随优选酵母接种比例的升高而增加,顺序接种在提高乙酸酯和苯乙基类化合物含量上有明显优势.较高比例(4∶1)同时接种和顺序接种处理明显增加了酒样中总花色苷、黄酮醇、酒石酸酯的含量,显著提高了辅色花色苷比例.感官分析表明,高比例同时接种处理显著增强供试酒样果香和花香的同时,也增强了生青和动物味,而顺序接种处理适度增强果香和花香的同时却能降低不良气味.综上,优选胶红酵母与酿酒酵母不同接种处理的混合发酵干红葡萄酒具有差异明显的色泽风味质量特征,顺序接种适度增香的同时没有生成不良气味的风险,并且有利于改善色泽质量.

为解析西北地区干红葡萄酒的质量相关理化指标的溯源判别功能,以新疆、宁夏和内蒙古乌海产区共27款干红葡萄酒为材料,基于分光光度法分析检测与色泽、味感和香气质量相关的花色苷、单宁、酒石酸酯等指标,且进行香气特征的感官量化分析.统计分析结果表明,CIELab色空间和花色苷等色泽指标中前两个主成分占总体方差71.08％,判别干红葡萄酒年份的效果明显,但对不同葡萄品种和产地的判别效果不佳.单宁、多酚等味感相关理化指标的前两个主成分占总体方差的65.93％,对干红葡萄酒产地和年份的判别效果较好,但不能有效判别品种.酒石酸酯、总酸和香气特征等指标中前两个主成分占总体方差的83.10％,表现出较好的产地和品种的判别效果,而对年份的判别效果一般.色泽、味感和香气相关的总计20个理化指标数据在主成分分析中表现出更好的产地、品种和年份的判别效果,前两个主成分占总体方差的67.32％.聚类分析能将葡萄酒产地准确地分为3类,准确率超过90％.基于分光光度法开发的色泽-风味理化指标的大数据具有判别我国西北地区干红葡萄酒产地、品种和年份的潜在应用前景.

Pichia fermentans Z9Y-3 and its intracellular enzymes were inoculated along with S. cerevisiae in synthetic grape must to modulate fruity ester production. The levels of ester-related enzymes, ester precursors, and fruity esters were monitored every 24 h during fermentation. Results showed that the levels of ethyl acetate, acetate higher alcohol esters (AHEs), short chain fatty acid ethyl esters (SFEs), and medium chain fatty acid ethyl esters (MFEs) were significantly enhanced in mixed fermentation. Pearson correlation analysis further revealed that higher alcohols and fatty acids played a more important role in fruity ester production than enzymes; Particularly, the correlation coefficient between fatty acids and MFEs was 0.940. In addition, supplementation of medium chain fatty acids (7.2 mg/L) at the metaphase of single S. cerevisiae fermentation improved ethyl acetate, AHE, SFE, and MFE production by 42.56%, 21.00%, 61.33%, and 90.04%, respectively, although the high level of ethyl acetate might result in off-flavors.

Mixed fermentation of Pichia fermentans and Saccharomyces cerevisiae was designed to circumvent the problem of weak aroma in Chinese spine grape wines. Spine grape, “Xiang Pearl”, was used for wine production by red wine-making processes. Physicochemical indices were measured using titratable and spectroscopic methodologies. Volatiles were quantified by SPME-GC-MS, and aroma attributes were analyzed by trained panelists. Results showed mixed fermentation benefited color properties by improving total anthocyanin, polymeric anthocyanin, and total tannin contents. The content of varietal compounds, except those of thiols, were reduced, whereas fermentative compounds contents, especially those of higher alcohols, esters, and phenylethyls, were increased by mixed fermentation. Sensory analysis showed mixed fermentation enhanced fruity and floral traits in wine; this was confirmed by mathematical regression showing elevated levels of fermentative volatiles dominated the contribution to pleasant aroma, whereas reduced content of varietal compounds, with the exception of thiols, correlated negatively with favorable characteristics.

The dynamic pattern of volatiles during Pinot Noir winemaking in monsoon climate with yeast extracellular extract (EE) treatment was analyzed. EE from selected Pichia fermentans and Rhodotorula mucilaginosa strains, and almond β-glucosidase were added after 12-h alcohol fermentation, and the volatiles were determined every 24 h by GC-MS. After 6-month storage, wine aroma was evaluated instrumentally as well as by well-trained panelists. Results showed that enzyme treatments improved the contents of both varietal and fermentative volatiles. The levels of C6 compounds, terpenes, and higher alcohols increased constantly during alcohol fermentation, whereas acetates, short and medium chain fatty acid ethyl esters, phenylethyls, and fatty acids increased first, followed by gradual decrease. EE treatment retarded the decrease of fruity ester content in wine. Mathematical regression between wine aroma and volatiles showed that the relatively higher contents of acetates, ethyl esters, and C13-norisoprenoids in 6-month EE-treated wine were responsible for the improvement in floral aroma intensity.

The chemical profiles and aroma contribution of terpene compounds in Meili grapes and wine were analyzed. Bound terpene compounds were extracted using methanol, purified using Amberlite XAD-2 resin, concentrated in methanol/ethyl acetate, and enzymatically hydrolyzed to release aglycones. Free terpene compounds were identified using solid-phase microextraction (SPME) coupled with gas chromatography-mass spectrometry (GC-MS). Wine aroma characteristics were quantified by a trained sensory panel. Seventeen terpene glycosides were quantified in grapes and wines as pentosyl-glucopyranoside, the content of which ranged from 804 to 836 mu g/kg, and from 155 to 192 mu g/L, respectively. Eight free terpenes were present in wines with their content ranging from 40.1 to 59.7 mu g/L. Linalool was abundant both in bound and free terpenes, and mathematical regression revealed that terpenes, especially linalool (contribution efficient > 0.4), contributed heavily to Meili wine aroma. Finally, a molecular rearrangement scheme based on linalool was proposed in Meili grape and wine.