Changes in polyphenol fractions and bacterial composition after in vitrofermentation of apple peel polyphenol by gut microbiota

The changes in polyphenol fractions after in vitro fermentation of apple peel polyphenol (APP) by gut microbiota as well as the effects of APP on the growth, pH value, short-chain fatty acids (SCFAs) production and intestinal flora composition of gut microbiota fermentation were firstly explored in this study. The relative abundance of Lactobacillus in the APP group was 49.55% with an increment of 49.40% compared with the blank group, while that of Bifidobacterium was 13.32%. Moreover, the flora produced 37.093 ± 0.478 mM of SCFAs including acetic acid, propionic acid, butyric acid and valeric acid during the process of fermentation, thus reduced the environmental pH value. In addition, polyphenol fractions in APP were altered by gut microbiota fermentation to some extent, for example, glycosides were hydrolysed to aglycones. These findings suggested APP as a potential prebiotic agent to alleviate the disorder of intestinal flora.     

Changes in the content and antioxidative activity of β-carotene and its metabolite vitamin A during gastrointestinal digestion and absorption and optimisation of HPLC-based detection

The β-Carotene (BC), an important precursor of vitamin A (VA), possesses antioxidant activity but is fat-soluble and has low bioavailability. In previous in-vitro assays evaluating antioxidant and 2,2′-azobis(2-amidinopropane) dihydrochloride (AAPH) free radical scavenging, both BC and VA showed a strong ability to scavenge radicals and protected cells from oxidative stress. Here, we used artificially simulated gastrointestinal digestion and Caco-2 cell absorption models to evaluate the bioavailability of the BC during gastrointestinal digestion and absorption using high-performance liquid chromatography (HPLC) analysis. We observed high absorptive and transfer rates of BC and detected retinol metabolites (Vitamin A). Therefore, BC can be detected in the acidic gastrointestinal environment using HPLC. Optimised method provided better separation of BC and VA in the column, improving the accuracy of the test results.     

全二维气相色谱-飞行时间质谱解析红烧乳鸽的挥发性组分

以癸酸乙酯为内标物,采用全二维气相色谱-飞行时间质谱(GC×GC-TOFMS)对市售红烧乳鸽中的香气成分进行了半定量测定和分析。结果共鉴定出111种化合物,分别为醇类21种、酯类15种、醛类14种、酮类12种、酸类3种、硫类10种、烷烃类8种、烯类8种、吡嗪类8种、呋喃类2种、其它10种。总相对百分含量最大的是硫类物质,其次是醛类和醇类物质。硫类物质中含量比较高的有二烯丙基二硫、烯丙基甲基二硫和1-烯丙基-2-异丙基二硫烷,其含量分别为:20653.10μg/kg、2338.33μg/kg、1006.57μg/kg。醛类里己醛、戊醛和苯甲醛的含量是最高的三种,分别为4836.47μg/kg、469.91μg/kg、442.10μg/kg。醇类化合物中1-辛烯-3-醇、2-乙基-1-己醇、1-戊醇含量较高,分别为1204.27、1134.45、422.35μg/kg。酯类、酮类、吡嗪类等其他物质也构成了红烧乳鸽丰富的肉香味。鉴定出的化合物中含量最高的是二烯丙基二硫,其次是己醛和烯丙基甲基二硫,这三种化合物的OAV值也比较高,对红烧乳鸽的香气贡献比较大,是红烧乳鸽的主要特征香气成分。     

发酵酱油中生物胺的产生及其控制研究进展

酱油由高蛋白大豆为主要原料经微生物发酵而来，其具备生物胺形成的条件。该文从传统酱油发酵过程出发，对生物胺形成机制、影响因素和控制技术进行综述。阐述发酵酱油中生物胺的种类及含量、检测方法及产生物胺的微生物；生物胺的形成主要与发酵体系中的pH、温度和含盐量等影响因素有关，除此之外，原料中大豆的种类和比例也对生物胺的产生具有一定影响；优化传统发酵工艺、筛选安全的发酵菌株、添加合适的生物胺抑制剂等控制技术能有效地减少酱油中生物胺的含量，并且提高酱油的食用安全性。     

红曲改善客家黄酒的品质

本研究采用HPLC法研究不同酒曲配方对酿造客家黄酒时产生的风味物质有机酸的影响,考察红曲对黄酒发酵过程中有机酸风味、总量的影响。发酵30d时三种酒样的有机酸总量差异明显,采用酒药、麦曲酿制的黄酒(酒样Ⅱ)最高,单用红曲(酒样Ⅲ)次之,红曲、酒药、麦曲复配(酒样Ⅰ)最少,分别为33.83 g/L、27.72 g/L和22.67 g/L。其中,Ⅰ、Ⅱ、Ⅲ号酒样中挥发性酸与非挥发性酸的比例分别为1:4、1:1和2:1;酒样中乳酸含量差异较大,Ⅰ号酒样最高,为11.40 g/L,Ⅲ号酒样最少,为6.02 g/L;乙酸含量在三种酒中较接近,约5.5 g/L;Ⅰ、Ⅱ号酒样中琥珀酸含量较接近约为5 g/L;丙酸在Ⅱ、Ⅲ号酒样中含量大,但在Ⅰ号酒样中未检出。另外,Ⅰ号酒样中还测出少量的苹果酸和柠檬酸。结果表明,在客家黄酒酿造时添加适量红曲,有助于维持客家黄酒的酸味平衡,提升味觉层次感。     

Health-promoting effects of dietary polysaccharide extracted from Dendrobium aphyllum on mice colon,including microbiota and immune modulation

The health-promoting effects of a polysaccharide (DAP) purified from Dendrobium aphyllum, on mice colon were investigated. The results indicated that consumption of DAP facilitated the differentiation degree of CD4⁺ T cells to Th₁, Th₁₇ and Treg cells; and depressed the differentiation degree to Th₂ cells, since DAP up-regulated IL-6 expression (from 1.08 ± 0.24 to 3.40 ± 0.36). Besides, oral administration of DAP reduced the gastrointestinal transit time from 255 ± 1.21 to 164 ± 0.46 min, decreased the pH from 6.70 ± 0.27 to 5.54 ± 0.31, improved faecal water-binding capability from 59.4% ± 0.35 to 63.5% ± 0.22. Additionally, the increase in four health-promoting short chain fatty acids were observed, which might result from the enrichment of the relative abundance of health-promoting microbiota genera, including Porphyromonadaceae and Ruminococcaceae. The DAP-induced up-regulation of the genus Erysipelotrichaceae might be related to the homeostasis in both Th₁/Th₂ and Treg/Th₁₇.     

Effects of methyl cellulose-based coating on physiochemical properties and chemical hazards of Chinese fried dough cake during storage

Coating has been used as a practical method to ensure the physiochemical properties and reduce the chemical hazard of fried foods. Methyl cellulose (MC) was used as a coating material to pretreat Chinese fried dough cake (CFDC) before frying. The results showed that the water content, hardness and L* value of the 1% MC coated sample were 31.67%, 848.54 g and 51.62, respectively, at the seventh day at 25 °C. Coating contents 1% MC could reduce the oil content, hardness, and extent of browning and improve the physiochemical properties of CFDC on 7 days of storage. Coating contents 1% MC also reduced the acid value, peroxide value, p-anisidine value, malondialdehyde content, 4-hydroxy-2-(E)-hexenal content, 4-hydroxy-2-(E)-nonenal content, acrylamide content and glycidyl ester content in CFDC on 7 days of storage. Our work contributes to the control of the oil content and chemical hazards for fried food during storage by applying an edible coating.     

强碱催化亚油酸共轭反应动力学研究

在假设反应一步完成,且为不可逆恒容反应的基础上,建立了强碱催化亚油酸共轭反应的幂函数动力学模型,同时,经理论推导得到了机理模型。并通过实验拟合确定了2个模型的参数。结果表明:反应物的初始浓度、催化剂浓度、温度对反应速率都有重要影响,第1步为速率控制步骤。幂函数模型适用于催化剂浓度、温度等条件变化较大,且对预测结果要求不高的过程。而对于那些催化剂浓度、温度等条件恒定不变的过程,机理模型能提供准确的结果预测。     

Changes in flavour characteristics and bacterial diversity during the traditional fermentation of Chinese rice wines from Shaoxing region

As a traditional alcoholic beverage, Chinese rice wine is quite popular for its unique flavor and high nutritional value. In this study, we investigated the changes of flavor compounds in varying stages of fermentation by HS-SPME-GC-MS and HPLC. In addition, 16s rDNA-PCR was utilized to analyze the changes of bacterial communities during fermentation of Chinese rice wine from the Shaoxing region. It was noted that the content of flavor compounds including esters, higher alcohols, amino acids and organic acids was different in varying stages of fermentation. In general, the flavor compounds of Chinese rice wine were mainly produced after pre-fermentation. The results also showed that the bacterial community structures and diversity of Chinese rice wine varied significantly during different fermentation stages, and more than 10 genera of bacteria was detected in Chinese rice wine fermentation broth. Among these specific bacteria identified in the study, Lactobacillus (the predominant genus) and Bacillus might take an active part in flavor development in Chinese rice wine. This implied that these bacteria might play significant contributions on the flavor of Chinese rice wine.     

Profiles and concentrations of heterocyclic aromatic amines formed in beef during various heat treatments depend on the time of ripening and muscle type

Heterocyclic Aromatic Amine (HAA) profiles and concentrations depended on several factors. The largest changes in the HAA profile were observed in meat ripened (chill stored) for 5–10 days. Amines whos concentration varied most prominently included: Phe-P 1, harmane, AαC, IQ, IQx, PhIP, MeAαC, and MeIQx. HAA concentrations were strongly correlated with concentrations of the above compounds. Time of storage significantly affected the HAA profile and concentration. The profile changed dynamically for storage times up to 10 days. For longer times the profile stabilized, only the HAA content increased.A novel, highly precise and accurate HAA analytical method was developed for this study. Results may help to optimize meat processing technology from the point of view of reducing concentration of HAA formed during heat treatment, including the most carcinogenic; IQ, IQx, MeIQx and PhIP amines.