Interdelta PCR指纹图谱法区分鉴定沙城产区酿酒酵母

运用Interdelta PCR 指纹图谱分析技术,对从沙城产区龙眼葡萄相关的葡萄园土壤、酿酒设备和自然发酵过程中分离得到的54 株酿酒酵母(Saccharomyce cerevisiae)进行亚种水平的区分鉴定,研究不同酿酒酵母的分布和变化规律。结果表明：54 株酿酒酵母产生7 种指纹图谱,代表7 种不同的基因类型,基因型Ⅰ～Ⅶ分别占所分离菌株的31.5%、11.1%、7.4%、42.6%、3.7%、1.85% 和1.85%。自然发酵中后期有4 种基因类型的酵母菌,酿酒设备表面3 种,葡萄园土壤中2 种。通过聚类分析软件处理所得数据作出树形图,可直观地看出亚种第Ⅰ和第Ⅳ的亲缘关系最近,而第Ⅶ与其他亚种的亲缘关系最远。     

低温真空干燥焙制荔枝干、龙眼干的研究

研究了荔枝、龙眼真空干燥时间、真空度、温度等的影响,提出适宜的工艺参数,研制了高质量的荔枝干、龙眼干。     

鲜龙眼肉挥发性化学成分的GC/MS分析

利用GC／MS技术对鲜龙眼肉的挥发性化学成分进行了分析，分离出38个组分，鉴定出苯并噻唑，苯并异噻唑，新戊酸6－宁烯脂等27种化合物。     

Identification of (−)-epicatechin as the direct substrate for polyphenol oxidase from longan fruit pericarp

Postharvest browning of longan fruit results in a short life and a reduced commercial value. The experiments were conducted to separate, then purify and finally identify the polyphenol oxidase (PPO) substrates that cause longan fruit to brown. PPO and its substrates were, respectively, extracted from longan fruit pericarp tissues. The substrate for longan PPO was separated and purified using polyamide column chromatography, Sephadex LH-20 column chromatography and silica gel column chromatography, respectively. The substrate was further identified by 0.5% FeCl₃ solution and enzymatic reaction with longan PPO. On the bases of UV, ¹H NMR, ¹³C NMR, and ESI-MS data, the direct substrate for the PPO from pericarp tissues of longan fruit was identified to be (−)-epicatechin. Furthermore, the contents of (−)-epicatechin of pericarp tissues of longan fruit of two major cultivars were determined by high performance liquid chromatography (HPLC). The HPLC analysis exhibited that the contents of (−)-epicatechin of fruit pericarp of ‘Shixia’ and ‘Chuliang’ were 0.26 and 0.56 mg/g on fresh weight (FW) basis at harvest and 0.15 and 0.09 mg/g FW after 3 days of storage. The more rapid decrease in the (−)-epicatechin content of ‘Chuliang’ was due to the oxidization catalyzed by PPO, which was in agreement with the higher browning index.     

Classification of longan fruit bruising using visible spectroscopy

This research showed the potential of using visible spectroscopy for classification of non-bruised and bruised longan fruits. The visible spectra of bruised and non-bruised longan fruits were acquired from 400 to 700 nm with 10 nm resolution by the spectrophotometer. The principal component analysis (PCA), Partial Least Square Discriminant Analysis (PLS-DA) and Soft Independent Modeling of Class Analogy (SIMCA) were used to develop classification models. The Partial Least Square Discriminant Analogy (PLS-DA) showed better classification accuracy than SIMCA with 100% correctness. The result was found to be helpful for the application in the industry for on-line and portable application.     

Intestinal microbiota are involved in the immunomodulatory activities of longan polysaccharide

It is difficult for polysaccharides to be directly absorbed through the intestine, which implies other utilization mechanisms involved in the bioactivity performance of polysaccharide. In this study, the multi‐omics approach was applied to investigate the impacts of longan polysaccharide on mouse intestinal microbiome and the interaction between the polysaccharide‐derived microbiome and host immune system. According to the result, the longan polysaccharide showed a significant improvement in the typical intestinal immunity index of mice. Meanwhile, at the taxonomy level, the intestinal microbiota from the control group and polysaccharide group were highly distinct in organismal structure. At the functional level, a significant decline in the microbial metabolites of pyruvate, butanoate fructose and mannose in the control group was found. Additionally, a significant increase was observed in the succinic acid and the short‐chain fatty acid, including acetic acid, propionic acid and butyric acid, in the polysaccharide group. Furthermore, the multi‐omic based network analysis indicated that the intake of longan polysaccharide resulted in the changes of the intestinal microbiota as well as the gut metabolites, which led to the enhancement of host's immune function under the stress conditions. These results indicated the polysaccharide‐derived changes in intestinal microbiota were involved in the immunomodulatory activities.     

龙眼壳黄色素提取及稳定性研究

对龙眼壳黄色素的提取工艺及其稳定性进行了研究,结果表明:以50%乙醇溶剂作为提取剂,料液配比为1︰20,温度为70℃,提取时间为2 h是最佳提取工艺条件;龙眼壳黄色素在酸性、温度低于70℃、有氧化剂(H2O2)的加入下稳定,但在强碱、光照、高温及还原剂(Na2SO3)和防腐剂(苯甲酸)下不稳定。     

Effect of chitosan/nano-silica coating on the physicochemical characteristics of longan fruit under ambient temperature

A novel chitosan/nano-silica hybrid film was prepared using tetraethoxysilane as precursor by in situ sol–gel process, and characterized by transmission electron microscopy. Its effect on preservation quality of longan fruits (Dimocarpus longan Lour. cv Shijia) was investigated under ambient temperature. The present study revealed that the excellent semi-permeable film of chitosan/nano-silica markedly extended shelf life, reduced browning index, retarded weight loss and inhibited the increase of malondialdehyde amount and polyphenoloxidase activity in fresh longan fruit. In addition, the peroxidase activity of longan fruit coated with hybrid film was lower than that in other treatment fruits. Decreases in the contents of total soluble solids, titratable acidity and ascorbic acid were also significantly inhibited by hybrid films. These data indicated that the chitosan/nano-silica coating might provide an attractive alternative to improve preservation quality of fresh longan fruits during extended storage.     

龙眼酒的发酵工艺研究

以龙眼果汁为主要原料进行酒精发酵,在单因素实验基础上,选取初始pH、初始糖度、SO2添加量为影响因素,选取酒精度（20℃）和总香味物质含量为响应值,应用中心组合Box-Behnken实验设计建立数学模型,进行响应面分析。研究结果表明,在初始糖度28.5%,初始pH3.96,SO2添加量58.8mg/L最优条件下,得到最大酒精度（20℃）和总香味物质含量分别为15.17°和2.322g/L,接近于理论预测值为15.28°和2.329g/L,表明用响应面分析法优化得到的工艺参数准确,对工艺设计和生产具有较强的指导价值。      

龙眼粗多糖提取的影响因素及工艺的研究

本文以龙眼干果肉为原料,对龙眼粗多糖提取的影响因素及工艺技术进行了研究,采用单因素试验和L9(33)正交试验,研究了料液比、温度、时间对多糖提取率的影响,采用水浸提、Sevag法结合酶法脱蛋白、乙醇醇析提取、离心等方法来提取龙眼粗多糖.结果表明:料液比和温度是影响多糖提取率的主要因素;最佳工艺为:料液比1:40、温度80℃、时间4h,在最佳提取工艺时,龙眼的粗多糖提取率可高达21.94%.