红葡萄酒中单宁分析方法与感官收敛性的关系

研究目的是使用多种分析方法评价红葡萄酒收敛性与单宁浓度之间的相互关系。选择40个红葡萄酒样品,使用不同的分析方法测定单宁含量,包括在280nm处的吸光度、4-二甲基氨基肉桂醛、蛋白质沉淀、间苯三酚反应以及凝胶渗透色谱法,结果显示：红葡萄酒中单宁测定方法与感官收敛性之间存在明显差异。感官收敛性与蛋白质沉淀方法的相关性最大（r^2=0.82）,其次为间苯三酚法（r^2=0.73）和凝胶渗透色谱法（r^2=0.74）,表明蛋白质沉淀法是感官收敛性最有用的分析方法。     

Temperature Affects Astringency Removal and Recurrence in Persimmon

Astringency was removed from‘Triumph’persimmons by immersion in water at 40°C for 5 hr or 60°C, for 1 hr. Similar treatments at 20° and 80°C, had no effect on astringency reduction. Subsequent application of 80% CO₂ for 48 hr was effective for 20°C-treated fruit but not for 80° C-treated fruit, which became nonastringent only after exposure to acetaldehyde. Extending the 60°C treatment beyond 2 hr resulted in recurrence of astringency, which was not reduced by subsequent CO₂ treatment. Astringency also recurred in CO₂-treated non-astringent fruit, when exposed to high temperatures. The disappearance and recurrence of astringency correlated with amount of methanol-soluble tannins.     

Phenolic composition of European cranberrybush (Viburnum opulus L.) berries and astringency removal of its commercial juice

Phenolic composition of the European cranberrybush (ECB) (Viburnum opulus L.) juice was determined using high‐performance liquid chromatography. The juice contained 2037 mg kg^?1 chlorogenic acid, which was 54% of total phenolics, and several other phenolics such as (+)‐catechin, (?)‐epicatechin, cyanidin‐3‐glucoside, cyanidin‐3‐rutinoside and six different glucosides of quercetin. Because of its strong astringent taste, the juices were treated with various doses of two different types of activated carbons (Granucol Bi and Granucol Ge) in order to remove phenolic compounds. Results revealed that both types of activated carbons were equally effective on astringency removal (P < 0.01). A 20–30% reduction in total phenolics was achieved by application of 2.0–3.0 g L^?1 activated carbon which also removed unpleasant taste and odour.     

果酒中多酚氧化酶及其性质的研究

对山楂酒中含有的六种分子量不同的多酚在多酚氧化酶作用下,测定氧化前后其涩度的变化.发现多酚物质的氧化作用能够加重果酒的苦涩味.并对山楂中的多酚氧化酶进行提取,测定其基本特性,确定了底物、温度、pH值对其活性的影响,并进一步测定其酶动力学曲线,发现多酚氧化酶催化的最适温度是25℃,其最适pH是6.5,其作用的最适底物是儿茶酚,其米氏常数是1.077×10-2M.     

Linking chemical reactivity and protein precipitation to structural characteristics of foliar tannins

Tannins influence ecosystem function by affecting decomposition rates, nutrient cycling, and herbivory. To determine the role of tannins in ecological processes, it is important to quantify their abundance and understand how structural properties affect reactivity. In this study, purified tannins from the foliage of nine species growing in the pygmy forest of the northern California coast were examined for chemical reactivity, protein precipitation capacity (PPC), and structural characteristics (¹³C NMR). Reactivity of purified tannins varied among species 1.5-fold for the Folin total phenol assay, and 7-fold and 3-fold, respectively, for the acid butanol and vanillin condensed tannin assays. There was about a 5-fold difference in PPC. Variation in chemical reactivity and PPC can be largely explained by differences in structural characteristics of the tannins determined by ¹³C NMR. In particular, the condensed versus hydrolyzable tannin content, as well as the hydroxylation pattern of the B-ring and stereochemistry at the C-2–C-3 position appear to influence reactivity. Due to the large differences in chemical reactivity among species, it is necessary to use a well-characterized purified tannin from the species of interest to convert assay values to concentrations. Our results suggest that structural characteristics of tannins play an important role in regulating their reactivity in ecological processes.     

矿石浸泡水对绿茶茶汤风味的影响

泡茶用水的离子种类及含量是影响绿茶茶汤风味品质的关键因素。为了开发泡茶专用水及其相应设备,以不同种类矿石(石英石、麦饭石、富锶滤料、弱碱滤料、高总溶解固体(TDS)滤料)为研究对象,探究矿石浸泡水对绿茶茶汤风味品质的影响。矿石浸泡水研究结果显示,石水比、浸泡时间、浸泡温度对不同种类矿石浸出规律的影响有显著差异,高TDS滤料浸泡水所含离子含量最高,石英石的溶出稳定性最佳,矿石浸泡水的最佳处理为室温下石水比1∶50,浸泡时间5 min。矿石浸泡水水质分析结果显示,5种矿石浸泡水煮沸后电导率均增大而变化幅度小于10μs/cm,pH值之间存在显著差异(P<0.05),表明矿石浸泡水电导率受温度影响小,而pH受温度影响大。矿石浸泡水所含阳离子(K⁺、Na⁺、Mg²⁺、Al³⁺、Ca²⁺)中Ca²⁺是引起矿石浸泡水电导率增大的主要阳离子,随着电导率的增加绿茶茶汤涩味显著增强,其中Ca²⁺含量与茶汤涩味强度呈极显著相关性(P<0.01)...     

遗传算法在水库(群)优化调度研究中的应用综述

介绍了遗传算法在水库(群)优化调度中的应用背景及算法的收敛性,讨论了水库(群)优化调度中遗传算法的基本应用步骤以及存在的问题,给出了算法的各种改进方法,并对遗传算法的应用前景进行了展望.     

基于遗传算法的车灯线光源优化设计

采用遗传算法建立了遗传算法曲面反射点搜索模型,将其用于特殊反射点的寻找。经过多次试验确定遗传算法中所涉及参数的值,最终找出抛物面上的特殊反射点,建立线光源发光功率(P)和线光源长度(L)的函数关系,求出最低功率时线光源的长度。实验表明,该模型算法准确,速度快,收敛性好,适应性强,适用于非规则的,任意曲面点的搜索。     

一种改进麻雀搜索算法的收敛性分析及应用

针对麻雀搜索算法易陷入局部最优、收敛速度慢等问题,提出一种改进的麻雀搜索算法.首先,采用佳点集策略对麻雀种群初始化,增加种群多样性,提高算法的收敛速度和精度;其次,采用黄金正弦策略优化发现者位置更新过程,进一步平衡算法的全局探索与局部开发能力;最后,采用Levy飞行策略优化跟随者位置更新过程,扩大其搜索空间,改善易陷入局部最优的问题.通过建立马尔科夫链模型从理论角度证明改进算法的收敛性,并选取5个标准测试函数与其他经典群智能优化算法从仿真实验角度验证改进算法的有效性.利用改进算法对变分模态分解参数和回声状态网络参数进行优化,搭建ISSA-VMD-ESN模型并应用到短期电价预测中,通过仿真实验进一步验证了改进算法的优越性.