保持名优绿茶"三绿"的技术措施

名优绿茶要求干色翠绿或嫩绿,汤色碧绿,叶底嫩绿.顾客判断名优绿茶质量好坏的主要条件是翠绿、细嫩,翠绿是卖相好的重要标志,名优绿茶的竞争,首先是色泽竞争.但往往因炒制或贮藏不当,色泽深暗或黄暗,严重影响名优绿茶的品质和经济效益.因此,保持"三绿"是提高名优绿茶品质,促进名优绿茶生产的关键.根据笔者实践,     

名优绿茶常温保鲜技术初步研究

茶叶是季节性生产、全年消费的产品,特别是名优绿茶集中在春季生产,一般具有较长的贮藏期.若贮运保管不当,极易发生褐变陈化.研究证明成品茶由于受到水分、氧气、温度、光照等外界因素的综合影响,使其内含物质发生一系列化学变化.茶叶水分含量与茶叶贮藏品质最为密切.茶叶对光的反应也很敏感,温度的高低直接影响到化学反应的速度,温度高,茶叶陈化速度快.     

茶多酚浓度对绿茶饮料稳定性的影响研究

比较了不同茶多酚浓度下绿茶饮料灭菌、贮藏过程中的感官与理化品质变化。研究结果表明,不同茶多酚浓度绿茶饮料稳定性差异较大,灭菌、贮藏过程中,绿茶饮料外观颜色变深、变红,茶多酚、儿茶素含量显著下降,黄酮化合物、没食子酸含量显著上升,咖啡碱、氨基酸含量略有下降,感官风味品质明显下降,熟汤味明显;随着茶多酚浓度升高,绿茶饮料的感官理化品质变化趋势加剧,高温贮藏（37℃）变化程度明显高于低温贮藏（4℃）。当茶多酚质量浓度为400~600mg/L时,绿茶饮料稳定性相对较好。     

名优炒青绿茶挥发性成分研究进展

香气是评价茶叶品质的关键指标之一,众多香气化合物通过复杂的相互作用决定了茶叶的香气品质.名优炒青绿茶一般具有滋味好、香气高的特点,是我国优质绿茶的典型代表.近年来,关于名优炒青绿茶香气成分的研究逐渐增多,但针对不同名优炒青绿茶挥发性成分的组成特点等尚缺乏系统阐述.综述了近二十年来名优炒青绿茶挥发性成分的研究进展,汇总已...     

名优绿茶的包装保鲜技术

科学试验和生产实践证明,茶叶具有很强的氧化、吸湿特性,在贮运过程中由于水分、氧气、温度、光照等因素的影响,品质极易陈化劣变,失去原有的新鲜风味。特别是名优绿茶,品质要求高,原料细嫩,各种水溶性物质含量较高,且又集中在雨水较多、空气湿度较大的春季生产,如果包装贮运不当,更易吸湿失风,甚至劣变。因此,名优绿茶包装保鲜的要求比大宗茶更高,意义亦更大。笔者就其包装保鲜技术作些介绍,仅供参考。一、几种常见包装材料的特性 1.聚乙烯(PE)     

试论曼拉德反应在名优绿茶加工中的合理应用

本文就如何利用曼拉德反应提高手工名优绿茶与机制名优绿气的香气，提高我省名优绿茶品质作出扼要阐述，这对当前我省名优绿茶生产具有一定的参考价值。     

名优绿茶贮藏保鲜技术研究进展

名优绿茶集保健性和艺术性于一体 ,是中国的特色产品 ,近几年来 ,出口量和国内消费量呈现出不断增加的发展趋势 ,其产值占茶叶总产值的 40 %～ 50 %。据统计 ,发达国家人均茶叶年消费量在 2 kg以上 ,而我国的人均茶叶年消费量不到 0 .3 kg,并且名优绿茶消费占到 3 0 %～ 40 %。名优绿茶是随着人们生活水平的提高而新近发展起来的一类高附加值的茶叶产品 ,是各茶叶企业创品牌、提高经济效益的主要产品之一。然而名优绿茶的生产和加工集中在春季 ,使得大部分产品需经一个受温度、光照、氧气、水分等因素影响的货架期 ,造成品质劣变。结果去年…     

浅议名优绿茶加工的标准化问题

《中国茶叶》2011年第5期《浅谈名优绿茶加工的标准化问题》（张正竹、夏涛、方世辉、宛晓春）,笔者阅后深感启发,名优绿茶加工的标准化,不仅仅是一项加工工艺的标准化,更重要的是提高名优绿茶的品质,关系名优绿茶产业的经济效益及产业稳定大发展问题。     

绿茶贮藏中质变原因的分析

本文根据实验结果,对炒青绿茶在不同贮藏条件下所发生的品质变化,进行了分析讨论,证明绿茶贮藏中的变质主要是品质成分的氧化作用,而水分和温度则是品质变化的氧化条件,仅起加速或延缓作用。研究还表明,在诸品质成分中,维生素C与感官品质的变化关系最为密切,因而,维生素C保留量可作为绿茶品质变化的重要化学指标。不过,维生素C保留量的下降率只有在10—15％以上时,感官品质的变化才能显示出来。     

谈名优绿茶的审评

随着人民生活的不断提高,名优绿茶的产销发展很快,产值和产量每年以翻番的速度递增,各地茶叶主管部门也经常举行各种名茶鉴定会和名茶评比会,因此,名优绿茶的审评显得越来越重要。下面,笔者拟就名优绿茶的审评提些看法,供同事们参考。 1.名优绿茶的给分名优绿茶的审评应先定品质档次再给分。给某一品质因子打分时,应先看这个品质因子属甲级、乙级还是丙级。如没有发现疵次,定为甲级,给94分中准分,再根据品质高低加或减1～4分;如发现造型、色泽欠佳,香味稍钝,汤色叶底欠润,应看其程度,定为乙级或丙级。乙级给84分,丙级74分,再     

白砂糖干燥与冷却机理及影响

砂糖的含水量、装包温度和仓储条件对其贮存保质具有重要影响。本文从白砂糖的含水分特性、干燥机理和生产过程环节等对白砂糖干燥与冷却的影响进行深入分析。由于结晶过程的包裹现象,砂糖含水分可分为表面和内部水分,白砂糖干燥过程只能去除前者。生产过程中煮糖、分蜜操作对内部水分含量有影响。贮存过程的内部水分的扩散是砂糖降质的根本原因,而装包温度和贮存条件是影响内部水分扩散的外在条件。     

Accelerated ageing of wheat grains: Part II-influence on thermal characteristics of wheat starch and FTIR spectroscopy of gluten

Wheat quality characteristics are influenced by different factors such as moisture content, storage time and temperature. In this study accelerated ageing of wheat grains was carried out by increasing moisture content (16, 18 and 20%) and keeping the samples in different temperatures (30, 40 and 50 °C) for different periods (2, 5 and 8 days). After milling, the thermal properties of starch and structure of gluten were investigated using Differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR); respectively. The experimental set up was designed using response surface methodology and the three distinct factors were combined by central composite design. Results showed that increasing moisture content caused a decrease in onset, peak and end set temperatures of gelatinization while increasing storage time and temperature increased these parameters. By progressing storage time the band intensity of thiol groups decreased while that of disulfide groups of gluten increased indicating an improvement in gluten quality. Increasing moisture content from 16 to 20% and higher storage temperature (50 °C) decreased intensity of disulfide bands.     

局部发热过程中进口大豆品质劣变规律研究

进口大豆在海上运输及储藏的过程中,容易因环境温湿度变化使得大豆局部含水量升高,从而引起局部发热,导致品质劣变。本文采用120 kg含水量16%和含杂量50%大豆局部包埋的方式,室温下常规储藏,模拟探究其局部发热条件及品质变化。结果表明：水分含量高的大豆更容易发热,对品质变化影响较大,包埋水分含量为20%的大豆在储藏21 d后,粗脂肪含量下降了0.95个百分点,酸价上升了4.36 mg·g^-1,总不饱和脂肪酸含量下降了0.92%,蛋白持水性下降了1.09 g·g^-1,持油性上升了0.78 g·g^-1,乳化活性指数和乳化稳定性分别增加了3.38 m²·g^-1和2.59%。而包埋120 kg含水量16%的大豆和包埋120 kg含杂量50%的大豆发热慢,发热温度较低,大豆粗脂肪、蛋白品质指标变化趋势相似,但是变化幅度较小。     

Accelerated ageingof wheat grains: Part I- Influence on rheological properties of wheat flour

Natural ageing is defined as handling and storage of freshly harvested grain for several years under storage condition to achieve suitable flour quality after milling. Accelerated ageing of wheat which is obtained using higher temperature during a specific storage time under controlled relative humidity may improve the quality of wheat flour. The present study addresses the effect of accelerated ageing on the rheological properties of wheat flour produced by freshly harvested wheat. The process of accelerated aging was performed by three different factors including rise in wheat moisture content (16, 18 and 20% w/w), control of storage temperature (30, 40 and 50°C) and control of the storage time (2, 5 and 8 days) using a central composite design. After the grain milling, rheological properties of wheat flour of different treatments were studied. Results indicated that promoting the storage time to 8 days and temperature up to 40°C could improve rheological properties such as dough stability, dough development time and farinograph quality number. This phenomenon may be due to oxidation and rearrangement of disulfide bonds resulting in increasing strength and improving flour quality. Increasing moisture content and storing in higher temperatures resulted in weakening rheological properties.     

稻谷储藏特性与技术要点

水稻是我国的主要粮食作物,如果在储藏期间发生霉变、发芽,会导致稻谷品质劣变或者丧失生命力,造成重大损失。影响稻谷储藏的因素有温度、稻谷含水量、储藏的方式等。本文介绍了稻谷在储藏中易发生陈化变质、变黄、生虫霉变等问题的原因,并针对这些问题提出了一些解决办法,同时阐述了稻谷储藏的技术要点,以期为稻谷的储藏提供合理的方法。     

Effect of thermal packaging temperature on Chinese steamed bread quality during room temperature storage

In order to investigate the influence of different packaging temperature on thermal-vacuum packaged Chinese steamed bread (CSB) quality under room temperature storage, the packaging temperatures of 50 °C, 70 °C and 90 °C were set respectively to study the effect on the packaging vacuum degree (VD) and starch retrogradation properties. The VD and moisture content of thermal-vacuum packaged CSB significantly increased with the increase of the packaging temperature from 50 °C to 90 °C, while the hardness of CSB decreased, and there was no significant difference in moisture migration during room temperature storage. The results of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and small angle X-ray scattering (SAXS) indicated that CSB packaged at different temperatures formed B-type crystals, leading to an enhanced the ordered and dense state of starch structure, and the semi-crystalline growth ring structure disappeared during storage. The influence of different packaging temperatures on VD of CSB could effectively hinder the formation of ordered and dense state of CSB starch, consequently delaying the crystallization of amylopectin and inhibiting the progress of staling. The result of this study is of great significance for improving the quality of starchy foods and guiding the industrial development of Chinese steamed bread.     

贮藏期对花生种质籽粒成分影响研究

常温干燥贮藏是植物种质资源保存的重要方式之一。研究表明,在常温干燥条件下,经过11年的保存,花生不同类型籽粒成分发生程度不同的变化,其中总糖含量随贮藏时间而增加,蛋白质和粗脂肪含量整体呈降低趋势,脂肪酸中除油酸含量随贮藏时间延长而升高外,棕榈酸与亚油酸含量均降低。VE除多粒型与中间型外,其余类型花生种质均随贮藏时间延长而降低。同时,花生种质的外观品质性状不随贮藏时间延长而发生显著变化。     

Influence of airflow rate on chip potato storage management

Through-the-pile ventilation is a common practice for potatoes stored in bulk. Research was initiated in 1986 to study the influence of ventilation rate on the temperature, moisture and market quality of bulk stored chip potatoes. Ventilation rates up to 168 m³ hr^?1 t^?1 were used. All ventilation rates achieved the required temperature and humidity control. Fan operation time (hours) was not reduced proportional to the increased ventilation rate. The higher ariflow resulted in proportionally less time being spent to correct pile temperature differentials. The Atlantic variety potatoes were utilized for potato chip production in all three seasons studied. Market quality after storage, measured by tuber sugar content, chip color and chip defects, was similar for all ventilation rates. For the last two storage seasons studies, the potatoes were marketed from the storage research bins at high levels of quality following 115 to 142 days of storage. Average weight losses for the airflow rates used were not statistically different. However, potato weight loss uniformity was proportional to increased ventilation rates.     

水稻种子在不同气候区室温贮藏的适宜含水量及存活特性

 将不同含水量水平的两个水稻品种幸实(粳稻)和桂朝2号(籼稻)分别贮藏在三亚、南昌、北京、西宁、乌鲁木齐和哈尔滨等6个不同气候类型地区。通过11年的逐年生活力测定,研究了水稻种子室温贮藏的适宜含水量及其存活特性。结果表明,水稻种子经适当干燥后其生活力和活力没有显著下降。但当种子含水量在30％以下时种子的生活力和活力受到影响。获得了水稻种子在三亚、南昌室温贮藏时（贮藏温度不是恒定的）的适宜含水量,且适宜含水量50％~65％具有地域的广适性。相对于其他含水量,适宜含水量种子在贮藏过程中,其生活力快速下降阶段推迟,且适宜含水量上限和极差与贮藏地点年均温和≥0℃积温呈显著或极显著负相关,且适宜含水量下限与之呈显著或极显著正相关。种子在年均温度相同的西宁和乌鲁木齐的贮藏效果不同,≥0℃积温和气候温差波动的差值可能是其主要影响因素。     

Modeling of desorption of Alfalfa (Medicago sativa) stems and leaves

The equilibrium moisture content of agricultural products is necessary to optimize drying process and helps to keep the quality of the product during the period of storage. The main aim of this research was to find the best model which could define well, the exchange of moisture between alfalfa (Medicago sativa) and the surrounding air. The desorption isotherms of alfalfa (stem and leaf) were determined separately by using the saturated salt solutions method at three temperatures (25, 50 and 70 °C) within a range of 5-90% relative humidity. Experimental curves of desorption isotherms were fitted to modified equations of Henderson, Halsey, Oswin and Chung-Pfost as well as the GAB model and then evaluated visually by using residual plots and also by some statistical error parameters. The modified Halsey model was found to be the most suitable for describing the relationship between equilibrium moisture content, relative humidity and temperature.