稻米中脂肪酸值测定方法的研究

建立了稻米中脂肪酸值的滴定新方法。样品以石油醚提取后，过滤，加入50％乙醇溶液，以酚酞为指示剂，用KOH标准溶液滴定至下层溶液呈微红色。该方法回收率为96．66％-100．77％，相对标准偏差为0．29％-3．56％。本方法的选择性和精密度均优于乙醇提取法，滴定终点变化敏锐。     

Chemical Constituents and Post-Harvest Prospects of Pandanus amaryllifolius Leaves: A Review

The leaves of Pandanus amaryllifolius Roxb. are widely used for flavoring food items. Extensive work has been done on agro parameters and propagation techniques as well as isolation and identification of the important chemical constituents such as volatile compounds, proteins, alkaloids and flavonoids. This review focuses on the possibilities of using the leaves in food and nonfood industries with particular reference to its aroma component. The major aromatic compound, 2-acetyl-1-pyrroline, has commercial significance as a flavor constituent that imparts the characteristic aroma of scented rice varieties such as basmati rice in India and in several Asian rice varieties. The compound can be added to nonaromatic rice varieties and other food formulations. The location and concentration of 2-acetyl-1-pyrroline in both Pandanus amaryllifolius and aromatic rice has been studied, as has the feasibility of extraction of 2-acetyl-1-pyrroline using different methodologies. The different methods for processing and preservation of this flavor compound are reviewed as are the application potential for flavor enrichment. Further, the therapeutic value of Pandanus amaryllifolius leaves and their importance in other areas as a source of phytochemicals and insecticide has also been documented.     

不同水分含量巴西大豆储存期间的品质变化

为科学判定我国进口巴西大豆在储存期间的品质变化,采用模拟储存试验的方式,对不同水分含量巴西大豆在储存过程中粗脂肪、脂肪酸值和脂肪酸相对含量的变化进行监测。结果表明,巴西大豆在储存6周后,营养指标会出现不同程度的变化,储存28周时粗脂肪含量下降0.52~1.76个百分点,脂肪酸值(KOH)升高3.38~105.48 mg/100 g,亚油酸和亚麻酸的相对含量均呈现不同程度的下降。超过安全水分值(12%)越高,大豆品质下降越明显。低于安全水分值的大豆在储存18周后,品质开始发生较明显变化。因此,认为低水分含量(≤12%)大豆最佳储存期在18周内,高水分含量(>12%)大豆最佳储存期在6周内。通过试验不仅能够准确判定巴西大豆储存过程中的品质随时间的变化,也可以指导国家和地方大豆储备库对大豆的管理,保证大豆安全储存。     

贮藏温度及时间对不同类型商品乳酸度的影响

为研究不同贮藏温度及时间对不同类型商品乳酸度的影响情况。选取超高温(UHT)灭菌乳、巴氏灭菌乳、乳饮料、酸牛奶各10盒,将每种类型的商品乳分成2组,开封后进行贮藏。一组放入0~4℃的冰箱冷藏,另一组放在常温下贮藏。分别在0, 1, 2, 3, 4, 5和6 d测定各组商品乳的酸度。结果表明,酸牛奶、UHT灭菌乳和巴氏灭菌乳放在常温下贮藏时酸度分别在第1,第3和第3天出现显著性差异(p<0.05),在低温下贮藏时酸度均未出现显著性差异(p>0.05)。乳饮料在常温和低温下贮藏1 d后酸度均出现显著性差异(p<0.05)。4种类型的商品乳放在低温下贮藏时更能保持酸度的稳定。     

比较代谢组和转录组学揭示“19香”水稻香气物质组成及其形成途径

基于气象色谱-质谱联用（Gas Chromatography-Mass Spectrometry,GC-MS）对广东省龙川市和连山市种植的“19香”乳熟期籽粒胚乳的挥发性代谢物进行代谢组学分析,结合转录组技术挖掘香气物质形成的相关基因,探讨产地对香稻香气物质形成的影响。通过主成分分析（Principal Component Analysis,PCA）、偏最小二乘法判别分析（Partial Least Squares Discriminant Analysis,PLS-DA）对原始数据进行多元统计分析。结果表明,“19香”异地种植后其挥发性物质含量发生变化,其中有14个香气物质的相对含量达显著差异。通过KEGG富集分析发现次级代谢物的生物合成对香气物质含量具有显著影响。在转录水平上以连山组为对照,龙川组样本有56个显著上调表达基因和89个下调表达基因,且主要参与有机物的分解代谢和多糖代谢等生物进程,差异表达基因发挥着糖基键的水解酶活性和氧化还原酶活性等分子功能,此外类胡萝卜素合成途径为显著富集通路。综上所述,不同种植环境对香稻的香气物质含量影响较大,其中乳熟期糖类代谢活动、胁迫应答相关机制可能是种植环境中调控香气物质含量的关键因子。     

Sensory Characteristics of Frankfurters as Affected by Fat, Salt, and pH

Acceptable processing and flavor profile characteristics of frankfurters were achieved near a pH of 6.0. As salt increased, hardness, juiciness, saltiness, and flavor intensity scores increased. As fat increased, juiciness scores decreased (at salt levels > 1.3%) due to substitution of water for fat. In addition, increased fat resulted in decreased off-flavor. Model predictions suggested that acceptable frankfurters could be manufactured with a minimum of 11.25% fat and 1.3% salt at pH 6.0.     

储存粳米脂肪酸值和酸度变化规律的研究

研究了不同温度条件下储藏粳米脂肪酸值和酸度的变化,结果表明:10℃和15℃储存的粳米脂肪酸值含量变化不显著,但超过20℃储存的粳米脂肪酸值呈现明显的上升趋势,温度越高上升速度越快;粳米酸度均无显著差别;脂肪酸值和品尝评分值之间有很高的相关性,而酸度和品尝评分值之间的相关性差;低温下粳米可以安全储藏1年。     

小麦粉中脂肪酸值测定提取条件优化

目的优化测定小麦粉中脂肪酸值的提取条件。方法采用GB/T 5510-2011《粮油检验粮食、油料脂肪酸值测定》中苯提取法测定,后分别使用95%乙醇、无水乙醇作为提取试剂,振荡提取时间为30、20、10min。结果用50.0mL无水乙醇代替苯,在环境温度20℃,频次为100次/min振荡器振摇10min,提取液静置3 min的条件下,测定小麦粉中脂肪酸值数值分别为31.14、26.32和34.98 (KOH) mg/100 g,用苯提取法测定数值为30.47、25.93和34.84 (KOH) mg/100 g,二者差值均在精密度范围内。结论可以采用无水乙醇代替苯用于测定小麦粉的脂肪酸值。     

稳定型大米增香剂的研究

本文模仿天然食品加工中所产生风味物的途径,制备了目前国内尚属萌芽阶段的反应型香精作为大米增香剂,并对该增香进行了感观评定和ＧＣ－ＭＳ分析。     

大米增香的反应型香料的制备

模仿天然食品加工中产生风味物的途径 ,制备了目前国内尚处萌芽阶段的反应型香料 ,作为大米主增香剂 ,并利用排序检验法优化了制备反应型香料的反应条件 ;同时对该反应型香料和增香米的顶空气体进行了GC MS分析 .     

Apple Cultivar Variations in Response to Heat Treatment and Minimal Processing

Eleven apple cultivars were subjected to heat treatments at various times and temperatures. Susceptibility to browning during heat treatment and after heat treatment was evaluated. Changes in firmness, respiration rate, soluble solids and acidity of slices prepared with heat treated apples were measured. Incidence of browning was dependent upon cultivar and heating temperature; Liberty, Monroe, RI Greening and Rome were very susceptive, while McIntosh, NY 674 and Empire were less susceptive. Golden Delicious and Delicious showed relative strong tolerance to heat. Apples that received heat treatment at 45°C produced slices with less browning and firmer texture compared to non-treated apples. The positive effect of heat treatment might help produce high quality minimum processed fruits.     

黄酒酸度与其他指标的相关性探讨

黄酒以大米、黍米为原料,酒精含量一般为14％vol～20％vol,属于低度酿造酒。试验以酸度作为黄酒一项重要的理化指标,在后酵设置不同打耙次数和酸度值来寻找合格的产品标准,确定符合产品指标的工艺和产品的企业指标,为生产工艺的制定提供实施依据。     

Short communication: Effect of refrigerated storage on the pH and bacterial content of pasteurized human donor milk

Once pasteurized donor milk is thawed for its administration to a preterm or sick neonate, and until it is administered, it is kept refrigerated at 4 to 6°C for 24 h. After this time, unconsumed milk is discarded. This time has not been extended, primarily because of the concern of bacterial contamination. The aim of this study was to determine the changes in pH and bacterial count when pasteurized donor milk was kept under refrigeration for a prolonged period (14 d). In this prospective study, 30 samples of pasteurized donor milk from 18 donors were analyzed. Milk was handled following the regular operating protocols established in the neonatal unit and was kept refrigerated after thawing. pH measurements and bacteriology (on blood agar and MacConkey agar plates) were performed on each sample at time 0 (immediately after thawing) and then every day for 14 d. Changes in pH of samples over time were evaluated with linear mixed-effects regression models. A slow but gradual increase in milk pH was observed starting from the first day [mean (±SD) pH of 7.30 (±0.18) at time 0 and 7.69 (±0.2) on d 14]. No bacterial growth was observed in any of the samples throughout the complete trial except in one sample, in which Bacillus flexus was isolated. In conclusion, pasteurized human donor milk maintains its microbiological quality when properly handled and refrigerated (4–6°C). The slight and continuous increase in milk pH after the first day could be due to changes in the solubility of calcium and phosphate during refrigerated storage.     

大米储藏保鲜技术研究进展

大米是人类主要食品,大米保鲜目的是防止大米在仓储、市场流通和消费者存放过程中生虫、长霉及延缓其陈化,大米主要储藏技术包括常温储藏、低温储藏、气调(自然缺氧、充CO2、充N2、真空)储藏、化学储藏等常规保鲜法:一些新的技术如辐照技术、纳米技术、微波技术和涂抹保鲜技术等也已开始研究应用。该文介绍大米储藏保鲜技术现状及几种新型保鲜技术。