A COMPARISON OF THE EFFECTS OF TEMPERATURE,ENZYME SOURCE,AND SEQUENCE OF DIGESTION ON NEUTRAL DETERGENT FIBER1

ABSTRACT A number of methods for determining dietary fiber have been suggested. Thus, ten modifications of the neutral detergent fiber (NDF) procedure were compared using spinach, bread, and parsnips. Use of Bacillus subtilis alpha amylase resulted in lower (p < .01) NDF values than did porcine pancreatic amylase. Amylase obtained from B. subtilis may contain other enzymes such as hemicellulase and cellulase in small amounts. These enzymes would be undesirable since they may remove some of the fiber fraction, hence the reported NDF would be lower. Temperature of incubation, 21°C or 37°C, did not significantly affect fiber values. Samples predigested with amylase had higher (p < .01) fiber values in a high starch food than samples in which amylase incubation occurred after detergent digestion. NDF values may have been higher because starch was less available for enzymatic hydrolysis before the detergent digestion. When amylase was added directly to the detergent solution after refluxing, NDF was not significantly different (p < .05) from that quantified by the official AACC method or most of the other treatments. Implications of these findings are discussed with respect to their significance in practical applications.     

STRUCTURE AND COLOR CHANGES DUE TO THERMAL TREATMENTS IN DESALTED COD

Cod (Gadus morhua) has a great importance in some European countries, either due to fish production and exportation volume or because of its high consumption. Desalted cod (3.94 ± 0.04% salt content and 73.49 ± 0.06% water content) has a limited shelf-life due to the microbial activity and the autolytic proteolysis affecting product texture. Thermal treatments can be used to preserve the cod, but these can cause changes in color, fish muscle tenderization through protein denaturation and collagen breakdown. In this research, steam blanching (5 min), water blanching (1 min) and microwave heating (5 W/g, 2 min) were applied to desalted cod. The effect of these treatments on color (CIEL*a*b* coordinates), mechanical properties (shear and TPA tests) and microstructure of cod were analyzed. Thermally treated cod were lighter, slightly yellowed and softer. From color data and microstructural observations, heat induced changes in cod were a little smaller than in microwave heated cod.     

COMPOSITIONAL CHANGES OF STRAWBERRY DUE TO DEHYDRATION, COLD STORAGE AND FREEZING–THAWING PROCESSES

Strawberry is an excellent source of food ingredients, although compositional changes might occur in improperly controlled processing, affecting product quality. In this article, changes in sugar composition (glucose, fructose and sucrose), citric acid, water and total soluble content, as induced by partial dehydration and freezing–thawing processes, were analyzed in strawberries (var. Camarosa). Osmotic dehydration (OD) with 65 °Brix sucrose solution, air drying (AD) at 45C, or combined treatments (OD–AD) were applied to reduce strawberries’ water content to 70–85%. Fresh and dehydrated samples were frozen (?40C, 24 h) and stored (?18C, 30 and 180 days). All samples processed by OD and OD–AD showed a significant sugar gain, and depending on the dehydration treatment, total or partial sucrose hydrolysis was observed. Dehydration treatments caused small losses of citric acid. During the freezing–thawing process, drip loss and enzymatic action also cause changes in sugar concentration, especially in OD‐treated samples.     

FOLATE LOSSES IN BEEF LIVER DUE TO COOKING AND FROZEN STORAGE1

Raw, broiled and fried beef liver samples were stored at ? 20°C in either vacuum or air-saturated packages. At periods of 0, 30, 60 and 90 days the folates were extracted in a 2% ascorbate solution and analyzed by the Lactobacillus casei microbiological assay. The folate content of raw beef liver was higher than previously reported which could be partly due to the ascorbate level used and the precautions taken during the extraction procedure. Broiling was shown to cause a 41% loss in folate activity while frying caused a 50% loss. Further losses in vitamin activity occurred during frozen storage, especially in nonvacuum packages, but stabilized after 30 days.     

固相萃取分离苹果汁中富马酸的方法研究

将固相萃取技术应用于苹果汁中富马酸的分离和富集。通过对固相萃取的主要影响因素进行研究，确定了最佳条件：用0．1mol／L氢氧化钠溶液调节果汁pH值至7．0，用4mL的0．1mol／L氢氧化钠活化柱子，取25mL的果汁上样，再用4mL去离子水淋洗柱子，最后用1．5mL 0．1mol／L的硫酸溶液洗脱富马酸，将洗脱液直接上液相色谱检测。果汁样品中富马酸的回收率为60．8％～79．4％。     

灵芝活性成分的提取与检测

多糖和三萜两大类活性物质是灵芝的主要活性成分，是目前最有开发前途的保健食品和药品新资源之一，也是保健食品功能因子的研究热点。综述了从灵芝中提取多糖和三萜类物质的提取工艺及含量检测的研究进展。     

热风式干燥对甘薯膳食纤维中抗性淀粉含量的影响

研究低温预风干后高温快速风干处理对甘薯膳食纤维中抗性淀粉含量的影响.低温预风干温度对甘薯膳食纤维中抗性淀粉含量的影响效果显著,而高温快速风干的温度和时间对抗性淀粉含量的影响效果不显著.低温预风干温度和抗性淀粉含量间的变化呈非线性关系.提高抗性淀粉含量的最佳工艺参数为:30℃低温预风干60h,再在60℃高温快速风干1 h,抗性淀粉含量可达11.26%.     

苹果多酚的乙醇提取和大孔树脂纯化工艺研究

研究乙醇提取和大孔树脂纯化苹果多酚的工艺条件.通过单因素和多因素试验考察操作条件对乙醇提取率的影响因素;利用静态试验考察大孔树脂纯化苹果多酚的吸附性能和洗脱参数.试验结果表明,乙醇提取苹果多酚的最优工艺条件为乙醇浓度80%,提取温度80℃,料液比1:3(g/L),总提取时间为60min;XDA-7型树脂纯化苹果多酚的最优工艺条件为吸附温度25℃、时间为2h,提取液浓度为0.50 g/L-0.60g/L、pH值为5,解吸温度30℃,解吸液为70%的乙醇溶液.     

双相溶剂萃取技术提取酱油渣中油脂和大豆异黄酮的研究

利用正己烷-乙醇-水构成的双相溶剂萃取技术同时从酱油渣中提取油脂和大豆异黄酮,采用正交设计方法,考察温度、时间、乙醇浓度、乙醇用量、正己烷用量对油脂和大豆异黄酮提取率的影响,并用极差分析方法对正交试验结果进行分析。确定最优的提取条件：温度60℃、乙醇浓度80％、乙醇用量0．071g／mL、正己烷用量0．1g／mL、时间2h,在此条件下,油脂提取效率为99．2％,大豆异黄酮提取效率为94．5％。     

核桃叶黄酮微波辅助提取及抗氧化性研究

采用微波辅助提取核桃叶黄酮,讨论微波萃取时间、温度、乙醇浓度、固液比、原料粒度等因素对黄酮得率的影响,研究核桃叶黄酮、Vc、BHT、TBHQ的抗氧化性.结果表明:最佳提取条件为萃取时间6min、萃取温度60℃、乙醇浓度60%、固液比1∶30(g/mL)、原料粒度40目～80目时,核桃叶黄酮得率达6.86mg/g;在抗氧化性方面,0.08 g/L的核桃叶黄酮与0.06 g/L的BHT和0.04g/L的TBHQ还原能力相当.     

HEAT AND MASS TRANSFER FUNDAMENTALS APPLIED TO FOOD ENGINEERING1

There is a need for deeper qualitative and quantitative understanding of the heat and mass transfer mechanisms underlying various techniques for food production, processing, preservation and storage. This is important for the development of new food sources, for more economical and energy-efficient processing of food from existing sources, for better food quality and quality control, and for adherence to new regulations such as nutritional labeling and shelf-life dating. Several classes of food-processing problems are presented where advances can be made on the basis of improved understanding of heat and mass transfer mechanisms. These include cases of competing transport, cases where transport competes with kinetics of chemical or biochemical reactions, and cases where determination and understanding of the rate-determining factor are needed. Specific examples are drawn from drying processes, leaching and extraction, freezing, sterilization and enzyme deactivation, and artificial cultivation.     

葡萄根际线虫优势种类及其为害

线虫病在我国葡萄园中普遍发生,其中根结线虫（Meloidogyne)是大多数地区的优势种群,造成的危害最大。螺旋线虫（Helicotylenchus)、钱线虫（Paratylenchus)、矮化线虫（Tylenchorhnychus)及剑线虫（Xiphinema)也普遍发生。由线虫造成的直接和间接损失相当严重,应给予足够的重视。     

HEAT SENSITIVITY,OPTIMUM pH AND CHANGES IN ACTIVITY OF SORGHUM PEROXIDASE DURING MALTING AND MASHING

Peroxidase activity was demonstrated in dry and germinating sorghum seeds. The specific activity increased about 14-fold during malting for a 96-hour period. On the average about 41% of peroxidase activity was located in the endosperm, and the remaining 56% in the acrospire and rootlet of sorghum malt. The crude enzyme extract retained 77%, 17.5% and 7.6% of activity after heating at 60°, 70° and 80°C, respectively. More than 50% of the peroxidase activity in the finished malt survived mashing at 65°C. Optimum activity was recorded at pH 5.5 which falls within the observed pH range of sorghum worts. The level of residual peroxidase activity in the wort differed with sorghum species.