Low Temperature Sweetening in Susceptible and Resistant Potatoes: Starch Structure and Composition

Starch isolated from ND 860–2 potatoes, which were resistant to chillsweetening, had higher amylose and lower amylopectin as well as a higher crystallinity as compared to starch isolated from Norchip potatoes, which were susceptible to low temperature sweetening. ND 860–2 starch exhibited greater resistance to α-amylase attack and amorphous swelling as well as higher gelatinization temperatures and onset swelling temperatures than starch isolated from Norchip. Examination of starch granule structure using bright field light microscopy indicated crystalline concentric rings in ND 860–2 not seen in Norchip. Scanning electron microscopy of granules incubated with a-amylase indicated more intact ND 860–2 starch granules compared to Norchip. These data strongly suggest that starch granule composition is a factor differentiating the low-temperature sweetening sensitive cultivar from the resistant potato seedling.     

Starch Gelatinization in Cold Temperature Sweetening Resistant Potatoes

Differential scanning calorimetry was used to compare temperatures, enthalpies, and kinetic constants for starch gelatinization in tubers of Solarium tuberosum L, var Norchip and a cold sweetening resistant selection, ND 860-2, in an attempt to correlate cold sweetening susceptibility with starch granule stability. For corresponding heating rates, ND 860-2 onset and peak temperatures were higher (p0.05) while differences in enthalpies and activation energies were not (p>0.05) different. Activation energy for amorphous swelling was 281 kJ mol^?1 higher, and the minimum temperature to induce crystallite disruption was 3.5°C higher, for ND 860-2 granules. Results indicate greater stability in ND 860-2 granules and suggest granular stability contributes to cold sweetening resistance.     

加工用马铃薯"低温糖化"机制的研究

以克新１号马铃薯品种为材料,对贮藏期间块茎的碳水化合物,相关酶活性及造粉体膜结构的变化进行研究。结果发现：与１０℃贮藏相比,４℃贮藏条件下,还原糖和总糖的含量显著增加,成“低温糖化”现象,引起马铃炸片色泽变深;碳水化合物代谢过程中有关的淀粉酶,淀粉磷酸化酶及转化酶活性更高,更有利于淀粉向还原糖的转化;造粉体膜结构的完整性在贮藏过程中发生变化,电导率更高,膜的硬坏更为明显。     

Modeling Low Temperature Blanched Carrot Firmness Based on Heat Induced Processes and Enzyme Activity

A kinetic texture model was developed describing the low temperature blanching firming effect. The rupture stress of carrots during blanching at 55°, 65° and 75°C and subsequent cooking at 95° and 100°C was measured. Firming effects were highest at 55° and 65°C although shorter blanching times were needed at 65°C. Model parameters were estimated by non-linear regression analysis on these measurements. The model summarized the biochemical mechanisms occurring in the cell wall during processing. The model was suitable for process design purposes as well as for gaining a better understanding of the firming process.     

耐低温螺旋蓝细菌诱变株的诱变及特性研究

为了获得能适应较低生长温度的菌种,对极大螺旋蓝细菌进行紫外诱变,通过低温筛选获得了生理性状稳定的耐低温诱变株.其中两个诱变株YB01和YB02在10、15和20℃低温条件下生长速率显著高于出发藻株,诱变株的胡萝卜素和不饱和脂肪酸的含量也比出发藻株明显提高,是两株较理想的诱变株.对YB02株的抗低温生理进行研究发现,其光合放氧速率和体内积累的脯氨酸含量明显高于出发藻株.此外,对YB02进行了二次诱变,获得两株在低温条件下生长速率更快的诱变株YB020l和YB0202.     

酶法水解甘薯工艺条件研究

甘薯经过粉碎、打浆后用α-淀粉酶,果胶酶及纤维素酶酶解,采用苯酚硫酸法测定酶解液中葡萄糖含量,确定不同酶作用甘薯最适条件。研究结果表明,α-淀粉酶、果胶酶和纤维素酶酶解甘薯最适温度,pH值,最佳酶解时间,最适加量分别为：40℃,5,20min,200U／mL;40℃,4．5,2h,150U／mL;50℃,5,6h,15U／mL。     

耐低温乳酸菌在盐渍发酵青菜中的应用研究

将耐低温乳酸菌以1‰的接种量用于盐渍青菜原料,食用盐含量为5-7%,经一个月盐渍处理,总酸含量均为0.6%以上,亚硝酸盐含量为1mg/kg以下。     

Effects of Low Temperature and Modified Atmosphere on Sugar Accumulation and Chip Color in Potatoes (Solanum tuberosum)

Storage of Norgold and Russet Burbank tubers at 3°C in air led to accumulation of sucrose and hexose and a decline in chip color quality to unacceptable levels (Hunter L values less than 40) within 2 wk. Storage in modified atmospheres of 1000 ppm ethylene in air and low oxygen delayed decline in color by 6-8 wk compared with storage in air. Storage in 1000 ppm ethylene apparently reduced rate of conversion of sucrose to hexose. The low oxygen atmosphere appeared to reduce extent of sucrose accumulation and rate of sucrose conversion to hexose during storage.     

黄牛皮低温酶脱毛的研究

对低温条件下的黄牛皮酶脱毛进行了研究.结果表明:在低温条件下进行黄牛皮酶脱毛是可行的,脱毛过程中酶活力损失小,脱毛液中可溶解胶原含量低,约为高温酶脱毛的1/2.组织学检测显示,脱毛后的皮样粒面形态完好,毛孔清晰,无松面、无烂面现象.低温酶脱毛适宜的条件是:温度l8～25℃、液比0.5～1.5、pH值7.5～9.0、蛋白...     

Enzyme Activity Levels in Beef: Effect of Postmortem Aging and End-point Cooking Temperature

While it is known that meat flavor varies as a function of end-point cooking temperature, storage time, and activity of endogenous hydrolytic enzymes, little is known about the interrelationship of these three factors with flavor. Several endogenous enzymes and proteins with potential involvement in meat flavor were investigated. The data indicate two main observations: (1) enzymes are redistributed to new intracellular compartments during postmortem aging. (2) enzyme activity is temperature dependent over the range examined (20-80°C) with some enzymes such as cathepsins B & L retaining a high level of activity (>20% of that at 20°C) at temperatures above 70°C. Thus, the combined effect of postmortem aging and cooking, via enzyme redistribution and enzyme activity, respectively, influence the production of flavor compounds and precursors.     

糖萜素及不同温度对异育银鲫消化酶活力的影响

选取相同生长阶段、体重均匀的异育银鲫160尾,随机分为5个组,每个组16尾,每个组设2个重复。糖萜素的添加水平为0、0.5、0.9、1.2和1.5 g/kg。结果表明:在适宜的温度范围内,试验2组异育银鲫的蛋白酶、淀粉酶和脂肪酶活力最高,其次是试验1组和试验3组,对照组最低。蛋白酶适宜温度为40~50℃,淀粉酶适宜温度为30~40℃,脂肪酶适宜温度为30~40℃。糖萜素对异育银鲫消化酶活性具有正向促进作用,但在不同添加水平上,消化酶活性增强的程度不同,其适宜的添加量为0.5~0.9 g/kg。     

极低频交变磁场对过氧化氢酶活性的影响

以酶活和相对酶活为指标考察了极低频交变磁场对过氧化氢酶活性的影响。结果表明:不同磁场强度、频率及酶液pH、处理温度都会造成过氧化氢酶的活性变化,其变化趋势是随着磁场处理时间的延长,总体上其酶活和相对酶活降低。但就温度而言,当处理温度55℃下,相对酶活远高于100%,4 h达到最高值2 142.86%。圆二色谱测定表明,25℃磁场处理后酶的α-螺旋和β-折叠的总量小于对照组,55℃磁场处理后酶的α-螺旋和β-折叠的总量大于对照组,可推测过氧化氢酶在此条件下形成具有相对耐高温的结构。     

Influence of Temperature and Time on Cooking Kinetics of Potatoes

To study cooking kinetics, slices (6 mm thick, 30 mm diameter) of 3 potato varieties were treated in water at 90°, 100° and 110°C for varying times. Sensory, chemical and physical properties were investigated. Changes during cooking at constant temperature were mathematically described by a 0 order (texture, taste) and a 1st order (shear force, dry matter, pectin, soluble amylose, cell size) equation. The starch content remained constant. Temperature dependence of the rate constant could always be described by a first order equation. The z-values, which are necessary to calculate Cvalue for practical heat treatments, could be determined. Correlations established between kinetics of different properties showed that behavior of certain potato properties may be predicted by shear-force measurement.     

酶转化淀粉低温上浆性能的研究

研究了酶转化淀粉在低温下的粘度、粘度稳定性、粘附性及浆膜性能,利用酶转化淀粉混合浆对涤棉纱进行低温上浆,并测试其浆纱性能。实验结果表明,酶转化淀粉在低温条件下有较低的粘度、较好的流动性及粘度稳定性,对涤棉纱的粘附性较好,浆纱的强伸性能好,耐磨性能优异,毛羽贴伏效果明显。     

不同抗性烟草品种内源激素对赤星病胁迫的响应差异

为进一步明确烟株内源激素与赤星病抗性的关系,以抗赤星病烟草品种净叶黄和感病品种长脖黄为研究对象,通过盆栽种植并接种赤星病菌,比较不同抗性品种内源激素含量对赤星病胁迫的响应差异。研究结果显示,在赤星病胁迫下,净叶黄、长脖黄的脱落酸（ABA）含量和乙烯（ET）释放量均呈上升趋势,而生长素（IAA）以及细胞分裂素（CTK）含量表现为降低。同时,赤星病胁迫导致净叶黄的赤霉素（GA）、茉莉酸（JA）含量增加,引起长脖黄的JA含量降低,GA含量则先增加后降低。与净叶黄相比,长脖黄的ABA含量增幅较小,而GA、IAA、CTK与JA含量降幅较大,并且ET释放量较高。综上,在赤星病胁迫下,内源激素的含量差异以及变化幅度可以反映不同品种的抗病能力。     

Optimization of Low Sodium Salts Mix for Shoestring Potatoes

Several studies have shown the close relationship between the sodium consumption and health problems such as hypertension and cardiovascular disease. Thus, the demand for products with reduced sodium content, but with sensory quality, is increasing every day. In this context, this study aimed to optimize a low sodium salts mix using sodium chloride, potassium chloride, and monosodium glutamate to the development of shoestring potatoes with low sodium content and high sensory quality, through mixture design and response surface methodology. The salts mix that promotes the same salting power and similar sensory acceptability that the shoestring potatoes with 1.6% sodium chloride (ideal concentration) and at the same time promotes the greatest possible reduction of sodium, about 65%, should provide the composition as follows: 0.48% of sodium chloride, 0.92% of potassium chloride, and 0.43% of monosodium glutamate.     

酶的失活

作为一种具有催化活性的无毒蛋白质,酶能在十分温和的条件下高效地催化底物反应。对于造纸工业,酶用于制浆、漂白、废水处理及打浆,在降低能耗、改善纸浆性能等方面都显出独特的优越性,但酶受多种因素的影响而极易丧失活性,因此,在贮藏及应用当中应十分注意。一般地,酶要避免接触高温和酸性、碱性溶液以及一些有机溶剂如乙醇、丙酮、乙醚等。在温度超过３５～５５℃,以及溶液的ｐＨ值小于４或大于９时都会引起失活。当然,不同酶具有不同的最适宜的温度及ｐＨ值,一般有机溶剂浓度高于３%,在室温下就能使酶引起变性。冷藏可使大多数酶的有效期…     

pH值、温度和作用时间对JW-2号蛋白酶活力的影响

研究了pH值、温度和作用时间对JW-2号蛋白酶活力的影响.结果表明,JW-2号蛋白酶的最适作用温度在65 ℃左右;最适作用pH值在11左右;随着作用时间的延长,JW-2号蛋白酶的活力逐步下降.     

pH值、温度和作用时间对JW-2号蛋白酶活力的影响

研究了pH值、温度和作用时间对JW-2号蛋白酶活力的影响。结果表明，JW-2号蛋白酶的最适作用温度在65℃左右；最适作用pH值在11左右；随着作用时间的延长．JW-2号蛋白酶的活力逐步下降。