A_2菌产蛋白水解酶的分离纯化

利用A2菌种液态摇瓶发酵产蛋白水解酶,后采用硫酸铵分级沉淀、Sephadex G-75凝胶过滤层析、DEAE离子交换层析对粗酶液进行分离纯化后,蛋白酶比活力达到521.47U/mL,纯化倍数是粗酶液的3.52倍,回收率为8.71%。通过SDS-PAGE凝胶电泳得到单一条带,并测得其相对分子质量约为30kDa。     

动物蛋白水解酶法制备梅鱼鲜味酶解液的研究

以梅鱼为原料,采用动物蛋白水解酶,以鲜甜味游离氨基酸总量为指标,水解制备梅鱼鲜味酶解液。在单因素的基础上,采用响应面分析法得出酶解的最佳条件:温度40.7℃、pH7.68、[E]/[S]0.84%,时间4 h,制得的酶解液鲜甜味游离氨基酸总量为115.159μg/mL,海鲜味特征明显。     

酶改性大豆分离蛋白在高蛋白奶中的应用研究

研究了大豆分离蛋白经Alcalase碱性内切蛋白酶轻度酶改性后 (DH 4 5 %～ 8 2 % )功能特性的变化规律。结果表明 ,改性大豆分离蛋白的持水能力、溶解度以及乳化活力指数均随着水解度的增加而增加 ,泡沫稳定性、粘度随着水解度的增加而降低 ,起泡能力则随着水解度的增加先增大而后降低。此外 ,改性后的大豆蛋白应用于高蛋白奶中可获得高稳定的乳浊液体系     

大豆未消化蛋白的功能性质研究

在生产大豆肽的过程中,会产生大量的蛋白残渣即未消化蛋白。本文以大豆分离蛋白为对照,对未消化蛋白进行基础分析和功能评价。结果表明,大豆分离蛋白制备成未消化蛋白,蛋白含量从90.70%降为82.15%,醇溶蛋白从45.94%降为39.16%。未消化蛋白与大豆分离蛋白相比,持水性、乳化性、乳化稳定性略微下降,持油性显著上升,可以应用于与持油性相关的肉制品加工、乳品生产等相关行业。     

大豆分离蛋白厂豆清的酶解与利用

本文对大豆分离蛋白厂豆清的主要成分进行了分析，并以豆清为原料，利用根霉R_2和酸性蛋白酶作用，经发酵、酶解、过滤、调配、灌装与灭菌等生产出一种富含氨基酸的清凉饮料，其色泽金黄，有特殊发酵香味，口感淡爽，总氨基酸含量446．gmg／100ml。     

大豆分离蛋白水解用酶的筛选研究

研究了不同蛋白酶对大豆分离蛋白的水解情况,筛选出 Protamex酶作为大豆分离蛋白的水解用酶。      

大豆分离蛋白水解用酶的筛选研究

研究了不同蛋白酶对大豆分离蛋白的水解情况,筛选出 Protamex酶作为大豆分离蛋白的水解用酶。     

大豆分离蛋白与染料木素共价交联对蛋白表征和结构的影响

探究大豆分离蛋白和染料木素的共价交联对蛋白表征和结构的影响。制备大豆分离蛋白与不同质量浓度染料木素（0、1.2、1.5、2.0 mg/mL）的共价复合物,通过探究粒径、Zeta电位、浊度、表面疏水性分析蛋白体系的表征变化,并采用紫外分光光度计、荧光分光光度计、傅里叶变换红外光谱仪分析蛋白体系的结构变化。结果表明：大豆分离蛋白与染料木素共价复合后,蛋白的中位径由135.6 μm最低减小至98.0 μm,Zeta电位绝对值由15.0 mV最高增大至21.4 mV,表面疏水性由216.0最低减小至115.5,总巯基含量由31.5 μmol/g最低减小至20.4 μmol/g。与对照组相比,共价复合物的浊度增加,并且实验组中SPI-Ge-1.2组低于SPI-Ge-1.5组和SPI-Ge-2.0组。光谱分析表明染料木素对大豆分离蛋白有猝灭效果,二者共价交联后蛋白质的色氨酸与酪氨酸残基所处的微环境疏水性减少,蛋白质二级结构中α-螺旋含量增多、β-折叠含量减少、β-转角含量增多、无规卷曲含量减少,并且加入1.2 mg/mL的染料木素对大豆分离蛋白的表征特征和结构影响效果更好。本研究结果表明在大豆分离蛋白中加入染料木素后,二者的共价交联能够影响蛋白的表征与结构。     

高功能型大豆分离蛋白研究及应用

利用改进分离蛋白生产工艺,即在白豆片萃取时采用正交设计优化工艺参数:萃取温度46℃,pH值7.5,水料比12:1,萃取时间30分钟。蛋白液酸沉时控制温度45℃,pH值调至4.4。同时采用先进酶解技术对蛋白质进行修饰改性,真空脱臭工艺除去豆腥味,制得分离蛋白蛋白质含量≥90％,NSI(氮溶解度指数％)≥90％,色泽纯正,风味良好,有良好分散性(冲调性)、溶解性、分散稳定性及乳化性,是一种优质分离蛋白,可广泛应用于乳制品,仿乳制品、饮料、面制品、化妆品等行业。     

单宁酸与大豆分离蛋白相互作用研究

利用荧光光谱、紫外光谱和圆二色谱,从分子水平研究单宁酸与大豆分离蛋白的相互作用。结果表明:单宁酸对大豆分离蛋白有较强的荧光猝灭作用,当单宁酸浓度小于6×10~(-6)mol/L(相对于大豆分离蛋白质量分数5. 1%)时,猝灭类型为静态猝灭,当单宁酸浓度大于6×10~(-6)mol/L时,同时存在静态猝灭和动态猝灭;单宁酸通过疏水作用与大豆分离蛋白结合,导致大豆分离蛋白的色氨酸和酪氨酸残基微环境亲水性增强,但对大豆分离蛋白的二级结构没有显著影响。     

海藻糖快速检测方法的建立与初步应用

海藻糖是生物体合成的、具有抗逆保护作用的天然二糖,在食品加工与贮藏、微生物发酵过程具有重要作用。该文采用前期获得的专一性海藻糖酶,建立了一种定量测定海藻糖的快速方法。该方法对海藻糖的检测限为0. 019 mg/m L,定量限为0. 1 mg/m L;海藻糖的线性检测范围为0. 1 mg/m L～150. 0 mg/m L,回收率为98. 80%～101. 33%。该方法操作简便快捷、特异性高、重复性好,在菌种改良与食品原料营养筛查等海藻糖快速定量检测中具有良好的应用前景。     

一种新型快速测定葡萄酒中挥发酸含量的方法

采用快速蒸馏仪缩短葡萄酒中挥发酸含量测定的蒸馏时间,优化样品前处理方式,建立了葡萄酒中挥发酸快速测定方法。该方法加标回收率为92.1%,日内精密度与日间精密度分别为1.01%与1.32%,测定样品的重现性好。对干型、半干型、半甜型、甜型葡萄酒样品中挥发酸含量进行检测,测定结果与国标方法相比较,无显著性差异(p0.05)。研究结果表明该方法相比于国标方法,操作更简单、准确和快速(单个样品检测缩短了约20 min)。     

一种快速测定酶活性的方法

目的探讨快速测定酶活性的方法。方法直接用生物传感分析仪测相对的酶活性,并与测定绝对酶活性的方法相对照,探讨它们之间的关系。结果直接用生物传感分析仪测相对酶活性可判断乳酸氧化酶的活性,与测定绝对酶活性的方法相比,它们存在着线性关系。结论直接用生物传感分析仪测相对酶活性是一种快速判断酶活性值的方法。它还可以测定谷氨酸氧化酶、葡萄糖氧化酶等的酶活性。     

1种快速检测微藻油脂的新方法

微藻油脂是一种非常重要的生物能源,微藻产油能力及油脂含量变化的快速分析在能源微藻的产业化过程中有着很重要的意义。文中以实验室分离的1株栅藻为研究对象,以有机溶剂提取法作为参照,利用磷酸香草醛反应法监测了在不同的糖浓度、氮浓度和磷浓度下栅藻油脂含量的变化。同时,对其他微藻,如小球藻、小环藻、脆杆藻等应用磷酸香草醛反应法进行总脂量分析。结果表明,磷酸香草醛反应法可以快速准确地检测微藻油脂的含量。     

A rapid method for iron determination in fortified foods

The objective of this study was to develop and evaluate a rapid method for iron determination in fortified and unfortified foods. Method: samples were mixed with an iron-extracting solution (1.2 M HCl, 0.6 M trichloroacetic acid, and 0.7 M hydroxylamine hydrochloride) and heated in a boiling water bath for 15 min. The mixtures were cooled and filtered. The filtrate was mixed with a chromogen reagent (0.03% bathophenanthroline disulfonic acid in 3 M sodium acetate). Iron concentration was determined by measuring absorbance at 535 nm. The accuracy of the rapid method was validated by comparing results to a standard laboratory method for iron determination. Results: the rapid method produced accurate results for the majority of the food samples tested, including wheat flour fortified with FeSO₄, electrolytic iron, NaFeEDTA, Ferrochel® or ferrous fumarate; powdered drink mixes, and enriched rice. However, results obtained using the rapid method were significantly lower than results obtained using the standard method for the enriched cornmeal (30.04 vs. 33.16 μg Fe/g; P=0.0118) and the enriched flour (41.90 vs. 47.28 μg Fe/g; P<0.0001). Conclusion: The rapid method is simple, inexpensive, and suitable for monitoring iron concentrations in fortified foods.     

A rapid method for measuring protease activity in milk using radiolabeled casein

A rapid means to detect the presence of protease activity in raw milk could be useful in predicting keeping ability of products made from that milk. A 30-min assay has been developed and compared with three other methods of detecting protease. Casein, [methyl-14C]-methylated-alpha was purchased from a radioisotope supplier. Concentrations of substrate from 2 to 20 nCi gave counts per minute, which increased linearly when counted with the Charm analyzer. There was not a significant difference in counting times of 10, 20, or 30 min. A mixture of sodium acetate and acetic acid precipitated nonhydrolyzed substrate with an efficiency of 97%. Comparison of the [14C] casein assay, a casein fluorescein isothiocyanate assay, trinitrobenzenesulfonic acid procedure, and the Hull procedure using protease from psychrotrophic bacteria revealed that the [14C] casein and casein fluorescein isothiocyanate methods were roughly equivalent and that the radiometric procedure was 10 times more sensitive than the trinitrobenzenesulfonic acid assay. The radiometric procedure was approximately 10(4) times more sensitive than the Hull procedure. The [14C] casein and casein fluorescein isothiocyanate methods were similar in time required, about 30 min, while the trinitrobenzenesulfonic acid assay and Hull method required about 1 h plus reagent preparation time. The [14C] casein procedure was most expensive per test; the other three were cheaper and similar to each other in cost.     

一种乳中钙含量的快速检测方法

目的建立血液中钙离子临床快速检测方法检测乳中钙含量的方法。方法样品采用盐酸+TX-100稀释,依据碱性(酸性)条件下钙与偶氮胂Ⅲ作用生成的蓝色复合物颜色与钙浓度正比的正比关系,在650nm波长处测定吸光度变化,经与钙校准液比较,计算出样品中钙含量。方法的准确度、精密度、稳定性等用乳中钙含量检测国标方法进行验证。结果建立的乳中钙含量快速测定方法与国标方法比较,准确度(偏差≤10%的符合率达到100%)和精密度(相对标准偏差为10%)方面均符合要求,且操作简单、成本低、安全性高,单个样品检测时间由原来国标方法的24h缩短至8min。结论该方法可应用于乳中钙含量快速检测,对生乳采购和液态奶市场筛查检测具有重要的应用价值。     

A simple and rapid colorimetric method for lactose determination in milk

A simple and rapid technique for the estimation of lactose in fluid milk and whey, utilizing trichloroacetic acid (TCA) as a precipitating agent, is outlined. The color development is based on the reaction of picric acid with lactose in the presence of phenol, sodium hydroxide and sodium bisulfate. This method can be completed within 10 min. There is no significant difference (p ≤ 0·05) between the results obtained by the proposed method and those obtained by the IDF method.     

雨生红球藻中虾青素含量快速测定方法

雨生红球藻中虾青素以虾青素单酯、二酯以及少量游离虾青素的形式存在,为了准确测定虾青素含量,通常需要将提取的虾青素酯水解转化为游离虾青素,再利用HPLC进行定量,操作耗时,不利于生产过程的快速监测。基于系统研究分光光度法直接测定细胞提取物中的混合虾青素含量和提取-酶解-HPLC法测定的关系,发现分光光度法估算的虾青素含量与HPLC法测定的准确含量之间具有良好的线性关系(r2=0. 997)。基于此建立了雨生红球藻虾青素快速测定方法,并对提取条件进行了优化。雨生红球藻粉(约5 mg)利用1 m L二甲基亚砜和6 m L丙酮进行1次提取,准确定容后,测定474 nm处的吸光度,根据吸光度与HPLC法虾青素含量间线性关系计算雨生红球藻中虾青素的含量。该方法操作简单,仅需10～20 min,测定准确,适于生产和流通环节的所需要的快速测定领域。     

A rapid method for the determination of nitrate and nitrite by chemiluminescence

Nitrite and nitrate + nitrite can be determined by selective chemical reduction to nitric oxide which is measured using a chemiluminescence analyser. The reducing agents are sodium iodide in acetic acid for nitrite and ferrous ammonium sulphate-ammonium molybdate for nitrate + nitrite. The concentrations of the reducing agents have been optimized to obtain the maximum yield of nitric oxide and the minimum coefficient of variation. Under these conditions, it is possible to inject repeated samples into the refluxing reducing agents and to obtain rapid evolutions of nitric oxide from which the determinations can be made. Nitric oxide has also been produced using the nitrite reagents from organic nitrites, a S-nitrosothiol, a pseudonitrole and N-nitrosamines. Similarly, an organic nitrate and some C-nitroso compounds respond to the method for nitrate but only to the extent of a yield of nitric oxide of about 10% of the theoretical. Very low or zero responses were evident from aliphatic and aromatic C-nitro compounds but not omega-N-nitroarginine which gave a large yield of nitric oxide using the reagents for nitrate. In general, however, concentrations of nitrate will be in considerable excess of those of related compounds which would interfere with the determinations. Nitrate can be determined either by difference in its mixtures with nitrite or by prior removal of the nitrite using ascorbic acid provided oxygen and nitric oxide are removed by degassing with nitrogen.