赛买提大蒜中大蒜素的稳定性研究

文章研究了不同因素对大蒜素稳定性的影响,结果表明:大蒜素在pH为3~5时较稳定,在pH为8~11时稳定性比较差;大蒜素对热不稳定,尤其当温度高于100℃时;有机溶剂和调和油对大蒜素有稳定作用;糖类对大蒜素有一定的保护作用,尤以β-环糊精和可溶性淀粉的保护作用最佳;添加0.5%~1.0%的VC对大蒜素有保护作用,而当添加量大于1.5%时,大蒜素含量下降迅速。     

高效离子交换色谱法研究植酸酶对小猪肠道微生物的影响

植酸酶作为一种饲料酶制剂，可以通过催化水解将磷酸盐从植酸中释放出来，因而可以提高饲料中磷的利用率，降低环境的磷污染，但是，植酸酶作为一种饲料酶制剂，是否对动物肠道微生物产生影响，并通过改变肠道菌群的生理平衡来影响动物的消化与吸收，这一问题尚没有明确的答案。本研究植酸酶在仔猪的玉米一豆粕型日粮中添加植酸酶，并利用色谱的手段对对照组和试验组小猪肠道微生物色谱行为进行表征，并分析了各菌群的糖苷酶及蛋白酶的活力分：布，发现添加植酸酶可以促进糖苷酶分泌型细菌的生长，这一数据对植酸酶在体内的作用机理提出了新的思路。     

植酸的抗营养作用及植酸酶在饲料中的应用(二)

５应用植酸酶制剂应考虑的几个具体问题５．１动物种类及年龄植酸酶制剂仅适用于各种非反刍动物。目前研究报道较多的是将植酸酶制剂用于鸡和猪。动物消化道中植酸的降解实际上有３种来源的植酸酶参与，即饲料中的植酸酶（包括植物性饲料中存在的植酸酶和添加的外源性植酸...     

添加酶制剂改善"双低"菜籽粕营养物质及能量代谢的研究

本试验研究了在“双低”菜籽粕中添加植酸酶、以及木聚糖酶、β—葡聚糖酶、果胶酶、纤维素酶等非淀粉多糖酶后营养物质代谢率和能量代谢率的变化情况，以及各种酶制剂的最佳添加水平。试验结果表明：添加植酸酶、木聚糖酶、β—葡聚糖酶、果胶酶可以改善“双低”菜籽粕中粗蛋白质、氨基酸的利用率及能量、粗脂肪、干物质、粗纤维的代谢率，并且酶制剂的添加量增加，“双低”菜籽粕中营养物质和能量的代谢率得到改善的幅度越大。     

酶制剂在面包粉改良中的应用

酶制剂是改良面包粉品质的有效途径,改良面包粉的酶制剂主要有淀粉酶、葡糖糖氧化酶、戊聚糖酶、脂肪氧化酶、脂肪酶、蛋白酶、谷氨酰胺转氨酶、植酸酶等,其作用机理和作用各不相同。面包粉中酶制剂既可以单一应用,也可以将多种酶复配应用,还可以和其它添加剂如乳化剂搭配应用,复合酶制剂效果更佳。     

外源酶对糙米中植酸降解的影响

利用外源酶制剂降解糙米中的抗营养因子植酸,以提高糙米营养价值。以植酸降解量为指标,考察pH值、温度、酶作用时间和加酶量对外源植酸酶作用的影响,并考察纤维素酶和果胶酶与植酸酶的协同作用效果。结果显示植酸酶作用的适宜条件为：酶用量0.4U/mL,作用温度50℃,pH5.2,浸泡时间4h;添加纤维素酶和果胶酶能有效促进植酸酶的降解作用,大大提高植酸降解率。外源酶制剂能有效降解糙米中的植酸。     

酶制剂在面包粉改良中的应用

酶制剂是改良面包粉品质的有效途径,改良面包粉的酶制剂主要有淀粉酶、葡糖糖氧化酶、戊聚糖酶、脂肪氧化酶、脂肪酶、蛋白酶、谷氨酰胺转氨酶、植酸酶等,其作用机理和作用各不相同.面包粉中酶制剂既可以单一应用,也可以将多种酶复配应用,还可以和其它添加剂如乳化剂搭配应用,复合酶制剂效果更佳.     

不同糖类对乌龙茶饮料品质稳定性的影响

茶饮料品质稳定性一直是饮料开发中重点关注的问题之一,不同糖类的添加对茶饮料色泽、风味品质和理化成分的稳定性影响效果不同。本文研究了不同糖类（白砂糖、果葡糖浆、赤藓糖醇）对乌龙茶饮料灭菌以及贮藏期间感官品质和理化成分的影响,结果表明,与对照组（未添加任何糖）相比,灭菌过程中,糖类对茶汤色泽的保护效果为赤藓糖醇>白砂糖>对照组>果葡糖浆,对风味品质的提高或保护效果为白砂糖>赤藓糖醇≈果葡糖浆>对照组,对维生素C和儿茶素的保护效果为赤藓糖醇>白砂糖>对照组>果葡糖浆,对茶多酚和咖啡因的影响不大;贮藏期间,糖类对茶汤色泽的保护效果为赤藓糖醇>白砂糖>对照组>果葡糖浆,对风味品质的提高或保护效果为白砂糖>赤藓糖醇>果葡糖浆>对照组,对茶多酚的保护效果为赤藓糖醇>白砂糖>对照组>果葡糖浆,对儿茶素的保护效果为赤藓糖醇≈白砂糖≈对照组>果葡糖浆,对咖啡因均没有显著影响。     

酶制剂对杂粮面包品质的影响

以小麦粉、小米粉、绿豆粉和荞麦粉为主要原料制作杂粮面包,通过分别研究α-淀粉酶、脂肪酶和木聚糖酶作为单一酶制剂和复合酶制剂对该种面包制作效果的影响及分析作用机制,优化杂粮面包的制作工艺技术。结果表明,单独添加α-淀粉酶能够明显增大面包体积,改善其口感和滋味;单独添加脂肪酶能改善面包色泽和切面纹理结构,但同时导致面包体积减小,口感发粘;单独添加木聚糖酶后,能够加速面团的发酵,提高面包制作过程的可操作性和稳定性;而三种酶制剂复合使用时,能产生协同效应,有效改善杂粮面包品质并且降低了酶制剂添加总量。     

五种单体酶配伍对肉仔鸡生长性能及非淀粉多糖消化率的影响

研究在小麦基础日粮中添加五种单体酶制剂(木聚糖酶、β-葡聚糖酶、纤维素酶、植酸酶和甘露聚糖酶)对1～21日龄肉仔鸡生长性能和非淀粉多糖(NSP)消化率的影响。试验将624只1日龄肉仔鸡按均匀设计方法随机分成13组,其中第13组为对照组,各处理组日粮为上述五种单体酶制剂的不同配伍添加在基础日粮中组成。结果表明,五种单体酶制剂的不同配伍能不同程度提高肉仔鸡生长性能和NSP的消化率。其最佳的配伍水平为:木聚糖酶450 u·kg-1、β-葡聚糖酶47 u·kg-1、纤维素酶333 u·kg-1、植酸酶135u·kg-1、甘露聚糖酶153 u·kg-1。     

聚乙烯醇环氧化载体制备及在植酸酶固定化中的应用

该文以聚乙烯醇为原料,利用戊二醛为交联剂,聚合得到交联球形聚乙烯醇,并将其与环氧氯丙烷反应用以固载环氧基团,得到可用于酶固定化的载体。讨论了交联聚乙烯醇球环氧基的固载条件和酶的固定化条件。植酸酶经过固定化后,机械性能和化学稳定性都得到提高,可以重复多次对植酸钠进行水解反应。同时对该自由酶和固定化酶进行酶学特性研究。发现自由酶和固定化酶的最适pH值分别为5.5和7.0,最适反应温度分别为55℃和70℃。植酸酶经固定化,提高了酶的操作、温度、pH值和贮藏稳定性。     

Effects of pre‐freezing,puree content and pasteurisation regime on colour stability of strawberry nectar made from puree

BACKGROUND: Heat treatment during processing of strawberry products has been proposed to negatively affect colour stability. Moreover, the role of enzymes with respect to colour stability is ambiguous when consulting the existing literature. The aim of the present study was to investigate the impact of various processing parameters (pre‐freezing, puree content, pasteurisation temperature and heating time) on the colour stability and anthocyanin monomer and L ‐ascorbic acid contents of strawberry nectars made from puree. In addition, the effect of different enzyme activities on colour stability during storage of strawberry nectars was investigated. RESULTS: Pre‐freezing of strawberries before processing had a significant positive effect on the colour stability of nectars made from puree. No significant effect on colour stability was found for higher puree contents. Increasing both the pasteurisation temperature and the heating time had a significant positive effect on colour stability. Results showed that colour degradation during storage was mainly due to residual enzyme activities. The shelf‐life of strawberry nectar could be extended about fivefold by adding an enzyme inhibitor. CONCLUSION: The colour stability of strawberry nectar made from fresh puree may be improved to some extent by an appropriate pasteurisation regime. Enzymes play an important role in colour degradation during storage of the nectar. Inactivation of these enzyme activities, however, could not be achieved even after a heat treatment at 90 °C for 60 min. Copyright © 2008 Society of Chemical Industry     

Effect of collagen preparations used as carriers of potassium iodide on retention of iodine and thiamine during cooking and storage of pork meatballs

The application of collagen preparations as carriers of iodine salts in the production of meat dishes was investigated in this study. Meatballs with addition of collagen fibre or collagen hydrolysate, both impregnated with potassium iodide, were cooked and cold‐ or freezer‐stored. After thermal processing and during storage of meatballs the iodine and thiamine contents were determined and compared to their contents in meatballs to which potassium iodide was introduced using iodized table salt. It has been shown that the application of both collagen preparations as carriers of potassium iodide increases the stability of this compound during cooking and storage of meatballs in comparison to its stability in products with iodized table salt. Collagen preparations, improving potassium iodide stability, also limit thiamine losses in the product. A more advantageous effect, both on iodine and thiamine retention, is achieved for the collagen preparation with a higher water binding capacity. Copyright © 2007 Society of Chemical Industry     

Physicochemical properties of soy protein prepared by enzyme‐assisted countercurrent extraction

Synchronous improvements of both nutritional properties and the flavour of protein by optimising preparation processes are highly challenging. The prehydrolysis of soy meals by cocktail enzyme (β‐glucosidase, phytase and acid protease) treatment and subsequent countercurrent extraction were designed based on similar hydrolysis conditions. The composition, flavour volatiles and physicochemical properties of soy proteins were investigated. Compared to alkaline extraction and acid precipitation, enzyme‐assisted countercurrent extraction significantly increased protein yield and carbohydrate content, accompanied by a decrease in protein purity. This protein exhibited larger molecular weight distribution, less flavour volatiles, higher thermal stability and surface hydrophobicity, as evidenced by higher denaturation temperature (T_d) and enthalpy change (ΔH) of protein. The conversion of isoflavone glycosides to aglycone and the partial degradation of phytic acid were observed for enzyme‐prepared soy proteins. These results suggest a feasible protocol for producing a nutrient‐improved soy protein with excellent flavour and thermal stability.     

HYDROLYSIS OF PHYTATE IN BROWN RICE-ADDED BREAD BY ADDITION OF CRUDE AND PURIFIED ASPERGILLUS NIGER PHYTASE PREPARATIONS DURING BREAD MAKING

Brown rice-added breads were prepared with and without crude and purified Aspergillus niger phytase preparations. By adding 30% (w/w) brown rice flour and no phytase preparation, the phytate (myo-inositol hexaphosphate; IP₆) content of the bread was increased and the loaf volume was reduced. The direct addition of a food-additive grade phytase preparation (3,000 U) resulted in a significant decrease in the IP₆ content. However, it collapsed the bread crust. The crude phytase preparation had significant protease and amylase activities. A simple chromatographic method for the separation of phytase activity from the protease and amylase activities was developed. By using purified phytase, the IP₆ content was reduced without any adverse effects on the rising of the bread, which indicates that protease and amylase may be responsible for the collapse of the crust by the commercial phytase preparation.

PRACTICAL APPLICATIONS

Phytate in unrefined cereals and beans lowers bioavailability of minerals. On the other hand, these materials are rich in health-promoting components. To reduce the phytate in them during processing, some commercially available phytase preparations are now used. However, we found that such preparation contains significant amylase and protease activities, which may cause adverse effect on the appearance and textural properties of final products. To solve these problems, a simple and inexpensive procedure for separation of phyatase from amylase and protease was developed in the present study. The purified phytase can reduce phytate in brown rice-added bread without adverse effect on rising of bread. These results would encourage prepare the phytase preparation in high purity in an industrial scale to improve nutritional value of unrefined cereal- and bean-based functional foods.     

氯化盐处理对绿豆芽菜植酸降解的影响

为降低绿豆芽菜中抗营养物质植酸含量,探究氯化盐对绿豆芽菜植酸降解的影响,研究了KCl、NaCl和CaCl2处理下绿豆芽菜的长势、植酸酶活性及植酸含量的变化,筛选了具有降植酸效果的氯化盐并优化了浓度组合。结果发现,NaCl和CaCl2能够促进植酸降解同时促进绿豆芽菜生长;单因素试验结果表明,1.6 mmol/L NaCl和6 mmol/L CaCl2降植酸效果最佳,且NaCl和CaCl2促进植酸降解作用有叠加效应。响应面法优化得到NaCl、CaCl2浓度分别为1.68 mmol/L和6.40 mmol/L时,植酸含量降低至8.04 μg/株,为对照的10.84%。     

Influence of selected factors on functional properties of textured milk proteins

Studies were made on the influence of two variable factors—fat content and added salt—on the following functional properties of textured milk proteins: water absorption capacity, thermal shrinkage, consistency, viscosity, fat absorption, emulsifying capacity and emulsion stability.
Variation in fat content of the product (11% and 15%) was obtained by introducing various amounts of fat to skim milk in the course of the production of textured milk proteins. The salt concentration of the preparation was modified by adding sodium chloride, Hamine polyphosphate mixture or both those salts jointly.
The results indicate that the functional properties of the preparation were influenced by the two above mentioned factors in a statistically significant manner. The higher fat content of the product (15%) was accompanied by better fat emulsifying capacity and emulsion stability and lower thermal shrinkage. The salts used for these studies were found to influence favourably the functional characteristics of the preparation. The addition of sodium chloride appears to be most expedient, as it improves important technological properties such as fat absorption and emulsifying capacities.     

Production of phytase by Aspergillus ficuum and reduction of phytic acid content in canola meal

Production of the phytase (EC 3.1.3.8) from Aspergillus ficuum in a submerged batch process was inhibited by high concentrations of glucose. The inhibition was overcome by applying a fed batch technique in the production of the enzyme. Tests carried out at different oxygen concentrations revealed that aeration had a beneficial effect on the production of the enzyme. The enzyme showed an optimum pH and temperature of 5·0 and 60°C, respectively. Preincubation of the enzyme preparation at 60°C resulted in relatively fast denaturation of the enzyme. Upon storage at 4°C it lost only 15% of its activity in 5 weeks. Aspergillus ficuum also produced phytase when grown on canola meal by a solid state technique. The enzyme catalysed degradation of the phytic acid present in the meal and completely eliminated it, rendering the commodity more suitable for animal feed. An apparent 10% increase in protein content of the canola meal was noted as a result of the growth of the microorganism.     

单宁酸功能化Fe3O4磁性纳米粒子固定化微泡菌褐藻胶裂解酶的工艺条件优化

该研究探讨单宁酸功能化Fe3O4磁性纳米粒子固定化微泡菌褐藻胶裂解酶的工艺条件.以单宁酸功能化磁性纳米粒子(TA-MNPs)作为固定化酶的载体,通过测定固定化酶的活力和酶活回收率优化微泡菌褐藻胶裂解酶的固定化条件,并利用傅里叶变换红外光谱和透射电镜对固定化酶的结构进行了表征.结果表明,固定载体量为10 mg时,微泡菌褐...