Cheese-making properties of vegetable rennet from sodom apple (Calotropis procera)

Yield, chemical composition and texture profile of cheese made with vegetable rennet from sodom apple leaves were compared with those of a direct acid cheese made with calf rennet. Yield, moisture, fat and protein contents were 14·47%, 49·70%, 26·15% and 20·0%, respectively, for cheese made with vegetable rennet and 12·45%, 44·80%, 29·84% and 20·4%, respectively, for the direct acid cheese made with calf rennet. Cheese made with vegetable rennet had less soluble nitrogen than that made with calf rennet despite the fact that vegetable rennet was more proteolytic in casein solution than calf rennet. Relative to that made with calf rennet, cheese made with vegetable rennet was harder, less cohesive and more gummy, presumably because of differences in chemical composition and physical characteristics between the cheeses.     

甲醇芽孢杆菌凝乳酶对马苏里拉干酪加工特性的影响

为了探究甲醇芽孢杆菌（Bacillus methanolicus）凝乳酶在马苏里拉干酪加工中的应用,分别以使用甲醇芽孢杆菌凝乳酶、混合酶制剂（含质量分数10%甲醇芽孢杆菌凝乳酶和90%商品凝乳酶）制作的马苏里拉干酪作为实验组,以商品凝乳酶干酪作为对照组,测定不同组别干酪成熟期间的蛋白水解特性、质构、风味和微观结构变化,研究甲醇芽孢杆菌凝乳酶对马苏里拉干酪加工特性的影响。结果表明,实验组干酪在成熟过程中pH值（4.6～5.3）、微生物数量（8.80～9.68（lg（CFU/g）））与对照组无显著差异（P＞0.05）;实验组干酪水分质量分数（混合酶干酪为（43.21±1.17）%、甲醇芽孢杆菌凝乳酶干酪为（46.15±0.94）%）均显著高于对照组（（41.08±1.04）%）,得率（混合酶干酪为（9.27±0.17）%、甲醇芽孢杆菌凝乳酶干酪为（9.46±0.16）%）也显著高于对照组（（8.98±0.13）%）（P＜0.05）;且实验组干酪的蛋白水解特性（pH 4.6时可溶性蛋白、酪蛋白水解程度和游离氨基酸质量分数）以及风味物质种类和相对含量等指标也优于对照组干酪。但是实验组中甲醇芽孢杆菌凝乳酶干酪保形性相对欠佳,感官评定得分偏低,混合酶干酪与对照组质构及感官基本得分一致,因此甲醇芽孢杆菌凝乳酶可以作为商品酶的部分代替品应用于干酪的生产中。     

Insights into milk-clotting activity of latex peptidases from Calotropis procera and Cryptostegia grandiflora

Latex fractions from Calotropis procera, Cryptostegia grandiflora, Plumeria rubra, and Himatanthus drasticus were assayed in order to prospect for new plant peptidases with milk-clotting activities, for use as rennet alternatives. Only C. procera and C. grandiflora latex fractions exhibited proteolytic and milk-clotting activities, which were not affected by high concentrations of NaCl and CaCl₂. However, pre-incubation of both samples at 75 °C for 10 min eliminated completely their activities. Both proteolytic fractions were able to hydrolyze k-casein and to produce peptides of 16 kDa, a similar SDS-PAGE profile to commercial chymosin. RP-HPLC and mass spectrometry analyses of the k-casein peptides showed that the peptidases from C. procera or C. grandiflora hydrolyzed k-casein similar to commercial chymosin. The cheeses made with both latex peptidases exhibited yields, dry masses, and soluble proteins similar to cheeses prepared with commercial chymosin. In conclusion, C. procera and C. grandiflora latex peptidases with the ability to coagulate milk can be used as alternatives to commercial animal chymosin in the cheese manufacturing process.     

苹果中正己醇降解酶的提取

采用不同方法从苹果中提取正己醇降解酶,优选最适的提酶方式,并在该提取方式下研究酶的初步分离纯化。结果显示:采用丙酮粉法提酶较适合,且SDS-PAGE电泳结果表明不同方法提取粗酶液和经硫酸盐处理后的蛋白在条带数量和分布上都有所变化。30%~70%为适宜的(NH4)2SO4盐析浓度,然后对酶液进行梯度盐析,初步纯化后正己醇降解率为88.56%±0.9847%。     

苹果中正己醇转化酶的提取及其特性研究

采用丙酮粉法提取苹果中的正己醇转化酶,研究其在粉剂和溶液状态下的低温贮藏稳定性以及温度和pH对粗酶液正己醇转化能力和稳定性的影响,绘制最适作用条件下粗酶液的反应曲线,考察正己醇初始浓度对反应速度的影响。试验结果表明,正己醇转化酶粉剂在贮存过程中能够很好地保持酶的活性;当正己醇质量浓度为1.3g/L时,酶的最适反应温度和稳定温度均为37℃,最适反应pH4.6,最适稳定pH5.4,最适反应时间2h;正己醇的最适底物质量浓度为0.7g正己醇/L;Fe2+、K+和Zn2+对酶的催化活性有促进作用,在较适浓度(分别为0.1、0.05、0.5mol/L)条件下,酶对正己醇的转化率分别提高1.48、1.10、1.08倍。     

姜汁凝乳的研究

分别以生姜挥发油及生姜蛋白酶粗提物进行凝乳试验,结果发现生姜挥发油不能凝乳,生姜蛋白酶能凝乳。探讨了影响凝乳的因素及其机理。     

莲雾花色苷提取工艺

以莲雾花为原材料,采用超声波辅助果胶酶法对莲雾花色苷提取工艺进行研究。确定超声波辅助果胶酶法提取莲雾花色苷工艺最佳条件,即:果胶酶浓度4.5 mg/g、pH 2.8、超声波时间30 min、超声波功率300 W。试验发现,在4~50℃环境下莲雾花色苷比较稳定。     

腰果梨抑菌活性物质提取工艺优化

对腰果梨抑菌活性物质的提取工艺进行研究,分析比较提取物对不同测试菌的抑菌效果。以金黄色葡萄球菌和白色念珠菌为指示菌,在单因素试验基础上通过中心组合试验设计分别对黄色、红色两种不同色泽腰果梨进行提取工艺优化。得出黄色腰果梨最佳提取工艺：乙醇体积分数70%,提取温度85℃,料液比1:13.9,提取时间2.65h;红色腰果梨最佳提取工艺：乙醇体积分数70%,提取温度85℃,料液比1:14.5,提取时间2.44h。经工艺优化后腰果梨提取物显著提高了抑菌效果。     

超声波辅助提取苹果渣多酚工艺

研究了超声波辅助提取苹果渣中多酚的工艺,利用二次回归正交旋转组合设计考察了乙醇体积分数、料液质量体积比、提取温度、提取时间对苹果渣中多酚物质提取率的影响;试验结果表明,各因子对提取率的影响大小依次是提取温度＞料液质量体积比＞提取时间＞乙醇体积分数;最佳提取工艺条件是:乙醇体积分数50%、料液比1 g:20 mL、提取温度60℃、提取时间24min;此条件下苹果多酚的提取率为3.80 mg/g.     

Phytochemical and Antimicrobial Evaluation of Aqueous and Organic Extracts of Calotropis procera Ait Leaf and Latex

The aqueous and ethanol extract of Calotropis procera leaf and latex were investigated. The leaves and latex from the plant were tested for antimicrobial activities. The bioactive constituents extracted from the leaf and latex were tested against pathogenic organisms (Eschericia coli, Salmonella typhi, Bacillius subtilis, Candida albicans, Aspergillus niger) using the Agar well diffusion method. The ethanolic latex extract showed significant activity against all the test organisms. The results revealed that ethanol is a more effective extractive solvent for antimicrobial activity of leaf and latex of C. procera. The ethanol extract of the latex gave the widest zone of inhibition (21 mm) against B. subtilis. All the extracts inhibit the growth of all the organisms except B. subtilis of which the aqueous extract has no effect. The Minimum Inhibitory Concentration (MIC) for the latex extract was between 3 and 7.5 mg/ml for bacteria, and 5.0 to 7.0 mg/ ml for fungi. For the leaf extract the MIC for bacteria was between 5.0 and 10.5 mg/ml and 11 and 15 mg/ml for fungi. The results also showed an increase in antimicrobial activity with increase in temperature. This study therefore revealed that C. procera latex extract demonstrated strong and better inhibitory activity on the test organisms than the leaf extract. These findings therefore provide an explanation for the traditional medicinal use of C. procera extracts.     

Modeling Milk Clotting Activity in the Continuous Production of Microbial Rennet from Mucor miehei

Production of microbial rennet, a milk clotting enzyme, from a commercial strain of Mucor miehei (NRRL 3420) was investigated in a continuously fed fermenter system for prolonged periods. The spherical film-wise growth of the culture has been accomplished and the effects of medium pH, mixing and dilution rates, and feed of D-glucose concentration on milk clotting activity was investigated. In model simulation studies, maximum milk clotting activity was generated from a multiple linear function. This was expressed in terms of fermentation medium pH, D-glucose, dissolved oxygen concentrations and dilution rate at the time of maximum milk clotting activity.     

苹果果肉中原花青素超声波的辅助浸提

以苹果品种"瑞林"为试材,通过正交试验比较研究了超声波辅助法与传统溶剂法提取苹果果肉中原花青素的效果,经筛选优化了苹果原花青素提取的技术参数.结果表明:超声波辅助法提取苹果果实中的原花青素的最佳条件为:乙醇体积分数50%、PH值为4、温度70℃.在此条件下提取2 h后,原花青素的最大提取量为0.14 mg/g;传统溶剂法提取苹果中原花青素的最佳条件为乙醇体积分数80%、pH值为4、温度90℃.在此条件下提取2 h后,原花青素的最大提取量为0.126 mg/g.利用超声波辅助增强了苹果果肉中原花青素的乙醇提取效果,即降低了提取温度,减少了溶剂用量,并使提取量增加了10.9%.     

Extraction and Characterization of Pectin from Apple (Malus Pumila. Cv Amri) Peel Waste

Abstract

Apple peel, the major waste in preserves manufacturing, contained 1.21% pectin. Peel waste could be stabilized with 600 ppm sulphur dioxide and 1% citric acid. Pectin extraction was better in citric acid than hydrochloric acid. The pectin powder was prepared by triple extraction with citric acid solution (1%) clarification through sedimentation, concentration (24°B), precipitation using ethyl alcohol, vacuum drying and grinding. Physico-chemical properties of pectin powder revealed moisture (10.0%), total ash (1.4%), equivalent weight (652.48), methoxyl content (3.7%), anhydrouronic acid (62.82%), degree of esterification (33.44%), acetyl value (0.68), and jelly grade (80).     

Effect of silk flower hay (Calotropis procera Sw) feeding on the physical and chemical quality of Longissimus dorsi muscle of Santa Inez lambs

The effect of different levels of silk flower hay (Calotropis procera Sw) in the diet of confined lambs by the substitution of the commonly used foraging broom corn hay (Sorghum bicolor L) was investigated to evaluate its possible effects on the growth and quality of the lamb meat. Twenty-four male Santa Inez lambs were divided in equal numbers into four treatment groups and fed diets containing 0%, 16.7%, 33.3% and 50% of silk flower hay (SFH). Growth rate, feed intake and meat quality were investigated. Mean daily gains of lambs were 170 g for control, 180.5 g for 16.7% SFH, 96.8 g for 33.3% SFH and 22.9 g for 50% SFH. The use of silk flower hay in the diet of Santa Inez lambs affected health of the animals and meat pH when the substitution of the forage was high, up to 50%; however, the general meat quality was not affected. Meat from animals fed with levels up to 50% SFH had physical (Aw, a^*, b^* and L^*) and chemical (moisture, ash, lipid, phosphorus, iron, phospholipid and fatty-acid profile) parameters comparable to the control group (0% SFH). Among the various levels of substitution (16.7%, 33.3% and 50%) of silk flower hay in the diet tried in this work, the use of 16.7% was found to be an attractive and technically viable option for the Northeast region of Brazil.     

酶法提取鲢鱼鱼骨食用明胶的工艺研究

以鲢鱼鱼骨为研究对象,采用酶法提取食用明胶。以明胶产率最大化,产品质量能够达到食用级别为目标,对明胶的酶解过程进行优化,然后按照食用明胶的国家标准对明胶产品的理化指标和微生物指标进行检测。结果表明:鲢鱼鱼骨明胶的提取中酶解过程的最优工艺条件为:p H 2、37℃、胃蛋白酶用量0.02 g/g干骨、时间3.5 h、料液比为1∶6.5。在最佳工艺条件下,鱼骨明胶的产率达到19.6%。对明胶产品的理化指标和微生物指标的测定,表明鲢鱼鱼骨明胶符合食用级明胶的规定,并且其凝冻强度和勃氏黏度均较高,质量较优。     

微波辅助提取苹果皮中果胶的研究

讨论利用微波辐射萃取法从苹果皮中提取果胶的不同因素的影响,通过实验确立微波条件下提取果胶的最佳工艺条件为:用盐酸调pH为1.8,用水作为溶剂,料液比为1∶20(g/mL),微波辐射功率为600 W,辐射时间为4 min,乙醇浓度为60%,提取率可达到12.9%。     

苹果多酚的提取及抗氧化活性研究

通过单因素及正交试验,对苹果多酚的提取工艺进行研究。确定苹果多酚的最佳提取工艺为乙醇体积分数30%、温度70℃、料液比1:6、提取时间45min,此时苹果多酚的含量为9.032mg/g。采用DPPH法和亚铁还原能力(ferric reducing ability of plasma,FRAP)法对苹果多酚的抗氧化活性进行研究,结果显示,它对DPPH自由基的清除率达到94.6%,此时其FRAP值为546.4μmol/L。