Effects of Ultrasound Treatment on the Properties of Chymosin

When chymosin was extracted by ultrasound curd tension and syneresis were significantly lower for Berridge substrate coagulated by the ultrasound-treated chymosin than by the control. Experimental chymosin had a shorter induction period and was more heat-sensitive than the control. Activation energy of chymosin obtained by ultrasound treatment was significantly lower than that of the control. Ultrasound treatment did not significantly change the chromatographic patterns of chymosin. Only two distinct enzymatically active proteins were observed with DEAE-cellulose chromatography. Electrophoretic properties were similar for chymosins obtained by ultrasound and control methods.     

Processing Parameters of Chymosin Extraction by Ultrasound

Conventional chymosin (rcnnin) production requires a prolonged extraction. An ultrasound method of chymosin extraction was developed for increased efficiency. Ultrasound extraction was carried out with Tekmar sonic disruptor (TK 1000) and Lauda circulator. Control extraction was carried out by shaking. The use of ultrasound resulted in a significant reduction of extraction time with increases in activity and yield of chymosin. The optimal parameters for ultrasound extraction were: specific intensity, 36 W/cm² at 20 kHz frequency; time of exposure, 80 min; temperature, 25°C; ratio of abomasa to extraction solution, 1:25; and activation time of prochymosin, 13.0-13.5 hr.     

Comparison of Conventional and Ultrasound Assisted Extraction Techniques of Yellow Tea and Bioactive Composition of Obtained Extracts

Yellow tea is the least investigated type of tea (Camellia sinensis), therefore, this study is focused on characterization of bioactive content of yellow tea extracts as well as application of inovative extraction techniques (ultrasound bath and probe) compared to conventional extraction, in water and aqueous ethanol media. Comparison of obtained extracts was based on total flavonoid (TFC) and nonflavonoid (TNC) content, HPLC analysis of individual polyphenols and methylxanthines, and antioxidant capacity. The highest TFC was detected in extracts obtained by ultrasound probe assisted extraction in aqueous ethanol as an extraction medium and the lowest in extracts obtained by ultrasound bath extraction (water and aqueous ethanol) with a trend of increase with prolonged extraction time. Conventional extraction was successful when combined with 75% aqueous ethanol as an extraction medium. Results of HPLC analysis and antioxidant capacity assays were generally in compliance with these results. This study proves that ultrasound probe extraction could succesfully be used for extraction of polyphenols and methylxanthines from yellow tea.     

苹果木烟熏液的品质特性

以苹果木烟熏液为研究对象,从感官品质、pH值、羰基化合物、酚类化合物、苯并（a）芘的含量、挥发性风味物质的组成和电子鼻分析等角度研究苹果木烟熏液的性质,并与目前市场上烟熏液产品进行比较。结果表明,苹果木烟熏液pH值为2.31,酚类化合物、羰基类化合物的含量分别达到9.94 mg/mL和7.91 g/100 mL,挥发性风味物质以酚类物质和醛类为主,相对含量分别为36.15%和17.58%,通过电子鼻主成分分析发现,苹果木烟熏液与其他几种烟熏液之间主成分有显著性差异,与市场其他烟熏液相比,在核心成分和特征性风味物质均有明显的优势,同时无苯并（a）芘检出,表明苹果木烟熏液具有良好的应用前景。     

Taste of Water-Soluble Extracts Obtained from Over-Fermented Tempe

Over-fermented tempe, known as tempe semangit, is popular in Indonesian culture, especially in Java, as an umami seasoning in traditional foods. The objective of this study was to characterize taste-active compounds in water soluble extracts of over-fermented tempe. Over-fermented tempe was prepared from fresh tempe in which the fermentation was prolonged (0 to 96 h). Free amino acids in the water soluble extract were analyzed and characterized for their taste activity values. Water soluble extracts contained umami and bitter tasting free amino acids at relatively high concentrations. Their umami and bitter taste activity values were higher than the taste threshold concentration. Water soluble extract from 72 h over-fermentation had a higher umami taste activity value than bitter taste activity, exhibiting the highest umami taste dilution factor. The high-performance liquid chromatography profile of water soluble extract fractions obtained using Sephadex G-25 gel filtration chromatography demonstrated that fractions having higher umami taste intensity had more hydrophilic components than hydrophobic components.     

Effect of Ultrasonic Treatment on the Extraction of Chymosin

Improvement of chymosin (rennin) production is limited by a prolonged extraction process. An ultrasonic method of chymosin extraction was developed to increase efficiency. The application of ultrasonic energy significantly reduced time required for the extraction process as a result of abomasum tissue dispersing, destruction of the cells, intensive blending, separation of particles, and increase of the interphase abomasum-extraction medium. The ultrasonic extraction process significantly increased yield of chymosin.Optimal technological parameters for extraction and properties of extraction medium were established: time of ultrasonic treatment (45 min), intensity of ultrasound (3.34 W/cm²), temperature of extraction medium (15°C), NaCl concentration in solution (5%), ratio of abomasum to extracting solution (1:18), NaCl concentration in solution (5%), ratio of abomasum to extracting solution (1:18), pH of solution (4.2 to 4.3), time of chymosin extract activation (7 h), degree of abomasum shredding (strips 5 to 8 mm wide), and time of abomasum swelling (20 min).     

生姜超临界CO2萃取物的抗氧化性研究

人们食用生姜有悠久的历史。生姜作为一种常用的辛香料，具有很好的抗氧化作用，它对于保障人们的健康、抗老防衰、防止食品腐败具有十分重要的意义。将不同方法提取得到的生姜提取物，以不同的浓度进行抗氧化性实验。采用Na2S2O3—I2滴定法及DPPH法测定了生姜提取物的抗氧化性。通过实验证明，生姜超临界CO2萃取物比生姜乙醇提取物对DPPH自由基清除活性要强。生姜超临界CO2萃取物在最佳浓度为0．20％（提取物与猪油的质量比）时对猪油的抗氧化性能最强。与乙醇浸提物相比，添加浓度相同时，生姜超临界CO2萃取物比生姜乙醇提取物最佳浓度为0．15％（提取物与猪油的质量比）时对猪油的抗氧化性更强。柠檬酸、酒石酸、抗坏血酸对生姜的超临界CO2萃取物有比较明显的协同效应，其中与抗坏血酸的协同作用最强。     

发酵法生产凝乳酶的概述

凝乳酶是干酪生产过程中的关键性酶,其主要作用是凝聚牛奶中的酪蛋白.本文简要介绍了凝乳酶的起源和它的凝乳机制.并着重阐述了微生物源凝乳酶的特点及研究者们在提高微生物凝乳酶活性降低其蛋白分解活力上所做的研究.     

崂山蘑菇抗氧化成分提取及其活性研究

用1：1的氯仿：甲醇超声提取崂山蘑菇成分，并用石油醚、乙酸乙酯和正丁醇依次进行萃取，利用DPPH法、α-脱氧核糖法和铁氰化钾还原法进行抗氧化实验。同时与BHT、没食子酸丙酯（PG）、没食子酸（GA）和抗坏血酸（AscA）4种合成抗氧化剂进行对照。结果显示乙酸乙酯提取物（EAF）具有较高的抗氧化活性。对其进行硅胶柱层析分离，得到6种纯化的组分（EAF—EAF6），其中EAF4具有最高的抗氧化活性，在50μg／ml浓度时，其清除DPPH自由基能力仅比AscA稍弱，比BHT、PG和GA强；清除羟自由基能力在所有测定浓度下（0．4、2、10、50μg／m1）均比4种合成抗氧化剂强；还原能力在所有测定浓度下均比BHT强；在10μg／ml时，比PG强：50μg／ml时，与PG相当。测定了崂山蘑菇各提取物总酚含量，结果发现总酚含量与抗氧化活性之间具有很好的相关性。     

微生物源凝乳酶的研究进展

本文简要介绍了凝乳酶的一般特性和凝乳机理 ,综述了微生物源凝乳酶的研究进展和利用基因工程生产凝乳酶的发展状况 ,最后对凝乳酶的生产与开发进行了展望     

超声处理对鹿茸菇贮藏品质的影响

为探究超声处理对鹿茸菇贮藏品质的影响,本实验以新鲜鹿茸菇为试材,经超声(35 kHz、300 W)处理10 min后,测定鹿茸菇感官品质及能量代谢相关酶等相关指标。结果表明,超声处理相较于对照组可以维持鹿茸菇较高的亮度,并保持较高的总蛋白、抗坏血酸、谷胱甘肽含量,提高总超氧化物歧化酶活力,明显降低褐变程度。与对照组相比,贮藏期间超声处理组ATP、还原型烟酰胺腺嘌呤二核苷酸磷酸(nicotinamide adenine dinucleotide phosphate,NADPH)、氧化型NADPH(oxidized NADPH,NADP⁺)含量处于较高水平,6-磷酸葡萄糖脱氢酶、H⁺K⁺-ATPase、Na⁺K⁺-ATPase、Ca²⁺Mg²⁺-ATPase活力较高,表明超声处理延缓了鹿茸菇品质劣变现象。因此,超声保鲜可以为采后食用菌保鲜提供参考。     

重组毕赤酵母生产凝乳酶发酵优化

为了获得毕赤酵母生产凝乳酶的最佳发酵条件,分别从起始诱导OD600、甲醇诱导浓度以及p H等方面研究了P.pastoris GS115在3.6 L发酵罐中表达微小根毛霉来源凝乳酶的高密度发酵,以恒溶氧反馈调节补加甘油和甲醇检测流加控制器在线监测流加甲醇。结果表明,在重组P.pastoris GS115/p PIC9k-chy起始诱导,OD600和甲醇诱导体积分数分别为150和2.0%,诱导p H为5.0时,发酵96 h凝乳酶活达到最大,为1 870 SU/m L,此时对应的生产强度和产物得率均达到最高水平,分别为19.48 SU/(m L·h)和2.42 SU/m L,总蛋白质质量浓度为0.64 mg/m L,凝乳活性与蛋白质水解活性的比值(MCA/PA)为63.43。     

小种红茶与工夫红茶品质特性的比较分析

以同一茶树品种、同一等级鲜叶制成的小种红茶和工夫红茶为研究对象,通过检测其主要生化成分、茶汤物理特性和挥发性化合物,对小种红茶和工夫红茶的品质特性进行比较分析。结果表明：小种红茶的茶多酚含量显著高于工夫红茶,咖啡碱、茶黄素、茶红素含量显著低于工夫红茶,可溶性糖、可溶性蛋白、游离氨基酸含量与工夫红茶相比差异不显著;工夫红茶的色差a*、b*值分别为8.38、39.19,沉淀量为246.78 mg/L,均显著高于小种红茶,小种红茶的色差L*值为29.16,透光率为76.53%,均显著高于工夫红茶,表明工夫红茶汤色较黄和较红,而小种红茶的茶汤澄清度更高;经检测和计算挥发性化合物的气味活度值（odor activity values,OAVs）,小种红茶和工夫红茶中OAVs大于1的香气成分分别有11 种和13 种,两者的香型分别为甜香浓郁和花香明显,其中小种红茶的主要呈香物质包括β-紫罗酮、苯甲酸甲酯、芳樟醇等,工夫红茶的主要呈香物质包括β-大马酮、β-紫罗酮、苯甲酸甲酯、己醛等;工夫红茶特有且OAVs大于1的香气成分为β-大马酮和己醛,这2 种成分可能是工夫红茶香型区别于小种红茶的有效呈香化合物。     

微波和超声处理对麦麸研磨特性及全麦面团品质的影响

麦麸经过微波与超声处理后,研磨筛分成粗（280~450 μm）、中（154~180 μm）、细（≤71 μm）三种粒径,再将不同粒径麦麸回添至面粉中制成全麦面团,以此探究微波和超声处理以及不同粒径对全麦面团的全质构、动态流变学性质以及游离巯基的影响。麦麸的相对酶活与粒径分布表明,超声处理和微波处理均能较好提升稳定化效果和粉碎效率,且超声处理组的效果更好（P<0.05）。面团的品质显示,随麦麸粒径减小,微波处理组的硬度和胶黏性呈现下降趋势,内聚性呈现上升的趋势,超声处理组的硬度和胶黏性均小于微波处理组（P<0.05）;微波组弹性模量和黏性模量随着麦麸的粒径减小而减小,同种粒径时,超声处理组弹性模量和黏性模量均小于微波处理组;随麦麸粒径减小,各处理组的游离巯基含量逐渐降低,且超声处理组的游离巯基含量降低幅度大于微波处理组（P<0.05）。微波与超声处理及麦麸粒径的减小均能有效改善面团的品质,且超声处理的麦麸对面团品质影响相比微波组更显著。     

Characterization of Actin and Myosin Extracts Obtained Using Two Improved Laboratory Methods

Actin and myosin are the most important contractile proteins in the muscle. Numerous authors developed different methods for isolation and purification of myofibrillar proteins. The aim of this study was to obtain suitable actin and myosin extracts from post-rigor porcine muscle to be used in further studies, such as testing the proteolytic activity of microbial cultures. Actin and myosin were quantified in the extracts using spectrophotometric methods, yielding 0.17 and 0.22 mg/mL, respectively. The isolation methods proposed in this study provided low contaminated extracts, showing purity percentages of 74.36 % in the case of actin and 65.43 % for myosin, as determined by sodium dodecyl sulfate–polyacrylamide gel electrophoresis. Subsequently, these extracts were sterilized through a 0.22-μm polyvinylidene difluoride filter with no significant retention observed. In conclusion, the procedures described in this work for actin and myosin isolation can be recommended for microbiological studies requiring sterilized pure muscle proteins extracts.     

根霉产凝乳酶的固态发酵条件优化

对根霉产凝乳酶固体发酵条件进行研究。通过单因素分析和响应面试验设计,确定根霉产凝乳酶的发酵条件及发酵培养基的最佳组成为:24℃发酵7d;麸皮与江米质量比为0.96:1、培养基固液比(m/V)为0.99:1、奶粉添加质量分数为0.81%,所产的凝乳酶活力达到72.92SU/mL。     

超声处理对大豆分离蛋白凝胶和感官特性影响

采用超声技术对大豆分离蛋白进行处理,探索超声处理条件对大豆分离蛋白的凝胶特性和感官特性的影响。以20 k Hz超声频率在不同处理功率、时间、温度和大豆分离蛋白分散液p H值对大豆分离蛋白进行处理。试验结果表明随着超声处理强度的增强大豆分离蛋白的凝胶特性变弱,感官评分降低。大豆分离蛋白分散液在p H8.0和9.0时超声处理形成的凝胶品质最高。超声处理配合蛋白分散液p H调整能够用来对大豆分离蛋白进行改性。     

不同杀菌方式对香椿芽菜品质特性的比较分析

为探究杀菌方式对香椿芽菜品质特性的影响,采用超高压技术(UltraHighPressure,UHP)、微波联合紫外杀菌技术(Microwave-Ultraviolet,MW-UV)以及传统热杀菌技术对香椿芽菜进行处理,通过感官评价及菌落总数比较不同方式的杀菌效果,然后测定亚硝酸盐和生物活性成分含量、色泽、香气成分种类及相对含量来综合评价杀菌方式对香椿芽菜品质的影响。结果表明,UHP杀菌效果最好(菌落总数0.92 cfu/g),其次是MW-UV(1.28 cfu/g),巴氏效果最差(6.80 cfu/g);UHP处理组样品各指标值均优于其他方式,但对主体香气成分中萜烯类化合物影响显著,相对含量降低28.16%;MW-UV处理组色泽劣变严重,但其香气成分与对照组最接近;巴氏杀菌较好地保留香椿芽菜原有色泽及香气成分,但对生物活性成分的损失率较大(总多酚、总黄酮、总生物碱损失率分别为6.94%、18.39%、3.61%);高压蒸汽灭菌(High-Pressure Steam Sterilization,HPSS)处理后,香椿芽菜的各项指标值均劣于其他样品。综合对比,UHP技术和MW-UV技术优于传统巴氏杀菌和HPSS方式,能较好的保持香椿芽菜的品质。