发酵剂对熏马肠脂肪酶活力的影响

主要研究发酵剂对熏马肠发酵成熟过程中脂肪酶活力的影响。结果表明,酸性脂肪酶活力、中性脂肪酶活力、磷脂酶活力在发酵成熟过程中持续下降,并且发酵剂组的三种酶活力在添加发酵剂后显著高于空白组(p0.05)。通过相关性分析表明,在熏马肠发酵成熟过程中,发酵剂组中的三种酶活力与p H、水分含量及盐分含量呈极显著相关性(p0.01)。     

平板扩散法粗略确定碱性脂肪酶的活性

通过对圆弧青霉PG3 7所产碱性脂肪酶活性测定方法的研究和比较 ,建立了一种快速、直观、灵敏的固体琼脂平板脂肪酶活性测定方法 .利用脂肪酶在一定条件下分解三丁酸甘油酯所释放出的游离脂肪酸使指示剂 (维多利亚蓝 )变色的原理 ,根据变色圈直径的大小对酶活性进行粗略分析 ,特别适合于酶提纯过程中大批量样品酶活性的估测以及酶活性条带和其它蛋白质条带的区分 .     

超高压对脂肪酶活性及构象的影响

研究了压力、保压时间、pH值等对脂肪酶活性的影响,并且通过圆二色光谱和内源荧光光谱研究了脂肪酶的构象变化。结果表明,经过70℃、pH 7.5、压力200 MPa、保压时间15 min的处理后,脂肪酶的酶活力比常压对照提高了32%;200 MPa下,随着保压时间延长,脂肪酶活性较稳定,相对酶活性均保持在120%以上;最适pH增加了0.5个单位。光谱分析显示,高压处理后,脂肪酶二级结构中α-螺旋含量明显升高,β-折叠含量降低,内源荧光中的色氨酸特征峰的荧光强度增强10%～20%。     

脂酶非均相催化反应生物传感器的研究

研究固定化脂肪酶在生物传感器上的响应,研制了能将脂肪酶催化底物所产生的电子转移过程转换为电流信号输出的电化学生物传感器,酯酶非均相反应体系温度为65℃,pH为7.7时验证脂酶活性的变化规律。测定反应体系电流强度的变化趋势为首先是平稳,反应开始电流逐渐增大,随着甘二酯逐渐增多,电流变化缓慢;当甘一酯的量逐渐增多电流也变大,反应结束电流趋于平稳。用液相色谱仪跟踪测定反应过程中底物的含量,结果显示测量相对误差仅为4.9%。证明利用脂酶非均相催化反应生物传感器测定酶催化底物反应的程度是可行的,为实现计算机连续在线检测提供了理论基础。     

各类微生物脂肪酶酶学性质及应用研究进展

微生物脂肪酶作为一类功能强大的催化剂,越来越受到人们的关注。微生物脂肪酶种类繁多,广泛存在于霉菌、酵母和细菌中,且不同微生物来源的脂肪酶其酶学性质、基因结构各不相同。对目前国内外研究较多的根霉脂肪酶、曲霉脂肪酶、青霉脂肪酶、毛霉脂肪酶、地霉脂肪酶、酵母脂肪酶和细菌脂肪酶的最适作用温度、最适pH及pH稳定性、底物特异性、酶活性影响、基因结构及其应用等方面进行了综述，并论述了食品加工业中脂肪酶的研究进展。     

乳酸菌发酵剂菌体自溶及产酶特性

使用自溶度不同的乳酸菌发酵剂来控制产品的成熟周期及感官风味,具有良好的指导意义和实用价值,本文通过对嗜热链球菌、德氏乳杆菌保加利亚亚种和乳酸乳杆菌自溶度的研究表明,菌体自溶特性除了与菌株密切相关外,培养条件也会对其产生一定影响;在一定范围内,菌体自溶度随培养温度和pH的升高而增大,但超出这一范围,过高的培养温度和pH又会抑制菌体的自溶;乳酸菌自溶速度越快,产生并释放的蛋白酶和脂肪酶酶活性达到峰值所需时间就越短;相同培养条件下,乳酸乳杆菌产脂肪酶酶活性最高,三个菌株(SY15、SY15-3、SY26)产酶活性达到24.11-46.23U;德氏乳杆菌保加利亚亚种产蛋白酶活性最高,四个菌株(LD1、LD1-3、LD3、LD3-3)产酶活性最低为27.63U(LD3-3)、最高为45.22U(LD1-3).在乳酸菌发酵剂的使用过程中,应根据实际需要对自溶度不同的菌株进行选择.     

脂肪酶凝胶电泳活性条带印迹技术

在固体琼脂平板测定法的基础上,以圆弧青产ＰＧ３７所产碱性脂肪酶为实验材料,试验了酶活性蛋白条带印迹方法,该方法根据脂肪酶在一定条件下分解甘油酯所释放出来的游防脂肪酸使指示剂维多利亚蓝变色的原理,将具有脂肪酶活性的蛋白条带在电泳凝胶中被原位显示出来,以区分酶活性条带和其它蛋白质条带。用ＳＤＳ－聚丙烯酰胺凝胶电泳测得ＰＧ３７碱性脂肪酶的分子量为２７５００Ｄａｌ。     

电场对脂肪酶二级结构及其活性的影响

脂肪酶被不同强度的电场处理5 min,用红外光谱法研究电场对其二级结构的影响,并测定酶活性的变化。实验结果显示:在1.0~6.0 kV/cm范围,电场作用对脂肪酶二级结构单元相对含量的影响程度不同。与对照组相比,处理组的α-螺旋和β-折叠含量普遍减少,减少幅度分别为4.9%~10.9%和3.2%~22.6%;β-转角和无规卷曲含量普遍增加,增加幅度分别为12.5%~37.7%和3.1%~24%。并且各种结构的含量在3.0 kV/cm电场强度条件下变化最为明显。经电场处理后脂肪酶活性显著增加,这与β-转角和无规卷曲含量的增加有一定的相关性。     

脂肪酶对革胡子鲶鱼糜凝胶品质的影响

以革胡子鲶为研究对象,在加工过程中添加脂肪酶,通过测定鱼糜凝胶强度、白度、持水力等指标,评价脂肪酶对鱼糜凝胶品质的影响,并通过测定二硫键含量、观察凝胶微观结构,进一步分析脂肪酶对鱼糜凝胶品质的改善效果。结果表明:在斩拌过程中添加脂肪酶比漂洗过程中添加效果更好,斩拌过程中添加0.75%脂肪酶后,鱼糜凝胶强度提升至原来的2.3倍,白度值增大了4.9%,脂肪含量降低34.5%,持水力变化较小。斩拌添加脂肪得到的鱼糜凝胶中二硫键含量高于漂洗添加组,且斩拌添加组鱼糜凝胶结构更加平整、致密。脂肪酶的添加能够有效改善革胡子鲶鱼糜凝胶品质,本研究为革胡子鲶鱼糜加工研究提供一定理论基础。     

酱曲源产脂肪酶肉葡萄球菌的选育及应用

为筛选酱曲中高脂肪酶活力的菌株以提升原料利用率,采用吐温-80和三丁酸甘油酯平板法、对硝基苯酚法及分子生物学鉴定,从酱曲中筛选出产脂肪酶菌株,并对其进行诱变选育,同时将选育菌株应用于酱曲制备。结果显示,筛选菌株JQZ10鉴定为肉葡萄球菌,经紫外诱变后酶活达3.92 U/mL,酶活提高了68%,且突变菌株在传代过程中产脂肪酶稳定性好。选育菌株应用于酱曲制备时,成曲感官没有明显的差异,同时添加原始菌株的成曲脂肪酶活性较单一米曲霉提高了48%,添加突变菌株的成曲酶活性提高了77%,且原始菌株和突变菌株之间差异显著(P<0.05)。研究结果表明,酱曲中选育的内源性肉葡萄球菌,可显著提高酱油成曲的脂肪酶活性,为酱油强化发酵和酱曲发酵剂开发提供了理论基础和菌株资源。     

Dipeptidyl peptidase activities along the processing of Serrano dry-cured ham

The activity of pork muscle dipeptidyl peptidases I, II, III, and IV was followed during the processing of Serrano dry-cured ham. The effects of NaCl, pH, and temperature on these enzymes have also been studied for a better understanding of their importance in ham processing. The lysosomal enzymes DPP I and DPP II showed maximal activity at pH around 5.5-6.0, i.e., close to the pH in ham. At low temperatures, only DPP I and DPP IV showed relevant activity. NaCl considerably inhibited DPP activities except DPP I which was only slightly affected. Dipeptidyl peptidases remained active during the whole process except DPP II whose activity disappeared after 240 days of dry-curing.     

风鸭加工过程中肌内和皮下脂肪水解特性研究

研究了控温控湿现代化工艺加工中风鸭肌内和皮下脂肪的甘油酯、磷脂、游离脂肪酸、理化指标的变化规律及内在相关性。采用三氯甲烷-甲醇溶液提取脂肪,固相萃取法分离脂肪,通过毛细管气相色谱分析游离脂肪酸的含量。结果显示:肌内脂肪中磷脂和游离脂肪酸含量比皮下脂肪变化显著,肌内脂肪水解是风鸭脂类物质变化的主体;肌内游离脂肪酸尤其油酸(18∶1)和亚油酸(18∶2)主要来自于肌内磷脂的降解,而皮下甘油酯和磷脂对皮下游离脂肪酸积累都有一定的贡献;棕榈酸(16∶0)、硬脂酸(18∶0)、油酸(18∶1)和亚油酸(18∶2)是风鸭游离脂肪酸主体成分。     

SUBCUTANEOUS ADIPOSE TISSUE LIPOLYSIS IN THE PROCESSING OF DRY-CURED HAM

ABSTRACT The activities of subcutaneous adipose tissue lipases and esterases were assayed at different stages (0 to 15 months) in the processing of dry-cured ham. The formation of free fatty acids during the process was also determined. Maximal generation of free fatty acids occurred during the first 10 months. Simultaneously, the triglyceride content decreased while the diglycerides increased during the aging period. Neutral and basic lipases showed maximal activity at the beginning of the process but only neutral lipase remained as the main enzyme responsible for the reported lipolysis during the drying ripening stages. Adipose tissue esterases showed excellent stability but the generation of volatile free fatty acids was negligible, suggesting a minor role of these enzymes.     

脂肪相关酶类在干腌肉制品风味形成过程中的作用

风味是消费者选择食品的主要依据之一。风味的形成是个复杂的生化反应过程,对其的研究至今依旧还未完全明晰。干腌肉制品由于其具有独特的风味而受到消费者的广泛欢迎,经过复杂的加工过程形成了其特征性风味物质,其中较大部分是由脂类水解、氧化而来,随之还会通过美拉德等反应形成各种风味物质。脂类物质是风味物质形成的前体物质,脂质的酶控反应是干腌肉制品风味物质产生的决定性因素。本文对国内外各类干腌肉制品中脂肪水解酶、磷脂酶和脂肪氧合酶在加工过程中的活性变化及其在干腌肉制品中的作用进行了归纳;概述了这几类酶对不同种类风味物质及产品感官品质的影响;综述了加工因素介导这些酶类对风味物质形成的调控作用。为科学认识干腌肉制品风味物质的形成机理、传统工艺改进和参数优化提供参考。     

Changes of intramuscular phospholipids and free fatty acids during the processing of Nanjing dry-cured duck

In this study, changes of intramuscular phospholipids and free fatty acids were tracked during the processing of Nanjing dry-cured duck. Phospholipids were identified and quantified by high performance liquid chromatography combined with UV and evaporative light scattering detectors. The types and quantities of free fatty acids and fatty acids derived from phospholipids were analyzed by capillary gas chromatography. The results showed that raw duck meat had high quantities of phosphatidylethanolamine, and phosphatidylcholine (37.95% and 54.07% of total phospholipids, respectively), which contained high percentages of polysaturated fatty acids. The percentages of total phospholipids, phosphatidylethanolamine, and phosphatidylcholine decreased during processing, with a concomitant increase in quantities of free fatty acids. The lipolysis of phospholipids, especially phosphatidylethanolamine is the main contributor to the increase of free fatty acids.     

HPLC、GC-MS结合多元统计分析方法探究不同地区板鸭风味差异

为探究不同地区板鸭风味物质的差异,采用高效液相色谱、顶空固相微萃取-气相色谱质谱技术(SPME-GC-MS)分析六种板鸭的肌苷酸含量和挥发性成分,并结合多元统计方法对风味物质进行综合分析。结果表明:肌苷酸含量有显著差异,其中南安板鸭肌苷酸含量最高,扬州板鸭含量较低。SPME-GC-MS共检测109种风味物质,在各板鸭中醛类是含量最多的物质;OAV分析得出11种关键挥发性风味化合物,其中苯甲醛、(E,E)-2,4-壬二烯醛是板鸭共有的关键风味物质;己醛、壬醛、萘、(Z)-2-庚烯醛、(E)-2-辛烯醛、(E)-2-葵烯醛、1-辛烯-3-醇、2-正戊基呋喃和芳樟醇是影响不同地区板鸭风味差异的主要物质。主成分分析提取3个成分累计贡献率达到85.017%,对不同地区板鸭区分明显,醛类、肌苷酸和酯类在PC1上贡献最大,是板鸭制品的主体风味物质;聚类分析也将不同地区板鸭分为3大类,将距离放大各板鸭聚为一类。通过OAV、主成分分析和聚类分析可知不同地区板鸭因风味物质和关键挥发性风味物质种类和含量等因素的变化而具有各自的特色。     

The role of muscle enzymes in dry-cured meat products with different drying conditions

Several muscle proteases (cathepsins, calpains, peptidases and aminopeptidases) and lipases (lysosomal acid lipase, acid phospholipase and adipose tissue lipase) are involved in important biochemical mechanisms taking place during the processing of dry-cured meat products which are directly related to the final quality. These enzymes are affected by the conditions typically found in the processing of dry-cured meat products, being dehydration one of the most important factors. This work is presenting the effect of different drying conditions, typical in the processing of dry-cured meat products, on the activity of muscle proteases and lipases as well as its relevance for the final product quality.     

The changes in the proteolysis activity and the accumulation of free amino acids during chinese traditional dry-cured loins processing

Twelve pieces of longissimus dorsi were processed into Chinese traditional dry-cured loins. The changes in the proteolylic enzymes activities, myofibrillar proteins degradation, and free amino acids content were investigated during processing. Compared with fresh piece (0 day), the cathepsin B + L and calpains activities decreased after dry-curing and maintained potential activities values of 23.25 and 15.04% in the final products, respectively. The myosin heavy chain (MHC) and C protein were intensely degraded at the dry-ripened stage; the 50 kDa desmin increased at day 2 and then disappeared at day 11. The total free amino acids content increased from 333.18 mg/100 g in the raw to 1096.54 mg/100 g at the end of the dry-ripening. This work provided a mechanism for the accumulation of free amino acids and predicted the proteolysis extent of myofibrillar proteins by monitoring the changes of three marker proteins (MHC, C protein and 50 kDa desmin) during Chinese traditional dry-cured loins processing.     

The Role of Muscle Proteases and Lipases in Flavor Development During the Processing of Dry-Cured Ham

The processing of dry-cured ham is very complex and involves numerous biochemical reactions that are reviewed in this article. Muscle proteins undergo an intense proteolysis, resulting in a great number of small peptides and high amounts of free amino acids. The enzymes responsible of these changes are proteinases (cathepsins B, D, H, and L and, to a less extent, calpains) and exopeptidases (peptidases and aminopeptidases). Muscle and adipose tissue lipids are also subject to intense lipolysis, generating free fatty acids by the action of lipases that, in a second stage, are transformed to volatiles as a result of oxidation. Sensory profiles of dry-cured ham are strongly affected by these enzymatic reactions. In addition, the activity levels of the muscle enzymes significantly depend on the properties of raw ham, such as age and crossbreeding as well as the process conditions such as temperature, time, water activity, redox potential, and salt content. Thus, the control of the muscle enzyme systems, mainly proteases and lipases, is essential for the standardization of the processing and/or enhancement of flavor quality of dry-cured ham.     

风干成熟工艺对风鸭脂质分解氧化影响的研究

以樱桃谷鸭为原料,通过对高温风干成熟和低温风干成熟工艺过程中鸭胸肉和皮下脂质TBARs 值、POV值及脂肪氧合酶活力的比较,研究加工过程中脂质分解氧化规律及其与工艺温度、盐分和时间的相关性。结果表明：风干72h 时,高温风干成熟加工过程中皮下脂肪的POV 值比低温风干成熟工艺降低了30.77%,脂肪氧合酶活力提高了7.26%,TBARs 值无显著变化;风干96h 时,鸭胸肉POV 值比低温风干工艺降低了62.50%;高温风干成熟过程中游离脂肪酸(FFA)总量与温度呈正相关,鸭胸肉中盐分和TBARs 值呈显著的正相关(p ＜ 0.05),可以认为盐含量与温度是影响风鸭制作过程中脂质分解氧化的主要因素。