奶酪中挥发性硫化物的风味贡献、检测方法及其生物合成调控的研究进展

奶酪中的硫化物主要包括甲硫醇、硫化氢、二甲基硫醚、二甲基二硫醚、甲硫基丙醛等,是奶酪关键气味物质之一,对于奶酪整体风味的形成有着重要贡献。本文在查阅相关文献的基础上,对常见奶酪中硫化物的组成、香气贡献进行了系统的综述,介绍了奶酪中测定硫化物的常用方法及其优缺点;总结了奶酪中硫化物的形成机理以及研究者们提出的生物合成调控策略,包括菌种筛选、微生物搭配组合、基因工程技术。最后对当前研究中存在的问题以及未来研究方向做了归纳与展望。为全面认知奶酪中硫化物风味及其形成和调控,开发更适合国人口味的奶酪产品和中国奶酪产业的转型升级提供理论参考。     

高达奶酪及其风味的研究进展

高达奶酪起源于荷兰,历史悠久,因其具有优异的风味和独特的外观而备受大众喜爱,在我国市场空间广阔且发展潜力巨大。该文综述高达奶酪的风味、外观及质构特征,罗列高达奶酪中的酮类、酸类、醛类、酯类等特征风味物质并阐述这些物质的形成机理,梳理高达奶酪风味形成的影响因素,如原料乳、硝酸盐和氯化钙、发酵剂及辅助发酵剂、涂层和成熟过程。最后结合当前我国奶酪的消费现状对未来高达奶酪的研究方向进行展望,以期为开发适合国人口味的高达奶酪,扩大高达奶酪的国内市场提供参考。     

内酯类化合物在食品中的风味贡献及形成机制

食品中的内酯类物质主要包括γ-内酯、δ-内酯、葫芦巴内酯、威士忌内酯,它们对食品整体风味的形成具有重要作用,能赋予食品奶香、水果香、坚果香、焦糖香等优良的风味特征,研究食品中内酯类化合物的风味贡献及形成机制具有重要意义。该研究综述了食品中常见的内酯类化合物,食品中内酯类化合物的组成及香气贡献,总结了对食品风味贡献较大的内酯类化合物的形成机制包括：δ-内酯和γ-内酯的羟基脂肪酸-内酯生成途径、一步分子内酯交换反应途径、葫芦巴内酯的羟醛缩合反应途径、果实中脂肪酸-酰基CoA-内酯形成途径、果实中不饱和脂肪酸-羟基脂肪酸-内酯形成途径等,并对当前研究中存在的问题和未来研究方向做了归纳与展望。为全面认知食品中内酯类风味化合物及其形成,改善食品风味并提高食品品质,实现食品产业转型和升级提供理论参考。     

NMR氢谱定量测定奶酪中总共轭亚油酸的含量

目的：建立用核磁共振定量法测定奶酪中总共轭亚油酸含量的方法,并与紫外分光光度法进行比较。方法：以1,2,4,5-四甲基苯为内标,采用5 mm BBO探头、脉冲序列noesyig1d、探头温度300 K、扫描次数128 次、脉冲延迟时间（D1）10 s。结果：该方法的加样回收率为93.33%,相对标准偏差（relative standard deviation,RSD）为4.20%;精密度RSD为0.99%,重复性RSD为3.17%,稳定性RSD为1.81%。结论：该方法前处理简单,无需标准品做参比,在对目标物完成定性、定量分析的同时还可以实现对非目标物的定性分析。与紫外分光光度法相比,该方法具有更好的专属性。     

细菌纤维素生物合成的酶系统及其调控体系

纤维素合成酶和UDPG（二磷酸尿苷葡萄糖）焦磷酸化酶是纤维素合成过程中的关键酶。环二乌苷酸系统是细菌纤维素生物合成中重要的调控体系。本文对此作一简单介绍。     

乳链菌肽生物合成及其调控

乳链菌肽是由乳酸链球菌的某些菌株代谢所产生的一种羊毛硫抗生素,对芽孢杆菌、链球菌、李斯特菌等许多革兰氏阳性菌有较强的抑制作用,是一种应用广泛的天然食品防腐剂。研究发现,乳链菌肽生物合成基因簇包括nisABTCIPRKFEG,与蔗糖发酵基因以及1个或多个噬菌体抗性系统和N5-(羧乙基)鸟氨酸酶的基因共同定位于染色体上的1个大的接合性转座子上,通过3个操纵子转录,并通过两组分调控体系的信号传导调控自身结构基因的表达。文章综述了乳链菌肽的分子结构、基因簇及生物合成调控机制。     

食品风味和食用香料的生物合成

本文详细综述了近年来采用生物技术合成食品风味剂的研究成果。生物技术制造食品风味剂可分为两大类．一类为复合型风味如奶制品,肉香等,一类为产生单一香料物质,如醇醛、酸、酯,杂环化合物。文中介绍一些产香的菌株和酶系,以及有关反应机制,特别对有生产价值者作了较详细说明。该技术制得食用香精香料为天然性,具有若干优点,是香精香料近年开发方向之一,亦是生物技术应用的新领域。     

3-甲基丁醛对奶酪坚果风味的贡献及其生物合成的研究进展

坚果风味是许多奶酪的特有风味,其中3-甲基丁醛对奶酪坚果风味有着重要的贡献。本文综述了3-甲基丁醛对奶酪坚果风味的影响,总结了3-甲基丁醛的生物合成途径、Strecker化学降解途径及奶酪中3-甲基丁醛含量的调控策略,并对将来的研究方向进行了展望,为开发适合中国消费者偏好、强化坚果味的奶酪产品提供理论依据。     

桃果实芳香挥发物及其生物合成研究进展

香气是反映桃果实风味品质的重要指标,近年来受到人们的广泛关注。现已从桃果实中鉴定出100多种挥发性香气成分,桃果实中芳香物质的合成受到遗传因素和外界环境等内外两类因素影响,相关酶控制其生物合成过程。本文从桃果实的芳香挥发物的组成成分及对桃果实香气的贡献角度,对桃果实主要挥发性芳香物质及其生物合成途径和其中涉及的主要酶展开讨论,分析不同品种及成熟度、不同贮藏条件和栽培管理措施等采前和采后因素对桃果实香气成分和含量的影响,就桃果实芳香代谢存在的问题进行了分析,并对前景进行展望,以期对今后的桃果实香气相关研究提供参考。     

植物类黄酮化合物生物合成调控研究进展

类黄酮化合物是植物次级代谢产物,具有多种重要的生物学功能,对人体健康具有潜在的有益作用,作为抗菌药物在植物与微生物的相互作用和防御反应中发挥重要作用。本文总结了类黄酮化合物的生物合成途径以及调控规律,重点综述了外界环境如光照、温度、水分、辐射、激素、矿物质和MYB、bHLH、WD40以及NAC等转录因子对类黄酮化合物合成的影响,加强这方面的研究,旨在为植物类黄酮功能性成分更好地开发和利用做出指导。     

Detection of Volatile Compounds of Cheese and Their Contribution to the Flavor Profile of Surface‐Ripened Cheese

The volatiles responsible for the typical aroma of cheese are produced mainly by lipolytic and proteolytic pathways and by the metabolism of lactose, lactate, and citrate. The volatile profile of cheese is determined by gas chromatography (GC), which includes the extraction, separation, and detection of volatiles. A wide range of extraction techniques is available, and technological improvements have been developed in GC separation and detection that enhance our understanding of the role of individual key volatiles to cheese flavor. To date, for surface‐ripened cheese, the main volatiles detected that contribute to flavor include acids, ketones, alcohols, and sulfur compounds. However, based on the limited number of studies undertaken and the approaches used, it appears that a significant degree of bias possibly exists that may have over‐ or underestimated the impact of specific chemical classes involved in the flavor of these types of cheese.     

Cheddar Cheese Ripening and Flavor Characterization: A Review

Cheddar cheese is a biochemically dynamic product that undergoes significant changes during ripening. Freshly made curds of various cheese varieties have bland and largely similar flavors and aroma and, during ripening, flavoring compounds are produced that are characteristic of each variety. The biochemical changes occurring during ripening are grouped into primary events including glycolysis, lipolysis, and proteolysis followed by secondary biochemical changes such as metabolism of fatty acids and amino acids which are important for the production of secondary metabolites, including a number of compounds necessary for flavor development. A key feature of cheese manufacture is the metabolism of lactose to lactate by selected cultures of lactic acid bacteria. The rate and extent of acidification influence the initial texture of the curd by controlling the rate of demineralization. The degree of lipolysis in cheese depends on the variety of cheese and may vary from slight to extensive; however, proteolysis is the most complex of the primary events during cheese ripening, especially in Cheddar-type cheese.     

Diacetyl as a Flavor Component in Full Fat Cottage Cheese

Diacetyl was detected at about 0.2 ppm using a two alternative forced choice procedure. Consumer acceptance for cottage cheese showed a small effect of added diacetyl, peaking at 1.0 ppm for aroma acceptance and flavor acceptance. Patterns of acceptance across diacetyl levels were similar for both frequent and infrequent consumers. Consumer acceptance tests conducted in a campus-based sensory testing facility gave similar results to tests conducted in a shopping mall, although the mall data were more variable.     

Accumulation of Some Flavor Compounds in Full- and Reduced-fat Cheddar Cheese Under Different Ripening Conditions

Reduced-fat cheese showed higher levels of ethanol and lower acetoin than full-fat samples throughout ripening regardless of conditions. Total headspace volatiles, as well as butanoic and hexanoic acids, increased with ripening time and temperature. Full- and reduced-fat cheeses developed distinctly different headspace volatile profiles throughout ripening. The effects of ripening conditions were more notable in full-fat samples. Ripening reduced-fat Cheddar cheese at an elevated temperature for a limited time may enhance development of some desirable volatiles such as butanoic acid.     

果味干酪加工工艺

以新鲜牛乳、香蕉果浆为原料,在新鲜软质干酪的制作基础上,研究了新鲜果味干酪的制作工艺。首先通过单因素实验和正交试验对影响牛乳凝乳效果的因素进行了初步探讨,确定了工艺参数:发酵剂的添加量为2%,pH为6.0,凝乳酶添加量为2g/L,CaCl2的添加量为0.03%。然后通过正交实验和感官评价对影响干酪风味的因素进行研究,白砂糖添加量为7%;黄原胶的添加量为0.5%;果浆的添加量为30%。最终制得的干酪不仅可以保持新鲜干酪特有的奶香味、质地和营养,还兼具有水果的香甜滋味。     

Goat Cheese Flavor: Sensory Evaluation of Branched-Chain Fatty Acids and Small Peptides

ABSTRACT: Small peptides (MW < 1000 g/mol) and volatile fatty acids of goat cheese were studied for their favorite properties. The threshold values of 4-methyl- and 4-ethyl-octanoic acids-responsible for the typical goat note were evaluated at pH 5 for orthonasal aroma in a citrate buffer and for retronasal aroma after incorporation in a cheese model. Though the concentration of the 4-ethyl- was lower than the concentration of the 4-methyl-octanoic acid in goat cheese, its relative impact on the typical goat flavor appeared more important because of its much lower threshold value. The small peptides, isolated by nano filtration of the ultrafiltered water-soluble extract at pH 5, were incorporated in the cheese model. Sensory evaluations with omission tests did not allow us to find any taste activity for this peptidic fraction.     

益生性植物乳杆菌对切达干酪挥发性风味形成的影响

将分离自西藏灵菇的益生性植物乳杆菌1-2通过在杀菌乳中添加活菌数8.0、9.0（lg（CFU/mL））和在排乳清后添加于凝乳块8.0（lg（CFU/g））的方式分别加入到切达干酪中,考察植物乳杆菌活菌数量、添加方式和成熟时间对干酪挥发性风味物质组成的影响。利用固相微萃取和气相色谱-质谱联用技术检测出对照组干酪的风味物质26种,益生菌干酪组风味物质30种,添加植物乳杆菌1-2可产生乙苯、十二烷、己醇和丙酮4种挥发性风味物质。成熟时间对干酪风味的影响最大,随成熟时间的延长,益生菌干酪组中苯含量显著增加,而对照组干酪在成熟12周时才检测到苯。益生菌添加量和添加方式对干酪挥发性风味的影响相似,丁酸受益生菌活菌数和添加方式的影响最大,益生菌干酪组成熟12周时,丁酸含量最高达对照组的3.96倍（P＜0.05）。在杀菌乳中添加益生菌活菌数8.0（lg（CFU/mL））组和9.0（lg（CFU/mL））组干酪中挥发性风味物质含量有显著差异,但在杀菌乳中添加高活菌数9.0（lg（CFU/mL））和在排乳清后添加低活菌数8.0（lg（CFU/g））于凝乳块中对干酪挥发性风味的形成具有相似的影响。本研究结果为改进益生菌干酪的加工工艺和风味品质提供了实验依据。