支链脂肪酸的来源与功能研究进展

支链脂肪酸主要包括单支链脂肪酸和多支链脂肪酸,多存在于人体皮肤及其分泌物、微生物细胞膜、乳制品及肉制品中。近年来的研究表明,支链脂肪酸对乳腺癌细胞、前列腺癌细胞和膀胱癌细胞等具有潜在抑制作用,此外,支链脂肪酸还有抑制新生儿坏死性小肠结肠炎发病率等抗炎作用。进一步对各种食物以及人体各组织中的支链脂肪酸进行检测分析,并对支链脂肪酸结构功能与作用机理进行深入研究,是目前支链脂肪酸研究的重要方向。     

奶山羊品种和养殖区对羊乳支链脂肪酸组成的影响

支链脂肪酸作为新兴生物活性物质备受关注。羊乳营养价值丰富,其支链脂肪酸组成和含量与母乳最为接近,分析影响羊乳中支链脂肪酸组成的因素对羊乳资源高值化利用具有重要的研究意义。本研究采用气相色谱-质谱法对萨能奶山羊、关中奶山羊2个品种和山东、陕西地区4个养殖区奶山羊的羊乳支链脂肪酸组成进行比较分析。结果表明:萨能奶山羊的羊乳中支链脂肪酸成分组成较关中奶山羊的羊乳中支链脂肪酸成分组成丰富,山东萨能奶山羊anteiso-C17∶0显著高于陕西省3个养殖区,陕西省3个养殖区羊乳的异构支链脂肪酸占比存在显著差异性(P<0.05)。本文从支链脂肪酸组成角度揭示了萨能奶山羊的乳营养更丰富,陕西地区萨能山羊乳和山东地区关中山羊乳中支链脂肪酸组成更加贴近母乳。     

支链脂肪酸的食源性分析及活性机理研究进展

支链脂肪酸是一种具有特殊支链结构的饱和脂肪酸,在自然界中广泛存在。与直链脂肪酸相比具有低熔点、低冻点、氧化稳定性和热稳定性好等独特的理化性质以及抗癌、抗炎和降脂等生理活性,使其具有优异的应用特性,有较高的市场价值。本文主要阐述了支链脂肪酸在母乳、畜产品、鱼类制品及其他食品中的分布特点,并对支链脂肪酸抗炎、抗癌、防治缺血及再灌注损伤、降脂的功能活性机理及应用研究进展进行了综述,以期为支链脂肪酸在功能性食品及特殊医学用途配方食品中的应用提供理论参考。     

直链淀粉和支链淀粉分子结构研究进展

淀粉是植物中储存能量的主要单元,是许多食物的主要成分和食品工业的重要主辅料,其由高度分支的支链淀粉和近似线性的直链淀粉组成。淀粉颗粒中的直链淀粉和支链淀粉的分子结构对于理解淀粉生物合成、结构与功能特性三者之间的关系至关重要,本文通过对直链淀粉的含量、结构和对淀粉颗粒结构的贡献及对支链淀粉分支链结构中的簇结构模型、构造单元骨架结构及结构层次等方面展开阐述,以期为今后淀粉中直链淀粉和支链淀粉的分子结构研究提供理论参考。     

羊毛脂中支链脂肪酸提取和富集的研究进展

摘要：支链脂肪酸（BCFA）具有抗癌、抗炎以及防治缺血再灌注损伤的功能,可直接用作营养补充剂,或作为合成支链脂肪酸结构脂的酰基供体原料,被广泛地应用于特殊医学用途配方食品和早产儿专用配方奶粉中。介绍了支链脂肪酸性质、生理功能及其新兴来源羊毛脂,综述了支链脂肪酸的制备方法,详细阐明了羊毛脂中支链脂肪酸提取和富集工艺,并对其未来发展方向进行了展望。     

稻米支链淀粉的结构及其遗传调控研究进展

随着人们生活水平的提高,对稻米品质的要求越来越高。支链淀粉结构是影响米饭质地,造成直链淀粉含量相同或相似的品种间稻米品质差异的主要原因。在综述了稻米支链淀粉的结构特征及其与淀粉理化特性的关系、支链淀粉合成相关基因与遗传调控的国内外研究现状的基础上,探讨了今后开展稻米支链淀粉结构的遗传调控机理和育种利用研究的方向,提出今后应加强支链淀粉结构与稻米食味品质关系的研究,进一步阐明支链淀粉合成调控的遗传机理,加强基于等位基因变异的优异基因发掘和育种利用研究,综合运用生物信息学和遗传作图等技术手段开展优异新基因的克隆和基因操作遗传改良。     

不同加工方法对鸭蛋蛋黄脂肪酸的影响

通过气相色谱-质谱联用技术对生鲜鸭蛋、生咸鸭蛋、鲜熟鸭蛋以及咸熟鸭蛋的蛋黄中的脂肪酸进行检测。结果表明:它们之间脂肪酸的种类基本没有发生变化,相对含量有所不同,对于鲜鸭蛋黄,腌制会使饱和脂肪酸和单不饱和脂肪酸增加,多不饱和脂肪酸和支链脂肪酸则有所减少,熟制会使饱和脂肪酸和单不饱和脂肪酸增加,多不饱和脂肪酸和支链脂肪酸有所减少。对于咸鸭蛋黄来说,熟制会使饱和脂肪酸和单不饱和脂肪酸减少,但多不饱和脂肪酸和支链脂肪酸有所增加。     

脂肪酸对基因表达的调控作用

脂肪酸是油脂的主要组成部分,对基因表达具有调控作用,这种调控作用与脂肪酸的种类、结构以及不同脂肪酸的比例有关。阐述了油脂中脂肪酸种类、结构、脂肪酸含量及比例与相关基因表达的调控效应关系,为进一步研究脂肪酸的功能和作用机制提供依据。     

不同泌乳期牦牛乳中奇数与支链脂肪酸的分布

采集全乳期（6、7、8月）和半乳期（3月）的牦牛乳,牧场海拔范围为2 835～3 719 m。采用气相色谱-质谱分析方法,对不同泌乳期牦牛乳中奇数与支链脂肪酸的分布进行分析。结果显示,海拔高度2 835～3 719 m的不同地区（果洛州、海南州、海西州乌兰县、海北州祁连县）牦牛乳中奇数与支链脂肪酸没有显著差异,在半乳期时,牦牛乳中的奇数脂肪酸含量差异显著（P＜0.05）,支链脂肪酸含量差异极显著（P＜0.001）。研究表明,半乳期时（3月）牦牛乳中的奇数与支链脂肪酸含量最高,在全乳期和半乳期,牦牛乳中奇数与支链脂肪酸的含量明显高于普通牛乳。     

大曲高温放线菌CICC 10681在不同温度下的脂肪酸代谢变化

通过RNA-seq结合实时荧光定量PCR研究了不同温度下大曲高温放线菌脂肪酸代谢相关基因差异表达,并利用气相色谱结合Sherolock全自动细菌鉴定系统研究了不同温度大曲高温放线菌脂肪酸的组成变化。结果表明:与45℃相比,大曲高温放线菌CICC 10681在55℃和60℃时与脂肪酸合成相关基因平均上调表达7. 3和8. 4倍,与脂肪酸分解相关基因平均下调表达7. 3和7. 6倍,与支链氨基酸分解相关基因平均下调表达5. 3和6. 0倍,与乙酰辅酶A合成相关基因平均上调表达2. 7和3. 1倍。大曲高温放线菌主要以饱和的直链和支链脂肪酸为主,随着温度升高,支链饱和脂肪酸呈下降趋势,直链饱和脂肪酸呈上升趋势。与45℃相比,大曲高温放线菌在60℃条件下的C_(16∶0)和C_(18∶0)的含量分别升高了1. 6和10倍。     

羊乳中膻味形成机制及脱膻方法的研究进展

羊乳中含有丰富的脂肪酸及其他营养成分,是能引起人体过敏的乳制品的良好替代品。研究表明,羊乳中膻味的强弱与品种、饲料、环境和加工条件等因素有关,其中以挥发性支链脂肪酸的影响最为显著。本文主要论述了羊乳中膻味来源、形成机制,并评述了物理化学方法(热处理、紫外线照射、吸附剂、膻味掩蔽剂)、生物发酵方法和改善饲养条件对降低膻味的作用效果,可为今后新型低膻味羊乳及制品的开发提供理论依据和研究思路。     

Volatile fraction and sensory characteristics of Manchego cheese. 1. Comparison of raw and pasteurized milk cheese

Manchego cheese can be manufactured from raw or pasteurized ewes' milk. An automatic purge and trap apparatus, coupled to a GC-MS was used to isolate. identify and compare the relative amounts of the volatile components of raw and pasteurized Manchego cheese during ripening. The majority of volatile compounds were more abundant in raw milk (RM) cheeses than in pasteurized milk (PM) cheeses. Alcohols and esters predominated in the profile of RM Manchego cheese, while methyl-ketones and 2,3-butanedione were quantitatively important in PM cheeses. Branched chain alcohols were much more abundant in RM cheeses. The discriminant analysis separated 100% samples into RM or PM cheeses by using only 16 volatile compounds. Aroma intensity was correlated with esters, branched chain aldehydes and branched chain alcohols in RM cheeses, and with esters, branched chain aldehydes, 2-methyl ketones and 2-alkanols in PM cheeses. Diacetyl was positively correlated with the aroma attribute 'toasted' and negatively correlated with aroma quality in PM cheeses.     

脂肪酸鉴定及其在牦牛乳、牦牛肉品质分析中的应用

利用气相色谱-质谱对不同来源的牦牛乳、犏牛乳和牦牛肉脂肪酸组成及含量进行检测,以功能性脂肪酸含量为指标对牦牛乳和牦牛肉的品质进行评价。结果表明:牦牛乳、犏牛乳和牦牛肉中分别鉴定出47、46、37种脂肪酸;不同月份、海拔的牦牛乳中BCFA含量和n-6/n-3比值整体差异极显著(P <0.001),对比发现8月份采自3 500 m夏季牧场的牦牛乳品质最优;犏牛乳中富含多种功能性脂肪酸,接近牦牛乳脂肪酸组成;两种饲养方式(放牧和舍饲育肥)牦牛肉中功能性脂肪酸含量和n-6/n-3比值差异显著,放牧牦牛肉中DHA、DPA、EPA、BCFA等功能性脂肪酸含量均显著高于舍饲育肥牦牛肉,相较于舍饲育肥牦牛,放牧牦牛的牦牛肉品质更佳。     

母乳中长链甘油三酯研究进展

母乳中甘油三酯的结构对于婴幼儿的脂肪消化吸收具有重要影响。作者所在团队前期研究结果显示,母乳脂肪天然富含中长链甘油三酯（MLCT）,是母乳中含量最丰富的一类甘油三酯,其质量约占总甘油三酯的30%,主要结构是一个中链脂肪酸和两个长链脂肪酸构成的单中链型甘油三酯（MLL）。母乳中几乎不含中链甘油三酯（MCT）。作者综述了母乳脂肪中MLCT的含量、组成、影响因素以及母乳与婴幼儿配方奶粉中甘油三酯的差异,总结了MLCT的消化特性,以及MLCT型母乳替代脂的研究进展,为新型配方奶粉脂肪的开发提供理论依据。     

人乳短链脂肪酸的组成、检测方法与消化代谢研究进展

短链脂肪酸(SCFAs)是指碳链长度在4~8的有机脂肪酸,也称为挥发性脂肪酸,在哺乳动物乳和胃肠道系统中含量较高。人类日常饮食的短链脂肪酸主要来自于牛羊乳。人乳中含有的短链脂肪酸可调节婴儿脂质代谢、降低肥胖风险,对于婴儿的生长发育具有重要作用。对人乳短链脂肪酸的组成、检测方法及其消化代谢进行综述,为人乳营养价值的研究和婴儿配方奶粉的开发研制提供参考。     

Studies on rumen metabolism. V.—formation of branched long chain fatty acids in cultures of rumen bacteria

When mixed rumen bacteria were incubated with isobutyrate-1-¹⁴C, the ¹⁴C-label was incorporated into branched long chain fatty acids with both odd and even numbers of carbon atoms. Tracer studies showed that the ¹⁴C-label from DL-valine-4-¹⁴C was incorporated into branched long chain fatty acids and also into straight chain fatty acids with odd numbers of carbon atoms. In addition, labelled isobutyrate and propionate were synthesised from valine and probably represent intermediates in the synthesis of the branched and straight chain fatty acids respectively.     

Milk fatty acids. I. Variation in the concentration of individual fatty acids in bovine milk

Data from 29 published experiments on Holstein cows, providing 120 dietary treatments, were collated to obtain means, standard deviations, and ranges for the concentrations (mg/g) of 26 major individual fatty acids in bovine milk fat. The influence of diet type (total mixed ration- vs. pasture-based diet) on concentrations of individual fatty acids was examined. Pairwise correlations for concentrations (g/kg) of individual fatty acids in milk showed that almost all of the individual de novo fatty acids were significantly correlated with each other and with the total concentration of de novo fatty acids. Concentrations of individual unsaturated preformed fatty acids were generally positively correlated with each other but were negatively correlated with concentrations of total de novo fatty acids. Substantial variation was found in the concentrations of individual milk fatty acids and, apart from those synthesized de novo, concentrations of individual fatty acids did not vary in concert. The adequacy of literature data for the development of a model to predict the production of the major individual fatty acids in milk is discussed. The limitations associated with the currently available studies that may be used in a predictive model are 1) failure of many publications to adequately describe dietary details, 2) reporting poorly defined milk fatty acids, 3) aggregating a number of closely related fatty acids under a single category, and 4) the selective reporting of only those fatty acids that are present in milk fat in appreciable quantities. Despite these limitations, the data are sufficient to enable development of a model to predict the concentrations and production of major individual fatty acids in milk fat. The extreme variability in concentrations of individual milk fatty acids and the complex matrix of positive and negative correlations among the concentrations of many individual fatty acids suggest that separate equations will be needed to predict the production of each individual milk fatty acid.     

Milk composition and flavor under different feeding systems: A survey of dairy farms

Understanding the influence of regional dietary factors on the flavors of milk and dairy products will provide consumers with more options and promote the conservation of regional resources and the original terroir. The objective of this study was to evaluate the influence of regional differences in feeding systems on the composition, fatty acid content, and flavor of pasteurized milk at the farm level. Nine dairy farms using grass silage (GS), 6 farms using maize silage (MS), and 4 farms using by-products (BP) as the characteristic feed components were chosen for this survey. Fresh milk was sampled once per month from September 2008 to February 2009 at each dairy farm. The percentages of GS, MS, and BP (soybean curd residue or brewer's grain) in the feed were 32.4, 22.1, and 15.1%, respectively. The milk fat, protein, and lactose contents did not differ among the milks from farms with different feeding systems. Fatty acids with chain lengths of less than C16 and saturated fatty acids were present at higher concentrations in the milks from the GS and MS farms than in the milk from the BP farms; conversely, fatty acids with chain lengths greater than C18 and unsaturated fatty acids (UFA), including mono- (MUFA) and polyunsaturated fatty acids (PUFA), were present at higher concentrations in the milks from the BP farms than in the milks from the GS farms. No significant differences were detected in milk flavor, evaluated as sweetness, body, texture, aftertaste, and palatability, between the milks from the farms with different feeding systems. The proportion of BP in the cow's diet was positively correlated with the concentrations of fatty acids with chain lengths greater than C18 and with UFA, MUFA, and PUFA. In contrast, the proportion of GS in the diet was positively associated with the levels of milk fat, protein, fatty acids with chain lengths less than C16, and SFA. The MUFA, PUFA, UFA, and fatty acids with chain lengths greater than C18 were not associated with any of the milk flavors. These results suggest the regional differences in feeding systems contribute to the differences in the fatty acid compositions of milk at the farm level. However, these differences do not influence the flavor of pasteurized milk. Thus, more specific feed profiles will be required to provide a specific regional flavor to pasteurized milk.     

Effect of dose of bovine growth hormone on milk composition: alpha-lactalbumin, fatty acids, and mineral elements

Tissue-specific effects of bovine growth hormone on lactating dairy cows were examined by analysis of milk composition. Milk samples were from 6 cows that received subcutaneous injections of 0, 5, 10, 25, 50, and 100 IU/d of growth hormone in a Latin-square design. Samples from the last 5 d of each 10-d treatment period were pooled for analyses of milk components. Concentration of alpha-lactalbumin in milk increased progressively across the treatment range up to 32% above controls (1.30 mg/nl) at the 100 IU dose. Specific alpha-lactalbumin synthesis (expressed as a percent of total milk protein) was also increased. Secretion of de novo synthesized fatty acids (short and medium chain length) in milk was increased, but response plateaued between the 50 and 100 IU/d. Secretion of preformed (long-chain) fatty acids progressively increased across the entire dose range. Thus, the percentage of long-chain fatty acids in milk increased at the highest doses of hormone. Changes in fatty acid composition of milk were apparently related to energy status; the milk response to 50 and 100 IU/d of growth hormone caused cows to be in or near negative energy balance. Exogenous growth hormone did not affect the concentration of calcium, phosphorus, sodium, iron, copper, and manganese in milk. Results are consistent with growth hormone functioning in homeorhesis to coordinate the partitioning of all nutrients to support the increased secretion of milk and milk components.