共查询到20条相似文献,搜索用时 15 毫秒
1.
2.
3.
Marilù Decimo Milena Brasca Juan A Ordóñez M Concepción Cabeza 《International Journal of Dairy Technology》2017,70(3):339-344
The ability of 15 psychrotrophic strains to release fatty acids C‐8:0 to C‐20:1 from cream by GC/MS and the substrate specificity of their lipases against selected triacylglycerols (TAG) were studied. The free fatty acids (FFAs) detected in the highest quantities were, in general, those of long (C‐16; C‐18) and intermediate (C‐12; C‐14) even‐numbered carbon chain and unsaturated C‐18:1 and C‐18:2. The ability of lipolytic strains to release fatty acids from milk fat varies according to the bacterial genus, among species and even with the strain of a given species. TAG breakdown by psychrotrophs may occur in a greater or lesser extent, but type and amount of released FFAs are not easily predictable. Pseudomonas rhodesiae showed the highest hydrolytic resistance towards all tested fatty acid triglycerides. 相似文献
4.
为了获得高含量的二十二碳六烯酸(DHA),对不同储藏温度对头孢霉脂肪酸组分的影响进行研究。将菌种储藏在20℃。4℃和-20℃三种温度下。比较不同储藏时间及菌种活化对菌丝脂肪酸组分的影响。结果表明菌种储藏温度、时间及发酵前菌种是否活化都影响脂肪酸组分。发酵前活化菌种。DHA含量均在10d达到最大:不活化菌种。20℃储藏菌种,DHA在20d可以达到最大:4℃,在25d可以达到最大:-20℃,在5d可以达到最大。除4℃外,其它两种温度下多不饱和脂肪酸变化和DHA变化趋势均一致。20℃,脂肪酸不饱和指数和18:3,18:2的变化与DHA变化一致。-20℃储藏菌种。如发酵前不活化菌种,其DHA,脂肪酸不饱和指数和多不饱和脂肪酸变化幅度均为六组最小。可能在这种温度下,菌丝调节脂肪酸变化的能力受到损伤。本研究可以为发酵生产多不饱和脂肪酸提供理论参考。 相似文献
5.
植物油脂中脂肪酸的分离与鉴定方法 总被引:16,自引:4,他引:16
本文介绍了油脂中脂肪酸的提取及脂肪酸甲酯的制备,应用硝酸银硅胶柱层析、反相液液分配层析和高压液相色谱等方法分离脂肪酸。采用气相色谱、氧化断链与远端化学修饰技术等手段鉴定脂肪酸结构。 相似文献
6.
Pasquale V Romano V Rupnik M Capuano F Bove D Aliberti F Krovacek K Dumontet S 《Food microbiology》2012,31(2):309-312
Clostridium difficile is an anaerobic bacterium commonly considered to be responsible for antibiotic-associated gastrointestinal diseases, ranging from diarrhea of varying severity to pseudomembranous colitis. The aim of this study was to assess the occurrence of C. difficile in marine edible bivalve molluscs, which, as filter feeding organisms, are able to accumulate particles suspended in water, including microorganisms. Samples of Mytilus galloprovincialis, Tapes philippinarum, and Venus verrucosa were collected from mussel farms and fishmongers in the province of Naples (Southern Italy). C. difficile was found in 49% of the 53 samples investigated. Sixteen isolates were grouped in 12 known different PCR ribotypes (001, 002, 003, 010, 012, 014/020, 018, 045, 070, 078, 106, and 126), whereas 10 additional isolates were grouped in 8 new PCR riboprofiles. Two toxinotypes (0 and V) were found. Fifty eight percent of the isolates were toxigenic. These findings indicate that toxigenic C. difficile strains can be isolated in bivalve molluscs. Marine filter feeding organisms, therefore, may be considered as reservoir of toxigenic strains of C. difficile. The ingestion of raw or poorly cooked contaminated seafood and the high temperature resistance of the spore-forming C. difficile could represent an important source of exposure and pose human health concern. 相似文献
7.
8.
9.
采用傅里叶近红外光谱结合偏最小二乘法(PLS)法建立了测定婴儿配方奶粉中的总脂肪酸、饱和脂肪酸和不饱和脂肪酸含量的近红外数学模型,并通过交互验证和外部检验两种方式考察了近红外数学模型的可靠性。通过选择不同的波长范围,采用平滑、矢量归一化、一阶求导、二阶求导和散射校正对近红外光谱进行处理,总脂肪酸、饱和脂肪酸和不饱和脂肪酸的校正模型相关系数(R2)分别为0.9337、0.9374、0.9020,RPD分别为3.63、3.65、2.90。结果表明近红外数学模型具有良好的预测性能。采用建立的模型对验证集中的20个婴儿配方奶粉样品进行预测,总脂肪酸含量、饱和脂肪酸和不饱和脂肪酸的预测值与化学测定值之间经配对t检验分析,与常规化学方法得到的检验结果无显著差异。 相似文献
10.
不同物种茶油脂肪酸组成及其在Sn-2位上的分布 总被引:1,自引:0,他引:1
试验以十五烷酸为内标,定量分析9种不同物种茶油的脂肪酸组成;用胰脂肪酶专一性地水解茶油甘油三酯中Sn-1和Sn-3位上的脂肪酸,并经薄层层析分离出Sn-2位甘一酯,采用气相色谱仪对Sn-2位脂肪酸组成进行测定。结果表明:9个不同物种茶油主要由棕榈酸、硬脂酸、油酸、亚油酸、亚麻酸5种脂肪酸组成,浙江红花油茶的油酸和不饱和脂肪酸的含量最高,分别为82.79g/100g和84.77g/100g;且脂肪酸之间存在一定的相关性;Sn-2位上的脂肪酸主要为油酸和亚油酸,短柱茶在Sn-2位的油酸和不饱和脂肪酸含量最高,分别为82.96%,92.89%。表明茶油是一种不饱和脂肪酸含量高且容易被人体消化吸收的油脂。 相似文献
11.
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. 相似文献
12.
目的 建立一种天然鱼肝油脂肪酸成分的气相色谱-质谱(gas chromatography-mass spectrometry)指纹图谱分析方法, 鉴定天然鱼肝油掺假问题。方法 脂肪酸经柱前衍生转化为脂肪酸甲酯后, 采用GC-MS联用方法测定脂肪酸指纹图谱, 选取13批具有代表性的样品建立共有模式, 选定15个脂肪酸峰为共有峰, 棕榈酸峰为参照物峰, 建立天然鱼肝油脂肪酸对照指纹图谱。借助“中药色谱指纹图谱相似度评价系统”软件, 以对照指纹图谱为参比, 计算样品指纹图谱相似度。结果 对收集到的48批样品经指纹图谱分析和相似度评价, 共检出3批掺假鱼肝油, 其中2批掺假鱼油, 掺假水平为20%及30%, 1批掺假植物油, 掺假样品比例约为6%。结论 本研究建立的脂肪酸GC-MS指纹图谱分析方法操作简便、准确可靠, 结合相似度评价方法, 为天然鱼肝油的质量控制和掺假鉴定提供了一种新的技术手段。 相似文献
13.
M. Carriquiry W.J. Weber G.C. Lamb L.H. Baumgard B.A. Crooker 《Journal of dairy science》2009,92(10):4865-4875
Multiparous cows (n = 59) were blocked by expected calving date and previous milk yield and assigned randomly to treatments to determine effects of bovine somatotropin (bST; Posilac, Monsanto Animal Agricultural Group, St. Louis, MO) and source of dietary fat on milk fatty acid composition during the first 140 d in milk. Diets were provided from calving and included whole, high-oil sunflower seeds (SS; 10% of dietary dry matter; n-6/n-3 ratio of 4.6) as a source of linoleic acid or a mixture of Alifet-High Energy and Alifet-Repro (AF; Alifet USA, Cincinnati, OH; 3.5 and 1.5% of dietary dry matter, respectively; n-6/n-3 ratio of 2.6) as a source of protected n-3 fatty acids (15.7% 18:3, 1.3% 20:5, and 1.3% 22:6). Treatments were derived from a 2 × 2 combination of supplemental fat source (SS, AF) and with 0 (SSN, AFN) or 500 (SSY, AFY) mg of bST administered every 10 d from 12 to 70 d in milk and at 14-d intervals thereafter. Milk fatty acid composition was determined in samples collected from 32 cows (8 complete blocks) during wk 2, 8, and 20 of lactation. Data were analyzed as repeated measures using mixed model procedures to determine the effects of diet, bST, week of lactation, and their interactions. Proportions of 18:3 (4.02 vs. 3.59 ± 0.16%), 20:5 (0.52 vs. 0.41 ± 0.02%), and 22:6 (0.11 vs. 0.02 ± 0.02%) were greater and the n-6/n-3 fatty acid ratio (7.40 vs. 8.80 ± 0.30) was reduced in milk from cows fed AF compared with SS. Proportions of de novo-synthesized fatty acids increased and preformed fatty acids decreased as lactation progressed, but bST administration delayed this shift in origin of milk fatty acids. Transfer efficiency of 18:3, 20:5, and 22:6 from AF to milk fat averaged 36.2, 4.9, and 5.2%, respectively. These efficiencies increased as lactation progressed, but were delayed by bST. Apparent mammary Δ9-desaturase activity and milk conjugated linoleic acid (cis-9, trans-11 conjugated linoleic acid) content increased through the first 8 wk of lactation. Based on the product-to-substrate ratio of 14:1/14:0 fatty acids in milk, there was an interaction of diet and bST because bST decreased apparent Δ9-desaturase activity in SSY cows but increased it in AFY cows (0.10, 0.09, 0.08, and 0.09 ± 0.01 for SSN, SSY, AFN, and AFY, respectively). Feeding Alifet-Repro increased n-3 fatty acids in milk and bST prolonged the partitioning of dietary fatty acids into milk fat. 相似文献
14.
15.
Calcium salts of high‐oleic sunflower oil (> 86% oleic acid) were prepared and fed at 0% and 7.5% of diet dry matter weight to 8 Holstein cows in early‐ to mid‐lactation in a cross‐over experimental design. Oleic acid content of milk fat increased from 26% to over 40% and cholesterol‐raising saturates were reduced from 41% to 33%. Latin American white cheese, queso blanco, was produced from modified and normal milk. No differences in firmness were found between cheeses using penetration‐compression testing with an Instron machine. Sensory difference tests indicated no significant differences between cheeses. Latin American white cheeses made with high oleic milk are similar to traditional cheese. 相似文献
16.
目的:对番荔枝籽中的油脂进行提取和脂肪酸组成分析。方法:采用索氏提取法对番荔枝籽中的油脂进行提取,甲酯化后运用气相色谱-质谱联用技术进行分析和鉴定。结果:番荔枝籽油得率为(24.17±1.08)%,番荔枝籽油脂中含有16种脂肪酸,主要的脂肪酸为油酸(42.91%)、亚油酸(38.53%)、2,6,10,14-四甲基十五烷酸(15.43%)、十八碳三烯酸(1.33%)、花生油酸(1.27%)和十七烷酸(0.52%)等,其中不饱和脂肪酸含量高达82.77%以上。结论:番荔枝油脂富含不饱和脂肪酸,具有较高的营养价值和保健功能。 相似文献
17.
A.I. Nájera M.A. Bustamante M. Albisu I. Valdivielso G. Amores N. Mandaluniz J. Arranz L.J.R. Barron M. de Renobales 《Journal of dairy science》2017,100(9):6962-6971
The aim of the present study was to evaluate the influence of rapeseed oilcake used for feeding sheep on the content of fatty acids (FA), tocopherols, retinoids, and cholesterol of milk and cheese, and on the sensory properties of cheese. Indoor animal feeding (in winter) is the highest cost of production for cheesemakers, and the inclusion of locally produced rapeseed oilcake in the concentrate feed formulation can reduce the cost of cheese production, as long as the quality of the cheese is not altered. The experiment was carried out in March (mid lactation) with 72 Latxa sheep from an experimental farm located in the Basque Country (northern Spain). Two homogeneous groups of animals (n = 36) were set to receive each a different diet based on commercial or rapeseed concentrate, respectively, and forage (Festuca hay). Animal production parameters were individually recorded for each feeding group, whereas bulk milk from each group was used for cheesemaking trials. The rapeseed concentrate had higher amounts of unsaturated FA (mainly C18:1 cis isomers, C18:2 cis-9,cis-12 and C18:3 cis-9,cis-12,cis-15) and tocopherols than the commercial concentrate. The inclusion of rapeseed oilcake in the diet of dairy sheep did not compromise animal production parameters or milk gross composition. Bulk milk and cheese from sheep fed rapeseed concentrate showed higher content of unsaturated FA and tocopherols than those from sheep fed commercial concentrate. No differences were observed in the content of retinoid in milk and cheese between feeding groups, whereas the cholesterol content was slightly lower in cheese made with milk from sheep fed rapeseed concentrate. Thus, milk and cheese from sheep fed rapeseed concentrate had a healthier lipid profile. In addition, the inclusion of rapeseed oilcake in the diet of sheep did not change the typical sensory attributes of Protected Denomination of Origin Idiazabal cheese. Therefore, rapeseed concentrate could be a good local resource for feeding sheep to improve the nutritional quality of dairy products and to provide higher returns to farms. 相似文献
18.
19.
20.
对林芝和那曲酥油脂溶性维生素和脂肪酸组成进行研究。结果表明:酥油中维生素E含量均为最高,分别为2020μg/100 g和1900μg/100 g,其次是维生素A含量,分别为345μg/100 g和311μg/100 g,维生素E和维生素A含量均差异显著(p<0.05)。维生素D3含量相对较少,维生素K2未检出。两种酥油分别检测到25种和20种脂肪酸,饱和脂肪酸含量及脂肪酸总量差异不显著(p>0.05),不饱和脂肪酸含量及功能性脂肪酸含量差异显著(p<0.05),饱和脂肪酸含量均占到总量的1/2以上,棕榈酸、硬脂酸含量最多。单不饱和脂肪酸含量分别为24.22%和32.66%,差异显著(p<0.05)。功能性脂肪酸主要有油酸(19.2%和29.7%)、亚油酸(0.52%和4.20%)、亚麻酸(0.65%和0.26%)、花生四烯酸(0.27%和0.15%),林芝酥油还含有少量的EPA(0.06%)和DPA(0.17%)。 相似文献