大豆脂肪氧化酶酶活性变化研究

采用分光光度法对大豆中三种脂肪氧化酶（同工酶）进行检测并测定脂肪氧化酶活性,研究表明：大豆粉碎后随着贮存时间的延长,脂肪氧化酶活性逐渐降低,大豆发芽后脂肪氧化酶活性降低了43%.     

乳脂肪分析仪检测乳及乳制品中脂肪含量

目的采用乳脂肪分析仪测定乳与乳制品中脂肪的含量,并与国家标准方法比对。方法以国家标准GB5009.6-2016的第三法碱水解法为依据,对样品进行在线碱水解,再用无水乙醚和石油醚抽提样品的水解液,通过蒸馏去除溶剂,最后测定溶于溶剂中的抽提物的质量,用乳脂肪分析仪测定乳及乳制品中脂肪的含量。结果本方法可检测不同食品中脂肪含量,平均回收率为97.5%,其重复性相对标准偏差(relative standard deviation, RSD)值(n=6)分布在0.08%～1.24%之间。用仪器法和国标法同时检测质控样品,其回收率和RSD结果显示仪器法优于国标法。结论乳脂肪分析仪集在线恒温水解、搅拌、分层、抽提于一体,操作简便快捷,结果准确,适用于乳与乳制品中脂肪的测定。     

脂肪测定仪测定香肠中脂肪含量的研究

采用脂肪测定仪测定香肠中脂肪的含量,结果表明,所测样品中脂肪的含量为8.2%,该方法简单、准确度高,适用于香肠中脂肪含量的测定。     

碱水解法测定乳及乳制品中脂肪的含量

目的建立简单、快速的碱水解法测定乳及乳制品中脂肪的含量。方法取0.5 g样品于离心管中,用10 mL纯水复溶后加入2 mL氨水(25%)水解并65℃水浴20 min。加入乙醇沉淀蛋白质并使用乙醚、石油醚提取样品中脂肪。将上清液提取至收集瓶中,蒸干提取液,称量收集瓶前后质量,计算样品中脂肪含量。结果此法测得样品脂肪含量为26.53 g/100 g,结果相对偏差为0.37%。测定值在质控样品值满意区间内,且符合国标规定的两次独立测定结果之差≤0.3 g/100 g的要求。结论本法测定乳及乳制品中脂肪的含量具有简便、快速、重现性好的优点,适合实验室日常样品测定及考核使用。     

索氏抽提示测定脂肪样品包装方式的改进

在索氏抽提法测定食品游离脂肪方法中，以纸卷法替代纸筒法包装样品，不仅可缩短一半以上的抽提，还解决了样品转移困难和包装易破的问题。     

食品中脂肪的超声提取快速测定法研究

食品中脂肪的测定一般采用国家标准检验方法,但这种方法存在操作时间长,步骤繁琐等问题.本实验采用超声波提取技术,对食品中脂肪的含量进行了提取测定.考察了超声消解时间、超声浸提时间、乙醚、乙醚一石油醚混合液等因素对测定结果的影响,用正交法确定了最佳条件.结果表明:本法处理样品时,不需要加热,缩短了样品提取时间,简化了测定步骤、大大节约了能耗,易于对大批量样品的脂肪含量的同时测定,并可借鉴于其它样品中有效成分的提取.     

猪肉烤制过程中脂肪含量和脂肪酸组成的变化

为研究不同烤制方式和时间对猪肉脂肪酸组成、脂肪含量、营养及风味的影响,以荣昌猪背最长肌为原料,经不同时间和方式的烤制加工后,分别测定各样品的脂肪含量和脂肪酸组成。结果显示,烤制方式主要影响样品的风味、营养以及肌内总脂、游离脂肪酸和甘三酯的脂肪酸组成;加工时间主要影响脂肪含量和磷脂的脂肪酸组成。因此采用烤制加工时,加工方式和加工时间的不同都会对猪肉脂肪酸组成、脂肪含量、营养及风味产生影响,加工方式对脂肪酸组成、营养和风味的影响更大,而加工时间对脂肪含量的影响更显著。     

酸水解法测定火腿肠中的脂肪

采用酸水解法测定火腿肠中脂肪的含量,结果表明,所测样品中脂肪的含量为9.27%,该方法简单、准确度高,适用于火腿肠中脂肪含量的测定。     

豆浆制备过程中大豆脂肪氧化酶的抑制与豆腥味量的关系

探讨大豆加工制备豆浆的过程中,有效抑制大豆脂肪氧化酶对降低豆腥味量的影响,为生产低含量豆腥味的豆浆提供理论与技术支持.通过抑制大豆脂肪氧化酶实验,即热水研磨大豆、热处理或化学处理大豆原料后再沸水研磨、大豆脱皮后隔氧研磨,对得到的豆浆样品采用静态顶空气相色谱质谱法测定13种豆腥味物质,比较定量数据获得最佳抑制脂肪氧化酶的...     

傅立叶变换近红外光谱在大豆蛋白质和粗脂肪 检测中的研究

目的本文以317份不同品种的大豆为原料,开展了大豆样品粉碎粒度的蛋白质和粗脂肪含量的近红外研究,以期建立大豆品质检测方法。方法 45份大豆粉碎样品经不同的过筛处理,对剩余的272份大豆样品在最优的粉碎粒度下建模分析。结果大豆粉碎过60目建模效果最好,蛋白质和粗脂肪含量近红外检测模型的内部交叉验证决定系数r~2分别为0.959和0.939;剩余272份大豆样品蛋白质含量的近红外检测模型的内部交叉验证相关系数为0.909,粗脂肪含量的近红外检测模型的内部交叉验证相关系数为0.918,外部验证蛋白质和粗脂肪决定系数R~2分别为0.944和0.911。结论近红外光谱技术可用于大豆品质指标的检测。     

食品中脂肪含量的测量不确定度分析与评定

采用索氏抽提法测定油炸方便面脂肪含量,通过建立数学模型确定油炸方便面中脂肪含量,分析测量过程中测量不确定度的来源,对测量测量不确定度来源进行A类评定和B类评定,确定了合成测量不确定度和扩展测量不确定度,最终得出油炸方便面中的脂肪测量不确定度,确定了脂肪测量不确定度的主要来源是自动脂肪测定仪引入的测量不确定度分量。     

软冰淇淋粉中脂肪含量测定不确定度评定

目的建立软冰淇淋粉中脂肪测定的不确定度评定方法,为简化评定方法和提高检测质量提供依据。方法分析碱水解法测定软冰淇淋粉中脂肪的不确定度的分量及其来源,并通过计算各分量的不确定度得出检测结果的合成标准不确定度。结果由不确定度的评定可知,对实验结果最主要的影响因素是称量各分量,其次为实验重复性,鼓风干燥箱温度变化对实验结果影响最小。本实验测得软冰淇淋粉中脂肪含量为(10.5±0.2)g/100 g(置信概率P=95%,包含因子k=2)。结论实验时要提高称量各分量的准确性,应在合适的操作环境使用称量天平,选择合适的精度和量程并且校准合格,尽量减少由这些因素导致的不确定度。     

Comparison of gas chromatographic methods for analysis of butyric acid in milk fat and fats containing milk fat

 The analysis of butyric acid (C4) is of importance for the determination of the proportion of milk fat in mixed fats. Three gas chromatographic methods were compared with regard to their precision for the measurement of C4, i.e. analysis of butyric acid methyl ester after trans-esterification of fat by sodium methylate (method A) or trimethyl sulphonium hydroxide (method B), as well as analysis of free butyric acid (method C), using an internal standard with each method. The examination of 30 milk fats which varied greatly in terms of their C4 content, using methods A, B and C, resulted in mean values of C4 of 3.42 g/100 g fat, 3.71 g/100 g fat and 3.06 g/100 g fat, respectively. The value determined using method B seemed too high, and this may have been due to the presence of co-eluting artefacts, whereas the value determined using method C was clearly too low, and can probably be attributed to losses during sample preparation. The standard deviation (SD) of 0.015 obtained from repeated analyses using method A was quite good. Results obtained using methods B and C had SDs of 0.029 and 0.074, respectively. Different levels of free fatty acids did not affect the results obtained using method A. When method A was checked by analysis of the reference fat, CRM 164, the C4 level determined was found to deviate from the certified C4 content of 3.49 (± 0.06) g/100 g fat by only 0.05 g C4/fat 100 g. Thus method A proved the most suitable for the determination of the proportion of milk fat in mixed fats by analysis of butyric acid. Received: 1 October 1997     

Comparison of gas chromatographic methods for analysis of butyric acid in milk fat and fats containing milk fat

 The analysis of butyric acid (C4) is of importance for the determination of the proportion of milk fat in mixed fats. Three gas chromatographic methods were compared with regard to their precision for the measurement of C4, i.e. analysis of butyric acid methyl ester after trans-esterification of fat by sodium methylate (method A) or trimethyl sulphonium hydroxide (method B), as well as analysis of free butyric acid (method C), using an internal standard with each method. The examination of 30 milk fats which varied greatly in terms of their C4 content, using methods A, B and C, resulted in mean values of C4 of 3.42 g/100 g fat, 3.71 g/100 g fat and 3.06 g/100 g fat, respectively. The value determined using method B seemed too high, and this may have been due to the presence of co-eluting artefacts, whereas the value determined using method C was clearly too low, and can probably be attributed to losses during sample preparation. The standard deviation (SD) of 0.015 obtained from repeated analyses using method A was quite good. Results obtained using methods B and C had SDs of 0.029 and 0.074, respectively. Different levels of free fatty acids did not affect the results obtained using method A. When method A was checked by analysis of the reference fat, CRM 164, the C4 level determined was found to deviate from the certified C4 content of 3.49 (± 0.06) g/100 g fat by only 0.05 g C4/fat 100 g. Thus method A proved the most suitable for the determination of the proportion of milk fat in mixed fats by analysis of butyric acid. Received: 1 October 1997     

Reduced-fat cheddar cheese manufactured using a novel fat removal process

Normally, reduced-fat Cheddar cheese is made by removal of fat from milk prior to cheese making. Typical aged flavor may not develop when 50% reduced-fat Cheddar cheese is produced by this approach. Moreover, the texture of the reduced-fat cheeses produced by the current method may often be hard and rubbery. Previous researchers have demonstrated that aged Cheddar cheese flavor intensity resides in the water-soluble fraction. Therefore, we investigated the feasibility of fat removal after the aging of Cheddar cheese. We hypothesized the typical aged cheese flavor would remain with the cheese following fat removal. A physical process for the removal of fat from full-fat aged Cheddar cheese was developed. The efficiency of fat removal at various temperatures, gravitational forces, and for various durations of applied forces was determined. Temperature had the greatest effect on the removal of fat. Gravitational force and the duration of applied force were less important at higher temperatures. A positive linear relationship between temperature and fat removal was observed from 20 to 33 degrees C. Conditions of 30 degrees C and 23,500 x g for 5 min removed 50% of the fat. The removed fat had some aroma but little or no taste. The fatty acid composition, triglyceride molecular weight distribution, and melting profile of the fat retained in the reduced-fat cheeses were all consistent with a slight increase in the proportion of saturated fat relative to the full-fat cheeses. The process of fat removal decreased the grams of saturated fat per serving of cheese from 6.30 to 3.11 g. The flavor intensity of the reduced-fat cheeses were at least as intense as the full-fat cheeses.     

脂肪替代品在食品中的应用

脂肪是食品的重要组成部分，但过量摄入会引发多种疾病，本文对脂肪替代品的种类及其在食品中的应用作了概述，并对其发展前景进行了展望。     

Comparison of enriched palmitic acid and calcium salts of palm fatty acids distillate fat supplements on milk production and metabolic profiles of high-producing dairy cows

A variable response to fat supplementation has been reported in dairy cows, which may be due to cow production level, environmental conditions, or diet characteristics. In the present experiment, the effect of a high palmitic acid supplement was investigated relative to a conventional Ca salts of palm fatty acids (Ca-FA) supplement in 16 high-producing Holstein cows (46.6 ± 12.4 kg of milk/d) arranged in a crossover design with 14-d periods. The experiment was conducted in a non-heat-stress season with 29.5% neutral detergent fiber diets. Treatments were (1) high palmitic acid (PA) supplement fed as free FA [1.9% of dry matter (DM); 84.8% C16:0] and (2) Ca-FA supplement (2.3% of DM; 47.7% C16:0, 35.9% C18:1, and 8.4% C18:2). The PA supplement tended to increase DM intake, and increased the yields of milk and energy-corrected milk. Additionally, PA increased the yields of milk fat, protein, and lactose, whereas milk concentrations of these components were not affected. The yields of milk de novo and 16-C FA were increased by PA compared with Ca-FA (7 and 20%, respectively), whereas the yield of preformed FA was higher in Ca-FA. A reduction in milk fat concentration of de novo and 16-C FA and a marginal elevation in trans-10 C18:1 in Ca-FA is indicative of altered ruminal biohydrogenation and increased risk of milk fat depression. No effect of treatment on plasma insulin was observed. A treatment by time interaction was detected for plasma nonesterified fatty acids (NEFA), which tended to be higher in Ca-FA than in PA before feeding. Overall, the palmitic acid supplement improved production performance in high-producing cows while posing a lower risk for milk fat depression compared with a supplement higher in unsaturated FA.     

Speciation of animal fat: Needs and challenges

The use of pork fat is a concern for Muslims and Jews, who for religious reasons avoid consuming anything that is pig-derived. The use of bovine materials, including beef fat, is prohibited in Hinduism and may also pose a risk of carrying the infectious agent for bovine spongiform encephalopathy. Vegetable oils are sometimes adulterated with animal fat or pork fat with beef fat for economic gain. The development of methods to determine the species origin of fat has therefore become a priority due to the complex and global nature of the food trade, which creates opportunities for the fraudulent use of these animal fats as food ingredients. However, determining the species origin of fats in processed foods or composite blends is an arduous task as the adulterant has a composition that is very similar to that of the original fat or oil. This review examines some of the methods that have been developed for fat speciation, including both fat-based and DNA-based methods, their shortcomings, and the need for additional alternatives. Protein-based methods, specifically immunoassays targeting residual proteins in adipose tissue, that are being explored by researchers as a new tool for fat speciation will also be discussed.     

驴脂组成成分及其油脂的品质指标分析

研究了驴脂的元素谱库、营养成分组成,测定了驴脂提取分离产物驴油的品质指标。以电感耦合等离子体质谱技术(ICP-MS)对驴脂中37种金属元素进行扫描分析,形成样本的元素谱库,结果表明驴脂中各金属元素均未达到检出限。以多质量分析器组合式质谱仪对驴脂进行MSn级扫描,最终获得驴脂中主要成分信息,发现驴脂主要成分中包含16种氨基酸及其衍生物类、11种有机酸、46种脂质以及糖类、维生素类等多种成分。采用超声辅助溶剂提取法得到的驴油相对密度为0. 908,水分含量为0. 68%,酸价(KOH)为0. 58 mg/g,过氧化值为0. 018 g/100 g,碘值(I)为85g/100 g。研究储存温度对驴油过氧化值的影响,结果表明驴油常温下即可储存。驴脂可作为食品、化妆品的研发原料,具有广阔的应用前景。