非脂乳固体和脂肪含量对酸牛乳粘度的影响

通过调整酸牛乳配方中非脂乳固体和脂肪的含量,使酸牛乳粘稠度发生变化,找出它们之间的关系。确定最佳粘稠度的配方。     

非脂乳固体和脂肪含量影响酸牛乳粘度的研究

通过调整酸牛奶配方中非脂乳固体和脂肪的含量,使酸牛乳粘稠度发生变化,找出它们之间的关系,确定最佳粘稠度的配方。     

复乳凝胶作为脂肪替代物 对鸡肉肠理化性质的影响

本实验将海带水提多糖以0%、0.25%、0.5%、0.75%、1.00%、1.25%的浓度添加到复乳凝胶中,以改善其持水性和热稳定性。并将1.00%多糖复乳凝胶以0%、15%、30%、45%、60%、75%替代度替代猪背脂,分析其对鸡肉肠持水持油性、乳化稳定性、质构与感官的影响。随着海带多糖浓度的增加,复乳凝胶的持水性和热稳定性增加(P<0.05),当添加量大于1.00%时,硬度、粘聚性、咀嚼性显著降低(P<0.05)。随着复乳凝胶替代猪背脂比例增大,鸡肉肠的持油性、乳化稳定性、硬度和咀嚼性显著提高(P<0.05),L^*值、b^*值逐渐增大,a^*值逐渐降低(P<0.05),当替代度为30%时,脂肪含量为9.29%;替代度为75%时,脂肪含量仅2.68%。感官评定结果显示,当替代度达到60%时,感官评分与对照组相似。由以上结果说明,复乳凝胶可替代鸡肉肠中60%的猪背脂,且保证了产品性质和质量。     

高压对牛乳理化性质和成分的影响

高压食品加工是一种非热杀菌技术,是指在室温或低温下用100-800MPa高压处理食品。与传统的热杀菌比较,它具有很多优点,不仅能杀死微生物钝化酶类,而对食品的营养成分和感官品质改变较小。本文综述了高压处理对牛奶物理化学性质和成分的影响。     

巴氏法测定牛乳脂肪的改进

对测定牛乳脂肪的巴布科克氏法进行了改进，首次定量确定了硫酸的滴加速度，且通过改变离心条件，大大缩短了测定时间，使其更适合于乳品分析。     

高压脉冲电场杀菌对牛乳理化性质影响的研究

高压脉冲电场技术是目前较受关注的非热加工技术之一。本文研究了高压脉冲电场技术对牛乳几种理化性质的影响。结果表明，不同电场条件下，牛乳的pH值、电导率、乳糖含量、蛋白质质量分数差异均不显著。     

脂肪含量对肉糜性质影响

在低脂肉制品制作中脂肪被水所取代 ,通过对不同脂肪含量 (30 %、2 0 %、1 0 % )肉糜乳化稳定性、色泽、质构等性质的测量 ,发现随着脂肪含量的降低 ,产品硬度值下降。各样品产量、成品稳定性与乳化稳定性具有相关性。试验结果表明 ,高温产品各种性质较低温产品差     

Influence of corn silage particle length on the performance of lactating dairy cows fed supplemental tallow

The objective of this study was to determine if the length of chop of processed corn silage influences the impact of supplemental fat on rumen fermentation and performance of dairy cows. We hypothesized that increasing forage particle length may alleviate the interference of fat on rumen fermentation. Sixteen Holstein cows averaging 120 d in milk were used in a replicated 4 x 4 Latin square design with 21-d periods. Treatments were arranged as a 2 x 2 factorial with 0 or 2% tallow (dry matter basis), and corn silage harvested at either 19 or 32 mm theoretical length of cut. The forage:concentrate ratio was 50:50, and diets were formulated to contain 18% crude protein and 32% neutral detergent fiber (dry matter basis). Cows were allowed ad libitum consumption of diets that were fed twice daily as a total mixed ration. Fat supplemented cows had lower dry matter intake and produced less milk fat relative to nonsupplemented cows. No effect of corn silage particle length was observed for dry matter intake and milk fat production. Proportion of trans-10 C18:1 and of trans-10, cis-12 conjugated linoleic acid was highest in milk fat of cows fed 2% supplemental tallow. Rumen pH was not affected by feeding tallow, and tended to be highest for cows eating the 32-mm theoretical length of chop corn silage diets. No effect of treatments was observed for rumen acetate-to-propionate ratio or rumen ammonia concentration. In this study, tallow supplementation had a negative impact on performance of dairy cows regardless of the corn silage particle length. Feeding tallow increased formation of trans-fatty acids in the rumen in the absence of significant changes in the rumen environment.     

均质法控制PET奶茶脂肪上浮的研究

采用物理方法——均质法控制奶茶中脂肪上浮,研究了不同的产品均质次数和奶粉均质方式对奶茶脂肪上浮的影响。研究结果显示,产品均质次数越多,所制备产品粒径越小,但随着均质次数的增加,粒径减小的幅度减小。奶粉的均质对奶茶产品脂肪上浮没有影响。粒度测量结果与奶茶脂肪上浮趋势一致。     

Milk fat globule membrane proteins are involved in controlling the size of milk fat globules during conjugated linoleic acid–induced milk fat depression

Milk fat globule membrane (MFGM) proteins surround the triacylglycerol core comprising milk fat globules (MFG). We previously detected a decrease in the size of fat globules during conjugated linoleic acid (CLA)-induced milk fat depression (MFD), and other studies have reported that some MFGM proteins play a central role in regulating mammary cellular lipid droplet size. However, little is known about the relationship between MFD, MFG size, and MFGM proteins in bovine milk. The aim of this study was to investigate the profile of MFGM proteins during MFD induced by CLA. Sixteen mid-lactating Holstein cows (145 ± 24 d in milk) with similar body condition and parity were divided into control and CLA groups over a 10-d period. Cows were fed a basal diet (control, n = 8) or control plus 15 g/kg of dry matter (DM) CLA (n = 8) to induce MFD. Cow performance, milk composition, and MFG size were measured daily. On d 10, MFGM proteins were extracted and identified by quantitative proteomic analysis, and western blotting was used to verify a subset of the identified MFGM proteins. Compared with controls, supplemental CLA did not affect milk production, DM intake, or milk protein and lactose contents. However, CLA reduced milk fat content (3.73 g/100 mL vs. 2.47 g/100 mL) and the size parameters volume-related diameter D_[4,3] (3.72 μm vs. 3.35 μm) and surface area-related diameter D_[3,2] (3.13 μm vs. 2.80 μm), but increased specific surface area of MFG (1,905 m²/kg vs. 2,188 m²/kg). In total, 177 differentially expressed proteins were detected in milk from cows with CLA-induced MFD, 60 of which were upregulated and 117 downregulated. Correlation analysis showed that MFG size was negatively correlated with various proteins, including XDH and FABP3, and positively correlated with MFG-E8, RAB19, and APOA1. The results provide evidence for an important role of MFGM proteins in regulating MFG diameter, and they facilitate a mechanistic understanding of diet-induced MFD.     

广西水牛奶脂肪含量对感官特性的影响

以荷斯坦牛奶为对照品,分析了广西水牛奶的主要成分、理化指标和粒径分布特点,发现两种牛奶的非脂乳固体、酸度、pH值等指标并无明显差异．水牛奶的蛋白质、脂肪、总固形物质量分数及电导率明显高于荷斯坦牛奶,特别是脂肪质量分数差异尤为明显。两种牛奶脂肪在粒经分布上也表现出不同的特点,水牛奶的脂肪粒径在0．5～20μm之间,而荷斯坦牛奶的粒径在0．5～10μm之间。为此,进一步比较分析了不同脂肪质量分数水牛奶的感官差异．发现水牛奶的风味受脂肪质量分数很大的影响．提示在开发水牛奶产品时应注意调节脂肪质量分数。     

粒径分析法研究络合剂对蓝莓果汁乳饮料稳定性的影响

采用激光粒度分析与离心沉淀分析方法,针对影响蓝莓果汁乳稳定性的络合剂进行研究,确定最佳的络合剂条件。同时为激光粒度分析在乳品领域的应用提供参考。     

Short communication: Effects of prill size of a palmitic acid–enriched fat supplement on the yield of milk and milk components,and nutrient digestibility of dairy cows

The objective of our experiment was to evaluate the effects of prill size of a palmitic acid–enriched fatty acid supplement (PA; 85% C16:0) on feed intake, nutrient digestibility, and production responses of dairy cows. Twenty-four primiparous and multiparous Holstein cows were assigned based on parity and production level to replicated 4 × 4 Latin squares balanced for carryover effects with 21-d periods. Treatments were a control diet (no added PA), or 2.0% PA added as a small prill size (PA-SM; 284 ± 12.4 µm), a medium prill size (PA-MD; 325 ± 14.7 µm), or a large prill size (PA-LG; 600 ± 17.4 µm) supplement. Overall, PA treatments increased milk fat content (4.25 vs. 3.99%), milk fat yield (1.48 vs. 1.39 kg/d), 3.5% fat-corrected milk (39.2 vs. 37.7 kg/d), and improved feed efficiency (fat-corrected milk:dry matter intake; 1.51 vs. 1.42) compared with control. Compared with control, PA treatments did not affect dry matter intake, body weight, body condition score, or yields of milk, protein, and lactose. The PA treatments increased neutral detergent fiber digestibility (44.8 vs. 42.4%) and reduced the digestibility of 16-carbon fatty acids (72.3 vs. 79.1%) and total fatty acids (76.6 vs. 80.3%). Compared with control, PA treatments reduced the contents of de novo synthesized milk fatty acids (23.0 vs. 25.8 g/100 g of fatty acids) and preformed milk fatty acids (36.3 vs. 39.1 g/100 g of fatty acids), but did not affect their yields. In contrast, PA treatments increased the content (40.8 vs. 35.1 g/100 g of fatty acids) and yield (570 vs. 436 g/d) of 16-carbon milk fatty acids compared with control. The PA prill size had no effect on dry matter intake, yield of milk and milk components, or feed efficiency. However, PA-LG tended to increase milk fat content compared with PA-SM (4.28 vs. 4.22%), and it increased 16-carbon fatty acid digestibility compared with PA-MD (74.2 vs. 71.0%) and PA-SM (74.2 vs. 71.7%). Additionally, PA-LG increased total fatty acid digestibility compared with PA-MD (78.1 vs. 75.6%) and PA-SM (78.1 vs. 76.0%). Results demonstrate that PA increased milk fat content and yield, and feed efficiency. Reducing prill size decreased fatty acid digestibility, but it had no effect on animal performance under the dietary conditions and prill sizes evaluated.     

Natural variation of bovine milk fat globule size within a herd

Native milk fat globule (MFG) size, pH, total fat, protein, and lactose composition in milk from individual cows was examined in autumn and spring 2012 and autumn 2013. Mean MFG diameters ranged between 2.5 and 5.7 µm. Some cows were observed to consistently produce small or large MFG throughout the sampling period, though trends were not consistent across all cows. Small-MFG milk contained more total polar lipids; however, the relative proportion of individual polar lipids did not differ with MFG size, with the exception of phosphatidylcholine, which was greater in small-MFG milk. No significant correlation between MFG size and proximate composition, including calculated fat yield or pH, was found. This work revealed a natural cow-to-cow variation in MFG size exists, which could potentially be exploited to improve the functionality of milk for manufacturing and some products.     

换脂牛奶的研究与开发

对以植物脂肪置换鲜牛奶中固有的动物脂肪进行研究,探讨不同的植物油脂、不同的添加量对换脂牛奶口感、口味的影响,并探讨乳化稳定剂、均质压力对产品稳定性的影响,确定了换脂牛奶的加工工艺。