牦牛“曲拉”精制干酪素工艺研究

由传统牦牛“曲拉”制得的干酪素品质不佳的主要原因是脂肪氧化、杂质过高，该文用改良的工艺流程，通过L₉(3⁴)正交试验，研究酶制剂和离心条件对“曲拉”所制干酪素品质的影响。结果表明：酶制剂最佳应用条件为料液温度38℃，pH值4.2，胰蛋白酶浓度1.0 g/kg(处理时间5 min)，脂肪酶浓度0.01 g/kg，乳糖酶浓度0.03 g/kg；最佳离心工艺参数为，转速16000 r/min、时间10 min、温度50℃。高速离心法和酶处理过程，既能除去料液中脂肪、乳糖、尘埃等杂质，又使制品溶解黏度、色泽、气味等明显改善。红外光谱检测，制品质量优于传统产品。     

乳源性生物活性肽对新生IUGR仔猪肝脏抗氧化功能的影响

本试验选择苏太初生IUGR仔猪10窝共20头,配对分为4组:胰岛素组(I组)、牛乳组(M组)、酪蛋白酶解产物组(CH组)和酪蛋白组(C组),饲喂3d后宰杀。另选5只初生IUGR仔猪立即宰杀,作为0d对照组(A组)。M组喂牛乳,I组在牛乳中添加2.5mg/L胰岛素;C组用1.5%酪蛋白水溶液取代10%(V/V)的牛乳,CH组用1.5%酪蛋白酶解液取代10%(V/V)的牛乳。宰杀后分析肝脏和血浆中SOD活性和MDA含量以及血浆中GPT和GOT水平。试验结果显示:酪蛋白酶解物可显著降低肝脏和血浆MDA含量,提高SOD活性(P<0.05),胰岛素可显著降低血浆中MDA含量(P<0.05);3日龄仔猪GPT和GOT均高于初生仔猪,其中I组、C组和CH组GPT均显著高于M组(P<0.05)。结果提示:胰岛素和酪蛋白酶解物可提高IUGR仔猪肝脏的抗氧化功能,促进肝细胞的生长发育。     

酪蛋白磷酸肽的生理功能及其促进动物机体对矿物质吸收的机理

酪蛋白磷酸肽(CPPs)是含有成簇的磷酸丝氨酸生物活性肽,其具有促进矿物质的吸收利用,增强机体免疫力等重要生理功能。本文主要综述了CPPs的主要生理功能及促进动物对矿物质吸收的机理。     

酪蛋白磷酸肽（CPPs）制备条件研究

研究了以牛奶酪蛋白为原料制备CPPs的工艺过程及条件。以氮、磷含量为指标,通过正交试验,确定了在胰蛋白酶作用下制备CPPs的最佳条件为：最适温度40 ℃,水解时间80 min,底物浓度15%,底物与酶之比为100∶1。     

皱胃灌注酪蛋白对湖羊瘤胃消化代谢及内分泌的影响

对4头安装有永久性瘤胃和皱胃瘘管的成年湖羊进行皱胃酪蛋白灌注，观察湖羊瘤胃消化代谢、血浆激素水平以及皱胃食糜中阿片样物质总活性的变化。结果表明皱胃酪蛋白灌注，使湖羊瘤胃总挥发性脂肪酸（TVFA）水平升高19．64％（P〈0．05），瘤胃微生物蛋白（MCP）水平升高10．78％（P〈0．01），血浆胰岛素水平上升115．80％（P〈0．01）。与此同时，皱胃食糜中的阿片样物质总活性增加了128．32％（P〈0．01）。结果提示，皱胃酪蛋白灌注可增加湖羊消化道食糜中阿片样物质总活性，同时改善其瘤胃代谢和内分泌调节。     

Inter‐related effects of dietary fat and protein level on growth performance in rabbits

Isoenergetic substitution of dietary corn oil for dietary carbohydrates enhances growth in rabbits. It was hypothesized that identical amounts of metabolizable energy in the form of corn oil are more effective than those of carbohydrates in reducing protein catabolism and thus sparing it for growth, which would imply that the fat effect is greater on a marginal than normal protein diet. Young growing rabbits were fed semi‐purified diets either relatively high (21.6 energy % protein) or low in casein (13.0 energy % protein) to which extra corn oil (21.1 instead of 5.3 energy %) was added at the expense of an isoenergetic amount of corn starch and dextrose. The addition of corn oil to the diet with 21.6 energy % protein indeed increased weight gain, but the addition to the diet with 13.0 energy % protein left weight gain unchanged. These results refute our hypothesis, because the low‐protein intake was not limiting growth. The enrichment of the high‐protein diet with extra corn oil did not affect nitrogen retention, whereas urinary nitrogen excretion was increased. These observations also are at variance with the idea that additional fat would spare nitrogen for growth.     

酪蛋白磷酸肽在动物钙营养中的研究进展

酪蛋白磷酸肽(CPPs)是含有成簇的磷酸丝氨酰基的生物活性肽,具有结合钙和促进钙吸收的功能。本文主要介绍酪蛋白磷酸肽在钙营养方面的研究利用情况。     

Effects of phenylalanine and threonine oligopeptides on milk protein synthesis in cultured bovine mammary epithelial cells

This study was conducted to investigate the effects of phenylalanine (Phe) and threonine (Thr) oligopeptides on α_s1 casein gene expression and milk protein synthesis in bovine mammary epithelial cells. Primary mammary epithelial cells were obtained from Holstein dairy cows and incubated in Dulbecco's modified Eagle's medium‐F12 medium (DMEM/F12) containing lactogenic hormones (prolactin and glucocorticoids). Free Phe (117 μg/ml) was substituted partly with peptide‐bound Phe (phenylalanylphenylalanine, phenylalanyl threonine, threonyl‐phenylalanyl‐phenylalanine) in the experimental media. After incubation with experimental medium, cells were collected for gene expression analysis and medium was collected for milk protein or amino acid determination. The results showed that peptide‐bound Phe at 10% (11.7 μg/ml) significantly enhanced α_s1 casein gene expression and milk protein synthesis as compared with equivalent amount of free Phe. When 10% Phe was replaced by phenylalanylphenylalanine, the disappearance of most essential amino acids increased significantly, and gene expression of peptide transporter 2 and some amino acid transporters was significantly enhanced. These results indicate that the Phe and Thr oligopeptides are important for milk protein synthesis, and peptide‐bound amino acids could be utilised more efficiently in milk protein synthesis than the equivalent amount of free amino acids.