牛奶纤维的新崛起

综述牛奶纤维在国外的开发历史,研究现状,纤维的性能特点以及制造工艺等。并对目前开发研制该种纤维在中国市场的意义进行评述。     

混料设计优化牦牛“曲拉”凝乳酶干酪素的工艺及产品的性质分析

为提高牦牛产业的附加值,以牦牛乳提取酥油后进行凝固沉淀,再经自然发酵、风干而成的蛋白质含量丰富的产品“曲拉”为原料,采用胃蛋白酶、木瓜凝乳酶和酵母凝乳酶复配成混合凝乳酶,通过单因素实验和混料设计对凝乳干酪素的制备工艺进行研究,并对干酪素的理化性质、红外光谱特性、热力学性质进行分析。结果表明,混合酶质量分数1%(其中胃蛋白酶∶木瓜凝乳酶∶酵母凝乳酶的质量比为0.60∶0.18∶0.22),在pH 6.3、45℃、添加质量分数CaCl 21%条件下,凝乳30 min,出品率为80.35%。混合酶法制备干酪素的理化性质、红外光谱特性和热力学性质与小牛皱胃酶干酪素差异不显著,而且符合GB31638—2016要求。     

等温滴定量热法探索酪蛋白磷酸肽单体与不同钙盐的相互作用

本研究探讨了在模拟小肠末端环境下酪蛋白磷酸肽（β-casein phosphopeptides(1-25),简称CPP）与不同钙盐的相互作用情况。实验以等温滴定量热仪为方法,以热力学参数、化学计量数及亲和力常数为指标,评价不同钙盐与CPP的相互作用情况。结果表明,CPP与不同钙盐两两相互作用,且均为由熵驱动的自发反应（pH 8.0,37 ℃）,该反应的主要推动力为离子相互作用力。不同钙盐与CPP反应时,焓变,熵变及自由能无明显差别（p>0.05）,而化学计量数和亲和力常数存在显著性差异（p<0.05）。CPP与葡萄糖酸钙,乳酸钙和氯化钙相互作用时,化学计量数较高（3~4 mol/mol）,而与天冬氨酸钙结合的化学计量数较低（2~3 mol/mol）。此外,相比其他钙盐,乳酸钙与CPP结合的亲和力常数最低。多肽与钙盐结合数高且亲和力较低时有利于小肠对钙的吸收。因此,相对于其他钙盐,CPP与乳酸钙结合可能更有利于小肠对钙的吸收。本研究为更好地了解CPP与不同钙盐溶液在模拟小肠末端环境下的热力学变化及结合情况奠定坚实的基础。     

添加剂在铜电解精炼中的作用及应用

添加剂在铜电解生产中起着重要作用, 根据多年从事铜电解技术工作的经验, 在分析添加剂作用及其影响因素的基础上, 对常用添加剂在实际生产中的作用及应用进行了总结与探讨。     

Influence of food matrix on absorption of flavour compounds by linear low‐density polyethylene: proteins and carbohydrates

The effects of differences in food matrices on the absorption of four flavour compounds (limonene, decanal, linalool and ethyl 2‐methyl butyrate) into linear low‐density polyethylene (LLDPE) were studied using a large volume injection GC ‘in vial’ extraction method. Food components investigated included β‐lactoglobulin (β‐lg), casein, pectin, carboxymethylcellulose (CMC), lactose and saccharose. β‐lg interacted irreversibly with decanal (P < 0.01) and suppressed absorption of the latter by LLDPE by more than 50% after 14 days of exposure. Casein was capable of binding limonene and decanal (p < 0.05) by hydrophobic and covalent interactions, resulting in decreased absorption of 40% and 90%, respectively. The absorption rates of limonene, and to a leaser extent decanal, were decreased in presence of pectin and CMC. Increasing viscosity slowed down diffusion of flavour compounds from the matrix to LLDPE. An increase of absorption (p < 0.01) was observed for linalool and ethyl 2‐methyl butyrate, due to a ‘salting out’ effect caused by lactose and saccharose. The absorption of decanal was decreased (p < 0.01) after 14 days of exposure in the presence of lactose, saccharose and CMC. There might be an interactive effect between a sugar (residue) and decanal. Knowledge of the composition of a food matrix and packaging material is necessary to estimate the amount of flavour absorption. © 2000 Society of Chemical Industry     

Effects of Silage Fermentation and Post-ruminal Casein Supplementation in Lactating Dairy Cows: 1—Diet Digestion and Milk Production

Two silages were prepared from the first-cut sward of timothy-meadow fescue and wilted to a dry matter (DM) content of 300 g kg^-1. One was ensiled with the addition of a formic-acid-based additive (4 litres formic acid (FA) per tonne) and the other with the addition of a bacterial inoculant (LAB) at a rate of 5×10⁶ colony forming units g^-1. Both silages were well preserved, but the extent of fermentation was greater in LAB-silage than in FA-silage as indicated by a lower concentration of water soluble carbohydrates (68 vs 177 g kg^-1 DM) and a higher concentration of lactic acid (147 vs 32 g kg^-1 DM). Four Ayrshire cows were used in a 4×4 Latin square experiment with 21-day periods to study the effects of silage fermentation and postruminal casein supplementation on silage intake, nutrient supply and milk production. The four treatments were FA-silage without casein (FA-0), LAB-silage without casein (LAB-0), FA-silage with casein (FA-C) and LAB-silage with casein (LAB-C). Both silages were given ad libitum with 8 kg day^-1 of barley without or with 400 g day^-1 of casein infused into the duodenum. Organic matter digestibility was lower (0·723 vs 0·753; P<0·01) for FA-silage than for LAB-silage. Cows offered FA-silage had a higher molar proportion of acetate and a lower proportion of propionate in ruminal fluid than cows offered LAB-silage. Microbial protein synthesis estimated from the output of purine derivatives in urine was greater (288 vs 260 g N day^-1; P<0·05) for cows given FA-silage compared with LAB-silage. Feeding LAB-treated silage tended (P<0·10) to decrease silage DM intake compared with FA-treated silage (10·61 vs 11·77 kg DM day^-1). Silage composition did not affect significantly milk yield or milk composition. Casein infusion increased milk yield (25·1 vs 27·1 kg day^-1; P<0·05), milk protein content (32·4 vs 33·8 g kg^-1; P<0·05) and protein yield (808 vs 905 g day^-1; P<0·01). The responses were similar for both silages. © 1997 SCI.     

Development of novel,nutritive antacid tablets based on milk proteins

Antacid tablets based on milk proteins were developed by a wet granulation method, with the aim of controlling the problem of hyperacidity in its early stages. Optimisation of the tablet formulation was carried out using milk protein ingredients, viz. rennet casein (RC) and whey protein concentrate (WPC), with mannitol used as a functional filler. An RC‐WPC ratio and a mannitol level of 1.96% and 10.75% w/w, respectively, were found to be optimum. The RC‐WPC ratio had a significant impact on buffering capacity (BC), tablet friability and density. The filler material, mannitol, also has an impact on BC and tablet density.     

高效液相色谱-串联质谱法测定婴幼儿配方奶粉中酪蛋白磷酸肽含量

建立一种同位素稀释-高效液相色谱-串联质谱法定量检测婴幼儿配方奶粉中酪蛋白磷酸肽（casein phosphopeptides,CPPs）含量的方法。经Q Exactive Orbitrap扫描,Uniprot蛋白质数据库初步确定CPPs所含肽段,根据质谱响应以及加标回收率等方法学验证实验进一步筛选确定CPPs的特征肽段。样品经过前处理后,采用ACQUITY UPLC BEH 300 C18色谱柱分离,多反应离子监测模式定量测定其中的CPPs特征肽。根据CPPs原料与CPPs特征肽含量的折算系数,从而确定出样品中CPPs的含量。方法学验证结果表明,所建立的方法在10～150?mg/100?g范围内线性关系良好,相关系数大于0.999。在高、中、低3?水平加标实验中,回收率在96.2%～100.2%之间,日间重复性在5.3%～7.8%之间。方法定量限为1?mg/100?g,可以满足婴幼儿配方奶粉中不同CPPs含量水平的定量要求。     

酪蛋白铁螯合肽的分离纯化及结构解析

为探讨酪蛋白铁螯合肽螯合机制,对比固定金属亲和层析和阴离子交换层析初分再结合Sephacryl S-100 HR凝胶过滤层析分离对酪蛋白铁螯合肽进行分离纯化效果,并通过紫外光谱、傅里叶变换红外光谱和液相色谱-质谱联用方法对纯化后多肽结构进行解析。结果表明,亲和层析与凝胶过滤层析法结合分离得到的酪蛋白多肽组分的铁螯合活性高于阴离子交换层析组分,其铁螯合活性可达39.56?μg/mg。紫外光谱和红外光谱检测证明酪蛋白肽和铁离子形成螯合物,羧基位点螯合前后发生变化;质谱鉴定出3?条肽段,氨基酸序列为HIQKEDVPSER、ITVDDKHYQK和TRLHPVQER,肽段中Glu、Asp、Gln出现频率高,侧链均含有C＝O键,推测多肽的羰基位是铁离子的主要螯合位点。