Hypocholesterolaemic effect of Bifidobacterium animalis subsp. lactis (Bb12) and trypsin casein hydrolysate

Hypercholesterolaemia is one of the most important risk factors in the development of cardiovascular disease. In this study, we report the in vitro potential of Bifidobacterium animalis subsp. lactis (Bb12) cultures and bovine casein hydrolysates formed by trypsin and Bb12 culture to reduce cholesterols levels. Cholesterol levels in vitro were reduced by up to 48% after incubation with Bb12 and up to 87% after incubation with trypsin hydrolysates, whereas unhydrolysed bovine casein did not affect cholesterol levels. Individual peptide fractions, obtained from size-exclusion chromatography, from casein hydrolysates formed by trypsin after a 48 h hydrolysis, reduced cholesterol levels by 2.7–50%. The molecular masses of these fractions, containing hypocholesterolaemic peptides, were below 1200 Da, as determined by LC-MS.     

Separation of casein from whey proteins by dynamic filtration

It has been proven that functional properties of milk proteins can improve the quality and nutritional value of foods. This paper investigates the separation of whey proteins from casein micelles using a Multi Shaft Disk (MSD) module and a rotating disk dynamic filtration module. The MSD module was equipped with 6 ceramic membranes of 0.2 µm pores. PVDF and Nylon membranes of 0.2 µm pores were tested in the rotating disk module. Permeate flux with the MSD module increased with TMP and rotation speed, reaching a maximum of 132 L h^− 1 m^− 2 at 1931 rpm. α-Lactalbumin (α-La) and β-Lactoglobulin (β-Lg) transmissions also increased with rotation speed, ranging from 25% at 1044 rpm to 40% at 1931 rpm . With a Nylon membrane, the rotating disk module yielded lower permeate fluxes than the MSD module, while when equipped with a PVDF membrane it provided higher permeate fluxes than the MSD, but casein micelles rejection was lower. α-La and β-Lg transmissions were higher with the rotating disk module, using Nylon and PVDF membranes, than for the MSD. From this comparison, it can be concluded that the MSD module gave the best compromise between high permeate flux, high α-La and β-Lg transmissions and high casein micelles rejection.     

Method to assess the quality of casein used as superplasticizer in self-levelling compounds

A fast and accurate method of assessing the quality of casein superplasticizer is presented. The method is based on analysis of the content of α-, β- and κ-casein proteins contained in whole casein by ion exchange fast protein liquid chromatography (FPLC). The chromatographic profiles of six commercial casein samples were determined, revealing that the amount of κ-casein present in the biopolymer is the main assessment criteria for the quality of casein. For high dispersing effectiveness, the content of κ-casein needs to be high. The reason is that at pH ~ 12, a high content of κ-casein results in submicelles possessing smaller size (diameter ~ 10 nm), as was proven by dynamic light scattering measurement (DLS). These smaller submicelles are supposed to adsorb on cement in higher amount than large submicelles. Using this FPLC method, the dispersing performance of any casein sample can be determined very quickly without physical testing of mortar.     

Observations of casein micelles in skim milk concentrate by transmission electron microscopy

The microstructure of casein micelles in ultrafiltrated (UF) skim milk concentrate at pH 6.5 and 5.8 was investigated by transmission electron microscopy using three different preparation methods. The volume fraction of the casein micelles in the UF concentrate was 62.8% (v/v) at pH 6.5 and fixation by glutaraldehyde revealed the close packing of micelles in the UF concentrate as well as a higher degree of micelle aggregation at pH 5.8. No details of the microstructure of the micellar surface or core could, however, be observed. Freeze-fracture of cryoprotected, i.e. glycerol, UF concentrate on the other hand, exposed the finer structures of the micellar core but no pH dependent differences were observed. As cryoprotection includes a dilution of the sample with glycerol, the packing of the micelles in the UF concentrate could not be observed. Undiluted UF concentrate exposed to rapid freezing using a propane jet followed by freeze-fracture exhibited development of ice crystals but rough areas on the micrographs were identified as fractured casein micelles. The micellar core appeared rougher and differences in the micellar core microstructure due to changing pH could be observed when this preparation method was used.     

Aqueous phase-separated biopolymer mixture compatibilized by physical interactions of the constituents

Summary A new way of compatibilization of an aqueous phase-separated two-component biopolymer system based on physical interactions of the constituents with a third biopolymer (compatibilizer) was suggested. The rheological behavior and the changes in morphology of the compatibilized mixtures were studied using a two-phase water-casein-alginate system, with the droplet morphology as a model. The time-dependent evolution of the microstructure of the compatibilized casein-alginate emulsion was investigated by image analysis using optical microscopy. Addition of 0.04–1.5 wt% of dextran sulfate as compatibilizing molecule to the emulsion leads to a considerable increase in the compatibility of casein with alginate and to a dramatic increase in storage and loss moduli (G’ and G”). Rheological differences could be correlated with differences in morphology, visible by optical microscopy.     

高效液相色谱法测定奶粉中酪蛋白磷酸肽(CPP)含量

建立了一种用高效液相色谱法测定奶粉中酪蛋白磷酸肽(CPP)含量的方法。结果表明:该法前处理简便,专一性好,灵敏度高,检出限为10μg/mL。在10～200μg/mL范围内线性回归方程为y=0.1113x+0.2131,R2=0.9994,回收率为95%￣105%,可用于测定奶粉中CPP的含量。     

Allergenic and immunogenic potential of cow's milk β-lactoglobulin and caseins evidenced without adjuvant in germ-free mice

Scope: In most animal models of allergy, the development of an IgE response requires the use of an adjuvant. Germ‐free (GF) mice exhibit Th2‐polarized antibody responses combined with defective immunosuppressive mechanisms. The sensitizing potential of milk proteins was investigated in GF mice in the absence of adjuvant. Methods and results: β‐lactoglobulin (BLG) and whole casein (CAS) allergenicity was evaluated by means of intraperitoneal injections without adjuvant. Injections of BLG induced significant IgE and IgG1 responses in GF mice, while CAS injections provoked the production of IgG1 toward κ‐ and αS1‐caseins. No significant antibody response was evidenced in conventional (CV) mice. After in vitro BLG‐reactivation, IL‐4, IL‐5, IL‐13 and IFN‐γ productions by splenocytes were higher in GF mice than in CV mice. Heat‐treatment decreased BLG allergenicity as indicated by the absence of IgE production in GF mice. However, heat‐treatment increased protein immunogenicity and led to the production of anti‐BLG and anti‐κ‐casein IgG1 in both GF and CV mice. This correlated with enhanced productions of IL‐4, IL‐5 and IL‐13 in BLG‐reactivated splenocytes from CV mice. Conclusion: Gut colonization by commensal bacteria appeared then to significantly reduce the susceptibility of mice toward the intrinsic allergenic and immunogenic potential of milk proteins.     

酪蛋白糖巨肽的生理功能及发展前景

酪蛋白糖巨肽（casein Glycomacmpepride，简称CGMP）是一种含有唾液酸的糖肽，用凝乳酶或酸性蛋白酶水解牛乳酪蛋白（主要是K-酪蛋白），乳清中含有CGMP。简述CGMP的化学结构、制备、检测方法、生物活性、研究现状及应用前景。     

毛细管区带电泳测定酪蛋白磷酸肽方法的研究

用毛细管区带电泳(CZE)对酪蛋白磷酸肽(CPP)进行了分离和测定。研究出的适宜电泳操作条件为:工作电压30KV、柱温25℃、毛细管长度50cm、内径70μm、进样量5sec(气压进样)、紫外检测波长200nm、缓冲液pH值9.2测定不同N/P样品的CPP含量分别为42.2％、50.0％、51.0％。     

酪蛋白糖巨肽超滤时间的优化探讨

酪蛋白糖巨肽具有抗感染,增强免疫力,防血栓,抗凝血等作用,在生物和营养方面具有广阔的市场前景。目的本实验在Hoist研究方法的基础上对超滤时间进行优化,旨在探讨超滤时间与酪蛋白糖巨肽粗提物体积间的关系,确定最佳离心时间,为工业化生产提供参考依据。方法根据酪蛋白糖巨肽在不同pH值下分子量不同的原理,采用30KD,3KD的超滤管在恒温条件下超滤10min,15min,加min,25min,30min,40min,研究超滤时间与酪蛋白糖巨肽粗提物体积间的关系。结果pH3．1时,使用30KD超滤离心管超滤最佳超滤时间20min;pH6．7时,使用3KD超滤离心管最佳的超滤时间30min。