Self-assembly of caseinomacropeptide as a potential key mechanism in the formation of visible storage induced aggregates in acidic whey protein isolate dispersions

The effect of whey source on heat-induced aggregation of casein and whey protein mixtures of relevance to infant nutritional product formulation

Sweet and, to a lesser extent, acid whey protein ingredients can be used for the formulation of infant nutritional products. Unlike acid whey, sweet whey contains caseinomacropeptide (CMP), a heat-stable peptide liberated from κ-casein during cheese and rennet casein manufacture. Four protein systems-sweet whey (SW) and acid whey (AW), with or without standardization for CMP protein content-were added to skim milk (50/50, wt/wt) and unheated or heated to 85 or 110°C. These 12 samples were assessed for physicochemical stability in the presence of added calcium at pH 6.8. The effect of CMP content on the physicochemical properties of the protein systems was also assessed. Without preheat treatment, mixtures of AW and skim milk (SM) were more heat stable than SW and SM, demonstrating the effect of whey protein type on heat stability. Preheat treatment of the SW in the presence of SM significantly improved the heat stability of the resultant protein systems on subsequent heating. All of the protein systems had significantly lower heat stability with the addition of Ca, although the reduction was significantly smaller for the heated protein systems than the unheated controls. The findings can help identify heating parameters and ingredients for optimizing processing stability and physicochemical characteristics of nutritional beverages such as infant formulations.

Rheological and microstructural characterisation of heat-induced whey protein isolate gels affected by the addition of caseinomacropeptide

Caseinomacropeptide (CMP) is derived from the chymosin cleavage of κ-casein during cheese production. This study developed gels from CMPs, which were isolated by different ultrafiltration systems, and whey protein isolate (WPI), and studied their rheological and ultrastructural characteristics. The 30% WPI gel showed high elastic modulus (G') values and stronger structure than the other samples with CMP. Another gel, with 50% protein, 30% WPI and 20% CMP sample isolated from the 30 kDa retentate, had a weaker structure and lower G' value. The third gel, with 30% WPI and 20% CMP sample from the 5 kDa retentate derived from the 30 kDa retentate, presented intermediate structural strength. Despite the increase in protein concentration from the addition of CMP, there was a decrease in the strength of the gel network. Different CMP isolation processes also contributed to differences in the microscopic analysis of gel structures with the same protein content.

Biological, functional and nutritional properties of caseinomacropeptide from sweet whey

Bioactive peptides derived from bovine milk proteins have gained much attention due to their health promoting functions. All over the world, cheese industry generates high volumes of sweet whey that could be used as an alternative source of bioactive peptide in nutraceuticals and food industry. Caseinomacropeptide (CMP) is a bioactive peptide derived from κ-casein by the action of chymosin during cheese manufacturing. CMP consist of two forms which are glycosylated (gCMP) and non-glycosylated (aCMP). The predominant carbohydrate in gCMP is N-acetylneuraminic (sialic acid) which gives functional and biological properties to gCMP. Due to its unique composition and technological characteristics such as wide pH range solubility, emulsifying, gelling, and foaming ability, CMP has received special attention. Therefore, there is an increased interest in researches for isolation and concentration of CMP. However, the isolation and purification methods are not cost-effective. It would be easier to optimize the conditions for isolation, purification, and utilization of CMP in nutraceuticals and food industry through deeper understanding of the effective factors. In this review, the structure of CMP, biological activities, isolation, and purification methods, the factors affecting functional properties and application areas of CMP in food industry are discussed.

Influence of desialylation of caseinomacropeptide on the denaturation and aggregation of whey proteins

The effect of the addition of caseinomacropeptide (CMP) or desialylated CMP on the heat-induced denaturation and aggregation of whey proteins was investigated in the pH range 3 to 7 after heating at 80°C for 30 min. The rate and temperature of denaturation, the extent of aggregation, and the changes in secondary structure of the whey proteins heated in presence of CMP or desialylated CMP were measured. The sialic acid bound to CMP favored the denaturation and aggregation of whey proteins when the whey proteins were oppositely charged to CMP at pH 4. A transition occurred at pH 6, below which the removal of sialic acid enhanced the stabilizing properties of CMP against the denaturation and aggregation of the whey proteins. At pH >6, the interactions between desialylated CMP and the whey proteins led to more extensive denaturation and aggregation. Sialic acid bound to CMP influenced the denaturation and aggregation behavior of whey proteins in a pH-dependent manner, and this should be considered in future studies on the heat stability of such systems containing CMP.

It All Starts with a Sandwich: Identification of Sialidases with Trans-Glycosylation Activity

Sialidases (3.2.1.18) may exhibit trans-sialidase activity to catalyze sialylation of lactose if the active site topology is congruent with that of the Trypanosoma cruzi trans-sialidase (EC 2.4.1.-). The present work was undertaken to test the hypothesis that a particular aromatic sandwich structure of two amino acids proximal to the active site of the T. cruzi trans-sialidase infers trans-sialidase activity. On this basis, four enzymes with putative trans-sialidase activity were identified through an iterative alignment from 2909 native sialidases available in GenBank, which were cloned and expressed in Escherichia coli. Of these, one enzyme, SialH, derived from Haemophilus parasuis had an aromatic sandwich structure on the protein surface facing the end of the catalytic site (Phe168; Trp366), and was indeed found to exhibit trans-sialidase activity. SialH catalyzed production of the human milk oligosaccharide 3’-sialyllactose as well as the novel trans-sialylation product 3-sialyllactose using casein glycomacropeptide as sialyl donor and lactose as acceptor. The findings corroborated that Tyr119 and Trp312 in the T. cruzi trans-sialidase are part of an aromatic sandwich structure that confers trans-sialylation activity for lactose sialylation. The in silico identification of trans-glycosidase activity by rational active site topology alignment thus proved to be a quick tool for selecting putative trans-sialidases amongst a large group of glycosyl hydrolases. The approach moreover provided data that help understand structure-function relations of trans-sialidases.