Caseins and their interactions that modify heat aggregation of whey proteins in commercial dairy mixtures

Recent advances in the bovine β-casein gene mutants on functional characteristics and nutritional health of dairy products: Status, challenges, and prospects

β-casein is the second most abundant form of casein in milk. Changes in amino acid sequence at specific positions in the primary structure of β-casein in milk will produce gene mutations that affect the physicochemical properties of dairy products and the hydrolysis site of digestive enzymes. The screening method of β-casein allele frequency detection in dairy products also has attracted the extensive attention of scientists and farmers. The A1 and A2 β-casein is the two usual mutation types, distinguished by histidine and proline at position 67 in the peptide chain. This paper summarizes the effects of A1 and A2 β-casein on the physicochemical properties of dairy products and evaluates the effects on human health, and the genotyping methods were also concluded. Impressively, this review presents possible future opportunities and challenges for the promising field of A2 β-casein, providing a valuable reference for the development of the functional dairy market.

Effect of pH and Shear on Heat-Induced Changes in Milk Protein Concentrate Suspensions

The effect of shear on heat-induced changes in milk protein concentrate suspensions was examined at different pH levels, revealing novel insights into micellar dissociation and protein aggregation dynamics. Milk protein concentrate suspensions, adjusted to pH of 6.1, 6.4, 6.8, or 7.5, underwent combined heat (90 °C for 5 min or 121 °C for 2.6 min) and shear (0, 100, or 1000 s-1) treatment. The fragmentation of protein aggregates induced by shear was evident in the control MPC suspensions at pH 6.8, irrespective of the temperature. At pH 7.5, shear increased the heat-induced micellar dissociation. This effect was particularly pronounced at 121 °C and 1000 s-1, resulting in reduced particle size and an elevated concentration of κ-casein (κ-CN) in the non-sedimentable phase. At pH 6.1 or 6.4, shear effects were dependent on sample pH, thereby modifying electrostatic interactions and the extent of whey protein association with the micelles. At pH 6.1, shear promoted heat-induced aggregation, evidenced by an increase in particle size and a significant decline in both whey proteins and caseins in the non-sedimentable phase. At pH 6.4, shear-induced fragmentation of aggregates was observed, prominently due to comparatively higher electrostatic repulsions and fewer protein interactions. The influence of shear on heat-induced changes was considerably impacted by initial pH.

Whey protein hydrolysates and infant formulas: Effects on physicochemical and biological properties

Whey protein hydrolysates are recognized for their substantial functional and biological properties. Their high digestibility and amino acid composition make them a valuable ingredient to hydrolyzed whey infant formulas, enhancing both product functionality and nutritional values for infant growth. It is important to understand the functional and biological properties of whey protein hydrolysates for their applications in infant formula systems. This review explored preparation methods of whey protein hydrolysates for infant formula-based applications. The effects of whey protein hydrolysate on the physicochemical and biological properties of hydrolyzed whey infant formulas were summarized. The influences of whey protein hydrolysates on the functional and nutritional properties of formulas from manufacturing to infant consumption were discussed. Whey protein hydrolysates are crucial components in the preparation of infant formula, tailored to meet the functional and nutritional demands of the product. The selection of enzyme types and hydrolysis parameters is decisive for obtaining "optimal" whey protein hydrolysates that match the intended characteristics. "Optimal" whey protein hydrolysates offer diverse functionalities, including solubility, emulsification and production stability to hydrolyzed whey infant formulas during manufacturing processes and formulations. They simultaneously promote protein digestibility, infant growth and other potential health benefits, including reduced allergenic potential, as supported by in vitro, in vivo and clinical trials. Overall, the precise selection of enzymes and hydrolysis parameters in the production of whey protein hydrolysates is crucial in achieving the desired characteristics and functional benefits for hydrolyzed whey infant formulas, making them critical in the development of infant nutrition products.

Influence of pH on Heat-Induced Changes in Skim Milk Containing Various Levels of Micellar Calcium Phosphate

The present study investigated the effect of micellar calcium phosphate (MCP) content and pH of skim milk on heat-induced changes in skim milk. Four MCP-adjusted samples, ranging from 67 to 113% of the original MCP content, were heated (90 °C for 10 min) at different pH values (6.3, 6.6, 6.9, and 7.2), followed by determining changes in particle size, turbidity, protein distribution, and structure. The results demonstrate a strong effect of MCP level and pH on heat-induced changes in milk, with the MCP67 samples revealing the greatest thermal stability. Specifically, decreasing MCP content by 33% (MCP67) led to a smaller increase in non-sedimentable κ-casein and a lower decrease in αs2-casein concentrations after heating compared to other samples. Lower MCP content resulted in a moderate rise in the average particle size and turbidity, along with lower loading of β-turn structural component after heating at low pH (pH 6.3). Notably, MCP113 exhibited instability upon heating, with increased particle size, turbidity, and a significant decrease in non-sedimentable αs2-casein concentration, along with a slight increase in non-sedimentable κ-casein concentration. The FTIR results also revealed higher loading of intermolecular β-sheet, β-turn, and random coil structures, as well as lower loading of α-helix and β-sheet structures in MCP-enhanced skim milk samples. This suggests significant changes in the secondary structure of milk protein and greater formation of larger aggregates.

Impact of ultrasound and protease addition on the fermentation profile and final characteristics of fermented goat and sheep cheese whey

Goat (GCW) and sheep cheese whey (SCW) are cheese by-products that can be fermented to develop a new product. However, the limited nutrient availability for lactic acid bacteria (LAB) growth and the low stability of whey are challenges. This work evaluated the addition of protease and/or ultrasound-assisted fermentation as tools to improve GCW and SCW fermentation and the final quality of the products. Results showed that the US/protease increased by 23-32% pH decline rate (for SCW only) and modified the separation of cream (≤ 60% for GCW) and whey (≤ 80% for both whey sources, with higher values for GCW) during storage, explained by changes in the microstructure protein, fat globules, and their interactions. Furthermore, the whey source/composition (mainly lower fat content in SCW) affected the destabilization rate and the LAB viability loss (1.5-3.0 log CFU/mL), caused by nutrient depletion and low tolerance at pH ~ 4.0. Finally, exploratory results showed that fermentation under sonication (with/without protease) resulted in 24-218% higher antioxidant activity in vitro than unfermented samples. Therefore, fermentation associated with proteases/sonication can be an interesting strategy to modify GWC and SCW, and the final process chosen depends on the desired changes in whey.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13197-023-05767-3.

Using casein and gluten protein fractions to obtain functional ingredients

Today, the food industry widely uses both animal and plant proteins. Animal proteins have a balanced amino acid composition, while plant proteins have more pronounced functional properties. However, both types of proteins can act as allergens, which limits their practical application. Therefore, we aimed to select optimal conditions for obtaining hypoallergenic mixtures based on casein hydrolysates and gluten proteins, which have good functional properties and a balanced amino acid composition. We used wheat flour (Makfa, Russia) with 12.6% of crude protein and 69.4% of starch, as well as rennet casein (Atletic Food, Russia) with 90% of protein. The methods included the Lowry method, the Anson method, Laemmli electrophoresis, ion-exchange chromatography, and the enzyme-linked immunosorbent assay. Protex 6L was an optimal enzyme preparation for the hydrolysis of gliadin, while chymotrypsin was optimal for the hydrolysis of glutenin and casein. The optimal amount for all the enzymes was 40 units/g of substrate. We analyzed the effect of casein, glutenin, and gliadin enzymolysis time on the functional properties of the hydrolysates and found that the latter had relatively low water- and fat-holding capacities. The highest foaming capacity was observed in gliadin hydrolysates, while the highest emulsifying capacity was registered in casein and glutenin hydrolysates. Further, protein enzymolysis significantly decreased allergenicity, so the hydrolysates can be used to obtain functional additives for hypoallergenic products. Finally, the mixtures of casein hydrolysate and gliadin or glutenin hydrolysates had a balanced amino acid composition and a high amino acid score. Also, they retained high emulsifying and foaming capacities. The study proved the need for mixtures based on wheat protein and casein hydrolysates, which have good functional properties and hypoallergenicity.

What is the impact of amino acid mutations in the primary structure of caseins on the composition and functionality of milk and dairy products?

The impact of amino acid mutations within the peptide structure of bovine milk protein is important to understand as it can effect processability and subsequently effect its physiological properties. Genetic polymorphisms of bovine caseins can influence the chemical, structural, and technological properties, including casein micelle morphology, calcium distribution, network creation upon gelation, and surface activity. The A1 and A2 genetic variants of β-casein have recently acquired growing attention from both academia and industry, prompting new developments in the area. The difference between these two genetic variants is the inclusion of either proline in β-casein A2 or histidine in β-casein A1 at position 67 in the peptide chain. The aim of this review was to examine the extent to which milk and ingredient functionality is influenced by β-casein phenotype. One of the main findings of this review was although β-casein A1 was found to be the dominant variant in milks with superior acid gelation and rennet coagulation properties, milks comprised of β-casein A2 possessed greater emulsion and foam formation capabilities. The difference in the casein micelle assembly, hydrophobicity, and chaperone activity of caseins may explain the contrast in the functionality of milks containing β-casein from either A1 or A2 families. This review provides new insights into the subtle variations in the physicochemical properties of bovine milks, which could potentially support dairy producers in the development of new dairy products with different functional properties.

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Impact of β- and other caseins on the casein micelle structure and functionality.

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Proline and histidine in β-caseins play a key role in casein micelle conformation.

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Chaperone activity of β-casein A2 towards heat-induced aggregation of whey protein.

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Gels prepared of milks with β-casein A1 possess a denser and firmer structure.

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Ordered structure of β-casein A2 led to improved emulsion and foam formation.

The Effect of Heat Treatment on Cow's Milk Protein Profiles

Milk is a food of high nutritional value processed by heat treatment. Heat treatment of milk is a technological process designed to inhibit the growth of microorganisms and extend the shelf life of products. The heating process directly affects the molecular structure of whey proteins by the process of denaturation. It leads to the formation of a whey protein−casein polymer complex. Based on these facts, milk heat-treatment conditions should be controlled during milk processing. This work focuses on describing the whey protein denaturation process and formation of the complex of whey protein with casein. The effect of heat treatment on individual milk protein fractions alpha-casein (α-cas), beta-casein (β-cas), kappa-casein (κ-cas), beta-lactoglobulin (β-lg) and alpha-lactalbumin (α-la) was studied by SDS-PAGE. Formation of the whey protein−casein polymer complex increased significantly (p < 0.05) on increasing the temperature and duration of the heat treatment.

Encapsulation of phenolic compounds within food-grade carriers and delivery systems by pH-driven method: a systematic review

In comparison to conventional encapsulation methods of phenolic compounds (PCs), pH-driven method is green, simple and requires low energy consumption. It has a huge potential for industrial applications, and can overcome more effectively the aqueous solubility, stability and bioavailability issues related to PCs by changing pH to induce the encapsulation of PCs. This review aims to shed light on the use of pH-driven method for encapsulating PCs. The preparation steps and principles governing pH-driven method using various carriers and delivery systems are provided. A comparison of pH-driven with other methods is also presented. To circumvent the drawbacks of pH-driven method, improvement strategies are proposed. The essence of pH-driven method relies simultaneously on alkalization and acidification to bind PCs and carriers. It is used for the development of nanoemulsions, liposomes, edible films, nanoparticles, nanogels and functional foods. As a result of pH-driven method, PCs-loaded carriers may have smaller size, high encapsulation efficiency, more sustained-release and good bioavailability, due mainly to effects of pH change on the structure and properties of PCs as well as carriers. Finally, modification of wall materials and type of acidifier are considered as efficient approaches to improve the pH-driven method.

Effect on Viability of Microencapsulated Lactobacillus rhamnosus with the Whey Protein-pullulan Gels in Simulated Gastrointestinal Conditions and Properties of Gels

Lactobacillus rhamnosus GG (LGG) has low resistance to low pH and bile salt in the gastrointestinal juice. In this study, the gel made from whey protein concentrate (WPC) and pullulan (PUL) was used as the wall material to prepare the microencapsulation for LGG protection. The gelation process was optimized and the properties of gel were also determined. The results showed the optimal gel was made from 10% WPC and 8.0% PUL at pH 7.5, which could get the best protective effect; the viable counts of LGG were 6.61 Log CFU/g after exposure to simulated gastric juice (SGJ) and 9.40 Log CFU/g to simulated intestinal juice (SIJ) for 4 h. Sodium dodecyl sulphite polyacrylamide gel electrophoresis (SDS-PAGE) confirmed that the WPC-PUL gel had low solubility in SGJ, but dissolved well in SIJ, which suggested that the gel can protect LGG under SGJ condition and release probiotics in the SIJ. Moreover, when the gel has highest hardness and water-holding capacity, the viable counts of LGG were not the best, suggesting the relationship between the protection and the properties of the gel was non-linear.