Colloidal Dispersion of Casein Micelles with Pea Protein via Homogenization
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Date
2021-04
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Abstract
As milk consumption has been declining, the dairy industry is looking for innovative processing methods and new products to attract the attention of consumers. Recent trends create an opportunity for the dairy industry to incorporate plant protein with milk protein, for potential applications to produce a high-protein, multi-sourced, functional ingredient. The demand for plant-based proteins is growing due to consumers' desire for high-protein health benefits, and sustainable, clean label products. Specifically, pea protein is increasing in popularity due to its fairly balanced amino acid composition with certain amino acids that assist in muscle synthesis, muscle expansion and energy production. Pea protein is a non-allergenic, gluten-free, and cost-effective plant protein. However, they can be a challenge to use in food systems because of their low solubility in water and undesirable bitterness. Ongoing research suggests that the bitterness of pea protein may be attributed to a variety of compounds, including secondary plant metabolites, phytochemicals, amino acids, and lipids. Nonetheless, methods of flavor masking the bitter notes are being developed. This study suggests the use of casein micelles, the major milk protein, as a particular system optimal for protein blending with high sensory acceptability to curtail the challenges of pea protein applications. Caseins are present in milk as a colloidal dispersion, a suspension of solid particles in an aqueous phase. The objective of this study was to create a stable colloidal dispersion of milk protein and pea protein to improve the solubility of pea protein, and to preserve or improve the functional properties of milk protein, such as coagulation ability, emulsion capacity, and foaming capacity. Specifically, the research presented below focusses on the process of creating the stable colloidal dispersion and investigating how the different proteins interact with one another. In this study, three different blends were created with varying ratios of milk protein-to-pea protein (90:10, 80:20, 50:50). When combined under normal conditions, there was a clear separation between the protein segments: an aqueous skim milk layer with a solid pea protein pellet. In our experimental procedures, the protein blends were subjected to three cycles of homogenization using a bench-top GEA 2-stage homogenizer at 4,000 psi and 4-100C. After homogenization, they were batch pasteurized at 630C and held for 30 min. to eliminate pathogenic growth. The resulting blends were a homogenous liquid, with no pellet formation, indicating that the insoluble pea proteins were interacting with the caseins in the aqueous phase. Analytical procedures and functional tests were used to analyze the resulting blends. Protein profiles obtained via HPLC analysis illustrated that some of the various proteins in pea were incorporating with the casein micelles. Upon coagulation of the liquid blends, protein gels were formed with various textures based on their ratio of milk-to-pea protein. The texture of the gels were similar to that of commercial queso fresco and hard tofu. Given the importance of these results, we furthered our research to analyze and characterize the specific pea proteins that were integrated with the casein micelle. The results from the amino acid sequencing indicated that vicilin, an insoluble pea protein, was the main protein incorporating with caseins. These results support the theory that the previously described method of cold-temperature homogenization can be used to create a colloidal dispersion in which insoluble pea protein may be incorporated with casein micelles in solution. Further sensory analysis will need to be conducted to determine the overall consumer acceptability of these blended mixtures, along with potential flavor masking strategies needed to be applied to combat the inherent bitterness of pea protein. In conclusion, this research highlights a promising application for other plant proteins, such as soy, hemp, rice and numerous other seeds/legumes, to be utilized within the dairy industry to help drive future product innovation while also meeting current consumer demands.
Description
Food, Agricultural, and Environmental Sciences (FAES): 1st Place (The Ohio State University Edward F. Hayes Graduate Research Forum)
Keywords
casein micelle, pea protein, homogenization