Grace, Mark (2019) Physical characterisation and stability of purified whey proteins in the presence of novel calcium salts. PhD thesis, National University of Ireland Maynooth.

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Abstract

The demand for highly concentrated whey protein solutions with a high mineral content is significant due to their versatility in providing the entire amino acid and mineral content needed in any stage of the life cycle, from infants to athletes. However, these products require extensive thermal processing to eliminate microbial growth, leading to protein instability during processing. Thermal instability can lead to precipitation, viscosity increases and heat exchanger fouling causing pressure increases, final yield reduction and ultimately leaving the final product to be un-aesthetic to the consumer. Whey consists of two major proteins, α-lactalbumin and β-lactoglobulin. The main nutrition source for infants is human milk which consists of predominantly the whey proteins α-lac (80%) and β-lac (20 %). Both the protein and mineral content of bovine and human milk differ; hence, the composition of bovine whey must be altered to produce infant milk formulae (IMF). The second commodity product for which whey protein is used is for sports drinks. In these products, the entire protein content is whey based, but the protein content is predominantly composed of β-lactoglobulin. For athletes the aim is to supplement a diet to allow better muscle recovery and maintain an adequate nitrogen balance to facilitate muscle protein synthesis. Therefore, there is a need to understand how supplementation of whey protein solutions with minerals, particularly calcium impacts the stability and processability of the protein, particularly at high protein concentrations, close to those of processing conditions. α-lac was extensively purified to attain a protein which is > 98% pure by SE-HPLC, free from β-lac contamination. The pure protein had a greater ability to refold after a thermal denaturation, when compared to solutions containing even small quantities of β-lactoglobulin. The effect of increasing calcium concentration (CaCl2) was then investigated using quasi-elastic light scattering (QELS) to assess solution stability and DSC to assess thermal stability. We found that by manipulating the protein: calcium ratio, it was possible to acquire a high concentration (100 mg ml-1) α-lac solution with added salts, beyond calcium concentrations normally employed during processing. We then probed the effect of adding calcium amino acid salts to whey proteins α-lactalbumin, β-lactoglobulin and their mixtures in Whey Protein Isolate (WPI) and examined the solution and structural stability of these protein in the presence of Ca(Gly)2 and Ca(Lys)2. The calcium amino acid salts alter both the solution and thermal stability of whey. There was also a significant impact on the distribution of protein aggregate sizes produced after heat treatment. Calcium amino acid salts may offer an alternative strategy for the supplementation of whey protein beverages with more desirable nutrient profiles and processing characteristics.

Item Type:	Thesis (PhD)
Keywords:	Physical characterisation; stability; purified whey proteins; novel calcium salts;
Academic Unit:	Faculty of Science and Engineering > Chemistry
Item ID:	16833
Depositing User:	IR eTheses
Date Deposited:	10 Jan 2023 15:04
URI:
Use Licence:	This item is available under a Creative Commons Attribution Non Commercial Share Alike Licence (CC BY-NC-SA). Details of this licence are available here

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