Process and ingredient interactions in the processing of advanced dairy based nutritional formulae
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Date
2024
Authors
McEntee, Sinead Alice
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Publisher
University College Cork
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Abstract
Advances in dairy protein fractionation and purification have resulted in a wide range of protein ingredients available for use in nutritional products such as infant formula with very different functionalities. In addition, the increased demineralisation of protein ingredients has concomitantly resulted in the production of large quantities of high-mineral containing permeates, which can be challenging to valorise into food applications. However, one major application for these permeates is in protein standardisation of fat-filled milk powders. A key requirement for many nutritional formulations, especially those targeted to infant nutrition or long shelf-life powders, is that they must be able to withstand high temperature processing. Typically, this is related to protein aggregation during heating; however, the content and ionic state of minerals present has a key influence on this aggregation. In this thesis, the thermal stability of protein ingredients with varying mineral contents were examined in model infant formula systems. Meanwhile, to understand the impact of permeate mineral content on the ionic environment and thermal stability of low protein skim concentrates, concentrates standardised with five different standardisation media, each with differing mineral contents and profiles depending on their source and processing history, were produced and subjected to simulated HTST treatment. Through this, a deeper understanding was developed of the interactions of proteins with other ingredients and mitigation strategies to control aggregation during heating.
The amino acid profile of acid whey makes it highly suitable for infant formula (IF); however, due to a higher calcium content than cheese whey, acid whey protein concentrate (WPC) is considered to have poor thermal stability, which has limited its incorporation into IF. During this study, it was found that the pH and temperature of ultrafiltration are key to determining the final calcium and phosphorous content of acid WPC, with increases in these parameters resulting in higher calcium phosphate levels in the final product. Subsequent manufacture of acid WPC 35, with elevated calcium and phosphorus levels, highlighted the challenges faced during downstream processing, such as high viscosity following evaporation. In addition, when added to a model IF system, this high level of innate calcium caused significant viscosity increases during heating. However, it was also shown that further demineralisation of acid WPC 35 to an acid WPC 60 significantly improved its thermal stability and so could be an option for increased usage of acid whey proteins in IF applications.
While much of this thesis focused on protein-mineral interactions in model IF systems, these interactions affect all nutritional dairy processes. The impact of minerals in permeate on the thermal stability of low protein skim concentrates could clearly be seen, with higher-mineral concentrates undergoing significant gelation during HTST treatment. However, by increasing pH, the viscosity of all permeate-standardised concentrates were significantly reduced following heat treatment, proving that, by controlling the ionic environment, heat-stable low-protein concentrates with a high mineral content are feasible.
In conclusion, throughout these studies, the role of minerals and their ionic state has been shown to play a key part not only in formulation thermal stability, but also in the composition and functionality of individual protein ingredients. The results of the work have shown that there can be significant benefits to the IF industry by using existing acid whey protein streams, in terms of amino acid and mineral profile. Tailoring the mineral content of acid whey during membrane processing could also further enhance the usage of this ingredient by improving high heat stability in IF applications. Finally, permeates, derived from MPC and WPC manufacture, have major applications in fat filled milk powder production, but vary widely in their impact on heat stability and viscosity, due to the significant variation in their mineral profile. Therefore, an in-depth understanding of the ionic state of minerals present, their potential interactions with proteins during processing, and possible interventions that could minimise protein aggregation is imperative to ensure high quality nutritional formulae can be produced efficiently.
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Keywords
Infant formula , Acid whey , Calcium phosphate , Minerals , Protein , Membrane processing , Thermal stability
Citation
McEntee, S. A. 2024. Process and ingredient interactions in the processing of advanced dairy based nutritional formulae. PhD Thesis, University College Cork.