Thermal processing techniques for improving protein-enriched beverage production

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Date
2019
Authors
Kelleher, Clodagh
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University College Cork
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Abstract
Growing consumer demand for convenient sources of high quality protein has led to a substantial global market for ready-to-drink, shelf-stable dairy protein beverages. These products have significant technical challenges associated with their manufacture due to the high processing temperatures required to render them microbiologically stable. Issues arise during thermal processing and storage as the high protein content leaves formulations susceptible to protein denaturation and aggregation, development of volatile compounds with associated off-flavours, increased viscosity, and sedimentation. This has driven dairy processors to seek out alternative formulation approaches and thermal processing techniques which can minimise the thermally-induced changes in the product, while still achieving the required shelf life. Relatively few studies have focused on a combined approach of investigating varied protein profiles in protein-enriched beverages with a range of thermal processing techniques. The objective of this research was to investigate the impact of composition and processing parameters on the physical behaviour of high-protein milk beverage systems across a range of thermal treatment systems. A new methodology for assessing the thermal stability, in terms of viscosity, for protein beverage formulations was also developed. Protein profile was shown to affect thermally-induced protein denaturation, with reductions in α-lactalbumin denaturation with an increasing casein proportion. Alterations in preheat treatment temperature significantly affected viscosity in protein systems upon concentration. The application of temperature-dependent viscosity models was demonstrated to be a useful, rapid tool in quantifying differences in product processing stability. Direct heating technology was applied to ESL- and UHT-treated whey protein solutions with a high protein content (4, 6 and 8% protein (w/w)) resulting in reduced protein denaturation, viscosity and less extensive changes to the volatile profile compared to tubular heating. A pilot-scale supersonic steam injection line was designed and integrated into an existing tubular heating plant with commissioning completed on skim milk. This novel heating system provided significantly greater reductions in protein denaturation than direct steam infusion and tubular heating for protein-enriched dairy beverage systems. The thesis provides new insights into interactions between milk proteins during thermal processing which influence the physical and volatile profile stability of protein beverages. The outcomes of the work have applications in such areas as high heat treatment processing of heat-sensitive milk proteins, allowing for minimised whey protein denaturation, reduced viscosity through formulation manipulation, and use of novel thermal technologies.
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Direct steam injection , Direct steam infusion , Protein-enriched beverages , Dairy protein , Supersonic steam injection heating
Citation
Kelleher, C. 2019. Thermal processing techniques for improving protein-enriched beverage production. PhD Thesis, University College Cork.