Cold microfiltration as an enabler of innovative dairy protein ingredient composition and techno-functionality

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Date
2022-08
Authors
France, Thomas C.
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University College Cork
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Abstract
Microfiltration (MF) of skim milk at warm temperatures (i.e., 45-55 °C) is common practise in the dairy industry; however, high rates of fouling and short run times due to fouling and microbial quality can occur when operating at these temperatures. The adoption of cold temperatures (i.e., ≤20 °C) provides opportunities to improve efficiency and overall sustainability of the process. However, it can affect the protein, mineral and enzyme partitioning during MF which can ultimately impact the functional properties of the final ingredients, although this has not been sufficiently studied within the cold MF range. This thesis systematically studies the effects of different temperatures within the cold MF range on processing performance and fouling, protein, mineral and enzyme partitioning and some of the consequences on the physicochemical properties of the resulting process streams. Lower processing temperatures, in the range from 20 to 4 °C, resulted in significantly higher concentrations of β-casein in the permeate, with κ-casein, α-lactalbumin and β-lactoglobulin not significantly impacted by alterations in processing temperature. Lower processing temperature also resulted in a lower rate of permeate flux decline during MF although higher mechanical (pump) and thermal energy consumption were measured for the lower processing temperature (i.e., 4 °C). Altering processing temperature had minor effects on plasmin activity in permeate streams although extensive plasmin-mediated hydrolysis was observed on storage; such plasmin-mediated hydrolysis had significant impacts on the temperature-dependent self-association of β-casein. Extensive diafiltration (DF) with water was performed at 4 °C, resulting in a β-casein-depleted micellar casein retentate which displayed superior heat stability when compared to a micellar casein retentate produced at 50 °C. The learnings obtained were applied to the final study in which different DF media were used, i.e., water and two simulated milk ultrafiltrates (SMUF) designed to resemble the mineral profile of ultrafiltration permeate produced at 10 and 50 °C. The use of both SMUFs resulted in similar protein partitioning and significantly improved the heat stability of the micellar casein retentates generated, compared to when water was used as the DF medium. The findings presented in this thesis constitute a significant advance in the understanding of the effects of processing temperature within the cold MF range on parameters of relevance in the optimisation of next generation protein ingredient development in the dairy industry.
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Membrane filtration , Cold microfiltration , β-casein , Plasmin , Protein partitioning , Mineral partitioning
Citation
France, T. C. 2022. Cold microfiltration as an enabler of innovative dairy protein ingredient composition and techno-functionality. PhD Thesis, University College Cork.