Studies on the gastric digestion of plant-based alternative milks : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Technology at Massey University, Manawatū, New Zealand
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Date
2022
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Massey University
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Abstract
Plant-based alternative milks are colloidal dispersions consisting of extracted plant protein, oil bodies and other biopolymers that resemble cow milk in appearance. In recent years, plant-based alternative milks have become increasingly popular because of their sustainability and perceived health benefits. However, little is known about the structural changes and colloidal stability of these milks during gastric digestion and how these changes impact the delivery and absorption of nutrients.
The aim of this PhD project was to understand the digestion behaviour of plant-based alternative milk in the gastric environment, with a focus on the changes in microstructure, colloidal stability, physiochemical properties and protein hydrolysis and their direct consequences on the kinetics of nutrient release and delivery. The impact of cow milk protein on the digestion behaviour of oat-based milk was also explored. State-of-the-art dynamic in vitro and in vivo gastric digestion models were employed for this project.
The results demonstrated that plant-based alternative milks made with different plant materials (almonds, soybeans and oats) behaved differently under gastric conditions, in particular, in terms of changes in microstructures, colloidal stability and protein digestibility. Almond milk oil bodies flocculated, coalesced and then quickly layered into an upper lipid-rich layer and a lower aqueous phase upon gastric digestion. Soymilk coagulated and formed small-sized particles which sedimented rapidly. In contrast, no significant changes in the structure and colloidal stability were observed in oat milk. These variations in colloidal stability resulted in different gastric release profiles of protein and lipid. These results highlight the role of intragastric structural properties as a determining factor in controlling the kinetics of delivery of macronutrients. This study also clearly showed the influence of cow milk protein on the structural and colloidal stability of the oat milk-cow milk blend during gastric digestion.
The findings from this thesis provide new knowledge and understanding of the gastric digestion of plant-based alternative milks and how their behaviours are different from cow milk. The knowledge gained from this PhD project may provide valuable information into the tailored design of novel plant-based alternative milk products or milk blended products for specific consumers' needs.
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Figures, Tables and Chapters are re-used with the respective publishers' permission.
Keywords
Dairy substitutes, Beverages, Plant products, Digestion