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    Emulsification Properties of Garlic Aqueous Extract: Effect of Heat Treatment and pH Modification
    (MDPI, Basel, Switzerland, 2023-10-10) Bravo-Núñez Á; Golding M; Gómez M; Matia-Merino L; Dai H
    Despite the broad research available in the literature dealing with garlic health benefits, little information is found regarding the functional properties of garlic components. The aim of this study was to evaluate the emulsification properties of garlic water-soluble compounds (GWSC), encompassing proteins, saponins, and carbohydrates, after heat treatment (10 min at 95 °C) or pH adjustments (2.5, 3.5, and 7.8). After the various treatments, the extracts were used as such or filtrated (0.45 µm), and 10% soybean oil-in-water emulsions were prepared using low (0.48%) or high (6.55% wt/wt) extract concentrations. Results showed that whereas at low GWSC concentrations, both heating and acidifying resulted in the formation of bigger oil droplet sizes (i.e., from d32 = 0.36 µm using unmodified extract to d32 = 7-22 µm at pH 2.5 with or without extract filtration), the effects were opposite at the highest GWSC concentration. In the latter, heat treatment clearly reduced the droplet size as observed from the micrographs as well as the degree of creaming, though the occurrence of depletion and/or bridging flocculation was still strong. The acidification of the extract at this high GWSC concentration significantly reduced the droplet size, as observed from the micrographs; however, a strong flocculation was observed. Removal of protein aggregates, and possibly also saponin micelles, from the extract resulted in an obvious increase in emulsion droplet size. This research brings valuable insights on this study and utilisation of novel natural food emulsifiers from plant sources.
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    Formation and characterisation of soluble whey protein aggregates for their use as an emulsifier and as a rheology modifier : a thesis presented in partial fulfilment of the requirements for the degree of Master of Food Technology at Massey University, Auckland, New Zealand
    (Massey University, 2021) Wagh, Salil
    Whey protein is widely utilized in the food industry as a functional ingredient for several applications like foaming, emulsifying, gelling and encapsulating agents. Soluble whey protein aggregates can be defined as colloidal intermediates between native proteins and insoluble precipitate of gel network. A significant body of work created in the last two decades has helped us to understand the role of essential process parameters like heating temperature, duration of heating, pH, ionic strength and protein concentration in the formation and characteristics of soluble whey protein aggregates. The heightened interest in soluble whey protein aggregates is because it expands the functionality of whey proteins by allowing it to be used as a rheology modifier and stabiliser in O/W emulsions and foams. Such a value-added functionality would allow soluble whey protein aggregates to be extensively used in food applications, especially high protein and low-fat food emulsions and emulsion gels. However, the research work on use of soluble whey protein aggregates in O/W emulsions is much less explored compared to studies on the formation of soluble whey protein aggregates. The key objective of the present experimental work was to demonstrate the use of soluble whey protein aggregates in protein rich O/W emulsions and improve our understanding on the influence of soluble whey protein aggregates on the characteristics of O/W emulsions in terms of physical properties, storage stability and stability against thermal treatment. A range of process conditions like heating temperature (68, 75 and 85°C), duration of heating (up to 60 min) and pH (6.9, 6.4, and 6.0) were investigated to understand their impact on the characteristics and yield of soluble whey protein aggregates. Soluble whey protein aggregates with varying particle size (40 nm to 130 nm) were developed and they were further utilized to prepare O/W emulsions with constant oil content (15% w/w) and varying oil content (10 to 30% w/w) to understand its impact on the physical characteristics and stability of O/W emulsions. This experimental study is an endeavour to build a toolkit to prepare high protein low fat emulsions and emulsion gels based on soluble whey protein aggregates.