PEA PROTEIN ISOLATE-GREEN TEA CATECHIN PICKERING PARTICLES FOR OIL-IN-WATER (O/W) EMULSION STABILITY
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2023
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An emerging trend involves replacing animal-derived proteins in food emulsions with plant proteins due to their positive clean label image and potential as sustainable ingredients. Among these plant proteins, pea proteins show promise in stabilizing oil-in-water (O/W) emulsions, but they tend to create insoluble clumps that can affect physical stability. One strategy to mitigate this is to complex or add polyphenols, which may improve the emulsifying properties of proteins. However, the impact on the non-adsorbed fraction, which can greatly affect physicochemical stability, is not clear. Therefore, this study aimed to assess the effects of pea protein and catechin concentration on O/W emulsion stability, while also evaluating the non-adsorbed fraction and lipid oxidation (over 14 days). Various concentrations of green tea catechins (ranging from 0.1 to 2 mg/mL) were complexed with pea protein isolate particles (1.5 g/100 mL) at pH 7. Subsequently, the aqueous phase and 10% canola oil were pre-homogenized and passed through a microfluidizer to create a fine emulsion. Induced heating at 90 °C for 30 min before homogenization was tested for emulsion optimization. Excess non-adsorbed protein was estimated by centrifuging the emulsions and quantifying the protein in the subnatant via a BCA assay. Overall, the study showed that while induced heating resulted in a reduced non-adsorbed protein fraction, samples without heating treatment yielded better outcomes in terms of average droplet size, zeta potential, and polydispersity index. HPLC analysis revealed that (-)epigallocatechin gallate hydrate was the primary catechin in the extract used for the emulsion formulation (85.26% of the total extract). Emulsion samples with higher catechin concentrations (2 mg/mL) potentially influenced protein adsorption at the oil-water interface, resulting in a greater non-adsorbed fraction (70.01 ± 27.22) compared to lower catechin concentrations (0.1-1 mg/mL). Confocal microscopy results indicated that at catechin concentrations of 0-0.5 mg/mL, protein particles encapsulated the oil droplets, while at 1-2 mg/mL, protein particles floated freely in the aqueous phase instead of coating the oil droplets. Moderate catechin concentrations (0.5 mg/mL) slightly reduced lipid oxidation compared to the control (no catechin), whereas lower catechin concentrations (0.1, 0.3 mg/mL) appeared to significantly increase lipid oxidation (P<0.05). These results provide valuable insights for the development of emulsions, indicating that factors such as an excess of protein and polyphenols can have notable effects on PPI-GTC emulsion-based systems. This work has broader industrial implications as it demonstrates strategies to enhance ingredient functionality in emulsion-based systems.
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Food science, Nanoscience, Nanotechnology, complex particles, green tea catechins, pea protein isolate, Pickering emulsions
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135 pages
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