High-pressure microfluidisation positively impacts structural properties and improves functional characteristics of almond proteins obtained from almond meal

Almond protein isolate (API) obtained from almond meal was processed using dynamic high-pressure microfluidisation (0, 40, 80, 120, and 160 MPa pressure; single pass). Microfluidisation caused significant reductions in the particle size and increased absolute zeta potential. SDS-PAGE analysis indicated reduction in band intensity and the complete disappearance of bands beyond 80 MPa. Structural analysis (by circular dichroism, UV-Vis, and intrinsic-fluorescence spectra) of the API revealed disaggregation (up to 80 MPa) and then re-aggregation beyond 80 MPa. Significant increments in protein digestibility (1.16-fold) and the protein digestibility corrected amino acid score (PDCAAS; 1.15-fold) were observed for the API (80 MPa) than control. Furthermore, significant improvements (P < 0.05) in the functional properties were observed, viz., the antioxidant activity, protein solubility, and emulsifying properties. Overall, the results revealed that moderate microfluidisation treatment (80 MPa) is an effective and sustainable technique for enhancing physico-chemical and functional attributes of API, thus potentially enabling its functional food/nutraceuticals application.

Effect of different homogenisation methods and UHT processing on the stability of pea protein emulsion

Pea protein is a very popular source of edible plant-based protein among legumes. In this study, the stability of ultra high temperature (UHT) processed pea protein emulsion prepared from 0.5 and 1.0% (w/v) pea protein concentrate (PPC) by two different homogenisation methods of microfluidisation (500 Bar) and ultrasonication (ultrasonicated for 1, 3 and 5 min) was investigated. In addition, the emulsion properties (particle and droplet size, flocculation, coalescence, zeta potential, hydrophobicity and creaming index) of PPC emulsions before and after UHT treatment were measured. The overall heat transfer coefficient (OHTC) versus time graphs were stable during UHT processing for both microfluidised and ultrasonicated PPC emulsions that indicates no fouling and good stability under the thermal treatment condition. Freshly prepared emulsion using 0.5 and 1.0% PPC and ultrasonicated for 5 min showed creaming index of 5.73 and 8.39%, particle size of 0.96 and 1.53 μm respectively. In addition, the fat droplet size for the above samples measured 1.05 and 1.85 μm for larger fat droplets and 0.51 and 0.72 μm for smaller fat droplets, respectively. However, after UHT treatment this emulsion destabilised due to protein aggregation as indicated by the high flocculation index (13.22 and 103.35%), particle size (1.59 and 3.23 μm) and droplet size (1.30 and 2.53 μm, for large fat droplets and 0.90 and 1.22 μm, for small fat droplets). After UHT treatment the microfluidised PPC emulsion using 0.5 and 1.0% PPC were the most stable with small particle size (2.85 and 0.36 μm), high zeta potential (-56.36 and - 27.30) and low creaming index (3.87% and 4.97%), respectively as compared to ultrasonicated samples. Overall, this study revealed that UHT treatment improved emulsion properties of the microfluidised PPC emulsion compared to the ultrasonicated PPC emulsion.

Influence of hydrolysis behaviour and microfluidisation on the functionality and structural properties of collagen hydrolysates

The functionality and structural properties of pig skin hydrolysates with different degrees of hydrolysis (DH, 10% and 20%) and microfluidisation (120MPa), prepared by pepsin and Alcalase® have been investigated in this study. Extensive hydrolysis can significantly improve the absolute value of the zeta potential and surface hydrophobicity. The particle distribution of hydrolysates decreased with increasing DH. The numbers of free sulfhydryl (SH) and disulfide bonds (SS) were significantly increased with increasing DH (p<0.05). Hydrolysates with a lower DH showed a better emulsifying property than those with a higher DH. Microfluidisation led to the transformation of structural and interfacial properties of the hydrolysates and increased the value of the zeta potential, S₀, and gel strength. Microfluidisation results in limited breakage of chemical bonds, the number of SS and SH bonds unchanged in the treatment. These results reflect the functionality and structural properties of collagen-rich pig skin hydrolysates.