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 shearing-induced lipolysis on foaming properties of milk.

BACKGROUND: The attraction of cappuccino-style beverages is attributed to the foam layer, as it greatly improves the texture, appearance, and taste of these products. Typical milk has a low concentration of free fatty acids (FFAs), but their concentration can increase due to lipolysis during processing and storage, which is detrimental to the foamability and foam stability of milk. There are contradictory results in reported studies concerning the effects of FFAs on the foaming properties of milk due to differences in milk sources, methods inducing lipolysis, and methods of creating foam. In this study, the foaming properties and foam structure of milk samples whose lipolysis was induced by ultra-turraxing, homogenisation, and microfluidisation (1.5-3.5 µ-equiv. mL-1 FFAs) were investigated. RESULTS: Compared with others, microfluidised milk samples had the smallest particle size, lowest absolute zeta potential, and highest surface tension; thus exhibited high foamability and foam stability, and very small and homogeneous air bubbles in foam structure. For all shearing methods, increasing FFA content from 1.5 to 3.5 µ-equiv. mL-1 markedly decreased the surface tension, foamability, and foam stability of milk samples. The FFA level that led to undesirable foam structure was 1.5 µ-equiv. mL-1 for ultra-turraxed milk samples and 2.5 µ-equiv. mL-1 for homogenised and microfluidised ones. CONCLUSION: Shearing-induced lipolysis greatly affected the physical properties of milk samples and subsequently their foaming properties and foam structure. At the same FFA level, lipolysis induced by microfluidisation was much less detrimental to the foaming properties of milk than lipolysis induced by ultra-turraxing and homogenisation. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Study into the effect of microfluidisation processing parameters on the physicochemical properties of wheat (Triticum aestivum L.) bran.

The physicochemical properties of wheat bran have an effect on its technofunctional and nutritional profile. The possibility to induce physicochemical modifications in wheat bran using microfluidisation was investigated. An I-optimal experimental design was used to investigate the effect of microfluidisation processing parameters (pressure, number of passes, bran concentration and initial particle size) on important properties of wheat bran (particle size, microstructure, chemical composition, water retention capacity (WRC), extractability, viscosity and sedimentation). With the parameters used in this study, microfluidisation reduced wheat bran median particle size to 14.8 µm and disintegrated starch granules from the attached endosperm. This coincided with an increased extractability of starch and arabinoxylan. While the initial particle size was of minor importance, a higher pressure, larger number of passes and lower bran concentration during microfluidisation resulted in a smaller particle size, higher WRC and extractability, and an increased viscosity and stability in a 2% wheat bran suspension.

Microencapsulation of cocoa liquor nanoemulsion with whey protein using spray drying to protection of volatile compounds and antioxidant capacity.

The aim of this study was microencapsulated a nanoemulsion of cocoa liquor with whey protein by spray drying, and evaluate the effect of different inlet drying temperatures on the properties of microcapsules. The nanoemulsion showed a particle size of 202.13 nm, PdI of 0.424, and ζ-potential of -25.20 mV. The inlet drying temperature showed differences in physicochemical properties of microcapsules. Microcapsules presented good thermal stability and protection against the melting of cocoa liquor. Microcapsules obtained showed excellent yields of polyphenolic compounds (78-93%), and high retention of volatile compounds, especially of pyrazines. Greater microencapsulation yield of bioactive compounds and retention of volatile compounds was obtained at higher drying temperature (180 °C). Excellent stability of polyphenols content, antioxidant capacity, and volatile compounds of cocoa liquor were observed during storage of the microcapsules at different temperature conditions, indicating the feasibility of this powder for its incorporation into functional foods.

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.

Effect of microfluidisation on antioxidant properties of corn bran.

The microfluidisation process was used to reduce the particle size and loosen the tight microstructure of corn bran. This process significantly increased corn bran's antioxidant activity exhibited through a surface reaction phenomenon and the extractability of phenolic compounds after alkaline and acid hydrolysis. For corn bran microfluidised through an 87 µm interaction chamber for 5 passes, the two most largely increased phenolic acids released after alkaline hydrolysis were p-coumaric acid (51.1%) and ferulic acid (45.1%). On the other hand, high shear stress during microfluidisation caused partial dispersion or dissolution of free phenolic compounds in water which was lost after the process. It was also found that bran residues after alkaline and acid hydrolysis still exhibited strong antioxidant activity via a surface reaction phenomenon, probably indicating the conventional method based on solvent extraction and relatively mild alkaline and/or acid hydrolysis underestimates the total phenolic content and antioxidant activity of corn bran.

Glycation promoted by dynamic high pressure microfluidisation pretreatment revealed by high resolution mass spectrometry.

The effect of dynamic high pressure microfluidisation (DHPM) pretreatment on the glycation of bovine serum albumin (BSA) was investigated. A detailed glycation map was obtained from high resolution mass spectrometry. Without DHPM pretreatment, only 7 glycation sites were identified, whereas the numbers were increased to 10, 11 and 11 when BSA-glucose was pretreated with DHPM at 50, 100 and 200 MPa, respectively, suggesting that DHPM pretreatment can significantly promote the Maillard reaction. Average degree of substitution per peptide molecule BSA (DSP) was used to further evaluate the glycation level under various DHPM conditions. All the DHPM pretreated samples exhibited elevated glycation level compared to the un-pretreated sample. With 100 MPa DHPM pretreatment, the protein showed the most significantly enhanced glycation extent. In addition, our results suggest that Maillard-type glycation followed by mass spectrometry analysis can be used to study the conformational changes when proteins are disturbed by external forces.