Shyam Suwal

The use of high hydrostatic pressure to modulate milk protein interactions for the production of an alpha-lactalbumin enriched-fraction

Disposal of whey, a co-product generated from the dairy industries, remains an important worldwide problem. However, considering its composition in high value proteins, some technological strategies have emerged for its optimal valorization. Separating alpha-lactalbumin (α-la) from beta-lactoglobulin (β-lg), the two major whey proteins (WP), remains quite challenging to scale up especially using eco-efficient technology due to their similar molecular weights. As a novel approach, we proposed to improve the fractionation of these WP and the recovery of α-la, using high hydrostatic pressure (HHP), an emerging and green technology, combined with acidification to pH 4.6. For this, model protein solutions containing α-la, β-lg and casein (CN – isoelectric, IC and micellar, MC) were treated by HHP and acidified to pH 4.6, with the aim of optimising HHP parameters (level of pressure and time) and the type of CN. The pressure treatment rendered β-lg insoluble forming aggregates with CN and precipitates after acidification to pH 4.6, while α-la remained soluble. Analysis of pressure-treated solutions before acidification showed two main categories of generated-aggregates: (1) κ-CN, αs2-CN and a large portion of β-lg, mainly linked via disulfide bonds, and (2) αs1-CN, αs2-CN, β-CN and a small amount of β-lg, supposedly linked through hydrophobic interactions. The pressure/time combination of 600 MPa/300 s generated the highest α-la purification degree (86%) and protein recovery (77%) using IC. Our experiments, performed on model dairy solutions, demonstrated that the HHP-based fractionation process could be employed in dairy whey processing for the recovery of highly valuable proteins such as α-la.

Evaluation of casein as a binding ligand protein for purification of alpha-lactalbumin from beta-lactoglobulin under high hydrostatic pressure

Fractionation of β-lactoglubulin (β-lg) and α-lactalbumin (α-la) using conventional separation technologies remains challenging mainly due to similar molecular weight. Herein, casein (CN) was used as ligand protein to specifically aggregate β-lg under high hydrostatic pressure (HHP) in order to separate α-la after acidification to pH 4.6. Specifically, we studied the effect of different concentration of CN on α-la purity and recovery. Model solutions of α-la, β-lg and CN (from 0 to 5u202fmg/mL) were pressurized (600u202fMPa-5u202fmin). After acidification and centrifugation of pressure-treated solutions, purity of α-la was increased up to 78% with a recovery of 88% for solution without CN. In contrast with our initial hypothesis, the presence of CN decreased β-lg pressure-induced aggregation and co-precipitation upon acidification and significantly reduced purity (∼71%). Therefore, our results suggest a chaperone-like activity of CN on β-lg pressure-induced aggregation which needs further investigation.

High hydrostatic pressure-assisted enzymatic hydrolysis improved protein digestion of flaxseed protein isolate and generation of peptides with antioxidant activity

Exploration of innovative high hydrostatic pressure (HHP)-assisted enzymatic hydrolysis of plant based food proteins may help improve peptide yield and bioactivity of hydrolysates. In this study, we performed enzymatic hydrolysis of flaxseed proteins using trypsin under HHP (100 and 300u202fMPa for 5 and 10u202fmin) to evaluate the effect of presurization on protein denaturation, degree of hydrolysis (DH), and peptide profile and bioactivity of hydrolysate. Spectrofluorimetric analyses showed that 300u202fMPa induced the maximum destablization of flaxseed protein structures. The same pressure level drastically improved the DH by 1.7 times as compared to that of control. Applying HHP did not modify the peptide profiles of flaxseed protein hydrolysates but their concentrations increased with severity of treatment. Similarly, peptide molecular weight distributions were affected by pressurization parameters, increasing mainly the relative abundance of 500-1500u202fDa peptides. Finally, pressurization at 300u202fMPa for 5 and 10u202fmin improved the antioxidant activity of flaxseed protein hydrolysates by 39 and 55%, respectively, compared to the control.