Unveiling the efficiency of pulsed electric field and ultrasonication in enhancing collagen susceptibility to enzymatic hydrolysis

Since collagen has naturally evolved to be durable, producing collagen hydrolysate with low molecular weight (LMW) peptides which typically results in high bioactivity is a challenge. Here, the efficiency of ultrasound (US) and pulsed electric field (PEF) pretreatments in enhancing the enzymatic hydrolysis of starfish collagen biomass (SFCB) and the antioxidant capacity of the resulting hydrolysate were evaluated. Both pretreatments significantly improved the degree of hydrolysis (DH) and reduced the required hydrolysis time compared to the conventional methods. The DH of SFCB hydrolysate pretreated with US reached 20 % at 60 min while that of the PEF treatment reached 21 % at 120 min, matching the DH of the conventional hydrolysis at 240 min. US and PEF hereby increased the collagen hydrolysate recovery, particularly compensating for a low enzyme-to-substrate ratio (0.5 % v/w). The pretreatments resulted in collagen peptides with significantly higher antioxidant properties, as assessed by ABTS and DPPH assays. The IC50 values of ABTS radical inhibition were found to be 0.68, 0.43, and 0.84 mg/ml for the collagen peptides produced by the US, PEF pretreatments and conventional enzymatic hydrolysis, respectively. Applying PEF and US pretreatment at an enzyme concentration of 0.5 % v/w, increased the proportion of collagen hydrolysate with MW < 10 KDa to 64 % and 59 %, respectively, compared to the conventional method which yielded only 43 %. The enhancements in the antioxidant activities were linked to the increased proportion of LMW peptides (<10 kDa) and elevated relative levels of antioxidative amino acids e.g. glycine, proline, basic amino acids, and hydrophobic amino acids in the peptides produced using US and PEF pretreatment. Overall, US and PEF pretreatments effectively increased collagen susceptibility to enzymatic hydrolysis, improving efficiency and generating peptides with superior antioxidant properties.