Enzymatic Digestion of Calf Fleshing Meat By-Products: Antioxidant and Anti-Tyrosinase Activity of Protein Hydrolysates, and Identification of Fatty Acids

Abstract

The food waste reduction through an efficient recovery of its valuable building molecules has become an important topic with a positive effect on the economy and the environment. In this work, the revalorization of slaughterhouse calf fleshing meat through its enzymatic hydrolysis is proposed. The proteolytic activity of 11 enzymes was initially screened and the four most efficient enzymes (papain, trypsin, pancreatin, and bromelain) were selected. The molecular profiling of the different protein/peptide fractions by the Linear Trap Quadrupole-OrbiTrap technique showed compositional differences due to the specificity of the enzymes' cleavage sites. In order to find a potential reuse of these hydrolysates, the analysis of antioxidant and, for the first time on fleshing meat hydrolysates, of anti-tyrosinase activities, was performed. Papain-digested samples were those showing the highest inhibition activity of tyrosinase enzyme (55.6%) as well as the highest antioxidant activity (3.52 g TEAC/L). In addition, the composition analysis of the lipid fraction was performed. The mono-unsaturated fatty acids resulted to be the most abundant lipid in all the samples with the exception of pancreatin-treated hydrolysates in which poly-unsaturated fatty acids were predominant. The present results seemed to support a possible valorization of isolated fractions from calf fleshing by-products, as food or feed ingredients, by the implementation of fraction isolation within the meat-processing pipeline.

Keywords: bioactive peptides; by-products valorization; fatty acids; protease; protein hydrolysates.

Figure 1

Optimized hydrolysis. (a) Quantification of hydrolyzed proteins (g BSA eq/L) in intermediate fractions obtained after calf fleshing hydrolysis at different digestion conditions. ND, average of not-digested control at 50 °C and 37 °C. Statistically significant differences among different hydrolysate samples were indicated by different letters, according to one-way ANOVA followed by post hoc Tukey’s multiple pairwise comparison (p < 0.05). Data are the mean ± SD (n = 4). (b) SDS-PAGE (Sodium Dodecyl Sulphate - PolyAcrylamide Gel Electrophoresis) profile of samples: A, standard marker; B, papain hydrolysate; C, pancreatin hydrolysate; D, bromelain hydrolysate; E, trypsin (B) hydrolysate.

Figure 2

Quantification of antioxidant activity (a) and anti-tyrosinase activity (b) in intermediate fractions obtained after calf fleshing hydrolyses at different digestion conditions. ND, average of not digested control at 50 °C and 37 °C. Statistically significant differences among the same analysis were indicated by different letters, according to one-way ANOVA followed by post hoc Tukey’s multiple pairwise comparison (p < 0.05). TEAC, Trolox equivalents antioxidant capacity. Data are the mean ± SD (n = 4).