This study aimed to utilize enzymatic treatment and pressurized hot water extraction (PHWE) to recover soluble food-grade protein and collagen peptides from mechanically deboned chicken meat (MDCM), a side-stream from the meat industry. Food-grade enzyme blends Ermitase 1 and Ermitase 2 were used to fractionate the mechanically deboned meat into fat, soluble protein, and solids. Response surface methodology was utilized to optimize treatments to maximize the protein yield. At the optimum conditions (hydrolysis time 240 min, E:S 0.27%, and a hydromodule 1 L/kg), the enzymatic treatment produced high protein yield, approximately 90%. The protein hydrolysates showed a good solubility index, but weak gelling properties. The PHWE of the bones resulted in a high nitrogen yield, approximately 87%, at the optimum conditions of 190 °C and 83 min. Peptides in the bone extract were in the range of 0.5–13.7 kDa. Overall, our study highlights the importance of response surface methodology to optimize parameters for mechanically deboned chicken meat enzymatic and PHWE treatments to achieve high yields of protein for food applications and low-molecular-weight collagen peptides for cosmetic applications. The crucial role of protein and peptide prices was observed in preliminary profitability analysis.

Aims The aim of the study was to investigate the isomerization of linoleic (LA) and linolenic acids (LNAs) into their conjugated isomers by Propionibacterium freudenreichii DSM 20270 and utilize this feature for microbial enrichment of blackcurrant press residue (BCPR) with health‐beneficial conjugated fatty acids. Methods and Results First, the ability of P. freudenreichii to isomerize 0.4 mg ml^‐1 of LA and LNA was studied in lactate growth medium. Free LA and α‐LNA were efficiently converted into conjugated linoleic (CLA) and α‐linolenic acid (α‐CLNA), being the predominant isomers c9,t11‐CLA and c9,t11,c15‐CLNA, respectively. The bioconversion of α‐LNA by P. freudenreichii was more efficient in terms of formation rate, yield and isomer‐specificity. Thereafter, free LA and LNAs obtained from hydrolyzed BCPR neutral lipids, by lipolytically active oat flour, were subjected to microbial isomerization in BCPR slurries. In 10% (w/v) slurries, a simultaneous enrichment in c9,t11‐CLA and c9,t11,c15‐CLNA of up to 0.51 and 0.29 mg ml^‐1 was observed from starting levels of 0.96 mg LA ml^‐1 and 0.37 mg α‐LNA ml^‐1, respectively. Conclusions This study shows that growing cultures of P. freudenreichii DSM 20270 are able to simultaneously enrich BCPR with health‐beneficial conjugated isomers of LA and α‐LNA. Significance and Impact of Study This study demonstrates that microbial isomerization technique can be utilized to enrich lipid‐containing plant materials with bioactive compounds and thereby enable valorization of low value plant‐based side streams from food industry into value‐added food ingredients.