Abstract
Valorising protein-rich by-products from the meat and fish processing industries is an important approach to sustainable food biotechnology. This study aimed to develop and evaluate an acid–enzymatic hydrolysis technology to produce a protein hydrolysate (microbiological peptone) from meat and fish processing by-products, with potential application as a nitrogen source for microbial cultivation and food biotechnology processes. We investigated secondary meat by-products (bovine rumen, lung, rennet, and meat-and-bone materials), porcine gastric mucosa and pancreas as enzyme sources, and fish by-products (bream, perch, skin, fins, and bones). A total of 72 experimental hydrolysate samples were analysed, including 18 acid, 18 alkaline, and 36 enzymatic hydrolysis variants. We optimised hydrolysis conditions by evaluating the raw material ratio, reagent concentration, pH, temperature, enzyme dosage, and processing time. The optimum process used acid–enzymatic hydrolysis with 3% orthophosphoric acid, followed by enzymatic treatment with 2% porcine pancreas and 8% porcine gastric mucosa at 45–50 °C and pH 6.9, with a fish-to-meat raw material ratio not exceeding 30%. Under these conditions, the hydrolysate contained 15.2% total nitrogen, 4.5% amino nitrogen, 13.5 ± 0.5% dry matter, and a hydrolysis coefficient of 0.94. Drying at an inlet air temperature of 180 ± 1 °C produced microbiological peptone with a final moisture content below 7%, meeting the requirements of GOST 13805-76. The obtained microbiological peptone exhibited satisfactory physicochemical, organoleptic, and microbiological quality characteristics. The proposed acid–enzymatic process demonstrates the potential for converting protein-rich meat and fish processing by-products into microbiological peptone and may represent a promising nitrogen source for microbial cultivation and selected food biotechnology applications. Further studies are required to confirm industrial scalability and broader food-related applications