Industrial enzymatic hydrolysis of chicken viscera and bone materials: effect on protein recovery and product properties

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Enzymatic hydrolysis is an efficient strategy for valorizing chicken rest raw materials, yet the influence of industrially relevant process design on protein recovery and product functionality remains insufficiently described, especially for sediment fractions. This paper evaluates how key hydrolysis parameters affect protein recovery, degree of hydrolysis (DH), amino acid composition, and quality properties of hydrolysates and sediments from chicken viscera and bone materials. Eleven hydrolyses were performed using endogenous and commercial enzymes under varying pre-treatments, water additions, and hydrolysis times. Protein recovery in hydrolysates increased during the first 60 min, while DH continued to rise up to 120 min. For viscera, heating raw material to hydrolysis temperature accounted for 45–66% of total hydrolysate protein recovery, compared with 18%−30% for bone materials. Both viscera and bone hydrolysates achieved high protein contents. A substantial share of bone material proteins was recovered in sediments, characterized by lower DH and higher ash content. Thermal pre-inactivation of endogenous enzymes shifted protein recovery from hydrolysates to sediments, and reduced water addition decreased hydrolysate protein recovery and DH while increasing these parameters in sediments. The amino acid composition of hydrolysates and sediments reflected raw material composition. Viscera hydrolysates exhibited higher DH and superior emulsifying properties, whereas bone hydrolysates showed higher water-holding and oil-absorption capacities. These results demonstrate that targeted control of processing parameters is essential for influencing the distribution of protein between fractions and their properties. Both hydrolysates and sediments represent valuable protein products, emphasizing the need to consider the entire process when optimizing industrial enzymatic hydrolysis.