Optimisation for production of fish protein hydrolysate from Nile Perch (Lates niloticus) by-products

Abstract

The global rising concern for food and environmental security has forced established industries such as fish processingto explore new areas of improvement. In Kenya thus far, no studies have been carried out to explore the use of enzyme technology in the possible recovery of products of high nutritional value from industrial co-streams. Recent advances in the field of enzyme technology have led to the development of new functional products with various properties to address this concern. Fish protein hydrolysate (FPH) is one of the results of such advances, resulting in a product with high quality protein possessing a good amino acid profile.Nile Perch is the predominant species fished from Lake Victoria, and is a major export commodity. The present study was carried out to determine the most suitable enzyme and corresponding concentration (enzyme/substrate ratio) required to hydrolyse Nile Perch (Lates niloticus) heads and frames (by-product) within a suitable time, to obtain a final fish protein hydrolysatewith desirable protein recoveries.Heads and frames (tissue-intact by-product) was obtained from W.E. Tilley, an exporter based in Nairobi,and hydrolysed using three commercially available food grade enzymes: Alcalase, Protex 30L, and Bromelain from pineapple stem. For unhydrolysedby-product, the Biuret and Kjeldahl methods were chosen to analyse percentage protein content, determined as 18.42 ± 0.04 and 20.4 ± 0.47 %, respectively. Moisture, ash/mineral, and lipid content were found to be 58.8 ± 1.26, 10.82 ± 1.99, and 7.86 ± 0.63 %, respectively. Optimisation for enzyme concentration involved two-hour reactions using 0.5 and 1.0 % enzyme/substrate ratio for each enzyme. Bromelain gave best recoveries, determined by the Biuret method, with an enzyme/substrate ratio of 1 %, yielding a protein recovery of 68.2 %. Optimisation for hydrolysis time followed four/six-hour reactions with Bromelain, with a change in enzyme batch between the two reactions. v The four-hour reaction yielded a final protein recovery of 97.7 %, while that of six hours yielded a recovery of 68.2 %. The six-hour batch was retained for freeze-drying to obtain powder FPH.The optimal conditions for hydrolysis were determined to be a reaction time of 4 hours with a Bromelain:Substrate concentration of 1%. The moisture, ash/mineral, lipid and protein content of the final FPH where; 14.8 ± 0.67, 5.3 ± 0.4, 9.8 ± 0.31 and 68.2 ± 1.03%, respectively. All analyses were performed in triplicate and subjected to standard deviation calculations for mean results.The high protein content indicated that a nutritious soluble FPH could be obtained from Nile Perch by-products. It maypossibly be used in food fortification, nutraceuticals, pharmaceuticals, and microbial growth media.Further characterization of the FPH is necessary to determine bioactive and nutritionalproperties of the product, before their applications can be taken to market