Obtaining, evaluation and microencapsulation of bioactive protein hydrolysates from by-products of common carp (Cyprinus carpio)
AutHor: Juan Zamora Sillero (Currículo Lattes)
Supervisor: Dr Carlos Prentice Hernández
Co-supervisor: Dr Jose Maria Monserrat
Co-supervisor: Dr Adem Gharsallaoui (Université Claude Bernard-Lyon 1, França)
Inappropriate management of aquaculture by-products and the fish industry can have a major ecological impact and significantly affect the economic viability of the sector. Enzymatic hydrolysis is an efficient technique to add value to these by-products by producing peptides with a large amount of essential amino acids and varied biological activities such as antioxidant, antihypertensive, and neuroprotective, among others. The objective of this thesis was to obtain protein hydrolysates from the beneficiation by-product (head, viscera, carcass and skin) of the common carp (Cyprinus carpio), to evaluate in vitro and in vivo its antioxidant capacity and to microencapsulate the hydrolysates with antioxidant activity.In Chapter I, a review work was carried out on different methods for the production of protein hydrolysates as well as an examination of current research evaluating the bioactive properties of hydrolysates from fish by-products. In Chapter II, the antioxidant capacity of protein hydrolysates was evaluated in vitro. For this, the by-product of common carp was hydrolyzed using the enzymes Alcalase (A) and Protamex (P) to achieve hydrolysis (DH) degrees of 10 and 15%. The antioxidant capacity in vitro against peroxyl radicals and DPPH radicals was investigated as well as the antioxidant activity in vitro in hippocampal cells HT-22. Hydrolyzate A15 showed the highest antioxidant activity (p <0.05) against the DPPH radical. Hydrolyzate P15 showed the lowest activity against peroxyl radicals (p <0.05).The measurement of the intracellular concentration of reactive oxygen species (ROS) in the HT-22 cell system revealed that P15 (1.25 mg / ml) reduced the ROS concentration (p <0.05). In Chapter III, the in vivo antioxidant activity of carp hydrolysates was evaluated. A feeding test was carried out to evaluate the effect of dietary supplementation of hydrolyzate A15 on the antioxidant status of zebrafish (Danio rerio). The zebra fish were fed for 44 days with four different diets containing increasing levels of hydrolysates (0 g Kg-1; 25 g Kg-1; 50 g Kg-1; 100 g Kg-1) and at the end of the test were collected the gills, brain and muscles to assess total antioxidant capacity against peroxyl radicals (ACAP) and lipid peroxidation (TBARS).In the muscle, the lipid peroxidation was reduced in the muscle of the fish fed with the diet supplemented with 50 g Kg-1 of hydrolyzate (p <0.05). Lipid peroxidation in the brain was reduced (p <0.05) in all groups when compared to the group fed the hydrolyzate-free diet. Finally, in Chapter IV of this thesis, the effect of microencapsulation of hydrolysates by complex coacervation with pectin and subsequent spray drying on the antioxidant activity of hydrolysates was evaluated. For this study, muscle hydrolysates and carp by-products hydrolysates were evaluated. The results revealed that microencapsulation and spray drying of hydrolyzate suspensions reduced antioxidant activity (p <0.05). On the contrary,microencapsulation by complex coacervation with pectin and subsequent spray drying had no significant effect on antioxidant activity (p> 0.05). However, the present thesis work demonstrated that the enzymatic hydrolysis of the by-products of the processing of common carp is an effective technique that allows the release of peptides with antioxidant and neuroprotective activity with great potential for use in the pharmaceutical and food industry.