Protein hydrolysate from yellowfin tuna (Thunnus albacares) red meat for oxidative and structural stabilisation of microencapsulated fish oil

Abstract

Microencapsulation by spray drying is a well-accepted technique for protecting fish oil against oxidative deterioration. However, the severe operational conditions during spray drying destabilise the emulsion, leading to capsule collapse and induction of auto-oxidation. Consequently, use of food grade anti-oxidants and cross-linkers has been suggested to ensure oxidative stability and structural integrity of the microcapsules. A promising option in this regard is the employment of antioxidant peptides or protein hydrolysates, which also serve as filling moieties when used as wall polymer, owing to their reduced molecular size. Moreover, protein hydrolysates are considered to improve the stability of the emulsion during atomisation. Hence, in the present study an attempt has been made to compare the efficacy of yellowfin tuna red meat hydrolysate of known antioxidant potential as wall and core polymer, for encapsulating sardine oil. The primary wall materials used in the study were sodium caseinate, gum arabic and maltodextrin. The efficacy of hydrolysate as wall material was evaluated by replacing the sodium caseinate and keeping the proportion of all other polymers constant. Oil encapsulate was also prepared with tuna protein hydrolysate as core material together with sardine oil to evaluate the extent of protection offered against auto-oxidation of fish oil. Oil encapsulates were characterised based on morphological, physical parameters including SEM, DSC, FTIR as well as fatty acid profile, encapsulation efficiency, flow properties, colour, moisture, hygroscopicity and invitro digestibility studies. Storage studies of sardine oil and oil encapsulates under accelerated, chilled and room temperature conditions indicated better oxidative protection to oil encapsulates compared to liquid oil. Tuna protein hydrolysate had more protection efficiency against fish oil oxidation when used as core material than when used as wall material.