Effect of serine protease inhibitor from squid ovary on gel properties of surimi from Indian mackerel

Effects of serine protease inhibitor from squid ovary (SOSPI) and egg white powder (EWP) on gel properties of surimi from Indian mackerel (Rastrelliger kanagurta) were investigated. Breaking force of gel increased when SOSPI levels increased up to 2%. However, EWP showed higher efficiency in increasing breaking force of resulting surimi gel. Nevertheless, SOSPI (0.5-3%) had no effect on deformation. Trichloroacetic acid-soluble peptide content in surimi gel decreased when the levels of SOSPI and EWP increased (p<.05). This was coincidental with more retained myosin heavy chain. Water holding capacity was increased with the addition of these protein additives, but resulted in lower whiteness. Microstructure study revealed that surimi gel added with 2% EWP was denser and had higher connectivity as compared to that containing 2% SOSPI. The SOSPI had no negative effect on sensory attributes and could serve as the alternative protein additive to improve gel strength of surimi. Practical applicationsSurimi from dark-fleshed fish is prone to degradation of myofibrillar proteins caused by the endogenous proteases, thereby lowering textural property. To tackle the problem, protease inhibitors (egg white, porcine plasma protein, and bovine plasma protein) have been used by the surimi industries. Due to drawbacks of some particular inhibitors (religious constraints, off-white color, off odor, etc.), the novel additives are still in demand. Ovary from squid processing industry, commonly discarded as the waste, can be an alternative natural protease inhibitor, which can improve the gel properties of surimi, especially produced from dark-fleshed fish.