Physicochemical properties of frozen Alaska pollock fillets and surimi as affected by various sodium phosphates

The physicochemical characteristics of frozen Alaska pollock fillet and surimi were investigated as affected by various phosphates (sodium tripolyphosphate (STPP), tetrasodium pyrophosphate (TSPP), trisodium pyrophosphate, sodium hexametaphosphate, and disodium phosphate anhydrous). Both phosphate-injected fillets and phosphate-added surimi along with cryoprotectant (5% sugar and 4% sorbitol) were subjected to 0, 3, and 9 freezing/thawing (F/T) cycles. The concentration of sodium phosphate retained in fillet was adjusted to 0.3% using poking (6 times), soaking (10 min), and draining (2 min). Trimethylamine-N-oxide demethylase (TMAOase) activity and formaldehyde (FA) concentration were found significantly higher in fillet than in surimi. As STPP and TSPP were more effective to control TMAOase activity of fillet and surimi than other phosphates, during repeated F/T, lower TMAOase activity, lower FA content, lower drip/cook loss, and higher salt-soluble protein extractability were observed. Texture toughness in fillet and surimi with STPP and/or TSPP were lower than other treatments. Practical applications: Two phosphates (STPP and TSPP) effectively minimized both freeze-induced and TMAOase-caused denaturation in fillets and surimi. As a result, texture toughening was reduced. TMAOase activity and FA content were significantly lower in surimi than fillets.