Abstract: In order to explore the correlation between the moisture mobility and quality changes in tilapia fillets under low temperature storage, fish fillet samples (about 130 g each) were frozen to an internal temperature of ?4 (traditional superchilling), ?8, ?12 or ?18 ℃ and stored for up to 28 days under modified atmosphere packaging (V(CO2) : V(O2) : V(N2) = 6:1:3). During the storage period, juice loss rate, total number of colonies, pH, total volatile basic nitrogen (TVB-N) content, color difference ΔE and water migration were measured and the correlation between water migration and other parameters was evaluated. The results showed that on the 7th day of storage, the highest juice loss rate was observe in the ?4 ℃ group. TVB-N content, total number of colonies, and ΔE value showed an upward trend during storage at all temperatures, and quality deterioration proceeded faster in the -4 ℃ group compared with the other temperature groups. pH slowly declined during storage ?18 ℃, while it showed an initial decrease followed by an increase at the other temperatures. Low-field nuclear magnetic resonance showed that the content of bound water content (A21) did not change significantly, the content of immobilized water content (A22) gradually decreased, and the content of free water content (A23) gradually increased with storage time. The most significant changes were observed at ?4 ℃, whereas the degree of water mobility at ?8 and ?12 ℃ was close to that at ?18 ℃. In general, A21, A22 and A23 were significantly correlated with ΔE and juice loss rate (P < 0.05) and also correlated with TVB-N content and pH. To sum up, the new superchilling technology at ?12 ℃ can be seen as a substitute for freezing to preserve fish quality.

Key words: low-field nuclear magnetic resonance; superchilling; modified atmosphere packaged tilapia fillets; moisture migration; quality change; correlation