Effects of freezing and thawing on the quality changes of tiger shrimp (Penaeus monodon) frozen by air-blast and cryogenic freezing

Effects of air-blast freezing and cryogenic freezing, thawing by microwave and refrigerator, and freeze–thaw cycle on changes in thiobarbituric acid (TBA), salt-soluble protein (SSP), %freezing loss (%FL), %thawing loss (%TL) and cutting force (CF) of tiger shrimp (Penaeus monodon) were investigated. Air-blast freezing was done at −28 ± 2 °C and air velocity of 4–8 m/s while cryogenic freezing was done at −70 to (−100) °C. Shrimps frozen at the air velocity of 6 m/s had the least %FL and similar CF to the fresh samples. Thawing method did not affect SSP and CF. Samples thawed by the microwave had higher TBA than those in refrigerator. Increasing the freeze–thaw cycle increased the TBA and CF but decreased the SSP. Combined effect of thawing method and freeze–thaw cycles affected %TL only. The histological examination of cryogenic-frozen shrimps showed an increase in spacing between the muscle fiber and torn muscle fiber bundles as the number of freeze–thaw cycles increased.