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 degrees C and air velocity of 4-8 m/s while cryogenic freezing was done at -70 to (-100)degrees 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. (c) 2006 Elsevier Ltd. All rights reserved.