Pre-cooked Pacific white shrimp (Li

Pre-cooked Pacific white shrimp (Litopenaeus vannamei) is an important shrimp product. However melanosis,
especially in the cephalothorax including carapace and internal organs, is more likely caused by
the remaining polyphenol oxidase (PPO) after pre-cooking. Thus, PPO from carapace and proteases from
hepatopancreas of Pacific white shrimp were characterised and the remaining activities of both enzymes
were monitored in pre-cooked shrimp during storage at 4 C. Based on activity staining using L-b-(3,4
dihydroxylphenyl) alanine as a substrate, PPO consisted of two isoforms with apparent molecular weight
of 210 and 220 kDa. No difference in activity band was observed when analysed under reducing and nonreducing
condition. Proteases from hepatopancreas were able to activate PPO to some degree. For the
in vitro study, both enzymes were quite stable when heated at temperature up to 70 C but the loss in
activities increased with increasing heating time (0–120 s). When Pacific white shrimp were pre-cooked
to obtain different core temperatures (50–90 C), different PPO and protease activities were retained.
Higher core temperatures were associated with lower PPO and protease activities, but higher cooking
loss. When the shrimp were pre-cooked at 80 C, the residual PPO and protease activities were 3.9%
and 5.4%, respectively and cooking yield of 95.6% was obtained. The resulting pre-cooked shrimp possessed
lower melanosis score during 7 days of storage at 4 C. Thus, pre-cooking of shrimp to obtain a
core temperature of 80 C, with a holding time of 30 s, could prevent the severe cooking loss and lower
melanosis during subsequent storage

ผลลัพธ์ (อังกฤษ) 2:

Pre-cooked Pacific white shrimp (Litopenaeus vannamei) is an important shrimp product. However melanosis,
especially in The cephalothorax including carapace and internal organs, is more likely caused by
The remaining polyphenol oxidase (PPO) After Pre-Cooking. Thus, PPO from carapace and proteases from
hepatopancreas of Pacific White Shrimp were characterized and The remaining activities of Both enzymes
were monitored in Pre-cooked Shrimp during Storage at 4? C. Based on Activity staining using Lb- (3,4
Dihydroxylphenyl) Alanine As a Substrate, PPO consisted of Two isoforms with apparent molecular Weight
of 210 and 220 kDa. No difference was observed in Activity band and Nonreducing When analyzed under reducing
condition. Proteases from hepatopancreas were able to activate PPO to some degree. For The
in vitro Study, Both enzymes were Quite Stable Temperature When heated at up to 70? C but in The Loss
Increasing activities increased with heating time (0-120 S). When Pre-Pacific White Shrimp were cooked
to Obtain different core temperatures (50-90? C), and protease activities were different PPO Retained.
Higher temperatures were Associated with Lower PPO core and protease activities, but Higher Cooking
Loss. When The Shrimp were Pre-cooked at 80? C, The residual PPO and protease activities were 3.9%
and 5.4%, respectively and Cooking yield of 95.6% was obtained. The resulting Pre-cooked Shrimp possessed
Lower Score melanosis during 7 days of Storage at 4? C. Thus, Pre-Cooking of Shrimp to Obtain a
core Temperature of 80? C, with a time of 30 S Holding, could Prevent The Loss and Lower Cooking severe
melanosis during Subsequent Storage.