Abstract
Kuruma prawn Penaeus japonicus was kept frozen at -20°, -30°, -40°, -50°, -60° and -80°C for 9 months or stored in ice for one week. At due time intervals, the muscle was an-alyzed for changes in various parameters such as water holding capacity, tyrosine content, protein composition, etc.
During frozen storage at -20° and -30°C, expressible drip increased from 22% at the start to 41% after 9 months, and tyrosine content from 5mg/100g at the start to 15mg/100g after 7 months. The pH of muscle showed a little increase. In contrast, all the parameters did not change significantly at or below -40°C.
Muscle protein composition remained roughly constant during frozen storage up to 9 months irrespective of temperatures adopted; 48-63% myofibrillar, 29-36% sarcoplasmic, and 2-12% alkali-soluble plus stroma proteins.
One-week ice storage gave results similar to those obtained during frozen storage at -20° and -30°C. The pH of muscle increased sharply from 7.0 at the start to around 7.9 after one week.
From these results, it was concluded that -40°C is reasonable to keep the quality unchanged for a long-term storage, though -20°C is low enough for a short-term storage up to a few months.
