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Mince of 98-wk-old spent hens was washed two times with 0.1% NaCl. Portions of unwashed and washed mince were mixed with a cryoprotectant (CP) composed of 4% sucrose, 4% sorbitol, and 0.2% Na-tripolyphosphate and were immediately frozen and stored at -20 C. Mince without CP was run as control. Textural properties of the stored mince and surimi were measured at 1-mo intervals for 6 mo, after being thawed at 4 C overnight, ground with 3% NaCl, and heated at 90 C for 15 min. For freeze-thaw stability study, minces were subjected to six freeze-thaw cycles. Each freeze-thaw cycle was carried out at 1 mo of storage. Textural quality parameters (gel strength, breaking strength, deformation, protein solubility, expressible moisture, cooking yield, folding test, drip-loss, and sensory scores) were decreased in both unwashed and washed mince, mostly during the early stages of storage. Washed mince showed significantly better textural properties than unwashed mince. Washing protected the gel quality of the hen mince from degradation during frozen storage. Cryoprotectants could not protect the gel strength or breaking strength, but deformation was slightly improved. Water-retention properties were protected, and folding test and sensory scores were well preserved in the mince with added CP. Cryoprotectants had a beneficial effect on frozen, stored spent hen surimi to protect the elasticity and cohesiveness of the gel.

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The contribution of transglutaminase (TGase) to the setting of fish flesh paste was studied using TGase-free actomyosin (AM) from five fishes. Sarcoplasmic proteins (SP) were extracted from each fish and one part of them was treated with N-ethylmaleimide in order to inactivate TGase contained in them (NEM-SP). The addition of SP to the AM paste promoted the cross-linking of myosin heavy chain during its setting and increased the breaking force of resulting suwari gel. In the breaking force, the gel added with SP was higher than the one added with NEM-SP by 40% for Alaska pollack and sardine, 20% for common horse mackerel and flounder, and less than 10% for Spanish mackerel. From the result and our previous study, it is presumed that TGase increases the breaking force of the suwari gel from the fish flesh paste nearly by a few ten per cent.

A recipe of shrimp cracker (a type of crispy biscuit) enriched with shrimp shell protein was developed from underutilized shrimp shell wastes and the effects of different amount of shrimp shell powders on the quality and shelf life of the products were studied. Shrimp industry wastes (head, appendages, carapaces, and shell) were thoroughly washed, dried in hot air oven at 60 ○ C for 24 h and ground by a blender. Fine shrimp shell powder thus obtained was used for making shrimp crackers. Hydrolyzed vegetable oil, was beaten by hand and other ingredients such as powder milk, sugar, oil, baking powder, flour and vanilla essence were mixed to make a dough. Various levels of shrimp shell powder (5%, 10%, and 20%) were mixed to the dough to enrich with shrimp protein. The dough was kept flatted in a tray, cut into pieces of different shape by dies and put into the oven at 100 ○ C for 8 minutes. Increasing the quantity of shrimp shell powder in shrimp crackers increased the protein content but the quality in terms of taste, color and flavor was slightly decreased. Using of 10% shrimp shell powder obtained the best quality shrimp crackers, in terms of both protein enrichment and sensory quality. Quality of shrimp crackers was tested by both subjective and objective methods. Products made with 10% shrimp shell powder had an acceptable bacterial load in refrigeration up to 45 days but in room temperature up to 30 days. Low storage quality in room temperature might be due to inadequate packaging in the laboratory condition. This research revealed that high quality protein fortified shrimp crackers could be manufactured from unutilized shrimp shell wastes.