nSHERY BULLETIN: VOL. 76, NO. 1 



Table 3. — Change in weight and analytical values with time of holding 2,100 g of hand-peeled, raw, 

 washed, pink shrimp meats in modified refrigerated seawater (MRSW) and ice. 



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800 



7 50- 



700 



650 



600. 



2 3 4 5 6 7 

 TIME OF HOLDING 



8 9 

 days 



10 11 12 



Figure l. — Recovery of hand-peeled, raw, washed pink shrimp 

 meats with time of holding 2,100 g of shrimp in modified refrig- 

 erated seawater (MRSW) or ice, expressed on a salt-free, 84% 

 moisture betsis and protein. 



Commercial shrimp peelers exert a strong 

 mechanical and washing action on the shrimp, 

 which leaches out soluble proteins. In part there- 

 fore, the final yield would be a function of the gross 

 weight of the landed whole shrimp and of the 

 amount of soluble protein present, which would be 

 influenced by the time and extent of action by 

 bacteria or enzymes. Because the MRSW system 



reportedly extends holding time, ex-vessel 

 shrimp — processed at an equal stage of quality 

 (say, 4-day ice and 8-day MRSW) and at an equal 

 water content — should give equal yields. In actual 

 practice, however, machine peeling efficiency 

 tends to be the controlling factor for yield. For 

 example, if shrimp were to peel too easily on the 

 machines, yields would be low because the meats 

 would be rubbed off on the rollers. Yields would 

 also be low if the shrimp were too difficult to peel 

 because some unpeeled shrimp would be discarded 

 at the inspection belt. Nelson and Barnett^ ob- 

 tained a 19% raw meat yield from pink shrimp 

 held in the MRSW system and processed through a 

 Laitram (Model A) machine peeler. 



Hand-Peeled, Washed, Cooked, 

 Pink Shrimp Meats 



The gross weights for hand-peeled, washed, 

 cooked meats obtained from the 2,100 g of whole 

 shrimp were considerably higher from the ice-held 

 shrimp than from the MRSW-held shrimp (Table 

 4). Under commercial processing conditions, infill 

 weights must be adjusted to compensate for the 

 high moisture content which would otherwise 

 cause low drained weights after retorting or freez- 

 ing. Consequently, to equalize the variable water 

 content between holding systems and samples, we 

 calculated the weight on a constant basis (salt- 

 free, 75% moisture) and found that the two holding 

 systems gave nearly identical recoveries except 

 for low recoveries during the first several days in 



^Nelson, R. W., and H. J. Bamett. Improved shrimp quality by 

 the use of RSW modified with CO2 gas. Unpubl. manuscr. 

 Northwest and Alaska Fisheries Center Utilization Research 

 Division, NMFS, NOAA, 2725 Montlake Boulevard East, Seat- 

 tle, WA 98112. 



76 



