PHYSICAL AND CHEMICAL CHANGES OF PINK SHRIMP, PANDALUS 



BOREALIS, HELD IN CARBON DIOXIDE MODIFIED REFRIGERATED 



SEA WATER COMPARED WITH PINK SHRIMP HELD IN ICE 



Fern A. Bullard and Jeff Collins* 



ABSTRACT 



Pink shrimp, Pandalus borealis, were held in carbon dioxide modified refrigerated seawater for 12.5 

 days and in ice for 11.5 days. Chemical tests for spoilage indicated that shrimp held in carbon dioxide 

 modified refrigerated seawater were acceptable up to 9.5 days and those held in ice up to 6.5 days. Data 

 on weight, yield, solids, carotenoids, protein, salt, and pH are given. When expressed on a constant 

 basis (salt-free, 75% moisture), the yield of cooked product calculated from the gross weight of whole 

 shrimp decreased rapidly during the first few days in either system. The yield of cooked meats from the 

 carbon dioxide modified refrigerated seawater system decreased from 18.3% at 0.5 day to 15.3% at 4.5 

 days but varied in the ice system between 14.0 and 15.5% over the useful holding {jeriod of 6 days. 



The advantages and disadvantages of the refrig- 

 erated seawater system (RSW) for holding fish and 

 shellfish are well documented and were recently 

 discussed by Barnett et al. (1971) and by Nelson 

 and Barnett (1971). Based on bacteriological mea- 

 surement and sensory evaluation, these authors 

 showed that rockfish, Sebastodes flauidus, can be 

 held in the RSW system modified by the addition of 

 carbon dioxide (MRSW) for longer periods of time 

 than in ice. The purpose of this study was to obtain 

 detailed information on the physical and chemical 

 changes that occur during time of holding of pink 

 shrimp in the MRSW system compared with that 

 of pink shrimp held in ice. 



EXPERIMENTAL 



Preparation of Pink Shrimp 



draining for 30 min resulted in nearly constant 

 weight. 



The MRSW holding portion of the experiment 

 was conducted as follows. Baskets of shrimp and 

 loose shrimp were alternately placed in the 

 MRSW tank containing a 3.5% brine at -1.7°C, 

 previously treated with carbon dioxide to 3.92 pH. 

 The final loading ratio of shrimp to brine was 1:1.4 

 (wt/wt). 



The ice holding portion of the experiment was 

 conducted as follows. Samples of shrimp for ice 

 holding were similarly rinsed, drained for 30 min, 

 and adjusted to 2,100 g each before being placed in 

 single layer cheese cloth "baskets" and covered 

 with ice and 38.5 kg (85 lb) loose shrimp. Loose 

 shrimp were mixed with ice to more closely simu- 

 late boat holding conditions. Fresh ice was placed 

 on the ice-held samples daily to insure a minimum 

 15-cm (6-in) cover over any given sample. 



Pink shrimp, Pandalus borealis, when received 

 by the laboratory, had been held for 2 h at ambient 

 temperature of -1.7°C (29°F) without ice aboard a 

 commercial fishing vessel. Shrimp were separated 

 from fish and after a brief rinse in cold freshwater 

 were placed in fiber glass-coated hardware cloth 

 baskets and rinsed again in cold tapwater for 2 

 min. The shrimp were then drained for 30 min and 

 the weight of each sample was adjusted to contain 

 2,100 g (4.63 lb). It had been established that 



Holding Tank and Refrigeration Unit 



A 568-1 (150-gal) fiber glass holding tank was 

 connected to a refrigeration unit by three 3.81-cm 

 (IVa-in) flexible plastic hoses. The brine was circu- 

 lated at 151 1/min (40 gal/min) through a shell and 

 tube heat exchanger with the capacity to chill 454 

 kg (1,000 lb) of shrimp and brine from 10° to -1.7°C 

 (50° to 29°F) in 3 h. Refrigeration was provided by 

 a conventional Freon^ 12 condensing unit. The 



'Northwest and Alaska Fisheries Center, National Marine 

 Fisheries Service, NOAA, P.O. Box 1638, Kodiak, AK 99615. 



^Reference to trade names does not imply endorsement by the 

 National Marine Fisheries Service, NOAA. 



Manuscript accepted June 1977. 



FISHERY BULLETIN: VOL. 76, NO. 1, 1978. 



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