Objective Tests Applicable to Quality Studies of Ice Stored Shrimp

Abstract

Objective quality tests are urgently needed by the shrimp industry to permit distribution and processing of individual catches of shrimp according to their expected storage life.Heretofore, organoleptic measurements of quality have been used almost exclusively for purchasing and grading shrimp products at various stages during their storage life. These tests are very useful for rapid examination of such products. Unfortunately, they are based on personal judgment and consequently result in numerous subjective differences which lead to disagreement in qualification of individual samples. The subjective differences render it desirable to supplement organoleptic testing with a more exact analysis based upon changes of certain constituents in shrimp during storage.Thorough organoleptic studies on shrimp quality (12) showed that definite taste changes occurred during ice storage, indicating that palatability and flavor change only slightly during the first few days of ice storage. The flavor is described as characteristic of "fresh" shrimp and is slightly sweet. This phase is followed by a period during which the shrimp no longer have this characteristic sweet flavor but instead are "flat" tasting. During this time, no off flavors associated with spoilage are noted. This second period is followed by another sharp change in flavor which denotes onset of spoilage. Repeated organoleptic studies with ice-stored shrimp by experienced taste panel personnel substantiated these three general flavor changes.Since these results show definite taste phases during ice storage of shrimp, useful objective tests must discern the three major taste changes.An ideal objective test would be one which would accurately and reproducibly give a numerical value of quality. The shrimp industry desires a test which can be correlated directly with the number of days shrimp have been in ice storage. It is rather doubtful that such a test can be perfected because physical and chemical changes are dependent not only on elapsed time of storage, but also upon treatment prior to storage and the environment from which the shrimp were obtained initially.Any measure of definite chemical changes occurring in shrimp during storage under various conditions can be used to determine relative quality provided appropriate comparisons are made. Except for several tests described below it is unlikely that specific chemical concentrations can be assigned as a means of qualifying a particular sample of shrimp since the initial content will differ depending on such facts as age, size, specie o r living environment. If analysis shows that a constituent such as ammonia nitrogen increases sharply after a specific storage time, and that slightly 611

Quality changes in lobster (Panulirus polyphagus) muscle during storage in ice

“…A rapid degradation of nitrogen-containing components has been indicated during spoilage of fishery products as spoilage begins. A trimethylamine nitrogen value of 1.5 mg/100 g of unshelled, headless shrimp has tentatively been specified as an objective index of spoiled shrimp (Baily et al, 1956). STOMte Tine ( DAYS)…”

“…Included are acid-soluble orthophosphate, trimethylamine nitrogen, amino nitrogen, extract release volume, pH, and bacterial count. At present, however, organoleptic measurements of quality are used for purchasing and grading seafoods at various stages during their storage life (Baily et al, 1956;Vanderzant and Nickelson, 1971; Cobb and Vanderzant, 1975;Farooqi et al, 1978).…”

Shelf-life of cooked edible crab (Cancer pagurus) stored under refrigerated conditions

“…Mendes et al, 2002), which is normally higher than in fish and mammalian species due to the higher content of non-protein nitrogenous compounds in crustaceans (Shahidi, 1994). Several authors reported pH 7.80e7.95 to be a critical margin for acceptability of shrimps and prawns (Bailey, Fieger, & Novak, 1956;Chung & Lain, 1979). Yet, as far as edible crab is concerned, the levels of pH acceptability for muscle were higher (around 8.20) and lower for brown meat (above 7.15).…”

Qualidade química e microbiológica de camarão-rosa comercializado em São Paulo

“…Bailey et al (1956) consideraram que em pH até 7,70 o camarão mantinha as características de um produto 'fresco", acima deste valor e até 7,95, era considerado de má qualidade, porém aceitável. Valores superiores a 7,95 tornavam desaconselhável o consumo do camarão.…”

“…Segundo Luna (1971) e Shamshad et al (1990), pH acima de 7,2 e de 7,6, respectivamente, caracterizavam produto não-comestível. Se considerado o limite estabelecido por Bailey et al (1956), pH 7,70, seis lotes (60%) dos analisados (Tabela I) estariam aptos para consumo. Mas em relação ao limite estabelecido por Luna (1971), pH 7,20, apenas dois lotes (20%) dos dez analisados poderiam ser consumidos.…”