Sensory, biochemical and microbiological changes and changes in SDS-PAGE patterns of myofibrillar and sarcoplasmic proteins were studied in shrimp (Penaeus merguiensis) muscle during storage at partial freezing temperature (-3°C; PFS) and in ice (0°C; IS). During PFS up to 20 days there were slight changes in biochemical parameters, apparently no changes in microbiological populations, and no changes in electrophoretic protein patterns. Rapid changes in these parameters occurred in IS over the same period. Sensory assessment of shrimps stored at PFS showed that a considerable increase in prime quality life was possible at this temperature over shrimps in IS. Prime quality life of shrimps in PFS was found to be 16 days, compared with 8 days in IS. Extension of prime quality life was attributed to the significantly slower rate of biochemical and microbiological changes at PFS compared with IS. Changes in sensory properties were associated with changes in some of the chemical properties.

served, however, and we feel that the severed area contributes only a minor amount to the total volatiles. There seems no other practical way of obtaining the volatiles from the leaves without introducing other artifacts from the soil, environment, plastic containers, etc. The volatile compounds in macerated wheat leaves reported by Hamilton- Kemp and Andersen (1984) are quite different from those found in the present work. As discussed in previous work [e.g., Buttery and Ling (1984)], damage to the plant material (maceration would cause extreme damage) gives rise to considerable oxidative enzyme activity that breaks down the plant lipid and carotenoid components to a relatively large amount of volatile aliphatic aldehyde and alcohol compounds that are not present in the intact plant [cf. Schwimmer (1981)]. Such enzyme-produced volatiles can completely obscure the original volatiles that may be 100 times less in concentration. The enzyme action might also destroy (e.g., oxidise) some of the volatiles present in the intact plant. To fully understand the attraction of insect pests to their specific host plants, it would seem of primary importance to identify the compounds emitted by the intact plant.Volatiles emitted by damaged plants may also be important in the attraction of certain insect pests.

Changes in inosine-monophosphate (IMP) and hypoxanthine (Hx) concentrations in shrimp muscle stored in ice for up to 20 days were correlated with taste panel evaluations of the sensory quality. A good correlation exists between IMP concentrations and flavor as well as total sensory scores. Absence of IMP in shrimp muscle and values of 2 micromole Hx, and over, per gram of shrimp muscle indicate doubtful quality. Measurement of Hx shows potential value as an index in assessing quality of ice-stored shrimp.