Study On The Shelf-life Of Sliced Raw Tuna Fish Using High-hydrostatic Pressure Technology

The study carried out is aimed at investigating the effects of high hydrostatic pressure (220MPa,275MPa) holding time (3min and 6min) on the maintaining the freshness of raw sliced fish and qualities changes during the storage period.The study is conducted as follows:1. To study the effects of high hydrostatic pressure on the safety of ready-to-eat of the raw sliced fish by evaluating the total bacteria count under the condition of 4±1℃through the storage period. We drew the following conclusions: (1) when the holding-time was determined, as the processing pressure increased, HHP can insignificantly inhibit or kill the bacteria. (2)The higher pressure, the better effects on the bacteria during the refrigerated period. At the end of 12 days, there was no found that the total bacteria count exceeded the standards according to the GB, which showed that HPP can extend the shelf-life of the raw slice fish.2. To study the effects of high hydrostatic pressure on the physic-chemical properties of the raw sliced fish by evaluating the pH,TVB-N and Drip losses. We drew the following conclusions: (1) the sample's pH after pressurized was obviously higher than the control samples'and the same during the refrigerated period. There were also different changes when applying the different pressure and the processing time. (2) HHP can significantly decrease the formation of TVB-N. None of the pressurized samples'TVB-N exceeded the level of 25mg/100g. (3) The drip loss in all the treated samples by pressure was higher than the samples untreated.3. To study the effect of high hydrostatic pressure on physical qualities such as texture,color and sensory attributes of the raw sliced fish. We drew the following conclusions: (1) there were no significant changes of the control sample's hardness during the 12 refrigerated days, and the springiness tended to decrease. Compared to the control, the hardness of the pressurized samples increased with the increase of processing pressure and holding-time. (2) After the pressure processing and during the storage days, with the increase of the pressure and the holding-time, the L* value increased and the color of the fish was more and more bright, meanwhile, the fish lost the transparency and became more opaque. Compared to the control group, all the pressurized samples'a*value decreased and the b* value increased with the extending of the pressure and holding-time. (3) The quality of sensory was different between the pressurized samples and the control samples. When the holding-time was determined, with the increase of the pressure, the character of sensory started to decrease and the same as the commercial value of the fish.