Research On The Technology Optimization Of Dryingand Quality Characteristics Of Crassostrea Rivularis

Dried Oyster, which is hugely popular in Guangxi and Guangdong. Drying oysters which can solve these problems, such as seasonal harvest, regional differences and the difficulty of transportation and storage, it also can stay the same shape and retain nutition and flavor of fresh oysters. Through on-the-spot investigation, the main drying technology of oysters in the local was still use illumination, which lead to a low production rate and poor quality. Therefor, this paper begined with the quality survey of the market products, and compared the quality of products by different drying methods, then the hot air-microwave combination drying process of dried oysters was optimized based on single factor experiments, and then the drying mathematical model of combinated drying was established, furtherthe water activity lowering agents was added to improve the quality of products. The studies were as follows:1. The quality charactersof dried oysters from the market were researched. The research studied six kinds of dried oysters, which were measured its chemical quality, color, texture and rehydration characters. The results showed those indexs values of six products were within GB/T 26940-2011, and there had differences in moisture content, color, hardness, springness and rehydration. The sensory score had positive relation with L* value and springiness, the correlation was 0.876,0.830 respectively.2. The quality of dried oysters by different drying methods were investigated. The qualities were compared according to the color, hardness, springness, rehydration rate, shrinkages, physical and chemical characters, sense and odour. The results showed that combination dried products had a high light, elasticity, rehydration rate, and low hardness, shrinkage, and the physical and chemical values were within GB/T 26940-2011. Comparing with the hot air drying, the drying time and energy of combination drying reduce about 40%, 46.24% respectively, doubling the drying capacity. The electronic nose could discriminate the odour of dried oyster by different drying methods, sulfide, methyl, nitrogen oxides were the main components of the volatile odor of dried oysters.3. Based on the single factor, the technology was optimized through a combination of the response surface and principal component analysis, the best conditions of process were:drying tempetature 68?, conversion moisture content of 39% and microwave power 490W.4. The mathematical model of combination drying was established. Drying properties of oysters were studied using hot air and microwave drying, the results found that internal moisture content diffusion played a main role in the drying process of oysters. The drying data were fitted to 6 mathematical models, and the mathematical model of combination drying was established.5. The influence in the quality of dried oysters by using water activity lowering agenes. The results showed that the glycerol and trehalose could reduce the water activity, and improve the color intensity of dried oyster. It could reduce the hardness of products by using glycerol, as same as the trehalose when in high concentrations. It could reduce water activity from 0.81 to 0.69 of dried oysters by using them together, and increase the value color intensity to 51.23, also keep hardness, springiness and rehydration rate better. The formula as follow:glycerol 4%, trehalose 3%.