Experimental Study On Detoxification Treatment And Microwave Vacuum Drying Of Starfish

Starfish are important natural enemies of aquaculture industry. How to utilize starfish effectively has become a major problem of aquaculture in our country. Starfish is rich in protein and due to completely amino acid composition and reasonable essential amino acids proportion, it is close to the high quality protein. It is potential for starfish utilizing as innovative protein feed resources. Excessive ingestion of starfish will result in death because of saponin, so saponin had to be removed before the utilization of starfish. In this study, experiments of detoxification method and microwave vacuum drying of starfish utilized as protein feed resources were carried out for the first time till now. Non-toxic dried starfish feed were obtained and preliminary processing method of starfish environment value-added development and utilization was provided.Experiments on detoxification of starfish were carried out and the effect of citric acid concentration, temperature, material liquid ratio and detoxification time on saponin desorption rates and protein retention rates were explored. Microwave vacuum drying kinetics of starfish after detoxification was studied systematically and the influence of microwave power density, pulse time and vacuum degree to the drying characteristics, energy consumption and protein retention of starfish was carried out. Experimental results indicated that:(1)During the experiments on detoxification of starfish, saponin desorption rates were improved and protein retention rates were decreased with citric acid concentration, temperature and time were increased. Protein retention rates could be reduced by increasing the material liquid ratio and saponin desorption rate was highest when the material liquid ratio was 1:10.(2) During the experiments on detoxification of starfish, the four factor rates of comprehensive degree were: time, temperature, material liquid ratio, citric acid concentration. The detoxification effect was better when the citric acid concentration was 0.1mol/l, temperature was 50℃, material liquid ratio was 1:8, detoxification time was 3h by orthogonal experiment with saponin desorption rate, protein retention rate and comprehensive score were 70.96%, 91.29% and 1.982 respectively.(3) During the microwave vacuum drying of starfish, the impact of microwave power density to the drying process of starfish was greatest. Drying rate would be accelerated and energy consumption would be reduced by higher microwave power density, however, protein retention rate would be reduced due to high temperature. The drying rate would be improved and energy consumption would be reduced due to longer pulse time and higher vacuum degree. Protein retention ratio would be improved by shorter pulse time and smaller vacuum degree. The Page model MR = exp(-Ktn) is a preferab description of starfish drying characteristics during the microwave vacuum drying process.(4)Response surface experiments on starfish of microwave vacuum drying test indicated that microwave power density, pulse time and vacuum degree had significant effect on the comprehensive score. An interaction was worked between microwave power density and the pulse time on comprehensive score. The optimal process parameter was microwave power density of 4w/g, the pulse time of 60 s and vacuum degree of 0.090 MPa.The average drying rate of starfish of 2.95%/min, energy consumption of 0.0118 kw.h/g, protein retention rate of 93.80% and the comprehensive score of 0.751 was obtained under this condition. The predictive value of absolute error was only 0.8% and the experimental values and theoretical values were consistent.