Experimental Study On Microwave Vacuum Drying Of Scallop Adductor Muscle

The production of scallop (patinopecten yessoensis) in2011was about25million tons inChina,90%of which were bred in Dalian Changhai County. It is appetizing and tasty, and is akind of popular aquatic products among customers. Its adductor muscle is rich inprotein, unsaturated fatty acids such as EPA and DHA, as well as pharmacologically activepolysaccharides. Current drying technique is far from meeting the qualitatively requirementsboth in domestic and foreign market, and that the low-temperature drying technology caneffectively improve the texture of the products to improve the storage performance, and avoidnutritional component being destroyed. In order to improve the domestic processing technicallevel, patinopecten yessoensis was taken as raw material, and experiments on different effects ofmicrowave power density, pulse intermittent time of microwave vacuum drying, air relativehumidity, velocity and temperature of heat pump drying on the scallop adductor muscle dryingtime, product quality and nutrient retention were carried out.Results of microwave vacuum drying experiments of scallops adductor muscle showed thatmicrowave power density and pulse intermittent time had significant influence on drying time ofscallop adductor muscle, increasing power density and shortening intermittent time wouldsignificantly shorten the drying time; the microwave power density and pulse intermittent timehad a certain influence on the drying quality, longer interval resulted in better shrinkage andrehydration rate as well as relatively smaller changes in color of dried scallop adductor musclewith the same microwave power density; and the microwave power density and pulseintermittent time had different effects on content of protein, crude fat, polysaccharides and fattyacids. In the experiment, higher nutrients retention would be obtained at lower microwave powerdensity and longer interval. The optimum conditions for microwave vacuum drying of scallopadductor muscle was the microwave power density of3W/g, and pulse intermittent time of10s-on/20s-off with the degree of vacuum of90kPa, with which dried scallop adductor muscle ofgood quality could be obtained, that was shrinkage rate of56.07%, rehydration rate of66.80%,color of light yellow and no crust on the surface, compact in texture and intact in the tissue, andthe wet basis moisture content could be reduced to below13%in only190min, the averageprotein, crude fat, polysaccharide content of dried materiels were relatively higher, namely76.38%,2.68%,5.91%, respectively, retention rates were93.18%,44.55%,71.26%, respectively,and the EPA and DHA content of total fatty acids were22.41%and32.15%, respectively, theretention rates were45.03%and44.65%, respectively.Results of heat pump drying experiments of scallop adductor muscle showed that therelative humidity had significant influence on the drying time, sensory quality and shrinkage rate.The drying time and shrinkage rate were both decreased with the humidity, but a relatively smaller humidity would result in larger cracks on the surface of material and consequently led tomore brittle and poor sensory quality. Wind velocity influenced the drying time, sensory qualityand the content of polysaccharides and fatty acid significantly. The greater the wind velocity, theshorter the drying time, the smaller the shrinkage rate, and the greater the rehydration rate, butbring about larger cracks and more brittle on the material surface. The drying temperatureinfluenced the drying time, sensory quality, color difference and the content of protein, crude fatand polysaccharide significantly. A relatively higher temperature would contribute to shorterdrying time, smaller shrinkage rate, greater rehydration rate and smaller color difference, butcould also decrease the protein, crude fat, polysaccharides retention rate. In this experiment,relative humidity of30%, wind velocity of0.6m/s, temperature of27°C was the optimumconditions of heat pump drying of scallop adductor muscle for the sensory quality was the bestand nutrient retention rate was the highest. The wet basis moisture content could be reduced tobelow13%in19.5h, The dried product was yellow and there were little cracks on the surface,part of the product were fragile, but no center collapse and crusts. The shrinkage rate was68.48%, rehydration ratio93.76%, the content of protein, crude fat and polysaccharide in thedried product were67.37%,2.90%,10.58%, respectively, and the retention rate were98.18%,59.69%,75.44%, respectively. The EPA and DHA content of total fatty acids were24.68%and28.25%, respectively, and the retention rates were59.86%and59.06%, respectively.