Study On The Drying Processing Of Zhikong Scallop (chlamys Farreri) And Its Rheological Characteristic

In this paper, Zhikong scallops (Chlamys farrer) which are one of the three majoreconomic species in China were chosen as the object of study. With using the physicalproperties test method, the quality, structure and rheological property changes ofscallops adductors during pretreatment, drying and rehydration processing werestudied. The purpose is to provide the theoretical basis and effective experimental datafor the production, processing and quality control of this kind of aquatic products. Themain research content is divided into the following three aspects.1. Optimization of scallops adductors pretreatment technology. On the basis oftraditional technology, the carrageenan was added to the impregnation solution, andthe pretreatment conditions were optimized. The optimum pretreatment conditionswere0.22%carrageenan concentration,5.27%salt concentration,20minutesimmersion time,105℃recoction temperature and5minutes recoction time. Comparedwith the fresh scallops adductors, the protein denaturation caused rheologicalproperties changed after pretreatment. The hardness, cohesiveness and flexibility wereincreased significantly. Compared with the traditional pretreatment processing, theoptimized processing can prevent basic ingredients losing before drying, and makescallops adductors closer to the fresh ones. Changes in rheological parametersshoweded that the optimized processing can significantly improve the rupture strengthof scallops adductors, and make it is not easy to damage. But the impact on otherrheological properties was not significant.2. Changes in quality and rheological properties of scallops adductors during thedrying processing. The changes in drying kinetics, quality characteristics, tissuestructure and rheological parameters under different drying conditions (cold-blast airdrying and natural air drying) were studied. The experimental results showed that, byboth these two kinds of drying methods, the shrinkage and rehydration rate weredecreasing with the increasing drying time and the reduction of moisture content. Asthe same time, the color gradually turned into brown and the basic ingredients turnedinto less. Because of the reduction of moisture content, the fiber structure alsochanged. The elastic modulus E, stress relaxation time and cohesiveness decreased,rupture strength and hardness increased. When the moisture content reached the samelevel (30%), the drying time by cold-blast air drying needed was only42%of naturalair drying. Compared with the traditional drying method, the cold-blast air dryingmethod can not only ensure the product hygienic and reduce the cost of time, but alsoobviously improve the quality. The major performance into the following areas, therehydration rate of cold-blast air dried samples was higher, shrinkage was moreuniformly, color was brighter and more beautiful, and the content of protein, ash, total sugar and fat were much. Combined with the results of scanning electron microscope,the configuration of muscle fibre was orderly and not deformed or curly. Therefore,the cohesiveness, springiness and chewiness of cold-blast air drying samples weregreater than the natural air dried ones, so the scallops adductors were invulnerable. Incontrast, as the result of the loss of water inequality, the natural air dried samples wereeasily broken and rupture.3. Changes in quality and rheological properties of scallops adductors afterrehydration processing. The best rehydration method was put the scallops adductorsinto20℃water for2hours. With this method, the rehydration rate can reach65.43%. The basic ingredients of three kinds of scallops adductors were compared.The content of basic ingredients in dried scallops adductors after rehydration was lessthan both the fresh and the boiled ones. The result of sensory evaluation experimentshowed that the dried samples were unable to restore the original color afterrehydration. But the changes of smell and palatable taste were not significant, so thespecial flavor of scallops adductors was kept. Besides, the hardness and chewinessamplified significantly and the adhesive property abated significantly. The rheologicalproperty of dried scallops adductors after rehydration was very different from both thefresh and the boiled ones. The elastic modulus and the viscous modulus increasedsignificantly, breaking strength decreased significantly. It was also showed from theexperiments that the dried scallops adductors was quite resistant to chewing.