Abstract:
Abstract: There is enormous quantity of Litopenaeus vannamei in China, and it is of great value to development and utilization. However, the research of shrimp processing technology, especially the peeling of shrimp, develops slowly in China. The peeling of the shrimp is mainly a manual process at present. Mechanical manipulation methods are being studied to improve the production efficiency and to extract the integral meat of Litopenaeus vannamei. This study took the Litopenaeus vannamei as the study object, and used shrimp intact rate and peeling rate as the main index. Considering the biological characters of shrimp, an extrusion type peeling device with dual rollers was designed in the experiments with equivalent reverse rotation angular speed to study the peeling performance and peeling process parameters. The sample shrimp with a body length between 110 mm to 130 mm were selected and kept fresh, and were peeled by dual rollers under the shearing and rubbing produced by the differential rotation and squeezing produced by relative rotation.The experimental study showed that such factors as removing or not removing the head, the length of the back opening, roller diameter, and roller gap etc., affects the shrimp peeling. Because there is heavy metal accumulation in the shrimp heads, extrusion peeling will make the shrimp heads rupture, which will influence the quantity and the texture of the shrimp. Before the experiments, all the heads of the sample shrimp were cut, and the length of the back opening was ranged into six ranks, from sections one to six. With reference to the relevant literature and analysis of the shape characteristics of shrimp, it was found that the suitable roller diameter is 80 -160 mm. In the experiments, three sizes were chosen: 80, 100, and 160 mm. Taking the shrimp intact rate and peeling rate as the test index, selecting the roller gap, the diameter of the rollers, and the shrimp back opening length as three factors, an orthogonal test was carried out and the results were analyzed. With the integrated balance method, the optimal parameters were selected to be 1 mm for the roller gap, 100 mm/80 mm for the diameter of the rollers, and six sections for the shrimp back opening length. Under these parameter conditions, the measured average peeling rate was 100%, and the shrimp intact rate was 60%. To obtain a better peeling effect, with the optimal parameters, the effects of the peeling device were analyzed to handle frozen pretreated shrimp. It was shown that the peeling rate and the intact rate gradually increased with an increase of frozen time, while the frozen temperature was unchanged. Meanwhile, when the frozen time was unchanged, the peeling rate and the intact rate increased with a gradual decrease of the temperature. The results showed that, under a pretreatment of -30℃ for 10 min, the peeling rate was 100% and the shrimp intact rate was 95%. The research results could provide reference for the design of shrimp peeling equipment.