| Summary: | 碩士 === 國立宜蘭大學 === 生物機電工程學系碩士班 === 100 === Dried radish was a common pickled food product, but its moisture content was up to 77% and the water activity was higher than 0.9. For long-term storage or long distance shipping, preservatives (benzoic acid) and salt were added. It seems unable to prevent spoilage if benzoic acid was added under the standards for dried radish product. Therefore, the manufactures add more benzoic acid in the products for long term storage. In order to resolve the high water activity problem, this study was to investigate the dried radish process, to evaluate the effects of salinity and sun drying time on the quality of dried radish products, and to evaluate the possibility to improve the production of dried radish products. Based on the investigation of dried radish production, there was an uniformity problem for salinity and benzoic acid residues when products were packed in box. This may cause the violation problem of benzoic acid residue when health department investigated the products. Based on the mass balance analysis for dried radish process, the yield of dried radish was about 27.29%. But nearly 66.74% of the salt used in the process was lost. The results of soaking experiment showed the wet basis salinity and benzoic acid residues of dried radish products reduced more than 50% after soaking 20 minutes. However, If the salinity and benzoic acid residues converted into dry basis, it showed that most of the salt and benzoic acid weren’t removed in the soaking process. Besides, 20% of the salt was added in the secondary sprinkling salt process, and the water activity can dropped to 0.743, but the dried radish product became un-edible due to salty flavor. If dried radish was sun dried for 3 days and more than 10% of the salt was added, the water activity was dropped below 0.8. Therefore, the benzoic acid residue can be controlled under the official standard.
Based on the Henderson Equation model, the equilibrium moisture content, salinity, and water activity of dried radish products were considered by using regression analysis to derive an equilibrium moisture content model for dried radish product. This model can be used for dried radish processing industry for product development. The physical properties (cutting strength, cutting energy flux, cutting distance) of dried radish product in creased with the increasing moisture content. The moisture content of dried radish increased after 60 minutes soaking, which recovered 93.82% comparing to original product. Although its cutting strength and cutting energy flux decreased after soaking, it seems that can not recover its physical properties back to the original condition.
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