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Abstract: Since most vegetables and fruits consist of many kinds of enzymes, enzymatic reactions such as oxidation reaction, browning reaction and discoloration present a problem to the frozen vegetable industry. In order to inactivate the enzyme system presented in the fresh vegetables thus achieving a better keeping quality during freezing storage, blanching is a necessary step in freezing preservation of vegetables It can be done either by steam or in boiling water, the time and temperature of blanching varied with the kinds of vegetables. In order to keep better quality, including color, flavor, aroma, taste, texture, and appearence of the frozen vegetables, a lot of chemical additives are occasionally used for this purpose. Because mushroom is one of the easily browning vegetables caused by enzymatic and chemical oxidations, there are many kinds of enzyme inhibitors or antioxidants recommended to prevent those quality lowering. Most mushrooms are frozen commercially either by air blast or plate freezing methods Problems may occur during freezing and storage of frozen mushrooms, e.g., loss of weight, decrease in nutritive value, tendency of product to stick together, and sometimes development of undesired color and off-flavor. Freezing of foods by individually quick freezing method was developed recently here in Taiwan (BCIQ, 1965-70) It seems to give a better quality frozen food in many ways. The product can be frozen at a much faster speed (TRESSLER et al, 1968) Several vegetables frozen by the IQF method were better in quality than those made by the conventional and plate freezing methods However, an extensive study of the effect of IQF on quality and total bacterial counts of the frozen mushrooms is needed. The objective of this work is to study the quality of frozen mushrooms influenced by chemical treatments before or after blanching and freezing methods. The effects of water blanching and chemical treatments on the total bacterial counts and Escheichia cohform colony as well as chemical residue retention in the product were also studied The physical, chemical, nutritional, and organoleptic quality of the frozen products are reported.
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