醬醪與甘酒共壓榨對醬油風味與品質之改善

Abstract

在一般醬油的製程中，鹽水發酵時間需6至8個月，於精製過程(refining step)中之高殺菌溫度(70-80°C)會造成劇烈梅納反應，使終產品顏色偏黑、風味過於濃郁。此外，發酵時使用高濃度鹽水會使醬油口味偏鹹。參考日本醬油產品特色以及製程，發現淡口醬油相較於常用的濃口醬油外觀顏色較淺、口味較清爽，這是由於兩種醬油的製程不同所致，淡口醬油其中一個關鍵製程為在壓榨醬醪之前添加米麴混合物，此方法對於改善醬油風味最有效率，這是由於不同發酵程度之米麴混合物可帶來不同風味。因此，本試驗選用甘酒作為米麴混合物，擬於醬油製作過程中，濃口醬醪壓榨步驟前添加，探討甘酒對生醬油於加熱過程中品質與風味之影響，亦期望藉由添加甘酒降低醬醪黏稠度以提高生醬油收率、降低鹽分含量並使其色澤呈紅褐色。試驗中，分別添加10%甘酒(發酵第3或5天)與3.5或5.5個月濃口醬醪共壓榨。添加甘酒於3.5及5.5個月醬醪可以分別提高醬汁收率1-2%及3-4%。並且於醬醪中添加10%甘酒可顯著性降低醬油鹽分含量。至於甘酒添加對醬油顏色的改變是有限的。由於應用淡口醬油添加米麴混合物的步驟，甘酒醬油風味物質中除了醇類以外其餘風味物質含量都不會超過未添加甘酒醬油，所以甘酒醬油的風味確實變得較清爽，不同於未添加者濃郁。另外，甘酒生醬油還原糖含量影響風味物質深遠，甘酒生醬油若還原糖含量高，則經過加熱後部分還原糖可提供醇類風味物質於甘酒醬油中。觀察PCA的結果，添加第3天甘酒於醬油中其特徵風味物質種類多樣化因此風味也較多元，有焦糖甜味的5-methylfurfural和furfural、果香味的ethyl butyrate和ethyl phenylacetate等，而添加第5天甘酒的特徵風味較單純，以提供酒香氣、麥香氣、甜味等的醇類為主，因此若希望添加甘酒後的醬油風味增添多一點焦糖香並帶有果香風味，則可以添加發酵程度較低的甘酒(發酵第3天)，而若希望酒香氣比較多者，則可以考慮添加發酵時間較長的甘酒(發酵第5天)。

In brine fermentation of normal soy sauce, the harvested koji is inoculated to a fermentation vessel held for 6-8 months. Then, the filtered raw soy sauce is heated to 70-80°C at refining step. Brine fermentation and refining steps results in a deep black color caused by intense Maillard reactions. Besides, a strong salty taste will be obtained in the Koikuchi shoyu when fermented with 22-25% (w/v) salt solution. In Japan, the Usukuchi shoyu has the characters of a lighter reddish brown color with milder flavor and aroma because of different shoyu making process. Adding a digestion mixture of rice koji before pressing is a key process and relatively efficiency to bring another flavors to soy sauce. The objectives of this study are obtaining a high-yield of filtered raw soy sauce, decreasing salt content and obtaining reddish brown color of Koikuchi shoyu by adding different fermentation times of rice Lao-Chao into moromi before pressing. The 10% rice Lao-Chao was added to aged moromi of Koikuchi shoyu and the mixture was pressed to get raw soy sauce. Moromi were fermented for 3.5 months (short fermented) or 5.5 months (long fermented) while rice Lao-Chao were fermented for 3 or 5 days. In this study, effects of adding rice Lao-Chao and heating on flavor of soy sauce were investigated. The yield of filtered raw soy sauce increased 1-2% while mixing rice Lao-Chao with short fermented moromi, and increased 3-4% with long fermented moromi. The addition of 10% rice Lao-Chao fermented significantly decreased the salt content in the final product.There is some limit for turning soy sauce color to reddish brown by adding rice Lao-Chao.The application of Usukuchi shoyu process byadding a rice koji can lead to milder flavor and aroma. Because almost all the flavor compounds are lower than their controls except alcohols. The reducing sugar contents in raw soy sauce with rice Lao-Chao are strongly related to flavor compouds after heating. If the soy sauces with rice Lao-Chao have higer reducing sugar contents, they will have higher alcohols. Looking at the result of PCA, adding rice Lao-Chao fermented for 3 days in soy sauce may lead to abundant flavor composition, like caramel with sweet flavor by 5-methylfurfural, furfural and fruity flavor by ethyl phenylacetate.The flavor will be simple when adding rice Lao-Chao fermented for 5 days in soy sauce. The characteristic of the soy sauces may have alcoholic, malty and sweet by alcohols. So if hoping caramel with sweet flavor, adding rice Lao-Chao fermented for 3 days in soy sauce. Or hoping slightly alcoholic flavor, adding rice Lao-Chao fermented for 5 days in soy sauce.