Effect of the Manufacturing Process (the Hardness of Steamed-cooked Soybeans and the Temperature During the Aging Process) on the Formation of Aroma Components of Red Salty Rice Miso with Aging

摘要

The influence of the hardness of steam-cooked soybeans and of the temperature during the aging process was investigated on the formation of aroma compounds of red salty rice miso. Soybeans with two levels of hardness were prepared by the conditions used for steam-cooking, and the temperature during aging process was set at 25°C or 30°C. The resulting four types of miso sample were analyzed after being aged for 0, 30, 60, 90, 120, 150 and 180 days. The principal constituents of each miso sample were evaluated by the standard method for miso analysis. An aroma concentrate of each miso sample was prepared by adsorption to a porous polymer, and then analyzed by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). 3-Methyl-1-butanol and 2-phenylethanol, which are quantitatively the main aroma compounds in red salty rice miso, and methionol, which is one of the characteristic compounds in miso, each showed a high concentration during the aging process at 25°C. In contrast, 4-hydroxy-2(or 5)-ethyl-5(or 2)-methyl-3(2H)-furanone (HEMF), a character-impact compound in miso, was present in greater quantity during the aging process at 30°C. The concentrations of these aroma components were little influenced by the hardness of the steam-cooked soybeans. The value for Y (%) in the chromaticity diagram decreased markedly during the aging process at 30°C. The formation of HEMF was considered to relate to the decrease of the value for Y (%).赤色辛口系米味噌の製造時における大豆の加熱処理条件と熟成温度の熟成中の香気成分形成への影響を検討した.(1) 赤色辛口系米味噌の熟成中の香気成分形成には熟成温度による影響は大きかったが大豆の加熱処理条件の影響は少なかった.(2) 赤色辛口系米味噌の各種香気成分の濃度を合計した値の40∼65%を占め,他の醸造食品にも共通して存在する3-methyl-1-butanolや2-phenylethanolの濃度と味噌の特有香気成分の一つであるmethionolの濃度は全期間を通して熟成温度25°Cでやや高く推移した.(3) 3-methyl-1-butanol,2-phenylethanol,methionolの熟成中の消長には蛋白溶解率やpHの変動の影響は少なく,醸造に使用した酵母の影響が大きいことが示唆された.(4) 特有香気成分のHEMFは熟成温度30°Cで形成量が多く,他の主な香気成分の熟成中の消長と大きな差が認められ,独自の生成機構を持つ化合物であると推測された.(5) 熟成中のHEMFの生成は色調Y(%)の変化と関連があり,Y値で約20%に低下するまでは行われることが示唆された.