各種水分活性下における乾のり中のアスコルビン酸の変化〔乾のりの品質保持に関する研究-1-〕

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The influence of water activity in (aw 0-0.6) on the degradation of the total ascorbic acid (the reduced form + the oxidized form) in dried laver "Nori" Porphyra yezoensis was examined at 15-18°C for a period of six months. The BET monolayer value moisture content of dried laver was 6.9% (equivalent to aw 0.17) and CAURIE'S safe storage moisture level was 7.3% (aw 0.20). The ascorbic acid content decreased with increasing water activity. At aw 0, 85% of ascorbic acid remained after six months of storage. The half life (θ1/2) of ascorbic acid was shorter at the higher aw:θ1/2 aw 0.1 was 41 days, but at 0.2 or above, θ1/2 became shorter than one month. A water condition for the safe storage of ascorbic acid was evaluated from the reducing rate of ascorbic acid in dried laver on each aw; it was determined ot be 4.14% (aw 0.053). This value was lower than the BET monolayer value, which agreed with the experimental data that ascorbic acid destruction proceeded at and below the BET monolayer value. The destruction of ascorbic acid was depressed by free-oxygen absorbers even though the water content (5.1%) was higher than control's (3.5%).
日本水産學會の論文