| Summary: | 碩士 === 國立屏東科技大學 === 食品科學系所 === 96 === Shiitake have long term cultivated history and commercialized production; it’s one kind of among edible mushrooms. When shiitake dried, their enzymes could transform from contain sulfur-compound to the special flavor molecule, lenthionine, took the fancy of the consumers. Shiitake also have a high nutrient-values food with the characteristic properties, like as rich protein and polysaccharides, low-calories, low-fat, so was called ‘vegetarian beefsteak’. Now recently healthy living conception was popular, pay much attention to shiitake’s affectiviness than before. Beside that, the 5’-nucleotides, free amino acids, saccharides and their derivates were combined with different food materials, could raise abundant mouth-tastes, and played the important effects. For the purpose of this study, the fresh or cool air-dried shiitakes were used as the experimental materials and study on heat process treatment, the change of 5’-nucleotides of shiitake were investigated. When soaked in water at 45 minitesw of fresh and dried shiitake, during fresh treatment to 40℃, the study found the percentage of water absorption maximum at 19.8% and 14.0%, respectively. RNA content of fresh shiitake is more than dried and according to the temperature increasing to reduced by heat treatment, from 128.6 to 50.4 μmol/g and 75.2 to 57.8 μmol/g, respectively. The temperature of heat treatment is over 40℃ and 50℃, respectively. The nuclease activities of dried shiitake and fresh shiitake were rapidly. The enzyme of phosphatase activities were declined over 50℃, either in fresh or dried shiitake. However, these two kind enzymes are not stable over 70℃. The fresh shiitake was soaked in water, the content of 5’-nucleotide in soaked liquid was found fresh shiitake less than dried, in contrast, in tissue, the 5’-nucleotide of fresh shiitake was more than dried. The content of 5’-nucleotide in the soaked liquid was increased according to the heat treatment temperature increased compared with dried shiitake liquids was above 1.5 times of fresh shiitake liquids. As the results of study, it could preliminary understand; even if the same food material, thought some kind process as dried treatment, that will decide the final fate of their applied or after used in different cooking to present their different feeling.
Key words: Shiitake (Lentinus edodes), 5’-nucleotides, temperature, heat
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