| Summary: | 碩士 === 國立中興大學 === 食品科學系 === 89 === Wood ears are common edible fungi in China. Five kinds of wood ears are already commercially available in Taiwan, including black, red, jin, snow and silver ears. Mushroom fruit bodies and mycelia can be used as foods and food flavoring, to produce specifically chemical and medical substances, such as water soluble polysaccharides, vitamins, organic acids, nucleotides and enzymes, as well as to pharmaceuticals such as antibiotics, anticancer and antidisease drugs. In addition, mushrooms can supply antioxidant substances. However, so far no complete information is available for the antioxidant properties of wood ears in Taiwan. However, studies on the physiologically effects of wood ears have not been conducted.
This research used wood ears as samples to study the proximate composition, antioxidant properties of methanolic extracts, the monosaccharide constituents and the structural analysis of polysaccharides. Their structures were elucidated by spectroscopic analysis and comparison with known compounds.
For all methanolic extracts from ear mushrooms, the antioxidant activity in the 1,3-diethyl-2-thiobarbituric acid method were moderate (38.6~74.6%) at 1.0 to 5.0 mg/mL. Methanolic extracts for red, jin and snow ears showed excellent antioxidant activity in the conjugated diene method at 5.0 mg/mL. At 5.0 mg/mL, reducing powers in the descending order of sonw＞black ≈ red ≈ jin＞silver ears. The scavenging effect of methanolic extracts from ear mushrooms on 1,1-diphenyl-2-picryl hydrazyl radicals (DPPH·) was excellent except for that from silver ears. Ear mushrooms were not good scavengers for hydroxyl free radicals but good chelators for ferrous ions. Naturally occurring antioxidants, including ascorbic acid, tocopherols and total polyphenols, were found in methanolic extracts. However, b-carotene was not detected. Total antioxidant components were 15.69, 30.09, 27.83, 49.17, and 31.70 mg/g for black, red, jin, snow, and silver ears, respectively.
In ear mushrooms, the total sugar contents of water extract and alkaline extract polysaccharides were 74~92%. The compositions of neutral monosaccharide were the major have xylose, mannose, glucuronic acid and some ears have glucose. Ear mushrooms of water extract and alkaline extract polysaccharides was separated using gel filtration, and showed a molecular weight of about 2×106 Da. Their structure were elucidated by 1H-NMR spectra of water extract and alkaline extract polysaccharides showed that they contained RCH3, RCH2, CH3-CO- and CH2O-. That can be have a b-D-glucan chain. IR spectroscopy showed that water extract polysaccharides contained OH, C-H, C=O, C=C, C-O, CH-O-CH-, but that alkaline extract polysaccharides not have C=O, C-O.
The thermal behaviors of water extract and alkaline extract polysaccharides were examined by DSC, except for silver ear showed one endotherm but the anther not have. It could be study their physiological activities, advance analysis. The research and X-ray can be have a b-D-glucan chain. For the application in healthy food, further research on the mechanism of polysaccharide properties is in progress.
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