| Chinese chestnut is in the family of Fagaceae Castanea and riched in nutrients. In the presented dessertication, the contents of nutrition compositions (amylopectin, amylase, crude fat, crude proten, water-solubility proten, reducing sugar, sucrose, glucose, fructose, energy value, organic acid, total polyphenol, total flavone) and the antioxidant activity of ethanol extracts of chestnuts from four regions (Qianxi of Hebei province, Huairou of Beijing, Yimen of Shandong province, Kuandian of Niaoling province) were determined and compared. Then the effects of thermal processing technology which include boiling, roasting and frying on the contents of nutritional compositions, antioxidant activity of ethanol extracts were investigated. To analyse the mechanism of aroma formation in chestnut thermal processing, the volatiles in processed chestnut, the model-reaction between six amino acids and three saccharides were determined by GC-MS. The obtained results were as follows:(1) Based on the dry weight (DW), the content of total starch in Chinese chestnut was between67.71-73.16%, with the highest in Qianxi and the lowest in Kuandian, and amylase accounting for96%. The content of lipid was between1.87-2.98%, with the highest in Huairou and the lowest in Yimeng; the content of crude protein and water-solubility protein was52-98and20.47-27.37mg/g respectively, with the highest in Qianxi and Huairou and the lowest in Yimeng. The reducing sugar content was between20.6-66.7mg/g, with the highest in Kuandian and the lowest in Qianxi. Sucrose content was between89.6-152.1mg/g, with the highest in Kuandian and the lowest in Yimeng. Glucose and fructose contents were between2.2-9.2and1.8-6.7mg/g respectively, with the highest in Kuandian and the lowest in Qianxi. The energy value was between1548-1696kJ/100g, with the highest in Qianxi and the lowest in Yimeng. The contents of organic acids were between2.00-3.49mg/g, with the highest in Kuandian and the lowest in Yimeng, oxalic acid, malic acid and citric acid was the main acids (accounting for97.8%); the total polyphenol and total flavone contents were between2.00-3.68and2.54-3.76mg/g respectively, with the highest in Huairou and Kuandian and the lowest in Yimeng. The total reducing power, DPPH-scavenging capacity and hydroxyl radical scavenging capacity of ethanol extract of chestnut was obviously lower than those of ascorbic acid. The content of total amino acid in Qianxi chestnut was6.11%DW, among which asparaginic acid, glutamic acid, and proline were the highest; the content of free amino acid were0.77%DW, asparaginic acid, glutamic acid, and arginine were the highest.(2) With the comparision of raw, boiled, roasted, and fried chestnut, the contents of starch, crude fat, water-solubility protein, reducing sugar, organic acids, total flavones and free amino acids in raw chestnut were decreased after thermal processing, but the contents of crude protein and total amino acids increased. The contents of sucrose, glucose, fructose, total polyphenols and the antioxidant activity of ethanol extracts changed slightly after thermal processing.(3) The main aromatic compositions in raw chestnut were aldehydes and esters. The characteristic volatiles in boiled chestnut were spiro[2,4]hepta-4,6-diene,3-heptanone,1R-,alpha-pinene, and in roasted and fried chestnut the main volatiles were4-hydroxy-2-butanone, dihydro-2-methyl-3(2H)-furanone, furfural,2-hydroxy-2-cyclopenten-l-one,3-carene,2-pentyl-furan. The main aromatic fragrance in mode-reaction was5-(hydroxymethyl)-2-furancarboxaldehyde, and pyrazine,2,5-dimethyl-. Furfural which was an aromatic fragrance in roasted and fried chestnut was found in the product of the reaction between asparaginic acid or glutamic acid and fructose or sucrose. The2-hydroxy-3-methyl-2-cyclopenten-l-one, which is similar to2-hydroxy-2-cyclopenten-1-one, one of the aromatic fragrances in roasted and fried chestnut, was found in the reaction between asparaginic acid and sucrose. |
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