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Effects of Hot Air and Microwave Drying on the Phenolic Components and Physicochemical Properties of Unripe Grapes (Qoura)

[ Vol. 16 , Issue. 5 ]


Loghman D. Razgeh , Ayub E. Fathabad , Nabi Shariatifar , Mohsen Esmail and Amin M. Khaneghah*   Pages 718 - 725 ( 8 )


Background: Unripe grape (Qoura) in the forms of either intact or juice can be used as a flavoring agent in several foods of Iranian cuisines such as soup and salad due to its sour taste.

Material and Methods: In the current study, the effects of microwave (270, 540, and 720 W) and hot air drying (40, 50 and 60°C) on the polyphenol components content and chemical properties (including chroma, hue angle, L* value, total color difference, soluble sugars, acidity, total phenols and phenolic components including rutin, gallic acid, hydroxybenzoic acid, syringic acid, p-coumaric acid, and resveratrol) of Qoura obtained from unripe white seedless grape were investigated.

Results: The obtained results showed that in both methods, by increasing the oven temperature and microwave power, the L value (The L* value was used to express the whiteness and darkness) was decreased. There was a notable reduction in the initial phenolic content of the sample (381.671 mg gallic acid/ 100 g) as a result of both of the used techniques. The initial content of resveratrol was decreased from 30.27 mg/100 g; to 23.07, 16.64, 10.73 mg/100 g sample in the samples treated with the air-drying method at 40, 50, 60°C, respectively. Also, by using the microwave in 270, 540, 720 W, it decreased to 5.77, 5.38. 5.26 mg/100 g sample at 270, 540, 720 Watt, respectively.

Conclusion: The results of the present study revealed that the drying method affects the amount of polyphenolic compounds and physicochemical properties.


Chemical properties, color, drying, grape products, polyphenol components, unripe grape (Qoura).


Food Science and Technology, Islamic Azad University of Tabriz, Tabriz, Department of Food Hygiene and Quality Control, Faculty of Veterinary Medicine, Urmia University, Urmia, Department of Environmental Health, School of Public Health, Tehran University of Medical Sciences, Tehran, Department of Food Science and Technology, Faculty of Agricultural Engineering, Urmia University, Urmia, Department of Food Science, Faculty of Food Engineering, University of Campinas (UNICAMP), Rua Monteiro Lobato, 80. Caixa Postal: 6121.CEP: 13083-862. Campinas. São Paulo

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