บทคัดย่องานวิจัย

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A non-destructive method for measuring the water potential of fruit and vegetables

J. J. Jobling, B. D. Patterson, S. Moradi and D. Joyce

Postharvest Biology and Technology Vol: 10 Issue: 1 Pages: 1-8

1997

บทคัดย่อ

A non-destructive method for measuring the water potential of fruit and vegetables

Water potentials of fruit and vegetables are usually measured with either pressure chambers or thermocouple psychrometers. Both methods demand considerable expertise and experience. The main disadvantage of the pressure chamber is the unknown influence of pressurization on tissue. Psychrometers suffer the problem that only pieces of tissue can be used. To overcome this problem we have devised a non-destructive measure of water potential. The proposed method is based on relative weight change of a series of salt solutions placed close to the epidermis. These solutions are contained inside patches which are made with one side of microporous polyethylene, allowing the exchange of water vapour between the tissue and the patch. Patches, each containing different concentrations of salt solution, are taped to the epidermis. The fruit or vegetable, with patches attached, is then wrapped in cling wrap and left to equilibrate overnight at constant temperature. The basis of the method is the assumption that the water potential of the salt solution in the patch which neither gains nor loses weight is equal to the water potential of the fruit or vegetable. This method has been tested in two ways: one using microporous bags containing solutions with known water potentials, and the other with carrots. Changes in water potential, osmotic potential, total soluble solids and relative water content of carrots stored for 3 days at 20°C and ambient relative humidity were monitored. The method accurately measured the water potential of salt solutions contained inside microporous bags and was able to measure a significant difference between fresh and stored carrots. This method could prove useful for use in storage or ripening experiments where the changes in water potential at the surface of intact commodities could be followed over time.