AT-2484 (RP-172) -- Transpiration Rates of Certain Fruits and Vegetables

Transpiration or moisture loss of fresh fruits and vegetables is a mass-transfer process in which water vapor moves from the surface of the fruit to the surrounding air. Water, the most abundant compound in fresh vegetables, forms a continuous liquid phase through the vegetables.

Some frequently used terms were first defined. Then a literature review was conducted with the following main objectives:

1. To compile a listing of transpiration rates of fresh fruits and vegetables (as listed below) reported in the literature over the past 50 years.
2. To translate the various units used in expressing.transpiration rates into SI units.
3. To evaluate the validity of various values presented for transpiration rates based on current knowledge of the subject and analysis of the methods used in the various determinations
4. To evaluate the results of the literature search to identify those fruits and vegetables for which sufficient information exists and to make recommendations on which commodities need additional research attention.
5. To evaluate the validity of different reported methods'used to measure transpiration rate and possibly recommend a standardized procedure to follow for determination of transpiration rates of fruits and vegetables.

The products for which data were obtained through a literature search were apples, brussels sprouts, cabbage, carrots, celery, grapefruit, grapes, leeks, lemons, lettuce, onions, oranges, parsnips, peaches, pears, plums~ potatoes, rutabagas, and tomatoes.

About 500 papers were obtained. These were screened and classified according to the usefulness of the material. They were reviewed to determine the transpiration rates of several fruits and vegetables, to use the discussion and results of the factors affecting transpiration, and to find and evaluate good experimental methods that could be recommended for future research in the area. The results are the subject of this paper.