Effects of processing on zinc levels in spinach, beef, and potatoes
1981
Rosenbloom, Nancy J. | Potter, Norman N.
Total zinc (Zn) and water-soluble Zn were determined before and after acid-enzyme digestion for spinach leaves, stewing beef cubes, and baking potatoes that had been treated by combinations of cooking, freezing, retorting, and storage at 31 degrees centigrade for 3 months. Zn and its water-soluble complexes were membrane-filtered to exclude substances larger than 5000 daltons. It was found that about 30-50% of the total Zn in spinach treatments and about 70-100% of the Zn in potato treatments were water-soluble; however, almost none of the endogenous Zn in beef was water-soluble. Essentially all Zn in spinach and potatoes, and about half the Zn in beef, was released following acid-enzyme digestion, independent of the processing method used. Acid-enzyme digestion and subsequent membrane ultrafiltration data suggest that most of the endogenous Zn in spinach and potatoes (and at least half the total Zn in beef) will be available for intestinal absorption, regardless of the processing method. (wz)
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