EFFECT OF REDUCED EVAPORATION ON THE PROVITAMIN A CONTENT OF LETTUCE IN REFRIGERBTED STORAGE¹

Abstract

Previously Harris, Wissmann, and Greenlie ( 1940) reported the results of an extended series of determinations which showed that high humidity and low air movement caused considerable improvement in the maintenance of ascorbic acid (vitamin C ) dnring refrigerated storage. Six vegetables stored at 65 per cent relative humidity and with an air movement averaging approximately 10 fe'et per minute showed 64 per cent greater destruction of ascorbic acid than when stored at 93 per cent relative humidity with an air movement averaging approximately two feet per minute. Results were also given of preliminary experiments using bioassay methods which indicated that vitamin A (more correctly provitamin A ) was better preserved in vegetables when stored under these conditions. The present paper is a report of an intensive study using lettuce as a typical important vegetable to determine more accurately the effect of humidity and air movement on the preservation of its provitamin A. EXPERIMENTAL PROCEDUREThe two refrigerators used in this study were identical with the two types used previously. The cabinet of the conventioiial refrigerator ( A ) had a relative humidity which averaged 69 per cent, while the food compartment of the special refrigerator (11) averaged 88 per cent. On the floors of both refrigerators there were pairs of covered "hydrators," designed for use in the household in the storage of fragile vegetable foods.The relative humidities were determined with four electrically operated psychrometers located (No. 1) in the center of the floor of the right hydrator, (No. 2) on a platform in the center of the lower shelf of Refrigerator A and in the same location in (No. 3 ) the right hydrator, and (No. 4 ) on a platform in Refrigerator 11. Temperature measurements were by thermocouples placed beside psychrometers No. 2 and No. 4. Publication KO. 191 from

Vegetable Vitamins, Loss of Vitamin C in Fresh Vegetables as Related to Wilting and Temperature

“…The literature on this subject is rather limited, inconclusive, and somewhat contradictory (7,3,(3)(4)(5)(6)(7)9). The present studies were undertaken to obtain additional information on the effects of wilting and of temperature on the loss of vitamin C in vegetables.…”

“…reaction would soon terminate because of thiamine destruction. Thiamine is much more resistant to heat in vegetable materials than in aqueous solutions (5). It would be expected that more acetoin would be formed in the vegetable during heating than is formed in aqueous solutions.…”

STORAGE AND MICROBIAL ACTION UPON VITAMINS OF THE B‐COMPLEX IN PORK1

“…Losses of ascorbic acid and carotene from fruits and vegetables have been demonstrated- Esselen, Lyons, and Fellers (1942) ;Gleim, Tressler, and Fenton (1944) ; Harris and Mosher (1941) ; Mack, Tapley, and King (1939) ; Mack, Tressler, and King (1936) ; Manville, McMinis, and Chuinard (1936) ; Mayfield and Richardson (1940) ; Tressler, Mack, and King (1936)-but less attention has been given to the vitamins in other foods, especially meats In one limited investigation Schveigert, McIntire, and Elvehjem (1944) found that in fresh hams the niacin and thiamin content decreased by eight per cent and the riboflavin content decreased by 15 per cent during two weeks' storage a t -4OC. (24.8OF.).…”