Carotene Losses in Freshly Cut Plant Tissues

Abstract

The carotene in hays and silages is the most important source of vita- min A for dairy cows. The amount of carotene in hays is largely dependent upon the curing process. Hays may contain relatively small amounts of carotene even though they were made from fresh, green plant materials with high initial carotene contents. In studying this loss of carotene during the hay-curing process Hauge (8) obtained evidence for the presence of a caro- tene-destroying enzyme in alfalfa. That there may be differences in enzyme activity in different plants is indicated by the work of Bolin (3) who found that when fresh plant material was stored at five degrees F. for ten months, the loss of carotene in alfalfa was 62.7 per cent while there was little or no loss in bromegrass, meadow rescue, orchard grass, and Kentucky blue grass. During the summer of 1941 the authors found that bluegrass, even though dry and brown in color due to lack of rainfall, contained a surprisingly large amount of carotene. This suggested the possibility that bluegrass might be low in the carotene-destroying enzyme. In studies with grasses and berseem, Seshan and Shen (12) concluded that neither mold or bacterial action affected carotene losses and apparently doubted that enzymes have any great effect upon carotene losses in these plants. With these facts as a basis, it seemed desirable to study the losses of carotene in various plant materials under conditions which were favorable to enzyme activity and under other conditions which inhibited enzyme actions. EXPERIMENTAL The relative enzyme activity of various plant materials was determined by the loss of carotene during an incubation period at a favorable tempera- ture. The difference in loss of carotene between two samples, the enzymes having been inactivated by heat in one and not in the other, may be at- tributed directly to the effect of the enzymes. Some samples were incubated in an atmosphere of nitrogen. Any decreases in carotene losses of auto- claved samples incubated in an atmosphere of nitrogen are probably due to inhibition of uncatalyzed oxidation. Any decreases in carotene losses of samples not autoclaved but incubated in an atmosphere of nitrogen should be due to inhibition of uncatalyzed oxidation and also to inhibition of catalyzed oxidation if the enzyme is aerobic. The plant materials, which had been secL~red fresh from the field, were immediately chopped into quarter to half-inch lengths and mixed. In the