The stability of beta-carotene in preserved, moist leaf protein

Abstract only - no further text The stability of S carotene in preserved, moist leaf protein. By N. W. PIRIE, In feeding trials in India, Jamaica, Nigeria and Pakistan dried leaf protein (LP) was used. Had fresh material been used, the results would probably have been even better because drying, especially with foods containing as much unsaturated fatty acid as LP, is usually deleterious. The moist press-cake of LP, which is usually at about pH 4, keeps for a few days at room temperature even in the tropics, but it is not always convenient to make LP so frequently as to allow unpreserved, moist material to be used. Press-cake containing 50 to 60% dry matter (DM) keeps for several weeks at 27' if the fluid pressed from it at the end of the isolation contains I 70 g sodium chloride or 6 g acetic acid/l (Pirie, 1980). Vitamin A deficiency is a serious problem in several countries where LP would be a useful dietary supplement. It is therefore important to know how much of the p carotene usually present (0.1 to 0.2%) in fresh LP is lost when preserved material is stored. There is little or no loss of p carotene when LP from elder, nettle, potato or wheat is stored for 2 weeks in the dark in the presence of air at 34' when it contains NaCl and 50% DM. In the same conditions, LP from lucerne loses 20 to 30% of its p carotene, but nearly all of it is lost with LP from Brussels sprouts tops or rape. With these two species, destruction is slower if the LP is preserved with acetic acid, is pressed so thoroughly that it contains 60-7070 DM, if air is excluded, or if cyanide is present. Exclusion of air would be troublesome, and hostility to the addition of even a minute amount of cyanide is to be expected. Other inhibitors are therefore being sought. Destruction is not, in a strict sense, enzymic: the LP used had been heated to 100'. The nature of the difference between NaCl and acetic acid, and between the species of leaf, is not yet clear. Some food tables record similar differences between the amounts of p carotene in fresh and salted vegetables. For example, the Food composition table for use in East Asia (Food and Agriculture Organisation, 1972) shows large differences with cabbage, Chinese cabbage, turnip greens and olives. Rothamsted Experimental Station, Harpenden ALg 2 JQ Pirie, N. W. (1980). Ind. J. Nut*. Diet. 17, 349.