Protection of carotenoids in alfalfa [Medicago sativa] leaf extracts by ethoxyquin addition and cold temperature storage
1996
Layug, D.V. (Nagoya Univ. (Japan). Faculty of Agriculture) | Oshima, M. | Ostrowski-Meissner, H.T. | Yokota, H.
Alfalfa leaf extracts were prepared by disintegrating fresh herbage, coagulating the green juice by steam injection and separating the curd from the deproteinized juice. Addition of ethoxyquin (w/v) into the green juice at 0.01, 0.02, 0.05, 0.10 and 0.20% levels prior to coagulation gave final concentrations of 0.11, 0.26, 0.70, 1.15 and 2.57% in the freeze-dried leaf extract, respectively. Samples, packed in vinyl bags and wrapped in aluminum foils, were stored for 40 weeks at 28, 5 or -18 degrees C. The lower the storage temperature, the lesser the reduction in carotenoid content was. The rate of loss of beta-carotene was much faster than xanthophylls. At high temperature (28 degrees C), ethoxyquin was essential to reduce the loss of carotenoids. Without it, recoveries of beta-carotene and xanthphyll in leaf extract were reduced to 3 and 15%, respectively, of the initial values within 40 weeks, but were improved to 30 and 50% by the addition of only 0.01% ethoxyquin. Further addition improved the recoveries a little further to 50 and 60%, respectively, at the highest application level. At low temperatures (5 and -18 degrees C), carotenoids were well preserved without ethoxyquin excepting beta-carotene at 5 degrees C. The recovery of beta-carotene at 5 degrees C was only 40% but was improved gradually to 90% with the increase of ethoxyquin levels. The decline of ethoxyquin in leaf extract at temperature above freezing implies that ethoxyquin itself be subjected to degradation. Only slight difference was observed between 5 and 28 degrees C in the ethoxyquin degradation
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