Tocopherol retention and vitamin E activity in frozen and canned immature seeds of five cultivars of common bean

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This paper investigates tocopherol retention and vitamin E activity in the seeds of five bean cultivars (flageolet type and grown mostly for their dry seeds) harvested at the wax stage of maturity. Seeds were analyzed raw, cooked and in three products prepared for consumption after 0 and 12 months of storage. These comprised frozen products obtained using the traditional method (blanching-freezing-frozen storage-boiling) and a modified method (boiling-freezing-frozen storage-defrosting and heating in a microwave oven), and canned products. Total tocopherols in fresh bean seeds were within the range 18.53-25.98 mg kg(-1) of edible portion. The most abundant form of tocopherol found in fresh seeds was γ-T isomer (87-91% of the total), followed by the α-T (5-7%) and δ-T (3-5%) forms; the β-T form was not detected. Cooking resulted in a 13-28% decrease in total tocopherols and a 17-31% reduction in vitamin E activity. In products prepared for consumption after 12 months' storage, total tocopherols and vitamin E activity were 13-53% and 23-60% lower, respectively, than in fresh seeds, with the highest losses being mainly in α-T content. The variety and cultivar or method of preservation had no effect on either tocopherol retention or vitamin E activity.