Investigations into the effects of processing on the retention of the carotenoid fractions of Leucaena leucocephala during storage, and the effects of processing on mimosine concentration

Abstract

Leucaena leucocephala leaves were subjected to several drying treatments followed by pelleting and/or inclusion of ethoxyquin as antioxidant and analysed monthly to determine rates of loss of carotenes and xanthophylls. Rapid sun drying yielded leucaena leaf meal with carotene and xanthophyll concentrations of 446 and 865 mg/kg, respectively, but considerable losses occurred during drying at 60 and 145°C, and as a result of blanching in hot water or ferrous sulphate solution. Loss rates of carotenes during storage were in the range 19–40 mg/kg per month, and of xanthophylls, 29–53 mg/kg per month. Carotenoids in sun-dried leaf meal were most stable during storage. Pelleting or inclusion of ethoxyquin did not reduce carotenoid loss rates below those of unpelleted leaf meal. The mimosine content of untreated sun-dried leucaena leaf meal was 3.2%, but the concentration decreased to 2.5 and 1.8% on drying at 60 and 145°C, respectively. The concentrations of mimosine in sun-dried leafmeals of water-blanched and ferrous sulphate-blanched leucaena were 2.0 and 2.1%, respectively. Treatments causing maximum losses of mimosine were those which brought about maximum losses of carotenoids.