Storage stability of Jatropha curcas L. oil naturally rich in gamma-tocopherol

Abstract

Jatropha curcas L. is an interesting tropical oil crop for biodiesel production. However, seed conservation until oil extraction may be a problem under high temperature and humidity. In this study, Jatropha curcas L. seeds grown in Mozambique and presenting 160mg/kg of gamma-tocopherol in their oil were stored for 42 days, in dark, at 35°C and 75% or 92% relative humidity (RH). Along storage, the oil was extracted and analysed in terms of fatty acid composition, tocopherol content, acidity, initial and final oxidation products (monitored by K232 and K270 values, respectively).Jatropha seeds presented an initial water content of 8.4% and an oil content of 45.7% (dry basis). The oil was rich in oleic (41.2%) and linoleic (38.8%) acids.Along 42 days of storage, the acidity increased from 0.8% to 7.4% and 25.3% and K270 increased from 0.07 to 0.25 and 0.46 in oils from seeds stored at 75% and 92% RH, respectively. Simultaneously, a decrease in gamma-tocopherol content was observed, which was more pronounced at 92% RH than at 75% RH (96% decrease versus 57% decrease). Gamma-tocopherol showed to protect the oil against oxidation principally during the second stage of oxidation. During the storage at 35°C, the fatty acid composition of the oils from seeds kept either at 75% or 92% of humidity, did not significantly vary throughout the test.