GC-FID and NMR Spectroscopic Studies on Gamma Irradiated Walnut Lipids

Abstract

Walnuts have an excellent fatty acid profile, beneficial for coronary heart diseases. A diet rich in walnuts has shown to decrease the total and LDL cholesterol levels as well as lipoprotein levels. In this study, the effects of different doses of γ-irradiation and different packaging conditions on proximate composition and fatty acid profile of walnuts (Juglans regia L.) were investigated merging data from different spectroscopic techniques. Walnuts moisture, ash, fat, and protein content as well as fatty acid profile were evaluated immediately after irradiation. GC-FID results showed that SFA increased and MUFA and PUFA decreased with the increase of irradiation dose. Moreover, MUFA/SFA and PUFA/SFA ratios decreased P<0.05 compared to control samples. Furthermore, NMR spectroscopy was implemented to examine possible discrimination patterns based on irradiation dose and packaging. This approach revealed the role of PUFA decrease with the parallel increase of irradiation dose while indicating the protective role of vacuum and MAP compared to air packaging. In conclusion, at irradiation doses of up to 5 kGy, the walnuts retained the nutritional benefits of its fatty acids, in particular MUFA and PUFA. Concerning the different types of packaging, greater stability in the nuts was observed using MAP packaging.