Effects of post-harvest treatments on concentrations and profile of fatty acids in fresh perennial ryegrass (Lolium perenne L.)

Plant lipids are complex, polar and highly unsaturated constituents of membranes. During collection and/or handling of a plant sample, the membrane integrity gets lost due to plant injury and losses of fatty acids (FA) can occur as a result of oxidative or enzymatic processes. Quantitative and qualitative effects of various post-harvest treatments on the concentrations and proportions of FA in herbage are not well known. In this study, effects of various post-harvest treatments regarding conditions following sample collection of perennial ryegrass were examined. The handling of the samples, before applying all pre-treatments, was uniform, i.e., all samples were put in a cooling box at 4°C and transported to the lab for approximately 30min. The moment when the samples arrived to the lab was considered “time zero”, and the applications of treatments started. We studied effects of two ways of sample handling (dry ice vs. no dry ice), two frozen storage temperatures (−80°C vs. −18°C) and two durations of frozen storage (1 day vs. 2 weeks) on concentrations and proportions of FA in cut herbage. The effects of the treatments appeared to be small and inconsistent, with exception of prolonged storage, which decreased FA concentrations, and increased the proportion of α-linolenic acid (C18:3). Contrary to expectation, using dry ice (rapid freezing) did not differ from slow freezing (without dry ice). Also, there were no effects of storage temperature (−80 or −18°C). Future research questions are discussed.