Influence of ionizing radiation on the free sugars content of several aromatic and medicinal plants

Irradiation is a versatile and effective conservation technique, applied to several food matrices. Based on this evidence, it is very relevant to study the effects of different irradiation conditions on the various molecules present in food [1]. Aromatic and medicinal plants are among the food products that need appropriate conservation technologies to expand their applicability [2,3]. The present study evaluated the effects of gamma radiation and electron beam on the composition of soluble sugars of four widely consumed plant species - A/oysia citrodora Palau, Melissa officina/is L., Melittis melissophyllum L. and Mentha piperita L.. After sample irradiation, using different doses (0 - control, 1 and 10 kGy), the individual sugars profile was evaluated by high performance liquid chromatography coupled to a refractive index detector (HPLC-RI). All the studied plants showed the presence of fructose, glucose, sucrose and trehalose. In general, after performing an individualized analysis of each species submitted to gamma irradiation, it was verified that the dose of 10 kGy provided a higher sugars content in M. officina/is and M. melissophyllum, while A. citrodora and M. piperita tended to have higher values in non-irradiated samples. The processing performed with electron beam resulted in a higher susceptibility of sucrose and trehalose molecules, which changed significantly in most of the cases. Considering total sugars, only small variations were detected. Thus, the results obtained may be a good guide to choose the type of irradiation or dose to be applied, according to the need to maintain or alter the profile of soluble sugars in the studied species.Foundation for Science and Technology (FCT, Portugal) by financial support to CIMO (PEst- OE/AGR/UI0690/2014) and for L. Barros and J.C.M. Barreira contracts. The authors also thank Prof A. Chmielewski, General Director of the Institute of Nuclear Chemistry and Technology, Warsaw. Poland, for allowing the electron beam irradiation of the samples; and to the company "MaisErvas - Aromaticas e Medicinais" for providing the plant material.