Stevia rebaudiana Bert. (Bertoni) has attracted the attention of scientists and industry in recent years for its properties, natural and low-calorie sweeteners, steviol glycosides (SGs), which are an alternative to sugar. The main SGs are stevioside (Stev) and rebaudioside A (RebA). They compose up to 40% of the dry weight of the leaf and are 300 times sweeter than sucrose, also they are thermostable making them favorable in the food industry [1, 2]. RebA has better water solubility and a milder taste, closer to sucrose, than Stev. Seed treatment by cold plasma (CP) is an environmentally friendly method used to improve various plant properties and stimulate secondary metabolites synthesis [3].
The aim of this study was to determine the effect of cold plasma (CP) seed treatment (2, 5, or 7 min) on Stev and RebA accumulation in stevia leaves at different growth weeks (8, 12, 14 and 20). Other biochemical traits such as amount of total phenolics, total flavonoids and antiradical scavenging activity were also determined.
The largest change in SGs concentration at week 8 was induced by CP 2 min and reached 141 mg/g, as compared to 103 mg/g in control. At week 12 and 14, the largest increase in SGs concentration was observed in CP 5 min group. At week 12, it increased from 123 mg/g in control to 161 mg/g, and at week 14 it was 331 mg/g as compared to 220 mg/g in control. At week 20, the SGs concentration decreased to 150 mg/g and CP had no effect. The amount of SGs in the leaves inversely correlated with the scavenging activity and the total amount of phenolics and flavonoids. It can be concluded that the effect of cold plasma had a positive effect on the accumulation of steviol glycosides at least until week 14 of vegetation.