Electrical stimulation of grape berries as new alternative for post-harvest infection management

Abstract

Viticulture stands out as a primary agricultural sector in the EU. However, an intensive regime of chemical pesticides is used to meet production standards. Consequently, the EU has taken measures to encourage the promotion of sustainable agrochemical practices. It has recently been demonstrated that low voltage and electrical current can also successfully destroy different type of microorganisms such as bacteria and fungi. However, the application of electric current has not been much explored for preventing early stages of fresh fruit rotting. As a result, an innovative setup was developed to study the effect of an alternating current (50 mA) on grapes previously contaminated with E. coli. A visual analysis of the state of degradation of the grapes 12 days after the electrical treatment allowed us to conclude that the contaminated grapes subjected to electrical treatment (at day 1) did not show visual contamination, when compared to the contaminated grapes without electrical treatment, presenting a similar appearance to the grapes used as control. The quantitative assay also confirmed this result since on the NB agar plates it was possible to visualize a significant reduction in colonies, corresponding to 2 log10 CFU/mL, indicating that approximately 99% of the E. coli previously attached to the berry surface was eradicated. This environmentally sustainable solution aims to reduce dependence on pesticides. Still, other studies will focus on validating its effectiveness against target microorganisms and optimizing a conductive network for applying electrical stimuli to a bunch of grapes.