Study on electrostatic field assisted freezing temperature storage of grapes

Freezing temperature (FT) storage is an effective way to inhibit the quality deterioration of fruits and vegetables. However, the freeze damage of fruits and vegetables is easy to occur due to the individual freezing point temperatures and the fluctuation of storage temperature during the storage period. Therefore, the freezing temperature storage assisted with high voltage electrostatic field (HVEF) was proposed as an optimization method. The thermodynamic characteristics and storage quality of Sunshine Rose grapes stored at freezing point temperature (−2.0 ∼ −2.4 °C) under different HVEF treatment intensities and methods were studied. The results demonstrated that the cooling rate of grapes treated by HVEF was faster and the freezing temperature was significantly reduced obviously, and this effect is significant with increasing HVEF intensity. Additionally, in aspects of the effects of freeze damage and quality during storage, the spoiled fruits rate and freeze damage rate of the 100 kV/m pretreatment were 14.5% and 8.3%, lower than that of the freezing temperature control group. HVEF of pretreatment and intermittent treatment significantly inhibited the accumulation of malondialdehyde (MDA) and the increase in the total number of colonies and polyphenol oxidase (PPO) activity during storage. The appropriate intensity of HVEF reduced the probability of grape freezing and the proliferation rate of microorganisms during storage, so that there is a higher commodity rate and sensory characteristics. Therefore, HVEF assisted treatment during freezing temperature storage will be a feasible way for further improving grape preservation quality.