Process parameters optimization for red globe grapes to enhance shelf-life using non-equilibrium cold plasma jet

Abstract

In this work, a non-equilibrium cold plasma jet (NECPJ) operated by a bi-polar pulse power source was designed and developed, and its impact on red globe grapes (Vitis vinifera) was analyzed for shelf-life enhancement. A total of 17 separate experiments were conducted using a Box-Behnken design to identify the optimum plasma process parameters, i.e., applied voltage, gas flow rate, and treatment time. Food quality parameters such as pH, total suspended solids (TSS), weight loss, total phenol and flavonoid content, vitamin C, contact angle, and firmness were studied. Field emission scanning electron microscopy (FESEM) images were also taken to see the effect of NECPJ treatment on grape surfaces and E. coli bacteria. The results showed that the linear, quadratic, and interaction effects of all three process parameters were statistically significant (p < 0.001, p < 0.01). Accordingly, the optimized plasma process parameters were identified as applied voltage 3.36 kV, gas flow rate 2.87 SLPM, and treatment time 1 min. A shelf-life study of twenty-eight days was done with and without plasma treatment. It was found that NECPJ-treated grapes had a higher shelf-life. The treated grapes contained higher levels of vitamin C, firmness, red grape color index, and total soluble solids than controls. It is inferred that NECPJ can help reduce red globe grape deterioration and maintain quality during post-harvest storage.