Effect of gliding arc discharge (GAD) plasma application on decontamination and quality of apricot kernel

The aim of this study is to investigate the potential of Glare Arc Discharge (GAD) plasma, one of the cold plasma species, to reduce the number of mold-yeast and total mesophilic aerobic bacteria (TMAB) naturally found in apricot kernels (Akçadağ-Malatya) and to increase storage stability. Different plasma parameters (distance between electrodes: 0,6; 0,8 and 1 cm; gas flow rate: 0,5; 0,7 and 0,9 ml/min) and application time (2, 6) using copper electrode and nitrogen gas , 10 min) was tested. When Box-Behnken trial design was used, optimum plasma conditions were determined as 0,9 ml/min gas flow rate, 0,6 cm distance between electrodes, 7,65 min (Plasma-I) and 4,18 min (Plasma-II). After plasma-I and II, the total number of mesophilic aerobic bacteria, mold-yeast and coliform bacteria of apricot kernels, color, water activity (aw), antioxidant activity (DPPH, FRAP and ABTS), free fatty acidity (FFA), tocopherol content, oil, the changes in acid composition and total phenolic substance content were determined. In addition, control and plasma treated samples were stored for 1 month in an oven at 60°C to determine their storage stability and for 1 month in an incubator at 25°C to determine their microbiological stability. After Plasma-I and Plasma-II application, it was determined that the initial mold-yeast count of the samples decreased by 22% and 12%, respectively, and 19% and 8% after storage. Plasma-I and Plasma-II application before storage; 8% and 2%, respectively, and after storage, 8% and 7% reductions in the number of TMAB compared to the control. The difference between control and Plasma-I in terms of moisture, water activity, phenolic substance and tocopherol content before storage, and the difference between control, Plasma-I and II treatments in terms of color and FFA were not found significant (p>0,05). On the other hand, it was determined that the amount of phenolic substance decreased by 0.7% and 41%, DPPH value 40% and 60%, FRAP value 11% and 30% in the samples treated with Plasma-I and II compared to the control. After storage, Plasma-I and II decreased by 8% and 39% in phenolic content, 48% and 57% in DPPH, and 19% and 34% in FRAP, respectively. This study showed that GAD-plasma application is a convenient and effective method for pre-decontamination of apricot kernels.