Effect of pin-to-plate atmospheric cold plasma (ACP) on microbial load and physicochemical properties in cinnamon, black pepper, and fennel

The current study aimed to investigate the influence of pin-to-plate atmospheric cold plasma treatment (ACP) on the microbial decontamination efficacy, physical (water activity, color, texture), and bioactive (total phenolic and anti-oxidant capacity, volatile oil profile) of three major spices cinnamon, black pepper, and fennel at three different voltages (170, 200, 230 V) and exposure time (5, 10, 15 min). The surface etching and oxidative reactions of cold plasma is anticipated to cause microbial decontamination of the spices. In accordance with this, the ACP treatment significantly reduced the yeast and mold count of cinnamon, black pepper, and fennel, resulting in 1.3 Log CFU/g, 1.1 Log CFU/g, and 1.0 Log CFU/g, respectively even at the lowest treatment at 170 V-5 min. While at the highest treatment of 230 V-15 min, complete decontamination in all the samples was observed due to the plasma-induced microbial cell disruption. The water activity of samples reduced post-treatment 0.69 ± 0.02 to 0.51 ± 0.03 for cinnamon, 0.61 ± 0.03 to 0.49 ± 0.01 for pepper, and 0.60 ± 0.02 to 0.43 ± 0.02 for fennel which further reassures better microbial stability. The color and textural properties were significantly unaffected (p > 0.05) preserving the fresh-like attributes. The total phenolic content was increased for cinnamon (2.26 %), black pepper (0.11 %), and fennel (0.33 %) after plasma treatment at 230 V-15 min due to the cold plasma surface etching phenomenon. However, the essential oil composition revealed no significant variation in all three spices' control and treated samples. Thus, the study proves the potential of the atmospheric pressure cold plasma for the complete decontamination of the investigated spices (cinnamon, pepper, fennel) without remarkable changes in the volatile oil profile.