Positive and Negative Impacts of Low-Pressure Cold Plasma as a Decontamination Method for Red Chili Powder (Capsicum Annuum L.)

Abstract

The microbial contamination of spices, including red chili powder, and the subsequent formation of toxins can cause adverse health effects. Chemical treatments to control microbial spoilage also leave hazardous residues. This research was designed to assess the potentials and limitations of low-pressure cold plasma (LPCP) decontamination of red chili powder. A medium-scale red chili processing facility was selected to assess the process and finished packed products were chosen for LPCP treatment. Microbial contamination levels in selected critical processing steps of red chili processing were assessed. Contaminating bacteria and fungi in the packed products were genetically identified. A radio frequency-powered (13.56 MHz) capacitively coupled plasma reactor with argon gas (120 cm3/min) at 0.3 mbar was used and treatment times were 3, 6, and 9 min. A 9-min treatment effectively reduced aerobic bacteria by 0.99 log colony-forming units per gram (CFU/g) and yeasts and molds (Y&M) by 2.41 log (CFU/g). The decimal reduction time (D value) for a bacterial mix comprising Bacillus velezensis, Bacillus subtilis, and Cronobacter sakazakii was 9 min and 11 s, while the D value comprising a fungal mixture of Aspergillus chevalieri and Aspergillus niger was found to be 3 min and 56 s. Scanning electron microscopic (SEM) images confirmed the progressive etching of powder surfaces. Significant reductions in water activity were found. The reduction of red color in red chili powder during the treatments was identified as the main negative aspect. Minor changes in attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) spectra confirmed the oxidation of color pigments with treatment.