Antibacterial Effects of Headspace Benzyl Isothiocyanates on Pseudomonas fragi in A Packaging System

Pseudomonas fragi is a dominant spoilage microorganism found in deteriorated fish, milk, and meats. The growth can be inhibited by releasing a strong antimicrobial agent in an active packaging system. Benzyl isothiocyanate (BITC) has shown antimicrobial effectiveness against various pathogenic and spoilage bacteria in a solid phase, but no reports on its antimicrobial activity in a gaseous phase are found. This study aims to investigate the Minimum Inhibitory Concentration (MIC) of BITC on bacterial inhibition of P. fragi in a food medium. Antimicrobial packaging containing medium inoculated by P. fragi was injected with BITC in different concentrations (0, 12.5, 125, 250, 500, and 750 ppm), and the BITC was kept released for 72 hours. The BITC concentration in the headspace was monitored using gas chromatography (GC), and the bacterial growth of P. fragi was also monitored. The bacterial growth was then described using the Gompertz model, and MIC was determined using the Inhibitory Sigmoid Emax model. The result revealed that BITC concentrations of 250 to 750 ppm had the greatest effects on the growth of P. fragi, while control and BITC concentrations of 1.25 ppm showed no difference. The bacterial growth was described using the Gompertz model with parameters: As (15.551 log10 CFU/mL) and λ (4.774 hours). Using the Sigmoid Emax model, the concentration-inhibition curve can be well described, and almost 1000 ppm or 1 mg/L was determined as MIC of BITC against P. fragi. Understanding the MIC allows applying the compound with sufficient and tolerant concentration for spoilage bacteria in packaged food.