Experimental investigation of integrated systems of precooling and plasma‐activated water‐based bacterial inactivation

Abstract

Plasma‐activated water (PAW) is produced by treating aqueous solution with cold plasma. PAW is rich in reactive oxygen and nitrogen species, making it a safe and efficient approach for the inactivation of pathogens. In this paper, two types of integrated systems of precooling and PAW‐based bacterial inactivation for fruits and vegetables were proposed. One is cold water precooling (CWP) and PAW, the other is differential pressure precooling (DPP) and PAW. The influencing factors of PAW preparation and the bacterial inactivation effect of PAW suspension were experimentally investigated. The results demonstrated that with the increase in preparation time, the pH decreased, with a concurrent increase in temperature, electrical conductivity, and redox potential. The physicochemical properties of PAW were affected by temperature, with the optimal temperature being about 17°C. As the preparation time and bacterial inactivation time increased, the decontamination effect of PAW against Escherichia coli increased in suspension bacterial inactivation. Conversely, with the decrease in PAW temperature, the bacterial inactivation effect weakened. Furthermore, PAW was applied through CWP and DPP combined with PAW for precooling snow peas. Soaking CWP showed a 2.1 log reduction of background bacteria after 10 days of storage. Spraying CWP showed a 1.1 log reduction of background bacteria after 5 days of storage. DPP showed a 0.8 log reduction of background bacteria after 10 days of storage, and the appearance of snow peas surpassed those of the control group. Integrated systems of precooling and PAW‐based bacterial inactivation indicated promising effects on maintaining the safety and quality of snow peas.Practical applicationsPAW is a sterilization method with the advantage of easy preparation, low cost, minimal chemical residue, and effective sterilization. PAW could be produced simply by discharge on the tap water, which is very practical for its up‐scale application. In this study, different parameters on the physicochemical properties of PAW were evaluated, which was helpful in designing industrial PAW‐producing equipment. Besides, integrated systems of precooling and PAW sterilization for fruits and vegetables were proposed, which showed prominent sterilization and good preservation effects. The integrated systems could maintain the freshness of fruits and vegetables and prevent bacterial contamination during precooling by combining PAW sterilization and precooling, which will help extend the shelf lives of fruits and vegetables. In addition, this combination will prevent agricultural product waste and maintain the safety of fruits and vegetables.