Study On Low-temperature Plasma Sterilization On Surface Of Fresh Wet Noodle And Design Of Sterilization Device

Noodles as a traditional food in China, the processing craft has a history of more than two thousand years. Due to demand for food continuous to rise and rapid development of technology over the years, industrial mass production of fresh wet noodles begins to enter the market, but it has difficult problems to solve, which are antisepsis and storage. The nature of perishable and sensitive to heat, there was no safe and effective sterilization on fresh wet noodles. The non-thermal dielectric barrier discharge (DBD) plasma treatment was a rapid, non-toxic and pollution-free bactericidal processing.This experiment was focused on the impact of survival condition of microorganism by the analysis of colony counting. With the non-thermal DBD plasma power and treatment time increased, the bactericidal effect of Escherichia coli, Staphylococcus aureus,Salmonella typhimurium and mold enhanced significantly. Likewise, the results were also obtained with decreasing non-thermal DBD plasma electrode distance.The water treated by non-thermal DBD plasma was detected through pH meter, digital conductivity instrument, ultraviolet spectrophotometer, the results proved that the plasma activated water contain a large amount of active material, such as charged particles and ions.The fresh wet noodles with non-thermal DBD plasma treatment were measured by Energy Dispersive X-ray Detector,there was reactive oxygen species (ROS) and reactive nitrogen species (RNS) attaching to the surface of fresh wet noodles after non-thermal DBD plasma treatment. The surface morphology of the bacteria and molds were observed by scanning electron microscope (SEM), and the cell membrane was damaged by non-thermal DBD plasma treatment. At the same time, the protein leakage of cells, the content of MDA in cells and changes of DNA were detected, it proved that both the cells chemical etching by the reactive oxygen and nitrogen species and the physical damage of the bacteria outer membranes induced by charged particles were involved in the sterilization process.The non-thermal DBD plasma treatment was firstly applied in fresh noodles surface sterilization. And furthermore, the quality of fresh wet noodles before and after non-thermal DBD plasma treatment were determined through the analysis of colony counting, texture analyzer, color meter, low-field nuclear magnetic resonance (LF-NMR), scanning electron microscope (SEM) and Fourier infrared spectrum (FTIR), respectively. Obviously, the non-thermal DBD plasma treatment had a bactericidal effect on surface of fresh wet noodles when the sterilization condition for treatment time was 20 s, power was 70 W, and electrode distance was 4 mm, respectively. Nevertheless, there was no significant change on texture, color, moisture distribution and structure properties of wheat gluten after non-thermal DBD plasma treatment.In conclusion, non-thermal DBD plasma treatment can be used for sterilization on surface of fresh wet noodles, leading to prolong the shelf-life of fresh wet noodles. It would provide a new idea of sterilization on other heat sensitive foods.