A new pasteurization technique uses plasma, vacuum packaging and hot water to inactivate food pathogens on buckwheat seeds, cutting the risk of food poisoning outbreaks without preventing the seeds from sprouting.
The technique, which reduces the total time for seed pasteurization,was developed by scientists at Kyonggi University in South Korea and tested in a study, ‘Inactivation of Salmonella Typhimurium and Listeria monocytogenes on buckwheat seeds through combination treatment with plasma, vacuum packaging, and hot water’, which was published in the Journal of Applied Microbiology, an Applied Microbiology International publication.
The study addresses rising concerns about foodborne outbreaks related to pathogen-contaminated low- water activity foods.
Food poisoning
“Recently, sprouts have become one of the most common causes of food poisoning, and seeds for sprouts were determined as the main contributor to sprout outbreaks,” explained corresponding author Professor Won-jae Song.
“Among them, buckwheat sprouts are rich in nutrients, so their consumption has recently been increasing worldwide. Buckwheat is also a low-water activity food and was judged to have a high risk of foodborne outbreaks, so pasteurization research was conducted on it.
“The technology used in this study was confirmed to have high commercial value because it can reduce the risk of foodborne outbreaks without affecting the germination rate, and has high temporal and thermal efficiency compared to other technologies.”
Buckwheat seeds
In this study, pasteurization research was conducted on buckwheat seeds, a low-water activity food. Because it is difficult to pasteurize foods with low water activity, a combination of DBD plasma, vacuum packaging, and hot water was used for effective pasteurization. As a quality measure, rutin and antioxidant capacity, which are the main substances in buckwheat, were measured.
“As a result of pasteurization, the combined treatment showed a synergistic ability to reduce microorganisms compared to the sum of the individual treatments of each technology,” said Professor Song.
“As a result of quality measurement, the combination treatment did not cause significant differences in all qualities compared to control.
“This study is believed to be a helpful technology for future food safety research by confirming effective microbial control and quality maintenance ability.”
Treatment time
The focus of the project was on reducing the total treatment time for seed pasteurization. Seeds are usually pasteurized by dry heat treatment which usually has a very long treatment time and can affect the germination rate of seeds.
“We could reduce the total treatment time by using hot water rather than dry heat, but hot water greatly reduced the germination rate of seeds,” Professor Song said.
“We tried to find a method for maintaining the germination rate and qualities during hot water treatment. Vacuum packaging increased the total treatment time, but it did not make significant changes in the germination rate of seeds and the quality of sprouts.
“Also, in this study, we used DBD plasma to replace hydrogen peroxide which can increase the germination rate of seed and microbial inactivation effect. It was difficult to set the plasma treatment conditions. The configurable power density range of the equipment used in the study was diverse.
“There were many cases where buckwheat seeds scorched at certain power densities and processing times, affecting quality. To solve this, a preliminary experiment was conducted to find the optimal conditions, and the final conditions of 120 W and 30 seconds were set.”
Synergistic effect
One surprise was that when confirming the pasteurization results, the microbial control ability of the combined treatment showed a synergistic effect compared to the single treatment.
Additionally, the combination treatment did not show significant differences compared to the control in antioxidant capacity, which is an important attribute of buckwheat.
“Because buckwheat is often distributed in the form of sprouts through germination, when the germination rate was measured, it was confirmed that the combination treatment maintained germination ability in the corresponding indicators,” Professor Song said.
Pasteurizing conditions
With an increase in buckwheat sprout consumption, an increase in foodborne outbreaks due to seed sprouts has been observed for several years - hence the importance of developing pasteurizing conditions for seeds for sprouts.
“We can achieve 5 log reductions of pathogens, which were recommended by NACMFC, without a detrimental effect on the germination rate of seeds and the quality of sprouts by using the combination treatment with plasma, vacuum packaging, and hot water,” Professor Song said.
“This pasteurization study was conducted in lab-scale conditions. To evaluate the applicability to the food pasteurization industry in the future, we recommend a process of judging or quantifying this through pilot-scale research.”
The team thanked Professor Won-jae Song for providing practical support to enable them to participate in research at the Food Safety Microbiology Laboratory, Department of Food and Biotechnology, Kyonggi University.
‘Inactivation of SalmonellaTyphimurium and Listeria monocytogenes on buckwheat seeds through combination treatment with plasma, vacuum packaging, and hot water’, appears in the Journal of Applied Microbiology, an Applied Microbiology International publication.
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