Inactivation of Indigenous Microorganisms and Salmonella in Korean Rice Cakes by In-Package Cold Plasma Treatment.

Joo Hyun Kang,Sea C Min,Jaewoo Bai

doi:10.3390/ijerph18073360

Abstract

The antimicrobial effects of in-package cold plasma (CP) treatment on Korean rice cakes (KRC) were evaluated. The CP treatment (25 kV) inactivated indigenous mesophilic aerobic bacteria by 0.8–1.0 log CFU/g, irrespective of the position of KRC in the package. The addition of a shaking step during CP treatment increased the reduction in microbes by ~1 log CFU/g. The microbial inactivation efficiency increased significantly when the treatment time increased from 1 to 3 min. Microbial inactivation activity was highest for packages containing eight rice cakes. The optimized CP treatment achieved a 2.0 ± 0.1 log CFU/g reduction in indigenous bacteria. In addition, the optimum CP treatment inactivated indigenous yeast and molds and Salmonella in KRC by 1.7 ± 0.1 log CFU/g and 3.9 ± 0.3 log CFU/g, respectively. No significant changes in color and firmness were observed, and the surface temperature of KRC did not exceed 22 °C after CP treatment. Moreover, CP treatment damaged the cellular membrane of Salmonella, mainly by inducing lipid peroxidation. This study demonstrates the potential use of in-package CP treatment for the non-thermal microbial inactivation of KRC.

Highlights

Rice cakes are a widely consumed ready-to-eat food in Asia, Korea, China, and Japan
The microbial inactivation efficiency against natural bacteria on Korean rice cakes (KRC) was 0.8–1.0 log CFU/g, regardless of the position of KRC in the packaging (p > 0.05), indicating that cold plasma (CP) was uniformly applied to each KRC sample (Table 1)
Different lowercase letters indicate a significant difference based on Tukey’s test (p < 0.05). These results are consistent with those obtained by Roh et al (2019), who reported that the inhibitory effect of in-package CP treatment on Salmonella on packaged chicken breasts during in-package CP treatment showed no significant difference with respect to the sample position [16]

Summary

Introduction

Rice cakes are a widely consumed ready-to-eat food in Asia, Korea, China, and Japan. KRC has a short shelf-life due to the high possibility of microbial contamination during the manufacturing process [2,3]. To extend the shelf-life of KRC, microbial disinfection using sodium hypochlorite (NaOCl) solution or alcohol is widely used commercially. Alcohol treatment generates an off-flavor [3]. To overcome these disadvantages, various methods have been evaluated for the inhibition of microorganisms in KRC, including altering the air composition in the packaging, adding organic acids and natural antibacterial agents (e.g., lactic acid and chitosan), and heating [2,6,7,8]. The aforementioned methods are still limited by the potential for microbial cross-contamination after treatment [9]

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Results

Conclusion