Abstract
As a nonthermal sterilization technology, electron‐beam irradiation (EBI) has attracted great interests for microbial inactivation in food preservation. In this study, the inactivation of inoculated Listeria innocua, natural microbiota, and quality of fresh noodles treated by EBI during refrigerated storage were evaluated. Results showed that the initial L. innocua population (6.38 log CFU/g) was significantly reduced to an undetectable level by treatment with 3.0 kGy EBI. Moreover, treatment with 3 kGy EBI significantly reduced the initial total bacteria counts and fungal counts (mold and yeast) from 5.66 and 3.15 log CFU/g to 2.90 and 2.11 log CFU/g, respectively. However, along with the storage process, the inoculated L. innocua and natural microbiota were recovered resulting in the increased populations of the spoilage microorganisms. Increasing the dose of EBI to 4.0 kGy or 5.0 kGy, the L. innocua population was inhibited to the undetectable level and the microbiological quality of the fresh noodles was kept in the acceptable level during the 28 day storage. In addition, changes of the physicochemical indicators including pH value, color, cooking characteristics, texture, and sensory of fresh noodles treated with EBI were delayed during storage. These results reveal that EBI treatment can improve the microbiological safety and shelf life of fresh noodles without impairing quality.
Highlights
Noodles are regarded as a traditional human diet, which have been consumed for thousands of years in many Asian countries, such as China, Korea, Japan, and Thailand, due to its convenience, nutritional quality, and palatability (Heo, Lee, Shim, Yoo, & Lee, 2013; Li, Zhu, et al, 2012a)
The initial amount of L. innocua inoculated on fresh noodles was 6.38 log CFU/g, which was significantly reduced to the undetectable level in the sample treated with electron‐beam irradiation (EBI) at 3.0 kGy within 7 days of storage
These results were in agreement with those obtained by Mahmoud (2012) who found that L. monocytogenes was able to recover and grow in smoked salmon treated with irradiation at less than 2.0 kGy during storage at refrigerated temperature, which could result in a high risk of listeriosis disease (Sudha, Lammerding, & Griffiths, 2000)
Summary
Noodles are regarded as a traditional human diet, which have been consumed for thousands of years in many Asian countries, such as China, Korea, Japan, and Thailand, due to its convenience, nutritional quality, and palatability (Heo, Lee, Shim, Yoo, & Lee, 2013; Li, Zhu, et al, 2012a). It is important to reinforce researches into a novel sterilization technology that could effectively prolong the shelf life of fresh noodle and maintain their flavor and taste. Compared with other irradiation methods, EBI, derived from high‐energy electron beams, has been used as a clean and environmentally friendly technology for industrial food processing and is regarded as a potential novel nonthermal sterilization with a greater power utilization rate and a lower operation cost (Wei et al, 2014). Kong et al (2014) reported that EBI effectively inactivated Escherichia coli inoculated on fresh blueberries and extended the shelf life of fresh blueberries without changing nutritional quality at doses ≤ 3 kGy. In this study we explored the sterilization effects of EBI on the inoculated L. innocua and natural microbiota in fresh noodles, as well as physicochemical quality including pH value, color, cooking characteristics, texture, and sensory during refrigerated storage. This study will provide better insights into the potential applications of EBI in the future
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