Bacteria in Raw Buckwheat Noodles and their Freezing Tolerance Capacity

Abstract

Raw buckwheat noodles served at soba restaurants lasts only one day. In order to keep raw buckwheat noodles for a long time, it is necessary to devise the process of producing and storing buckwheat noodles. Ultraviolet sterilization lamps were installed in the room from buckwheat flour preparation to raw buckwheat noodle production. The raw buckwheat noodles produced in this room lasted for 2 days without oxygen absorber and for 6 days with oxygen absorber under refrigerated storage. On the other hand, once frozen for long-term preservation, the raw buckwheat noodles lasted for 5 days without oxygen absorber and 9 days with oxygen absorber. As a result, raw buckwheat noodles can be refrigerated for up to one week. For the purpose of clarifying the bacteria that spoil raw buckwheat noodles under refrigeration, low-temperature bacteria were isolated and identified from raw buckwheat noodles and those that were frozen. By freezing raw buckwheat noodles, the number of viable bacteria was reduced by half. Pseudomonas sp., Hafnia paralvei, and Obesumbacterium proteus were identified as the freezing-sensitive bacteria, while Pantoea agglomerans, and Pseudomonas sp. were identified as the freezing-resistant bacteria. P. agglomerans accounts for the majority of the freeze-resistant bacteria and is considered to be largely responsible for the spoilage of raw buckwheat noodles under refrigeration.