In a collaborative research project with Gurunavi, Inc., a research group led by Tokyo Institute of Technology Life Science and Technology Associate Professor Takuji Yamada has uncovered the effect on fermentation micro-organisms and other constituents of takuan pickled radish of differences in their recipe and production environment by comparing the takuan from the cold, snowy region of Akita with that of the warm, sunny region of Aichi.
According to Yamada, “In order to research strongly-rooted regional food cultures, our focus turned to Iburi takuan from Akita and Atsumi takuan from Aichi, radish pickles made in ways that reflect local climate and cultural characteristics. We were provided samples by six pickle makers in Akita and Aichi for this project.”
Comparing the raw ingredient of the pickle, daikon radish of Akita and Aichi, the research group detected no statistically significant difference in surface microbial communities by region or drying method. Neither was there any difference in the microbial communities of the rice bran used.
However, significant differences were seen after pickling in both rice bran and the takuan surface microbial communities. Many types of microbe were detected in the Akita pickles. Meanwhile, higher proportions of lactobacillus and salt-loving microbes (halomonas, halanaerobium) were detected in the Aichi pickles, where these three species represented over 50% of microbes found.
It was thought that the key reasons for the emergence of these differences in the fermentation micro-organisms and other constituents were that while the cold climate of Akita limits the activity of micro-organisms, preventing the active fermentation that would lead to an increase in certain constituents, allowing a range of micro-organisms living on the raw daikon radish to survive. Meanwhile, in the climate of Aichi, statistical data analysis suggested potential lactic fermentation by lactobacillus and glutamate production by salt-loving microbes.
Yamada states, “Going forward, we plan to research two separate areas. On one hand, we would expand the study to other regions, further revealing the value of regional food cultures from a scientific perspective. On the other, we want to obtain more amino acid-fermenting bacteria that love salt, and apply them to more efficient production of amino acids.”