{"667350":{"#nid":"667350","#data":{"type":"news","title":"Want Better Kimchi? Make It Like the Ancients Did ","body":[{"value":"\u003Cdiv\u003E\r\n\u003Cp\u003E\u003Cspan\u003E\u003Cspan\u003EFermented foods like kimchi have been an integral part of Korean cuisine for thousands of years. Since ancient times, Korean chefs have used onggi \u2014 traditional handmade clay jars \u2014 to ferment kimchi. Today, most kimchi is made through mass fermentation in glass, steel, or plastic containers, but it has long been claimed that the highest quality kimchi is fermented in onggi. \u003C\/span\u003E\u003C\/span\u003E\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u003Cspan\u003E\u003Cspan\u003EKimchi purists now have scientific validation, thanks to recent research from \u003Ca href=\u0022https:\/\/www.me.gatech.edu\/faculty\/hu\u0022\u003EDavid Hu\u003C\/a\u003E, professor in the \u003Ca href=\u0022https:\/\/www.me.gatech.edu\/\u0022\u003EGeorge W. Woodruff School of Mechanical Engineering\u003C\/a\u003E and the \u003Ca href=\u0022https:\/\/biosciences.gatech.edu\/\u0022\u003ESchool of Biological Sciences\u003C\/a\u003E\u0026nbsp;at\u0026nbsp;Georgia Tech, and Soohwan Kim, a second-year Ph.D. student in Hu\u2019s lab.\u003C\/span\u003E\u003C\/span\u003E\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u003Cspan\u003E\u003Cspan\u003EIn a \u003Ca href=\u0022https:\/\/royalsocietypublishing.org\/doi\/10.1098\/rsif.2023.0034\u0022\u003Ecombined experimental and theoretical study\u003C\/a\u003E, Hu and Kim measured carbon dioxide levels in onggi during kimchi fermentation and developed a mathematical model to show how the gas was generated and moved through the onggi\u2019s porous walls. By bringing the study of fluid mechanics to bear on an ancient technology, their research highlights the work of artisans and provides the missing link for how the traditional earthenware allows for high quality kimchi.\u003C\/span\u003E\u003C\/span\u003E\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u003Cspan\u003E\u003Cspan\u003ETheir research was published in the\u003Cem\u003E Journal of the Royal Society Interface\u003C\/em\u003E. \u003C\/span\u003E\u003C\/span\u003E\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u003Cspan\u003E\u003Cspan\u003E\u201cWe wanted to find the \u2018secret sauce\u2019 for how onggi make kimchi taste so good,\u201d Hu said. \u201cSo, we measured how the gases evolved while kimchi fermented inside the onggi \u2014 something no one had done before.\u201d\u003C\/span\u003E\u003C\/span\u003E\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u003Cspan\u003E\u003Cspan\u003EThe porous structure of these earthenware vessels mimics the loose soil where lactic acid bacteria \u2014 known for their healthy probiotic nature \u2014 are found. While previous studies have shown that kimchi fermented in onggi has more lactic acid bacteria, no one knew exactly how the phenomenon is connected to the unique material properties of the container.\u003C\/span\u003E\u003C\/span\u003E\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u003Cspan\u003E\u003Cspan\u003EFirst, Kim obtained a traditional, handmade onggi jar from an artisan in his hometown in Jeju, South Korea, a region famous for onggi. Back at Georgia Tech, Hu and Kim first tested the permeability of the onggi by observing how water evaporated through the container over time. \u003C\/span\u003E\u003C\/span\u003E\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u003Cspan\u003E\u003Cspan\u003ENext, they installed carbon dioxide and pressure sensors into both the onggi and a typical, hermetically sealed glass jar. They prepared their own salted cabbage and placed it in both containers. They then used the sensors to measure and compare the change in carbon dioxide \u2014 a signature of fermentation. \u003C\/span\u003E\u003C\/span\u003E\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u003Cspan\u003E\u003Cspan\u003EHu and Kim also developed a mathematical model based on the porosity of the onggi. The model allowed them to infer the generation rate of carbon dioxide, since the onggi lets carbon dioxide out gradually. \u003C\/span\u003E\u003C\/span\u003E\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u003Cspan\u003E\u003Cspan\u003EThey concluded that the onggi\u2019s porous walls permitted the carbon dioxide to escape the container, which accelerated the speed of fermentation. The onggi\u2019s porosity also functioned as a \u201csafety valve,\u201d resulting in a slower increase in carbon dioxide levels than the glass jar while blocking the entry of external particles. Their data revealed that the carbon dioxide level in onggi was less than half of that in glass containers. \u003C\/span\u003E\u003C\/span\u003E\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u003Cspan\u003E\u003Cspan\u003EThey also found that the beneficial bacteria in the onggi-made kimchi proliferated 26% more than in the glass counterpart. In the glass jar, the lactic acid bacteria became suffocated by their own carbon dioxide in the closed glass container. It turns out that, because the onggi releases carbon dioxide in small rates, the lactic acid bacteria are happier and reproduce more. \u003C\/span\u003E\u003C\/span\u003E\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u003Cspan\u003E\u003Cspan\u003E\u201cOnggi were designed without modern knowledge of chemistry, microbiology, or fluid mechanics, but they work remarkably well,\u201d Kim said. \u201cIt\u2019s very interesting to get these new insights into ancient technology through the lens of fluid dynamics.\u201d \u003C\/span\u003E\u003C\/span\u003E\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u003Cspan\u003E\u003Cspan\u003EOnggi\u2019s semiporous nature is unique compared to other forms of earthenware. A clay container that leaks, but only slightly, is not easy to make. Terra cotta containers, for example, quickly leak water. \u003C\/span\u003E\u003C\/span\u003E\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u003Cspan\u003E\u003Cspan\u003E\u201cIt\u0027s amazing that, for thousands of years, people have been building these special containers out of dirt, but in many ways, they are very high tech,\u201d Hu said. \u201cWe discovered that the right amount of porosity enables kimchi to ferment faster, and these onggi provide that.\u201d \u003C\/span\u003E\u003C\/span\u003E\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u003Cspan\u003E\u003Cspan\u003EKim said that some artisans still use ancient methods when making onggi, but their numbers are decreasing. Now, the market is flooded with inauthentic versions of the vessels.\u003C\/span\u003E\u003C\/span\u003E\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u003Cspan\u003E\u003Cspan\u003E\u201cWe hope this study draws attention to this traditional artisan work and inspires energy-efficient methods for fermenting and storing foods,\u201d he said. \u201cAlso, the onggi are quite beautiful.\u201d \u003C\/span\u003E\u003C\/span\u003E\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u0026nbsp;\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u003Cspan\u003E\u003Cspan\u003ECitation: Kim Soohwan and Hu David L. Onggi\u2019s permeability to carbon dioxide accelerates kimchi fermentation. \u003Cem\u003EJ. R. Soc. Interface\u003C\/em\u003E. 2023.\u003C\/span\u003E\u003C\/span\u003E\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u003Cspan\u003E\u003Cspan\u003EDOI: \u003Ca href=\u0022https:\/\/doi.org\/10.1098\/rsif.2023.0034\u0022\u003E\u003Cstrong\u003Ehttps:\/\/doi.org\/10.1098\/rsif.2023.0034\u003C\/strong\u003E\u003C\/a\u003E\u003C\/span\u003E\u003C\/span\u003E\u003C\/p\u003E\r\n\r\n\u003Cp\u003EThis material was supported by the Woodruff Faculty fellowship and the NSF Physics of Living Systems student network.\u003C\/p\u003E\r\n\u003C\/div\u003E\r\n","summary":"","format":"limited_html"}],"field_subtitle":[{"value":"Researchers explain why kimchi enthusiasts are right when they say the highest quality fermented cabbage is made in traditional earthenware onggi."}],"field_summary":[{"value":"\u003Cp\u003EToday, most kimchi is made through mass fermentation in glass, steel, or plastic containers, but it has long been claimed that the highest quality kimchi is fermented in onggi. Kimchi purists now have scientific validation, thanks to recent research \u003Cspan\u003E\u003Cspan\u003Emeasuring carbon dioxide levels in onggi during kimchi fermentation, and developing a mathematical model to show how the gas was generated and moved through the onggi\u2019s porous walls.\u003C\/span\u003E\u003C\/span\u003E\u003C\/p\u003E\r\n","format":"limited_html"}],"field_summary_sentence":[{"value":"Researchers explain why kimchi enthusiasts are right when they say the highest quality fermented cabbage is made in traditional earthenware onggi."}],"uid":"34528","created_gmt":"2023-04-14 15:04:51","changed_gmt":"2023-05-23 19:11:13","author":"jhunt7","boilerplate_text":"","field_publication":"","field_article_url":"","dateline":{"date":"2023-04-13T00:00:00-04:00","iso_date":"2023-04-13T00:00:00-04:00","tz":"America\/New_York"},"extras":[],"hg_media":{"670550":{"id":"670550","type":"image","title":"A cross-sectional view of onggi showing fermenting cabbage. Credit: Korean Ministry of Culture, Sports, and Tourism.","body":"\u003Cp\u003EA cross-sectional view of onggi showing fermenting cabbage. Credit: Korean Ministry of Culture, Sports, and Tourism.\u003C\/p\u003E\r\n","created":"1681484721","gmt_created":"2023-04-14 15:05:21","changed":"1681484721","gmt_changed":"2023-04-14 15:05:21","alt":"A cross-sectional view of onggi showing fermenting cabbage. Credit: Korean Ministry of Culture, Sports, and Tourism.","file":{"fid":"253431","name":"cross-sectional views (copyright, Ministry of Culture, Sports and Tourism and Korean Culture)[87].jpg","image_path":"\/sites\/default\/files\/2023\/04\/14\/cross-sectional%20views%20%28copyright%2C%20Ministry%20of%20Culture%2C%20Sports%20and%20Tourism%20and%20Korean%20Culture%29%5B87%5D.jpg","image_full_path":"http:\/\/hg.gatech.edu\/\/sites\/default\/files\/2023\/04\/14\/cross-sectional%20views%20%28copyright%2C%20Ministry%20of%20Culture%2C%20Sports%20and%20Tourism%20and%20Korean%20Culture%29%5B87%5D.jpg","mime":"image\/jpeg","size":31343,"path_740":"http:\/\/hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/2023\/04\/14\/cross-sectional%20views%20%28copyright%2C%20Ministry%20of%20Culture%2C%20Sports%20and%20Tourism%20and%20Korean%20Culture%29%5B87%5D.jpg?itok=ojAs0zCn"}},"670551":{"id":"670551","type":"image","title":"David Hu (right), professor of mechanical engineering, and Soohwan Kim, a second-year Ph.D. student, with the onggi they used in fermentation experiments.","body":"\u003Cp\u003E\u003Cspan\u003E\u003Cspan\u003EDavid Hu (right), professor of mechanical engineering, and Soohwan Kim, a second-year Ph.D. student, with the onggi they used in fermentation experiments.\u003C\/span\u003E\u003C\/span\u003E\u003C\/p\u003E\r\n","created":"1681484755","gmt_created":"2023-04-14 15:05:55","changed":"1681484755","gmt_changed":"2023-04-14 15:05:55","alt":"David Hu (right), professor of mechanical engineering, and Soohwan Kim, a second-year Ph.D. student, with the onggi they used in fermentation experiments.","file":{"fid":"253432","name":"IMG_9232.jpg","image_path":"\/sites\/default\/files\/2023\/04\/14\/IMG_9232.jpg","image_full_path":"http:\/\/hg.gatech.edu\/\/sites\/default\/files\/2023\/04\/14\/IMG_9232.jpg","mime":"image\/jpeg","size":1029851,"path_740":"http:\/\/hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/2023\/04\/14\/IMG_9232.jpg?itok=SnJxKL9U"}}},"media_ids":["670550","670551"],"groups":[{"id":"1278","name":"College of Sciences"},{"id":"1275","name":"School of Biological Sciences"}],"categories":[],"keywords":[{"id":"192250","name":"cos-microbial"}],"core_research_areas":[],"news_room_topics":[],"event_categories":[],"invited_audience":[],"affiliations":[],"classification":[],"areas_of_expertise":[],"news_and_recent_appearances":[],"phone":[],"contact":[{"value":"\u003Cp\u003E\u003Ca href=\u0022mailto:catherine.barzler@gatech.edu\u0022\u003ECatherine Barzler\u003C\/a\u003E, Senior Research Writer\/Editor\u003C\/p\u003E\r\n","format":"limited_html"}],"email":["catherine.barzler@gatech.edu"],"slides":[],"orientation":[],"userdata":""}}}