Schools of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, USA.
School of Biology, Georgia Institute of Technology, Atlanta, GA, USA.
J R Soc Interface. 2023 Apr;20(201):20230034. doi: 10.1098/rsif.2023.0034. Epub 2023 Apr 5.
Since ancient times, Korean chefs have fermented foods in an onggi, a traditional earthenware vessel. The porous structure of the onggi mimics the loose soil where lactic acid bacteria is naturally found. This permeability has been purported to facilitate the growth of lactic acid bacteria, but the details of the process remain poorly understood. In this combined experimental and theoretical study, we ferment salted napa cabbage in onggi and hermetic glassware and measure the time course of carbon dioxide concentration, which is a signature of fermentation. We present a mathematical model for carbon dioxide generation rate during fermentation using the onggi's gas permeability as a free parameter. Our model provides a good fit for the data, and we conclude that porous walls help the onggi to 'exhale' carbon dioxide, lowering internal levels to those favoured by lactic acid bacteria. The positive pressure inside the onggi and the constant outflow through its walls act as a safety valve for bacteria growth by blocking the entry of external contaminants without mechanical components. We hope this study draws attention to the work of traditional artisans and inspires energy-efficient methods for fermenting and storing food products.
自古以来，韩国厨师就在一种传统的陶器翁吉中发酵食物。翁吉的多孔结构模仿了自然存在乳酸菌的疏松土壤。这种渗透性据称有助于乳酸菌的生长，但具体过程仍知之甚少。在这项结合实验和理论的研究中，我们在翁吉和密封玻璃器皿中发酵盐腌白菜，并测量二氧化碳浓度的时间历程，这是发酵的特征。我们使用翁吉的气体渗透性作为自由参数，为发酵过程中的二氧化碳生成率建立了一个数学模型。我们的模型很好地拟合了数据，我们得出结论，多孔壁有助于翁吉“呼气”二氧化碳，将内部水平降低到乳酸菌喜欢的水平。翁吉内部的正压和通过其壁的恒定流出，通过阻止外部污染物的进入，而无需机械部件，成为细菌生长的安全阀。我们希望这项研究引起人们对传统工匠工作的关注，并为发酵和储存食品产品提供节能方法。
