Bacteria in the lactic acid genus are one of the most commonly used microorganisms for fermentation. Lactobacillus sp.are rod-shaped, motile with peritrichous flagella and are facultatively heterofermentative. are spherical, ovoid and many are facultatively anaerobic. They can be found in wide range of environmental conditions and are facultative anaerobes or anaerobes. are cocci, found in pairs or short chains. are part of the genus lactic acid bacteria (LAB). Major phylogenetic groups of lactic acid bacteria and related gram-positive bacteria [13Įnterococcus sp., Lactobacillus sp. These bacteria produce extracellular proteases during alkaline fermentation. Bacteria in the Bacillus genus are rod-shaped and facultative anaerobes or obligate aerobes. Some common, key organisms involved in the fermentation of stinky tofu are Bacillus sp., Enterococcus sp. The “stinky” odour of stinky tofu comes from the ammonia released. This causes the release of ammonia, increasing the pH of the final products to around 8-9. These proteases will hydrolyze proteins to form amino acids and peptides during the fermentation process.
will dominate and secrete extracellular microbial proteases.
However, as the fermentation proceeds, microorganisms such as Bacillus sp. During this period, lactic acid bacteria are the dominant bacteria in the solution. In the beginning of fermentation, the pH of the stinky brine will decrease to around 4.7 because more lactic acid is being produced, corresponding to an increase in the number of lactic acid bacteria. Stinky tofu is considered to be alkaline fermentation, even though lactic acid is produced, because the end product contains ammonia. In addition, another study showed the levels and types of biogenic amines released during fermentation pose no toxicological concerns. During stinky tofu fermentation, one study showed there were no mutagenic activities present, hence during the production of stinky tofu, no carcinogens were created. Other than sanitary concerns arising from the usage of open fermentation, there is currently no health risk associated with stinky tofu consumption. Finally, the open fermentation process for stinky brine can take up to 6 months, allowing insect infestation and fungal growth. Thus, each batch of stinky tofu varies, causing an inconsistency in the quality and taste of each batch. These organisms come from the natural environment and are inoculated by chance. The microorganisms used to ferment the stinky brine usually originate from the original raw ingredients. Firstly, there are no production standards or standardized starter cultures for producing stinky tofu. Natural, open fermentation causes many production challenges.
Traditional Manufacturing Process for Stinky Tofu Production and Health Concerns Following, the tofu will be drip-dried overnight and cooked before consumption. Then, tofu is incubated and fermented in the stinky brine for 4-6 hours. Stinky brine, the fermentation liquid responsible for the “stinky” odour is produced by mixing the raw ingredients with a salt solution in water in big-mouth jars and openly fermenting for 2 to 6 months. In this method, the ammonia is not naturally produced from alkaline fermentation. A third method can involve the addition of chemical reagents such as ammonia to produce the “stinky” fragrance. Another formula may use a mixture of vegetables, and animal meat, including fish and shrimp. For instance, Stinky tofu can be produced using all vegetables, such as bamboo shoot, Spiny amaranth and winter melon. Fermentation of stinky tofu depends on the types of raw ingredients used, which varies from region to region in China. Open fermentation means the fermentation does not occur in closed containers. Stinky tofu is produced using natural, open fermentation. Stinky tofu can prepared by steaming, in stews, deep-fried or eaten cold and can be produced from soft or hard tofu. The “stinky” odour comes from the ammonia produced in fermentation of stinky brine, in which the tofu is then fermented in. It is a type of fermented tofu with a strong “stinky” odour hence its name stinky tofu. Stinky Tofu (chou doufu) is a traditional Chinese snack, usually sold in night markets or on street vendors. 6.1 New Production Method for Stinky Tofu.
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