Fermented bean curd

Fermented tofu(also calledfermented bean curd,white bean-curd cheese,tofu cheese,soy cheese,preserved tofuorsufu) is a Chinesecondimentconsisting of a form of processed,preservedtofuused inEast Asian cuisine. The ingredients typically are soybeans, salt,rice wineand sesame oil or vinegar. In mainland China the product is often freshly distributed. In overseas Chinese communities living inSoutheast Asia, commercially packaged versions are often sold in jars containing blocks 2- to 4-cm square by 1 to 2 cm thick soaked in brine with select flavorings.
According to the 1596Compendium of Materia Medicawritten by the Chinese polymathLi Shizhenduring the Ming dynasty, the creation of tofu is attributed to the Han dynasty PrinceLiu An(179 – 122 BC), prince ofHuainan. Manufacturing began during theHan dynastyin China after it was created.It is disputed whether Li Shizhen mentioned fermentation of tofu, however. A clear reference to fermented tofu appeared in the 1610Penglong Yehua(蓬櫳夜話), under the namehaifu(醢腐).
In 1818, EnglishmanBasil Hallwrote about a red, cheese-like substance served inRyukyu; he might be referring to fermented tofu. In 1855, Frenchman Baron de Montgaudry described the making of tofu and fermented tofu in writing.
InMandarin, the product is generally known asdòufǔrǔ(豆腐乳), "dòurǔ" (豆乳) orfǔrǔ(腐乳) — though in southwest China it is often known aslǔfǔ(卤腐). In English it is sometimes referred to as "soy cheese".
Fermented bean curd containsorganic acids, alcohol,estersand other flavor primitives. It contains a large amount ofhydrolyzed protein, free amino acids, fat, carbohydrates,thiamine,riboflavin,oxalic acid,calcium,phosphorusand other nutritional ingredients. It contains no cholesterol. The amount ofproteinin fermented tofu is about 12–22%.
Ho et al. (1989) compared the volatile flavor compounds of red fermented bean curd and white fermented bean curd. Red fermented bean curd contains much larger amounts of alcohols, esters, and acids than the white variety. This may be due to the fermentation of red rice byMonascusspp.The differences in nutritional properties and fermentation between the two varieties are accompanied by differences in flavor and colour.
TheFood Encyclopedia, written by Wang Su-Hsiung (1861) of theQing dynasty, made reference to preserved bean curd as superior to difficult-to-digest, hardened tofu especially for the elderly, children, and ill persons.Fermented bean curd is reportedly easier to digest than unfermented bean curd, because it is made through thefermentationprocess of mold, making the protein more digestible, absorbable, and richer invitamins. And the microorganisms decompose thephytic acidin the beans, making minerals such asironandzinc, which are initially poorly absorbed in soybeans, more easily absorbed by the body.So it may be easier for patients, elderly, or children to eat and absorb the nutrients.
It has been suggested that fermented bean curd may have certain health benefits, although there is insufficient data to confirm these claims. One report claims that the fermentation process generatesisoflavones, and that fermented bean curd could reduce the risk ofcoronary heart disease, lower blood pressure, and preventosteoporosis.
Fermented bean curd has a specialmouthfeelsimilar to certain dairy products due to the breakdown of its proteins which takes place during the air drying and fermentation. Lacking strong flavor prior to fermentation, fermented bean curd takes on the aroma and flavor of its marinade. The flavor is salty with mild sweetness.The texture and taste of fermented bean curd resembles a firm, smooth paste not unlike creamyblue cheese. (Indeed, this kind of tofu is sometimes called "Chinese cheese" in English.)Refrigerated, it can be kept for several years, during which time its flavor is believed to improve.
Fermented tofu is commonly used as acondiment, combined into sauces to accompanyhot pot, or consumed at breakfast to flavor rice,porridge,gruel,congee, orerkuai. Usuallyeither several bricks are placed in a small bowl covered in the flavored brine or one to one half bricks are placed into a bowl. Then, chunks are broken off the brick and consumed with a mouthful of porridge or gruel.  The brine may also be used for flavoring.
Fermented bean curd can also be added in small amounts, together with its brine, to flavor stir-fried or braised vegetable dishes (particularlyleafy green vegetablessuch aswater spinach). In theChaoshanregion of China, fermented tofu is the main ingredient used to make a stuffed biscuit known asfuru bing.
Both tofu and cheese are made from curds obtained from the coagulation of soy milk and dairy milk respectively. However, soybean curds are formed from the chemical destabilization of themicelles(usingcalcium sulfate,magnesium sulfate, etc.) allowing protein bonding while cheese curds are created from the enzymatic (rennet) hydrolysis of casein into para-casein. The bean curds are then simply pressed to producetofuand are thus bland and highly perishable, likeunaged cheese, while fermented bean curd, likeaged cheese, is ripened with microorganisms and thus flavorful and  long-lasting.
White preserved bean curdis the most common type and can be described without the white adjective. The flavor, color and aroma can be altered using various combinations of spices and seasoning in the brine with alterations in the commonly used combination of 10% rice wine and  12% salt.Those with no alcohol produces "small cheese cubes" (hih-fang) while those with double the alcohol content produces "drunken cheese" (tsui-fang).This variety is also available with chili and/or sesame oil. Seasonings can include anise, cinnamon,lemon juice,lemon zest, dried shrimp, and ham.  In addition, one can also obtain the curd dried, and without brine, which are then sold in paper cartons.
Red fermented bean curd(紅腐乳;hóngfǔrǔ, or南乳;nánrǔ) incorporatesred yeast rice(cultivated withMonascus purpureus) with the brining liquor for a deep-red color and distinctively thickened flavor and aroma.  A popular derivative of this variety has an appearance of ketchup and is seasoned with rose wine, caramel and natural sugar.
Stinky fermented bean curdis fermented for over six months and is also popular due to its strong creamy flavor.  However, due to its strong acrid smell, this variety is an acquired taste.Note that stinky sufu differs fromstinky tofuin appearance, consistency and salt content. Stinky sufu are made in the same cube-like shapes and has a similar smooth soft creamy texture as regular white sufu. In Taiwan, a green version is popular and made withsake lees, crushed leaves and a green mucor mold. It is then fermented for 12 hours and sold on the streets.
Chiang fermented bean curd(Chiang-doufu) is made with cubes of tofu soaked in either Chinese-stylemiso(Chiang) or soy sauce for several days. Usually reddish-brown in color and salty, it may be dried and fermented further and may also be mixed with sake lees. In Japan, miso is used.
In order to produce fermented bean curd, cubes of dried tofu are allowed to fully air-dry under hay and slowly ferment from aerial bacteria and fungal spores. Commercially available fermented bean curd is made by using dry firm tofu that has beeninoculatedwith the fungal spores ofActinomucor elegans,Mucor sufu,Mucor rouxanus,Mucor wutuongkiao,Mucor racemosus, orRhizopusspp.. This freshly fermented tofu is known as 'mold tofu' (霉豆腐).
The dry fermented tofu is then soaked inbrine, typically enhanced with Chinese rice wine, vinegar, chili peppers or sesame oil, or a paste made of rice and soybeans.  In the case of red fermented bean curd,red yeast rice(cultivated withMonascus purpureus) is added for color.Fermented bean curd is generally sold in small glass jars.