Soybean sauce (korean name : ganjang) is a solution extracted from the mixture of "meju" (fermented soybeans), water, and salt.
Completely boiled soybeans are kept in their original shape or in rectangular lumps until they are fermented by fungi and enzymes growing naturally in soybeans. Dried meju lumps are crushed into fine pieces and steeped in brine until they are further fermented and matured. The liquid is separated from the solid.
The liquid is called soybean sauce, while the solid is called soybean paste. The liquid and the solid are preserved until they are matured further. They are Korea's traditional soybean-fermented foods that are used as seasonings.
Soybean sauce is a fermented food made from soybeans rich in protein and amino acids. It was developed to meet the need for foodstuffs as meat was prohibited after Buddhism spread throughout Korea.
It provides rich protein and can be kept for a long period of time. Indeed, it is a scientific food carrying the wisdom of Korean ancestors.
Many Korean people believed that poor tasting soybean sauce would bring about great disasters in the year. Therefore, making soybean sauce has been one of the largest annual events for Korean women.
People judge the culinary skill of a homemaker by the taste of the soybean sauce they make. "Kan" in Kanjang (a Korean term for soybean sauce) means "salty."
Soybean sauce is referred to as "Jiryeong" in "Gyuhabchongseo" (a book about housekeeping, including cooking), and was called "Jireom" in Seoul. However, the origin of this term has not been known. It has been used together with "Kanjang," an old word for Soybean sauce found in "Hunmongjahoe."
Today, traditional Korean soybean sauce is made by steeping meju (fermented soybean) lumps in brine until the liquid is fermented. Imwonsibyukji (a culinary book written in 1827), however, states that in addition to soybeans, carbohydrate-containing grains like wheat, barley, and buckwheat were used as well in making soybean sauce.
The book also mentions 20 kinds of soybean sauces and 12 kinds of "shi" (fermented soybeans), implying that soybeans were fermented in powder or lumps by the end of the Joseon Dynasty.
It is not clear when and why Koreans began to ferment soybeans only in lumps.
Gyuhapchongseo(1869), written in the later part of Joseon Dynasty, records how to make soybean sauce in detail, the characteristics of good meju, when to make soybean sauce, and how to make brine.
According to this book, the desirable maturation period of soybean sauce is 60-100 days.
Traditional soybean sauce
To make traditional Korean soybean sauce, meju (fermented soybeans) must be made first. To make meju, boil soybeans and mash them before they cool down. Shape mashed soybeans into round or rectangular lumps and dry the lumps for 2-3 days. When cracks appear in the surface of the lumps, tie them with rice-straw ropes and keep at 27-28degrees Celcius for 2 weeks.
During this period, enzymes multiply inside and outside the lumps (Bacillus subtilis and Bacillus pumilus inside, Aspergillus and Mucor outside). Thus, the soybeans are fermented. Dry the fermented lumps under the sun.
Wash dried meju lumps and drain off water from them. Put them in an earthenware jar and pour brine over them until the lumps begin to float. Filter out impurities from the lumps. Put "soot" (Korean charcoal made by burning wooden pieces), jujubes, and hot peppers into the jar. Keep the jar in a place exposed to the sun so have the lumps become more fermented.
Wait 40-50 days for maturing. Ladle the liquid out of the jar and boil it until it is reduced to the desired volume. This final product is called "soybean sauce."
Improved soybean sauce
Pure micro-organisms are used for this soybean sauce. Mix cooked, defatted soybeans and roasted wheat flour in equal amounts and add Aspergillus oryzae. Keep the mixture in a fermentation room at 30 degrees Celcius (plus or minus 3). Control the temperature and humidity for Aspergillus oryzae to grow and proliferate well.
Mix the mixture with 18-21 Be brine and put the mixture into a tank. Keeping the temperature at a stable level, ferment and mature the mixture for 6 months. Press the mixture using a presser to separate the liquid from the solid.
The liquid is called "raw soybean sauce." Add saccharine, sterilize, and filter out impurities to make "improved soybean sauce."
Chemical soybean sauce
Chemical soybean sauce can be made in a short time by hydrolyzing protein with acid. Its taste and flavor are not as good as those of regular soybean sauce, but it is inexpensive.
Thick Soybean Sauce
Being preserved for over 5 years, thick soybean sauce tastes sweet and has a dark color. It is used in seasoning Yaksik (steamed glutinous rice mixed with honey, dates and chestnuts) and Jeonbokcho (a dish of chopped abalones boiled in oil and soybean sauce).
Medium Soybean Sauce
Medium soybean sauce is preserved for 3-4 years and is used in seasoning stews or vegetables.
Light Soybean Sauce
Being preserved for 1-2 years, light soybean sauce is soft and light in color. It is used in seasoning soups.
Japanese soybean sauce
This sauce is made from the mixture of soybeans and starch. It uses fungi for fermenting.
Korean soybean sauce
This sauce is made from soybeans only, without starch. It is fermented by enzymes growing in the soybeans.
Fish soy sauce
This sauce is made from fish bodies or intestines. It is fermented and matured by enzymes present in itself, without using micro-organisms. Fish sauce is little used in Korea, except for southern coastal areas, but it is commonly used in South-east Asian countries.
Acid-resolved soybean sauce
Amino acid is produced by hydrolyzing gluten, a by-product of defatted soybeans and wheat flour, after adding a certain amount of hydrochloric acid to it.
Amino acid is neutralized to pH 4.8-5.2 with a neutralizer (Na2CO2) and filtered to separate the liquid from the solid. This liquid is "acid-resolved soybean sauce." These days, acid-resolved soybean sauce is made by reducing MCPD, obtained by hydrolyzing gluten, using low-density hydrochloric acid.
Enzyme-resolved soybean sauce
This sauce can be made in many ways. For instance, fermented liquid is made by processing and fermenting defatted soybeans and wheat and steeping the mixture in cold brine (between -5 and 5degrees Celsius) for 2-3 days.
Another fermented liquid is made and enzymes are added to this liquid. Then, both liquids are mixed together and further fermented at 35-40degrees Celsius for 2-3 days.
The mixture is then steeped in cold brine and matured. This sauce is not produced in Korea.
Mixed soybean sauce
This sauce is made by mixing brewed soybean sauce, acid-resolved soybean sauce, and enzyme-resolved soybean sauce in an appropriate ratio.
This sauce combines the advantages of the three sauces while supplementing their disadvantages.
The soybean, an ingredient of soybean sauce, consists of 40% protein, 20% soluble nitrogen-free extract, 14% fermentable sugar, 10% water, 5.5% ash, and 5.5% vitamins.
Traditional Korean soybean sauce is made from soybeans only. The soluble carbohydrates contained in soybeans, such as sucrose, stachyose, and raffinose, are used by micro-organisms such as bacillus subtilis, lactic acid germs, enzymes, and fungi while the soybeans are fermented. Therefore, little carbohydrates remain in finished meju (fermented soybeans).
Because of a low content of fermentable carbohydrates, this fermented liquid diluted with brine contains 0.7% lactic acid, but alcoholic fermentation rarely occurs.
Protein contained in soybeans is decomposed by protease and peptidase, micro-organisms in fermented soybeans, so the contents of peptide nitrogen and amino nitrogen are very high. The content of glutamic acid is particularly high. Recently, the Ministry of Science and Technology funded a "Study of the Mass Production of Traditional Korean Soybean Sauce," a joint task of the Leading Technology Development Project. It has now become possible to make traditional soybean sauce with superior aroma and taste, containing 1.0-1.2% nitrogen and 1% alcohol as a result of complementing the alcoholic fermentation process of soybean sauce.
1. Prepare meju (fermented soybeans).
2. Put salt into a wicker (or bamboo) basket and place the basket in a large container. Pour water over the salt to make brine.
Pass brine through a fine sieve. Prepare an earthenware jar with a wide mouth to receive much sunshine. Sterilize the jar with hot water. Brush meju lumps clean, washing lump by lump in water.
3. Put washed meju lumps in the jar and pour brine over them.
4. Put clean charcoals (soot), peppers, and jujubes into the jar and keep it covered for 3 days. Open the jar to have it exposed to the sun.
5. Cover the jar with a piece of fabric net and wait for 40 days. Open the jar frequently to have the contents exposed to the sun. After 40 days, take out charcoals, peppers, and jujubes.
Prepare another jar and a sieve. Place the sieve at the mouth of the new jar and pass the liquid (soybean sauce) through the sieve into the new jar.
Many Korean people believed that poor tasting soybean sauce would bring about great disasters in the year. Therefore, making soybean sauce has been one of the largest annual events for Korean women.
Today, traditional Korean soybean sauce is made by steeping meju (fermented soybean) lumps in brine until the liquid is fermented. Imwonsibyukji (a culinary book written in 1827), however, states that in addition to soybeans, carbohydrate-containing grains like wheat, barley, and buckwheat were used as well in making soybean sauce. 
The book also mentions 20 kinds of soybean sauces and 12 kinds of "shi" (fermented soybeans), implying that soybeans were fermented in powder or lumps by the end of the Joseon Dynasty.
Traditional soybean sauce
Improved soybean sauce 
The soybean, an ingredient of soybean sauce, consists of 40% protein, 20% soluble nitrogen-free extract, 14% fermentable sugar, 10% water, 5.5% ash, and 5.5% vitamins. 
