Douchi, a traditional fermented bean product seasoning in China, is made from black beans or soybeans as the main raw materials.

1. technological process

black beans → screening → washing → soaking → draining (ty-ii) → cooking → cooling → inoculation → koji making → washing black beans → soaking FeSO4→ mixing salt → fermentation → drying → finished product (dried black beans)

1. Raw material selection.

2. washing: use a small amount of water to wash away sand impurities mixed in soybeans for many times.

3. Soaking: The purpose of soaking is to make black beans absorb a certain amount of water, so as to quickly achieve moderate denaturation during steaming; Make starch easy to gelatinize and dissolve out the nutrients needed by mold; Provide water necessary for mold growth. The soaking time should not be too short. When soybean absorption rate <: At 67%, the koji-making process was obviously prolonged, and the fermented douchi was not soft. If the soaking time is prolonged, the absorption rate >; When 95% soybean absorbs too much water, it will burst and lose its integrity, and the phenomenon of "burning koji" will occur when making koji. Douchi made after fermentation tastes bitter and is easy to rot and deteriorate. Therefore, we should choose soaking conditions at 4℃ for 15 minutes in production and processing, so that the absorption rate of soybean grains is 82%, and the volume expansion rate of soybean is 13%.

4. Cooking: The purpose of cooking is to destroy the internal molecular structure of soybean, make protein moderately denatured and easy to hydrolyze, and the starch can reach the gelatinization level, and at the same time, it can play the role of sterilization. The cooking conditions were determined as 1kgf/cm2, 15 minutes or 15 minutes at normal pressure.

koji-making

(1) The purpose of koji-making is to make cooked beans produce corresponding enzyme systems under the action of mold. Rich metabolites are produced in the brewing process, which makes Douchi have delicious taste and unique flavor.

(2) Take the cooked soybeans out of the pot, cool them to about 35℃, inoculate them with Shanghai Brewer 3.42 or TY-II, the inoculation amount is .5%, mix them well, keep the room temperature at 28℃, and observe them every 6 hours after 16 hours. It takes about 22 hours to make koji for the first time, which is mainly to loosen koji materials, increase gaps, reduce resistance, adjust product temperature, and prevent koji burning or mixed bacteria pollution caused by temperature rise. 28 hours for the second turn. The quality of koji-making can be improved when the koji is turned in time. If the koji is turned too early, the germinated spores will be inhibited, and if the koji is turned too late, bacterial pollution or koji burning will be caused by the temperature rise of koji. When the starter is covered with hyphae and yellow spores, the starter can be produced. The general koji-making time is 34 hours.

(3) The fermentation of fermented douchi is to decompose protein in beans by using protease produced in koji-making process to form a certain amount of amino acids, sugars and other substances, giving douchi its inherent flavor.

1. Wash fermented soybean: There are many spores and hyphae attached to the surface of fermented soybean koji, which are rich in protein and enzymes. If spores and hyphae are not washed, they will remain on the surface of fermented soybean koji, and after fermentation and hydrolysis, some of them will be soluble and hydrolyzed, but most of them are still attached to the surface of fermented soybean koji in the form of spores and hyphae, especially the spores have bitter taste, which will bring bitter taste to fermented soybean and cause dim color.

2. Add melanterite to make the beans black and increase the brightness.

3. Stewing: Add 18% salt, .2% melanterite and a proper amount of water to the finished koji, and soak for 12 hours.

4. fermentation: put the processed bean koji into a jar until it is 8% or 9% full, compact it layer by layer during loading, and keep it in a constant temperature room of 28℃ ~ 32℃ for fermentation. The fermentation time is controlled at about 15 days.

(4) after fermented, air-dried fermented soybeans are taken out of the tank and dried in the air at a certain temperature to obtain the finished product.