Vinegar production Technology of Sweet Potato

1. Technological process: raw material treatment-addition of bran koji and yeast-saccharification fermentation-acetic acid fermentation-salt and post-ripening-vinegar leaching-aging-sterilization and preparation-finished product

2. Key points of process operation:

① ingredients: 100kg of dried sweet potato, 50kg of crude grain sugar (rice chaff), 40kg of wine mother, 175kg of fine grain chaff, 50kg of bran koji, 40kg of acetic acid bacteria seeds, 3.75kg of salt.

② raw material treatment: dry sweet potato is crushed into powder and mixed with bran, 275kg of water is added while mixing, so that the water and raw materials are well mixed and absorbed. When finished, steam in a steamer for 1 hour, and then stew for 1 hour. Boil until well done. After cooking, put it on a clean mixing ground, sift through it, remove the pellets, stir and cool with exhaust air at the same time.

Add bran koji and wine mother to ③: cool the clinker to 30 °33 degrees Celsius in summer and below 40 degrees Celsius in winter, sprinkle with cold water for the second time, add about 125kg of water, stir once, and then flatten out. Then spread the finely crushed bran koji on the surface of the clinker, sprinkle the stirred yeast (that is, yeast culture medium) evenly, mix it evenly, and put it into the cylinder. The moisture content of vinegar fermented grains into the vat is about 60% and 62%.

④ saccharification fermentation: raw material saccharification and alcohol fermentation are carried out at the same time. After the vinegar fermented grains are put into the vat, spread out. Each cylinder is about 160 kg. The temperature measured by a thermometer should be 24-28 degrees Celsius (not more than 28 degrees Celsius in summer and 24 degrees Celsius in winter). The cylinder head should be covered with grass cover and the room temperature should be kept at about 28 degrees Celsius. When the temperature rises to 38 degrees Celsius, the fermented grains should not exceed 40 degrees Celsius. The method of pouring fermented grains is to set aside an empty cylinder every 10 to 20 cylinders, move the heated vinegar grains into the empty cylinder, pour the next cylinder into the newly empty cylinder, and turn it over in turn. After 5 hours and 8 hours, the temperature rose to 38 degrees Celsius, and the fermented grains were poured again. Since then, the normal temperature is between 38 and 40 degrees Celsius. After 48 hours, it gradually decreases and the fermented grains are poured once a day. On the fifth day, the temperature dropped to 3335 degrees Celsius, indicating that starch saccharification and alcohol fermentation were completed, and the alcohol content was about 8%.

⑤ acetic acid fermentation: after the saccharification and alcohol fermentation process, add 10kg rice chaff to each tank (high temperature in summer, rice chaff can be reduced to 8kg, low temperature in winter, slow temperature can increase to 12kg), acetic acid bacteria seeds 8kg. The method of mixing should be divided into upper and lower parts. First, sprinkle half of the rice chaff and acetic acid bacteria seeds in the tank, mix the upper half of the rice bran and acetic acid bacteria seeds with both hands and pour them into another empty tank; then add the remaining half of the rice chaff and acetic acid bacteria seeds into the lower half of the tank, mix well and merge into one tank. The temperature will not rise quickly on the first day, but will soon rise on the 2nd and 3rd day, when the temperature will be controlled at 39-41 degrees Celsius, which generally does not exceed 42 degrees Celsius. The fermented grains were poured once a day for about 12 days, and the temperature decreased gradually. The acetic acid content is determined by sampling every day, and the acetic acid content is more than 7.5% in winter and 7% in summer. When the temperature drops to about 38 degrees Celsius, acetic acid fermentation is completed.

⑥ ripening after adding salt: the purpose of adding salt is to restrain the growth of acetic acid bacteria and avoid burning fermented grains. Add 3 kg of salt per jar in summer and only 1.5 kg in winter. First, sprinkle half of the amount of salt on the vinegar fermented grains, mix half of the fermented grains with a handle shovel, move them into another tank, mix the remaining half of the salt into the remaining half of the tank the next day, mix well and merge into one tank. After adding salt for 2 days, the alcohol and intermediate products that did not turn into acetic acid were further oxidized to acetic acid, and esterification was carried out to improve the aroma and color.

⑦ vinegar: the so-called vinegar is to use water or thin vinegar solution to dissolve the acetic acid in vinegar. In order to avoid acetic acid turbidity, it is generally not necessary to pour vinegar by pressing. When dripping vinegar, put the vinegar fermented grains on the vinegar pool or wooden barrel false bottom, lay 1 or 2 layers of Reed mat on the false bottom, then add the thin vinegar left by the last vinegar, soak the vinegar fermented grains, soak the vinegar for 1 hour and 2 hours, open the bottom drain hole to obtain vinegar. According to this method, dilute vinegar is leached repeatedly, and the dilute vinegar obtained each time will be used for next time. After dripping vinegar, the residual amount of acetic acid in vinegar fermented grains is not more than 0.1%, and the yield of acetic acid (in terms of 5% acetic acid) is about 6% 10 times that of dried sweet potato.

⑧ aging: the purpose of aging is to improve the quality of vinegar and make it bright in color and mellow in flavor. Vinegar with acetic acid content less than 5.5% is generally not allowed to age, otherwise it is easy to deteriorate. There are two methods for the aging of vinegar. One is to age the vinegar fermented grains. The vinegar fermented grains which are ripe under salt are moved into the tank to be compacted, covered with a layer of salt, and capped with soil. Pour the fermented grains once after 15 days, and then seal the jar, usually dripping vinegar for another month. This method is only suitable for winter, but it is not suitable for burning fermented grains in summer. Another method is to put the vinegar into a cylinder, put a lid on the mouth and uncover it every 1-2 days. The time of uncovering is at night in summer and daytime in other seasons. the aging time is generally 30 days in summer and about 60 days in winter.

⑨ sterilization and preparation: put the vinegar into the clarification tank to precipitate, adjust the quality standard, in addition to the current products and high-grade vinegar without preservatives, general vinegar added 0.1% sodium benzoate as a preservative. Raw vinegar needs to be heated and sterilized, and the sterilization temperature is 80,000,000 degrees Celsius, and the final quantitative filling or bottling is the finished product.