Bitterness caused by unclean raw and auxiliary materials or improper selection: mildew, Qu powder metamorphosis by using data, rice husk of auxiliary materials is not steamed or steamed incompletely or mildewed; Use data with high fat content; Bulk liquor uses materials with high tannins for brewing production. The produced liquor has bitter or musty taste and other evil and miscellaneous flavors, which is mainly caused by the pollution of raw and auxiliary materials for brewing by harmful microorganisms, the oxidation of high fat and the division into some phenolic compounds in the process.
The shell of other raw and auxiliary materials contains more pentosan. Under the effect of microorganism, furfural with scorching and bitter taste will be produced; Baijiu can also produce furfural when cooking at high temperature, which is the original condition for bringing bitter substances to bulk liquor. Unreasonable ingredients: too much rice husk, too much or too little water, too much koji, or poor koji, and unreasonable distribution of new and old koji.
Our Baijiu bulk wine tells you: the filling material is too much, the cellar is empty, the yeast is overgrown, the yeast is self dissolved, the tyramol is formed and the yeast effect is affected. If the tyramol content is moderate, the liquor can have a pleasant aroma and a rich flavor. If the content is too high, the bitter taste will be severe. If the amount of starter is large and the protein content in the fermented grains is high, a lot of tyrosine will occur. After deamination and hydroxylation by yeast, more tyrosol will be generated, which will lead to the bitter taste of the wine.
The control temperature of production process conditions is unreasonable: high pit entry temperature, too fine or too coarse grain and starter powder damage, lax pit sealing, cracking and mildew of sealed pit mud, long accumulation time of fermented grains, etc. will lead to backburning taste, bitterness, spicy taste, mildew taste, etc. It is difficult to control the temperature in the early stage due to high pit entry temperature, and then it forms excessive temperature rise in the early stage, high temperature of fermented grains and long continuous time.
High temperature is conducive to the deamination of amino acids by yeast. High temperature of fermented grains makes yeast age and dissolve rapidly. The amino acids and tyrosine after autolysis will lead to the increase of high-grade alcohol and tyrosol content. The Baijiu liquor then has severe and persistent bitterness.
When the temperature is too high, the glycerol produced is easy to be divided into acrolein by yeast. Acrolein has continuous bitterness and strong irritation. If the accumulation time of fermented grains is long, there will be more invasive miscellaneous bacteria, faster glycerol separation and bitter taste. During distillation, if the steam is used too much in the early stage, coke pot phenomenon will occur, which will bring coking substances into the wine and produce bad coke bitterness.
Together with the fire and steam in the early stage, it will also bring other evil and miscellaneous flavors into the wine. The boiling point of most bitter substances is high, and the content of wine tail is high. Acrolein generally has more wine heads and fusel oil wine tails. Then, when steaming wine, we must "pick wine by quantity and quality, pinch the head and remove the tail".