In order to explore the reasonable index system of pit mud ecological monitoring in Yibin strong-fragrance Baijiu region, 32 samples were gathered from 6 Baijiu factories with similar process and raw materials. The significant difference in the sensory quality of Baijiu from these pits was distinguished, and the physicochemical indexes, the contents of main organic acids and bacterial flora of these pit muds were detected and the relationship between these indexes and flavor substances or flavor characteristics of Baijiu were analyzed. It was found that the pit mud in Yibin Baijiu region showed following characteristics: pH was about（4.66±1.43）, the titrated acid was about（1.04±0.75）mmol NaOH/10 g, the conductivity was about（711±321）μs/cm, the calcium ion content was about（32.6±67.0）mg/kg, the iron ion content was about（20.7±24.8）mg/kg, the available nitrogen content was about（97.1±42.4）mg/kg, the available phosphorus content was about （137±60）mg/kg, and the available potassium content was about（275±122）mg/kg, the contents of caproic acid, acetic acid, ethyl caproate, propionic acid, hexyl caproate and butyric acid calculated by 2-ethylbutyric acid were about（6.49±2.84）,（0.04±0.05）,（1.15±1.07）,（0.04±0.05）,（0.97±0.98）and（0.20±0.13）g/100 g respectively, and Caproiciproducens, Syntrophaceticus, Syntrophomonas, Clostridium, Lactobacillus, and Sedimentibacter were dominant bacterial genera. The pit muds with good sensory quality of Baijiu had the following common characteristics: the pH was moderately high to about（6.17±1.57）, and the acidity was moderately low to about（1.14±0.92）mmol NaOH/10 g; the contents of hexyl caproate in the pit mud that produces high-quality Baijiu tended to be higher, and the content of butyric acid tended to be lower; the abundance of Caproiciproducens, Caloramatoraceae, Peptostreptococcales-Tissierellales tended to be higher, the abundance of Sporosarcina tended to be lower. The results showed that the indexes of pit mud, such as pH, acidity, conductivity, calcium ion content, iron ion content, available nitrogen, phosphorus and potassium content, main organic acids and caproate ester content, and the abundance of dominant bacteria, can reflect the ecological status of pit mud from different aspects, and suitable for ecological monitoring indicators of pit mud in Yibin strong-fragrance Baijiu region.
