As we all know, the traditional new cellar wine quality is poor, and the new cellar mud needs to be naturally aged through continuous winemaking production for many years, but its aging time is long, far from meeting the needs of people's material life.
List of high-quality authors Artificial pit mud can not only shorten the aging time of pit mud, but also improve the quality of production, so it is increasingly used in the brewing and production of strong flavor liquor. At the same time, various studies on artificial pit mud have emerged one after another, such as the technology, strains, formulations and changes of flavor substances in the process of artificial pit mud, but there are few studies on the use of peat in artificial pit mud. Peat is the product of incomplete carbonization of dead plant residues under wetland conditions, and its water retention is strong, rich in organic matter, and low bulk density. The soil particles of peat are composed of organic matter and minerals, and the higher organic matter content is also compressible.
Due to this characteristic, peat is used in artificial pit mud, which can act as a sponge-like structure, which can absorb, store and release nutrients, which is difficult to find other soil or auxiliary materials to replace, and has a positive effect on the sensory and microbial growth of pit mud. Therefore, in this paper, the effect of peat on the cultivation process and results of artificial pit mud will be studied by tracking and determining whether peat is added to the cultivation process of artificial pit mud.
1 Materials and methods
1.1 Materials and Instruments
1.1.1 Materials.
Yellow mud, old cellar mud, cellar skin mud, bran, soybean meal, Daqu powder, yellow water, tail water, peat, dipotassium hydrogen phosphate, pit mud functional bacterial solution a, b, c, d.
1.1.2 Main instruments (Table 1).
1.2 Experimental Methods
1.2.1 Cellar mud cultivation method.
1) Schematic design (Table 2).
The number of cells in A, B, C, and D before inoculation was as follows: 196 108 ml, 175 108 ml, 213 108 ml, 159 108 ml; Set up 3 parallel experiments for each protocol.
2) Clean the ground, spread the yellow mud evenly on the ground, pour a certain amount of yellow water and tail water, and then evenly spread the peat, bran, soybean meal, koji powder, cellar skin mud, and old cellar mud layer by layer of the new brewing platform on the yellow mud in proportion and order, and then pour a certain amount of yellow water and tail water as needed.
3) Use a rake comb and a shovel to mix the raw materials and yellow mud evenly, and the functional bacterial liquid of the cellar mud is splashed in the way of sprinkling, and the cellar mud is mixed with a mixer while splashing the bacterial liquid.
4) After all the raw and auxiliary materials are mixed evenly and the cellar mud is soft and ripe, the cellar mud is piled up into long strips, patted with a shovel, covered with the cellar skin, and sealed with yellow mud around it, sealed and fermented for more than 90 days.
1.2.2 Data collection methods.
The temperature was measured regularly and fixed-point every day, and the physical and chemical indexes and the number of microorganisms were measured every 15 days, and the data in this paper were the average of three parallel experiments. After the cellar mud is cultivated, its quality is evaluated by experts and then used in winemaking production.
1.2.3 Detection methods.
Hexanoic acid counting method: hemocytometer method.
Temperature measurement: digital thermometer in the cellar.
Determination of moisture, pH value, ammonia nitrogen and available phosphorus: refer to the analysis of pit mud in the "Complete Book of Liquor Production Technology".
Determination of available potassium: refer to the determination of potassium in soil with reference to "Soil Agrochemical Analysis".
Determination of humus: refer to the "Determination of Humus Composition of Forest Soil". Cellar mud microbial enumeration method: dilution plate method.
2 Results and Analysis
2.1. The temperature rise of the cellar mud cultivation process
It can be seen from Fig. 1a and Fig. 1b that after the cultivation starts, the artificial cellar mud heats up rapidly, reaching the top temperature about 20 days, and the temperature rise range is 10 15. After about 10 days, it began to cool down slowly, and finally stabilized. There is no significant difference in temperature between peat and peat in Figure 1a, while the overall temperature with peat in Figure 1b is slightly higher than that without peat.
2.2. Changes in physical and chemical indexes during the cultivation process of cellar mud
2.2.1 Changes in moisture content during cellar mud culture (Fig. 2).
Organisms consume water during their growth, reproduction, metabolism, and release heat and water at the same time. It can be seen from Fig. 2a and Fig. 2b that the moisture in the cultivation process of artificial cellar mud showed an upward trend, but the increase was small, and it all changed in the range of 1%. Since the whole process of cellar mud culture is sealed, the increase of water indicates that the amount of water consumed by the metabolism of the microbial new brewing platform during the cultivation process of cellar mud is less than the amount of water produced by metabolism. The initial moisture of the pit mud in the peat group was about 2% higher than that in the peat group, and the water content in the whole culture period was higher than that in the peat group, indicating that the moisture of the peat-added group was higher than that of the non-peat group under the same moisture, which reflected the good water-holding performance of peat.
2.2.2. Changes in pH value during the cultivation process of pit mud.
During the cultivation process of pit mud, organic acids will be produced after microbial growth and metabolism. As can be seen from Fig. 3a and Fig. 3b, the pH value of the pit mud decreases slightly with the extension of the incubation time. The pH value decreased rapidly after 45 days of incubation, and the decline rate slowed down after 45 days until the end of culture. There was no significant difference in pH between the peat and peat groups, but the change range was smaller in the peat group, which may be due to the fact that peat had a certain buffering effect on the acid formed during the cultivation of pit mud.
2.2.3 Changes in ammonia nitrogen content during cellar mud culture.
It can be seen from Fig. 4a and Fig. 4b that the content of ammonia nitrogen increased significantly during the cultivation process of pit mud, showing a continuous upward trend. Most of the microorganisms in the pit mud belong to heterotrophic microorganisms, which decompose and utilize organic nitrogen such as proteins and amino acids to form inorganic nitrogen, and the change of ammonia nitrogen content in the pit mud can reflect the utilization of nutrients by microorganisms. The utilization rate of organic nitrogen by microorganisms was fast 45 days before the culture and slowed down after 45 days, which was similar to the change trend of the number of host microorganisms and bacteria in the pit mud, indicating that the change trend of ammonia nitrogen content may be related to the number and proliferation rate of microorganisms. The addition of peat had no significant effect on the ammonia nitrogen content of pit mud.
2.2.4. Changes in available phosphorus content during cellar mud culture.
As can be seen from Fig. 5a and Fig. 5b, the available phosphorus content showed a rapid downward trend in the early stage of the culture process, and decreased slowly after 30 days. A large amount of available phosphorus is required for microorganisms to form cell structures during the growth and reproduction process, and microorganisms grow logarithmically in the early stage of cellar mud culture, so the available phosphorus content of cellar mud decreases sharply 15 days before cellar mud culture. After 30 days, it decreased slowly, and was basically stable in the later stage.
The reason may be that the microorganisms consume the original available phosphorus in the pit mud and use the available phosphorus released after the death of microorganisms. In addition, microbial metabolism produces organic acids, which can promote the conversion of fixed phosphorus to available phosphorus, so as to achieve a dynamic equilibrium of available phosphorus in the later stage of culture. The available phosphorus content in scheme 1 was slightly lower than that in scheme 2, and the available phosphorus content in scheme 3 was slightly higher than that in scheme 4, and the addition of peat had no significant effect on the available phosphorus content of pit mud.
2.2.5 Changes in available potassium content during cellar mud culture.
In the process of growth and reproduction, microorganisms have less potassium requirements. There was no obvious rule in the available potassium content of the peat group in Figure 6a and Figure 6b, and the group without peat showed a downward trend overall.
2.2.6. Changes in humus content during the cultivation process of pit mud.
Humus is the organic matter formed by the decomposition of dead organisms in the soil by microorganisms, and is an important nutrient source for the growth of microorganisms in the process of cellar mud culture. It can be seen from Fig. 7a and Fig. 7b that the humus content showed a slow downward trend during the cultivation of pit mud, indicating that it was decomposed and utilized by microorganisms. The peat contained a small amount of humus, so the humus content of the peat group was slightly higher than that of the non-peat group, but the difference was small.
2.3. Changes in the number of microorganisms during the cultivation process of pit mud
2.3.1 Changes in the number of bacteria during the culture of the pit mud (Fig. 8).
As can be seen from Fig. 8a and Fig. 8b, the bacteria in the early stage of the fermentation process showed a rapid growth trend, and slowly decreased after a period of time. The reason is that in the early stage of cellar mud culture, the number of microorganisms is small, the nutrition is sufficient, and the microorganisms grow logarithmically. With the consumption of nutrients and the change of the environment in the cellar mud after the metabolism of the bacteria, the aging and death of some bacteria such as aerobic bacteria slowed down. In the end, the mortality rate is greater than the reproduction rate, and the number of microorganisms drops dramatically. In the early stage of pit mud culture, the growth rate and number of bacteria in the non-peat group were greater than those in the peat group, and the number of bacteria in the non-peat group decreased more in the later stage of culture, which may be due to the fact that peat contains a certain amount of microorganisms, which shows growth advantages in the late stage of culture and plays a certain role in supplementing the number of decaying bacteria. It may also be that peat releases stored nutrients that are available for microbial growth and utilization, slowing down the rate of decay.
2.3.2 Changes in the number of Bacillus during the culture process of pit mud.
It can be seen from Fig. 9a and Fig. 9b that the growth and change of bacillus is consistent with the change law of bacteria, showing a trend of first increasing and then decreasing, but the characteristics of the peat and peat groups are different from those of bacteria: the growth rate and quantity of bacillus in the peat and peat groups are basically the same before 45 days of culture, and after 45 days, the decrease of bacillus in scheme 1 is greater than that in scheme 2 and scheme 3 than in scheme 4, that is, the decrease in the peat group is greater. It may be that the peat itself contains a small number of bacillus and cannot supplement the number of decaying bacillus; At the same time, the functional bacteria of pit mud were facultative anaerobic bacteria, which had more growth advantages under microoxygen conditions. The porosity of peat brought more oxygen content to the pit mud, which inhibited the growth of functional bacteria in the pit mud to a certain extent, resulting in a significant decrease in the number of bacilli in the later stage.
2.3.3 Changes in the number of molds during the cultivation process of pit mud.
As can be seen from Fig. 10a and Fig. 10b, the number of molds decreases sharply in the early stage of cellar mud culture, and the number is very small in the later stage. The reason is that the mold is aerobic bacteria, and after the start of cellar mud culture, the number of microorganisms increases exponentially, consuming a large amount of oxygen, and the cellar mud environment in the middle and late stages of cultivation is difficult to meet the growth conditions, and the number declines rapidly. There was no significant relationship between peat addition and changes in mold count.
2.3.4 Changes in the number of yeast during the cultivation process of pit mud.
During the cultivation process of pit mud, the number of yeast showed a trend of first decreasing, then increasing, and then decreasing. Yeast belongs to facultative anaerobic bacteria, in the early stage of cellar mud culture, the mud pile heats up quickly, up to more than 45, high temperature and rapid oxygen consumption together lead to a sharp decline in the number of yeast, and exist in the original form of a new brewing platform with a small number of spores. After about 45 days of incubation, the yeast spores began to grow and the number of yeasts increased as the temperature of the mud pile decreased. In the later stage of cellar mud culture, the number of yeasts gradually decreased, the nutrients decreased, the acidity of the cellar mud changed. There was no significant relationship between peat addition and changes in yeast counts.
2.4 Sensory evaluation of pit mud
After the cultivation of artificial pit mud, the cultivation effect was compared by comparing its color, smell and feel, and the pit mud cultivated by the four schemes was all brown, with pure aroma, strong cellar flavor, soft and uniform, and no obvious sensory difference.
3 Conclusion
According to the analysis of the experimental results, the following conclusions can be drawn: (1) under the same moisture, the addition of peat is conducive to the storage and retention of pit mud; (2) Peat can provide a small amount of humus nutrients for pit mud; (3) Peat had a buffering effect on the acidity of artificial pit mud. (4) Peat had a certain buffering effect on the decay of bacteria in the pit mud, but the decay of bacillus was faster in the later stage of culture, and the effect on the number of yeasts and molds was not obvious. (5) Peat had no obvious effect on the contents of ammonia nitrogen, available phosphorus and available potassium in artificial cellar mud. (6) There was no significant difference in the sensory quality of pit mud cultured with peat and without peat.
Subsequently, the cultivated pit mud was applied to winemaking production and tracked in multiple rows, and the quality of basic wine production and the maturity of pit mud were compared, so as to make a scientific judgment on whether peat was needed to cultivate artificial pit mud.