Cellar mud plays an important role in the brewing process of strong aroma liquor, and is an important carrier for the habitat and growth and reproduction of wine-making microorganisms. With the passage of time, the physical and chemical indexes such as ammonia nitrogen, available phosphorus, available potassium and mineral elements in different years of the cellar mud show certain differences, which provides a reference for the study of the year and maturity of the cellar mud and the evaluation of the quality of the cellar mud. However, there are few studies on the particle characteristics and moisture retention characteristics of pit mud.
In this study, the differences of pit mud with time were further studied by comparing the conventional physical and chemical indexes such as pH value and moisture, combined with the particle characteristics and moisture retention characteristics of pit mud, so as to increase the theoretical basis for guiding the cultivation of artificial pit mud and improving the evaluation method of pit mud.
1 Materials and methods
1.1. Materials, reagents and instruments
Wine samples: See 12.1。
Reagents and consumables: sodium hydroxide, analytical pure, Chengdu Kelon Reagent Factory. Distilled water, provided by the laboratory.
Instruments and equipment: PH meter, Shanghai Thunder Magnetic; A soil hydrometer, experimental sieve, liquid-plastic limit tester, Cangzhou road instrument test instrument *** drying oven, Shanghai Yiheng. Other experimental instruments: beakers, graduated cylinders, thermometers, etc.
1.2. Experimental methods
1.2.1. Sample collection.
The cellar mud samples were taken from a famous winery in Sichuan, and the cellar mud years were 1 year, 10 years, 25 years, and 50 years, and the cellar mud of each year was taken from two different cellar pools. 5-point sampling, the sampling point is the original four walls of the new liquor Baijia platform in the cellar pool, the diagonal center of the cellar bottom, and the samples of the same cellar pool are mixed.
1.2.2. Determination of the pH value of the cellar mud.
The determination method refers to "Liquor Analysis and Detection".
1.2.3. Determination of cellar mud moisture.
The determination method refers to "Liquor Analysis and Detection".
1.2.4. Determination of the drying curve of cellar mud.
The air-dried cellar mud is sieved to remove the chaff shell, and then the air-dried cellar mud is added with distilled water to a saturated state (liquid limit). The pit mud in the water saturated state is put into the oven 105 to bake constant weight, during which the pit mud sample is taken out and weighed at certain intervals, the water loss rate and time are recorded and the drying curve of the pit mud is drawn.
1.2.5. Particle size analysis of cellar mud.
1) Preparation of pit mud suspension. Take the air-dried cellar mud and sieve 0075mm, the moisture content is measured, and the cellar mud is weighed according to the moisture content to make the dry cellar mud 30g; Add 200ml of distilled water and soak for 12h; The dispersant was added according to the pH value of the pit mud, and the dispersant used in this experiment was 05mnaoh20ml。The pit mud suspension was boiled for 40min, the suspension was cooled to room temperature, and all of it was transferred to a 1000ml graduated cylinder, and the volume was fixed to the scale.
2) Assay. Stir up and down the entire suspension depth in the graduated cylinder with a stirrer for about 30 round-trips to evenly distribute the suspension. Remove the blender and turn on the stopwatch at the same time. Measuring 05min, 1min, 5min, 15min, 30min, 60min, 120min, 240min and 1440min density. 10 20s before each reading, carefully place the density meter into the graduated cylinder to a depth approximately close to the estimated reading. The temperature of the suspension must be measured after each reading, with an accuracy of 05℃。
3) Calculation. According to the density meter reading and the following formula, the percentage of particles smaller than a certain particle size is calculated, and the particle size distribution curve of pit mud in different years is plotted.
where: k - particle size calculation coefficient; l——Effective settlement distance of soil particles; t - soil grain settlement time.
Where: l - effective settlement distance of soil particles; l0 - the distance from the center of the density meter to the lowest graduation value; L1 - the distance from the lowest scale value to each index of the glass rod; v——density meter buoys volume; A——1000ml graduated cylinder area.
2 Results and Analysis
2.1. Comparison of the pH value of cellar mud in different years
The pH value of the pit mud in different years is shown in Figure 1. The pH of the 1-year-old mud is 392, which was significantly lower than the pH value of the other three vintages (p 0.).05）。The pH of the 10-year-old mud is up to 479, the pH value of the cellar mud of the year 25 and 50 years is 448 and 432. With the increase of the year, the pH value of the pit mud decreased slightly, but not significantly. In general, the pH value of the new pit mud was low, and with the passage of time, the pit mud gradually matured, and the pH value of the pit mud increased to a certain extent, and tended to stabilize in a certain period.
2.2. Comparison of the moisture content of cellar mud in different years
The results of the determination of the moisture content of the pit mud in different years are shown in Figure 2. With the increase of the year of the pit mud, the water content of the pit mud showed an upward trend: the water content of the pit mud with a year of 1 year was 4452%, with a 10-year-old cellar mud moisture content of 4507% The difference was not significant. The moisture content of the 25-year-old and 50-year-old cellar mud was 52., respectively49% and 5889%, with a significant increase in moisture content.
2.3. Drying curves of cellar mud in different years
The slope of the curve represents the water loss rate of the pit mud per unit time, the larger the slope indicates the worse the water retention capacity, and the better the water retention capacity. The drying curve of the pit mud in different years is shown in Figure 3, and the slope of the curve shows a decreasing trend with the increase of the pit mud year, indicating that the longer the pit mud year, the better its water retention capacity. with 22. The experimental results confirm each other, the better the water retention, the higher the moisture content of the pit mud in the same process operation.
2.4. Particle size distribution of cellar mud in different years
In this experiment, the fine-grained pit mud (0075mm), and the particle size distribution of different cellar muds is shown in Figure 4. The particle size distribution curves of 1-year-old pit mud are quite different from those of 10-year, 25-year-old and 50-year, which can be completely separated, while the particle size distribution curves of 10-year, 25-year-old and 50-year-old pit mud have certain overlap or coincidence. The results showed that the particle composition of the one-year-old pit mud was quite different from that of the other three years. The specific particle size range and proportion are shown in Table 1. The 1-year-old cellar mud new brewing Baijia platform originally contained larger particles (0.05～0.075mm) has more particles, accounting for about 40%, and the large particles of the other three years only account for about 15%. From smaller particles (0002mm), with the increase of the year of cellar mud, the proportion of small particles showed an increasing trend.
3 Conclusion and Discussion
Taking the cellar mud of a famous winery in Sichuan Province in different years as the research object, the pH value, moisture, water retention and particle composition of the cellar mud of different years were compared. The pH value of the pit mud in different years showed a trend of first increasing and then stabilizing, which may be due to the acidic raw materials in the production process of the new pit mud, and more aerobic microorganisms were introduced, and its growth and metabolism were rapid, and the organic acids produced reduced the pH value of the pit mud.
With the progress of production, the pit mud tends to mature, and anaerobic microorganisms gradually occupy a dominant position, and the metabolism produces alkaline substances such as ammonium ions, which increase the pH value of the pit mud, and at the same time, the esterification reaction consumes some organic acids. The moisture content and water retention in the pit mud showed an upward trend, and there was a certain relationship between the moisture content and water retention capacity of the pit mud and the particle size of the pit mud. The higher the proportion of small particles, the better the moisture content and water retention of the pit mud. The amount of small particles in the pit mud is related to the nature of the raw soil on the one hand, and the material composition accumulated during the brewing process on the other. In this experiment, with the increase of the year of the pit mud, the particle composition of the mature pit mud and the new pit mud showed a certain regularity, which needs to be verified by further expanding the sample size, expanding the sampling range, and comparing big data.