② The optimum growth temperature of Acetobacter is 32℃. Controlling fermentation temperature can shorten fermentation time and reduce the chance of being contaminated by other bacteria.
③ There are two methods to produce acetic acid: direct oxidation and oxidation with alcohol as the substrate.
1 1. Experimental process: selecting grapes → cleaning → juicing → alcohol fermentation → fruit wine (→ acetic acid fermentation → fruit vinegar).
12. alcohol test: whether the juice produces alcohol after fermentation can be tested by potassium dichromate. Under acidic conditions, the reaction of potassium dichromate with alcohol is grayish green. Add 2mL of fermentation broth to the test tube, then drop 3 drops of H2SO43 with a concentration of 3mol/L, shake well, and finally drop 3 drops of saturated potassium dichromate solution at room temperature, shake well the test tube, and observe the color.
13. The inflation port is connected with an inflation pump for inflation during acetic acid fermentation; The exhaust port is used to exhaust carbon dioxide in the process of alcohol fermentation; The outlet is used for sampling. The vent should be connected to the bottle body through a long and curved rubber hose, and its purpose is to prevent microbial pollution in the air. The downward opening aims to promote the emission of carbon dioxide. When the device is used for brewing wine, the air inlet should be closed; When making vinegar, the air inlet should be connected with an air pump to input oxygen.
(1) releases a lot of CO2 produced by fermentation, and at the same time tries not to let oxygen enter the bottle, which is anoxic and acidic. (2) Salting, separating out the moisture in the tofu, hardening the tofu block, inhibiting the growth of microorganisms and avoiding the deterioration of the tofu block. (2) 12% extension is not enough to inhibit the growth of microorganisms. (3) Eliminate anaerobic respiration of miscellaneous bacteria.
The above knowledge source network is for reference only!