Experimental methods and steps of elective courses 1 "making fruit wine" and "making fermented bean curd" published by People's Education Press.

Flow chart of fruit wine production experiment;

Selecting grapes-cleaning-juicing-alcohol fermentation (forming fruit wine)-acetic acid fermentation (forming fruit vinegar)

As the saying goes, "no wine, no table" and "five things to open the door, oil and salt sauce vinegar tea". Wine and vinegar are traditional fermented products that people can't live without.

1. Basic knowledge

1. 1 Production principle of fruit wine

The microorganism used in (1) is yeast, and its dissimilation type is facultative anaerobic. The reaction formula of yeast fermentation is defined as follows: ① Aerobic conditions:

② Anaerobic conditions:

(2) The main environmental conditions affecting alcohol fermentation are temperature, oxygen and pH. ..

① The temperature of alcohol fermentation is generally controlled in the range of 18 ~ 25℃, and the most suitable temperature is 20℃.

② During alcohol fermentation, it is necessary to maintain anoxic and acidic environment.

[Thinking 1] Why do you often "ventilate before sealing" in the process of alcohol fermentation?

The purpose of "aeration" is to make yeast breathe aerobically and multiply in large quantities.

The purpose of "sealing" is to allow yeast to produce alcohol through anaerobic respiration.

[Thinking 2] What is the reason for the phenomenon of "water before wine" in the process of alcohol fermentation?

Yeast first produces water through aerobic respiration and then produces alcohol through anaerobic respiration.

[Thinking 3] Why does wine appear deep red?

In the fermentation process, the pigment in grape skin enters the fermentation broth.

[Thinking 4] How does yeast reproduce?

Yeast germinates and reproduces when the environment is suitable, and spores enter a dormant state when the environment is not suitable.

The principle of making 1.2 fruit vinegar

(1) The microorganism used is Acetobacter, and its dissimilation type is aerobic. When the oxygen source and sugar source are sufficient, glucose is reduced and decomposed into acetic acid; When there is no sugar source, ethanol can be converted into acetaldehyde and further converted into acetic acid. Clarify the reaction formula of acetic acid fermentation.

(2) The optimum temperature for acetic acid fermentation is 30 ~ 35℃.

[Thinking 5] What are the environmental factors that affect acetic acid fermentation? Oxygen and ph.

[Thinking 6] Vinegar bottles and undrained beer bottles have been left for a long time, forming a "white film" on the surface of vinegar and beer. How is it formed? Acetobacter is formed by mass reproduction.

2. Experimental design

2. 1 experimental process

[Thinking 7] The difference and connection between alcohol fermentation and acetic acid fermentation;

2.2 Design the fermentation device: Answer according to figure 1-4a and 4b.

(1) During alcohol fermentation, unscrew the bottle cap or open the exhaust port at regular intervals (12h). What is the reason?

CO2 will be produced in the fermentation process to prevent the bottle from bursting due to high air pressure.

(2) What should be paid attention to during acetic acid fermentation?

Oxygen should be continuously added to the fermentation broth.

(3) In the device of Figure 1-4b:

① The function of vent is to supplement oxygen in acetic acid fermentation;

② The function of exhaust port is to exhaust CO2 or residual gas during fermentation;

(3) The function of the discharge port is to facilitate sampling inspection and release the fermentation broth;

(4) the function of the flexible hose with a long exhaust port is to prevent the infection of miscellaneous bacteria in the air.

3. Fermentation operation

3. 1 material selection and treatment

Select fresh and high-quality grapes, then rinse, prune and juice them in turn.

[Thinking 9] What is the purpose of washing before pruning? Prevent mixed bacteria infection.

3.2 Prevent the fermentation broth from being polluted.

In order to prevent the fermentation broth from being polluted by miscellaneous bacteria, the juicer, fermentation device and other instruments used in the experiment were disinfected and the fermentation device was closed.

[Thinking 10] In actual production, the fermentation broth should be boiled. What is its purpose?

Eliminate miscellaneous bacteria in fermentation broth.

3.3 Control fermentation conditions

(1) After the fermentation broth is bottled, the remaining space is 1/3.

(2) The temperature of alcohol fermentation should be controlled in the range of 18 ~ 25℃, and the fermentation time should be controlled in the range of 10 ~ 12 days.

(3) The temperature of acetic acid fermentation should be controlled within 30 ~ 35℃, the fermentation time should be controlled within 7 ~ 8 days, and continuous ventilation should be maintained.

[Thinking 1 1] Why should the remaining space of 1/3 be reserved after the fermentation broth is bottled?

CO2 produced by fermentation is temporarily stored to play a buffering role.

[Thinking 12] During acetic acid fermentation, it is necessary to supplement oxygen to the fermentation broth. You think the most economical and practical method is to introduce sterile air into the fermentation broth.

4. Analysis and evaluation of results

4. 1 experimental phenomenon:

ferment

alcoholic fermentation

acetic fermentation

Smell and taste

Bubbles and foams

Fermentation broth color

muddy

Cloudy, forming a white film on the liquid surface.

4.2 Check:

Whether alcohol is produced after fermentation can be tested by potassium dichromate.

Principle (1): Potassium dichromate reacts with alcohol, which is grayish green under acidic conditions.

In order to control and understand the fermentation process, continuous sampling inspection was carried out, including raw material concentration, product concentration, fermentation bacteria content, dissolved oxygen and pH value.

(2) Methods: (Fill in the form and pay attention to the comparison principle)

5. Related links

In order to improve the yield and quality of fruit wine and vinegar, and inhibit the growth of other microorganisms, we should also directly add artificially cultivated excellent strains to the fermentation broth.

Production of sufu

Experimental principle: protein and fat in tofu are decomposed into small molecular peptides, amino acids, glycerol, fatty acids and so on. And then processed and pickled into fermented bean curd. Its main production process is inseparable from microbial fermentation.

Test materials and appliances: tofu block, knife, electric oven, dried zongzi leaves (or dried straw), Petri dish, incubator, salt, beaker, rice wine, sugar, spices (such as pepper, pepper, star anise, fennel, cinnamon, ginger, pepper, etc.). ), alcohol lamp, fermented bean curd bottle.

N 1。 Cut the tofu into 3×3× 1 cm pieces. The water content of tofu used should be about 70%, and it is not easy to form sufu if there is too much water.

N2。 Put the tofu block flat on a plate covered with dried zongzi leaves to provide strains and keep warm. Each piece of tofu is equally spaced, leaving a certain gap around it. Tofu is covered with clean palm leaves. When the climate is dry, wrap the flat plate with plastic wrap, but don't seal it too tightly to avoid excessive humidity, which is not conducive to the growth of Mucor.

N3。 Place the plate at the temperature of 15 ~ 18℃. About 5 days, the surface of tofu is covered with upright hyphae.

N4。 When Mucor grows vigorously and turns pale yellow, take out the zongzi leaves spread on it, so that the heat and moisture of the tofu block can be quickly dispersed, giving off a musty smell, which takes more than 36h.

N5。 After the tofu is completely cooled, pull out the hyphae connected with the tofu and arrange them neatly in a container for pickling.

N6。 The mass fraction ratio of Mucor covered tofu (blank) to salt is 5: 1. When the blank is cultivated, the side near the flat plate without upright hyphae evenly faces the edge of the glass bottle, and the blank is vertically placed in a container in layers. Add salt in layers, and increase the amount of salt with the increase of layers, and sprinkle thicker salt on the surface of the bottle mouth to prevent miscellaneous bacteria from entering from the bottle mouth. Marinate for about 8 days.

N7。 Rice wine and sugar are mixed with various spices according to different tastes to make brine soup. The alcohol content of brine soup should be controlled at about 65438 02%.

N8。 After cleaning the sufu bottle, steam sterilize it in an autoclave at 100℃ for 30 minutes. Put the salted tofu into a bottle, add the marinated soup and auxiliary materials, heat and disinfect the bottle mouth with alcohol lamp, and seal it with oil. It takes six months to mature.