I. Analysis of Teaching Materials

Elective 1 is a student-oriented elective course to learn scientific inquiry through experimental design and operational practice. This module focuses on cultivating students' scientific inquiry ability such as designing experiments, hands-on work, collecting evidence, and so on, and Topic 1, Production of Fruit Wine and Fruit Vinegar is a topic which is more closely connected with daily life and students have a deep understanding of. The production of fruit wine and vinegar is a topic that is closely related to daily life and the students have a deep understanding of. The study of this topic aims to let the students make traditional fermented food under experimental conditions, learn the relevant learning methods and basic operation skills, and understand its scientific principles.

II. Teaching Objectives

1. Knowledge Objectives:

To understand the principles of fruit wine and fruit vinegar production.

2, ability objectives:

①Students according to the principles of fruit wine production design fruit wine production process, experience the practical operation of the production of fruit wine

② in the fruit wine production results of analysis and evaluation of the link, to cultivate students' experimental analysis and rigorous thinking ability.

3. Emotional objectives:

Through the history of fruit wine making, cultivate students' national pride, while penetrating the STS education.

Three, teaching focus:

① Explain the principle of making fruit wine and fruit vinegar

② Design and make the device to make fruit wine and fruit vinegar

Four, teaching difficulties:

Control of the fermentation conditions in the process of making

Five, teaching process

Introduction:

In the long history of the Chinese nation, many things have gone before the world. In the long history of the Chinese nation, many things are at the forefront of the world, and so is wine, with its own glorious chapter. In the records of wine, there are many interesting legends about wine. The apes and monkeys said that the main food of the apes and monkeys is sugary fruits, apes and monkeys in the fruit ripening season to store a lot of fruits in the "stone puddle", after a period of time, there is a special flavor of the liquid outflow, which is the earliest fruit wine.

In the domestic market, more and more fruit wines have appeared in recent years, such as Chinese wolfberry wine, plum wine and so on.

Fruit wine and life - Although fruit wine contains alcohol, the content is very low compared with liquor, beer and wine, usually 5 to 10 degrees, and the highest is only 14 degrees. As a result, it is consumed by many adults as a soft drink after meals or before bed.

Fruit wines are simply wines that draw on all the nutrients found in fruits, which are rich in vitamins and amino acids needed by the body. Sometimes the nutrients that can't be absorbed even by eating raw fruit can be absorbed through fruit wine because the nutrients have been completely dissolved in the fruit wine. Fruit wines contain a large number of polyphenols, which can play a role in inhibiting the accumulation of fat in the body, so that people are less likely to accumulate fat and flab. In addition, compared with other liquors, fruit wines are a little more effective in caring for the heart and regulating women's moods.

Subject 1 starts from the background of the subject, and then introduces the production process of fruit wine and fruit vinegar in a more comprehensive way from the experimental principle, the schematic diagram of the experimental process and the information provided.

I. Basic Knowledge

1. Principles of Fruit Wine Making

Read the textbook and complete the following questions:

(1) What kind of microorganisms are needed for the production of fruit wine?

(2) What is the form, structure, distribution, species, and colonies of yeast?

(3) What are the types of metabolism of yeast and the reaction formula of its respiratory process?

(4) What is the appropriate temperature for yeast?

(5) Why is wine red in general?

(6) What is meant by fermentation? Is fermentation equivalent to anaerobic respiration? What is the practical application of yeast?

(1) Yeast Morphology, Structure, Distribution, Species and Colonies

①Morphology, Structure

Yeast is a unicellular fungus, belongs to the eukaryotic organisms, the size of the cell is 1~30um, round, oval and so on.

Think: What structures do you think are in the cells of yeast?

What do you think is the difference in cell structure between bacteria and yeast?

②Reproduction

Yeast reproduces by budding, division and sporulation, but mostly reproduces asexually by budding. When the temperature is low, spores are formed and become dormant, and when the temperature is suitable, germination is carried out, and the reproduction rate is fast.

③Colonies:

Discussion: do you know the colony of what? What does a colony belong to in ecology?

Yeast forms colonies on solid media with a moist, sticky, white or pink surface. (In liquid media, some form a bacterial film on the surface of the liquid, or yeast rings appear on the walls of the container, or produce a precipitate.)

④Survival environment

Nature, yeast is widely distributed, but mostly distributed in the sugar-containing high acidic environment, such as fruits, flowers, bark, (some can be born with insects ****, some make people sick, such as white pseudohyphae triggered thrush, lung infections. Some common yeasts found in food are brewer's yeast, grape juice yeast, Lupus (soy sauce brewing), globular mimetic yeast genus, powdered Picrosporum yeast, etc.). The soil is always a great home for yeast throughout the year.

Think: Is it necessary to sterilize grapes when fermenting to make wine? Why?

What is the relationship of other microorganisms to yeast?

(2) Types of metabolism of yeast and its respiration process

1) Respiration of yeast

Fruit wine cannot be made without yeast. Yeast is a parthenogenetic anaerobic microorganism.

Under aerobic conditions, the reaction equation is as follows: enzyme

C6H1206+6O2 6CO2+6H20+energy

Under anaerobic conditions, the reaction equation is as follows: enzyme

C6H12O6 2C2H5OH+2C02+energy

Think about it:

What should be done if yeast is to be mass-produced during fermentation?

What if alcohol is to be obtained? Why?

(3) Fermentation

1). Concept of Fermentation

Broadly: it is the process of mass production of various metabolites through the cultivation of microorganisms. It includes aerobic fermentation (e.g. acetic acid fermentation, glutamate fermentation) and anaerobic fermentation (e.g. alcoholic fermentation).

Narrow sense: refers to the anaerobic respiration of microorganisms (including alcoholic fermentation, lactic acid fermentation, etc.).

2). So: fermentation ≠ anaerobic respiration.

3). Applications:

Brewing, bun making, bread making, alcohol manufacturing, production of medicinal yeast tablets, production of vitamins, production of antimicrobials, etc.

(4) Temperature Requirements

The optimum temperature for propagation: 20°C;

The optimum temperature for alcoholic fermentation: 18~25°C.

Think: Do you know the reason why yeast needs suitable temperature?

What does the fact that yeast have different optimum temperatures mean?

Added: Effect of temperature on fermentation

Yeast can only live at certain temperatures. At temperatures below 10°C, yeast develops very slowly. As the temperature rises, the reproduction speed is accelerated, and 20 ℃ is the optimal reproduction temperature, when the yeast reproduction rate is fast and strong life. More than 35 ℃, yeast growth is inhibited, the rapid decline in the rate of reproduction, to 40 ℃ yeast stopped budding, began to appear dead. If you want to get high alcohol concentration fermentation liquid, reduce exactly the loss, must control the fermentation temperature.

Did you know?

1, in general, the reason for the red color of wine?

(In the process of fermentation, as the alcohol content increases, the pigment of the red grape skin also enters the fermentation liquid, making the wine red.)

2. What is the basis for the division of wine into categories such as dry red and dry white?

(1) Wines are divided into three types, white, red and rosé, based on their color.

White wine: made from white grapes and fermented with the skins separated from the juice;

Red wine: made from red grapes and fermented with the skins mixed with the juice;

Roast wine: the color is in between that of white and red wines, and the skins have a short fermentation time.

2. According to the sugar content of the wine is divided into four kinds: dry, semi-dry, semi-sweet and sweet.

Dry wines: less than 4 grams of sugar per liter;

Semi-dry wines: between 4 grams and 12 grams of sugar per liter;

Semi-sweet wines: between 12 grams and 50 grams of sugar per liter;

Sweet wines: more than 50 grams of sugar per liter).

(5) Source of strain:

(In the industrial production of fruit wine in order to improve the quality of fruit wine can also be directly in the fruit juice to add artificial cultivated yeast, for example: dry yeast or wine medicine)

2, the principle of fruit vinegar production

Read the textbook, think about the following questions:

(1) Acetobacter form? Cell structure?

(2) What are the practical applications of acetic acid bacteria?

(3) Types of metabolism in Acetobacter?

(4) Principles of making fruit vinegar?

(1) Morphology of Acetobacter

1). From elliptical to rod-shaped, single, in pairs, in chains, with flagellar motility or non-motility, do not form spores, is a prokaryotic organism, reproduces by division, the type of metabolism is heterotrophic aerobic. (The most important feature of acetic acid bacteria compared with yeast)

2). Application: vinegar, fruit vinegar

(2) The principle of fruit vinegar production ,

Acetobacteria are -a kind of aerobic bacteria, which can carry out vigorous physiological activities only when there is enough oxygen. The bacterial film observed on the surface of sour wine is formed by acetic acid bacteria multiplying in large quantities on the liquid surface. Experiments have shown that acetic acid bacteria are particularly sensitive to the oxygen equivalent, and when deep fermentation is carried out, even a short interruption of oxygen will cause the death of acetic acid bacteria. When oxygen, sugar source are sufficient, acetic acid Yin will grape juice fructose decomposition into acetic acid;

Enzyme

C6H12O6 →3CH3COOH (acetic acid)

When the lack of sugar source, acetic acid bacteria will be changed from ethanol to acetaldehyde, and then the acetaldehyde into acetic acid (the reaction simple formula is as follows). The optimal growth temperature of acetic acid bacteria is 30℃ a 35℃.

Enzyme

Enzyme

2C2H5OH+O2 →2CH3CHO (acetaldehyde) + 2H2O 2CH3CHO+O2 →2CH3COOH (acetic acid)

Transition: according to this principle, how do we design the program for making fruit wine and fruit vinegar?

Hint: Consider from the following three aspects: selection of materials, design of experimental setup, operation process

II. Experimental Design

1. Fruit Wine and Fruit Vinegar Experimental Process Schematic

Rinsing

Pressing

Alcoholic Fermentation

Acetic Acid Fermentation

Fruit Wine

Fruit Vinegar

Selecting Grapes

Read pages 3-4 of the textbook and discuss the experimental setups of students A and B:

A: Each time you exhaust the gas, you only need to loosen the cap of the bottle, don't uncover the cap completely; when you are making the vinegar, you open the cap of the bottle and cover it with a layer of gauze for the fermentation of the grape vinegar. (to prevent contamination of the fermentation broth, since stray bacteria may be mixed in at each step of the operation)

B: Analyze what are the functions of the aerating, exhausting, and discharging ports in the fermentation apparatus for fruit wines and vinegars, respectively. Why is the exhaust port connected to the bottle by a long, curved hose?

The aeration port is used to connect an aerator pump for aeration during acetic acid fermentation; the exhaust port is used to expel carbon dioxide during alcoholic fermentation; and the discharge port is used for sampling. The exhaust port is to be connected to the bottle through a long, curved hose, the purpose of which is to prevent contamination by airborne microorganisms. When the device is used to make wine, the filling port should be closed; when vinegar is made, the filling port should be connected to an air pump and oxygen should be fed in.

2. Experimental operation

(1) Selection and treatment of materials

Select fresh grapes, rinse the grapes before juicing and remove the branches and stems.

①Take 500g of grapes, remove the branch stalks and rotting leaves.

②, rinse the grapes with water 1-2 times to remove dirt. (Note that the number of times of rinsing should not be too much, why?)

Discussion: do you think you should rinse the grapes first or remove the stalks first? Why?

(You should rinse the grapes first and then remove the stems to avoid causing breakage of the grapes when removing the stems and increasing the chance of contamination by stray bacteria.)

(2) Sterilization

Discussion: what do you think should be done to prevent the fermentation broth from being contaminated?

(It is necessary to consider the whole process of fermentation making, because every step of the operation may be mixed with stray bacteria. For example, the juicer and fermentation unit should be cleaned; each time you vent the bottle, only loosen the cap, do not completely uncover the bottle, etc.)

①Juicer should be cleaned and dried.

②Fermentation unit should be cleaned and sterilized with 70% alcohol.

(3) Juicing

Rinse the grapes from the stem and put them into the juicer to extract the juice.

(4)Fermentation

①Fill the fermentation bottle with grape juice, leaving about 1/3 of the space

(as shown in the picture on the right), and close the filling port.

② During the process of making wine, the temperature is strictly controlled at 18 ℃ to 25 ℃, and the time is controlled at about 10 to 12 d. The fermentation can be monitored through the discharge port. Timely monitoring.

③The process of making grape vinegar, the temperature will be strictly controlled at 30 ℃ ~ 35 ℃, time control in the first 7 ~ 8d or so, and pay attention to the timely inflation through the inflatable mouth.

Three, the results of the analysis and evaluation

1. Due to fermentation, most of the sugar in the grape syrup is transformed into CO2 and C2H5OH, and a small amount of fermentation by-products. the C02 discharged more and more exuberant, so that the fermentation liquid appeared to be boiled, and CO2 discharged from the exhaust port, the phenomenon is most obvious after 10 days of fermentation. Fermentation process heat production, will make the fermentation liquid temperature rise, but the alcohol fermentation temperature should be strictly controlled at 18 ℃ ~ 25 ℃, the fermentation process, the peel on the pigment and other ingredients gradually dissolved in the fermentation liquid; in the surface of the fermentation vials, the generation of floating tanks of the lid.

2. Set up a control group, the grape juice autoclaved, respectively, into A, B two fermentation bottles, and each leave 1 / 3 space, group A add yeast, group B does not add, fermentation, can prove that the production of wine is due to the action of yeast. The simple and easy way to prove that acetic acid is produced in grape vinegar is to taste it or identify it with pH paper.

3. The wine produced is bright in color, crisp, soft, and has a strong fruit flavor; fruit vinegar has an amber or brownish-red color, with a characteristic fruity aroma, soft acidity, slightly sweet, not astringent.

Four, the subject of extension

Whether alcohol is produced after fermentation of fruit juice, you can use potassium dichromate to test. Under acidic conditions, potassium dichromate reacts with alcohol to show a gray-green color, the test, first add the fermentation solution 2mL in a test tube, and then drops of H2SO43 drops of the concentration of the amount of material for 3mol / L, shaking and mixing, and then finally add 3 drops of saturated potassium dichromate solution at room temperature, oscillate the test tube, and observe the change in color. Think about how the control should be designed if the results of the test are to be more convincing?

V. RELATED LINKS

1. In order to improve the quality of fruit wines and better inhibit the growth of other microorganisms, you can add artificially cultured yeast directly into the juice. The artificial cultivation of yeast, first of all, needs to obtain a pure yeast strain. How to isolate the yeast attached to the grapes and obtain a pure strain? You can refer to "Topic 2: Cultivation and Application of Microorganisms" for further information and try again.

2. When making fruit vinegar, you can also add acetic acid bacteria directly to the fruit wine. The strains of acetic acid bacteria can be purchased from local factories producing vinegar or strain preservation centers. You can also try to isolate acetic acid bacteria from vinegar, see Topic 2 for the method of isolation.

Related Knowledge:

Fruit wine is made with the anaerobic fermentation of yeast and fruit vinegar is made with the aerobic fermentation of Bacillus Acetovorans, both yeast and bacillus Acetovorans are microorganisms, what are microorganisms and which organisms belong to microorganisms?

1, the concept of microorganisms

Tiny form, simple structure, usually with a light microscope and electron microscope in order to see the organisms of the general term.

2. Classes of microorganisms

There are about 100,000 species of microorganisms;

Microorganisms are the richest resource of biodiversity on earth. After insects, microorganisms are the second largest group in the living world. However, due to the microscopic nature of microorganisms, and the limitations of research tools, many microbial populations cannot yet be isolated and cultured, and their known species remain a small proportion of the estimated species.

Exercise

2. Hint: Large-scale production requires more thorough consideration, such as the source and selection of raw materials, cultivation and selection of strains, equipment for fermentation, automated control of fermentation conditions, and how to strictly control contamination by stray bacteria; and so on. In addition, whether it is wine or grape vinegar, the fermentation solution tested in the experiment is not a product in the commercial sense. In the actual production, it needs to be precipitated and filtered, sterilized and bottled to obtain finished wine or vinegar. Wine also requires subsequent fermentation in certain facilities and conditions (such as oak barrels and cellars) to obtain a specific flavor and color.

3. Tip: You need to consider the plant, equipment investment, raw material procurement, the number of workers and wages, product categories, production cycle, sales channels, profits and other issues.