[experiment] Analysis of the factors affecting the acidity of coffee to study why coffee is sour.

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The source of coffee sourness is the difference between pleasant and unpleasant acids.

I. Summary

From grinding coffee beans to brewing a cup of delicious coffee is a knowledge, this experiment wants to find out the principle of brewing coffee by the principles learned in nature class, and confirm the classroom learning, in addition to brewing a good cup of coffee without acid, but also find the fun of natural science in coffee. It includes the following parts: 1. Filter paper coffee, siphon coffee brewing and 2. Nature and life science and technology water solution, temperature and heat principle application. Second, different coffee beans brewing, the more acid beans out of the coffee placed longer, the more acid coffee; siphon and more acid than filter paper. Third, filter paper coffee The higher the water temperature, the finer the coffee powder, the more acidic the coffee. The longer the coffee is placed, the more acidic it is, but the acidity can be reduced after adding creamer.

II. Motivation for research

Coffee shops are everywhere now, and drinking coffee, whether to refresh or enjoy the romantic atmosphere, has long been a part of our daily life, so we began to study coffee, and discuss with the teacher the principles contained in coffee.(Including aqueous solution, temperature and heat unit), in the process of brewing coffee, it seems that scientific experiments have been done to learn physics and chemistry, in addition, we also found that how to brew coffee out of their own coffee and coffee sold in the store is so much worse, only one acid word can be described, so we also want to know how to find the appropriate water temperature and coffee powder thickness to brew a fragrant, but not sour delicious coffee.

Purpose of the study

(1) Inferring the correlation between the brewing methods of filter paper coffee and siphon coffee and the physics and chemistry of junior high school.

(b) to understand the difference in ph of coffee extracted from different coffee beans by siphon and filter paper methods, and to place them at room temperature;

Observe the acidity of the coffee over a week. (3) The filter paper brewing method was used to test the effect of different water temperature and different thickness coffee powder on the pH of coffee solution. (d) changes in ph of filter paper coffee in a short period of time when sugar and creamer are added. (Change in acidity when drinking coffee)

Four, research equipment and equipment six kinds of coffee beans to be tested (Manteling, Brazil, Colombia, Mocha, Blue Mountain, Taiwan coffee beans)

pH meter, one cup, six manual bean grinders, one filter paper, one box.

A filter cup, a flask, an alcohol lamp, a stirring bamboo stick, an electronic scale, a measuring cylinder, a thermometer.

Flushing kettle 1

A process or method of study.

1. Experiment 1: Discuss the correlativity between the brewing of filter paper coffee and siphon coffee and the physics and chemistry of junior high school. (1) Filter paper dripping type

The filter paper dripping brewing method is mainly to mix the coffee bean powder with hot water, dissolve the taste of the coffee, and then penetrate

Filter paper drips out.

Corollary 1: Effect of Surface Area and Particle Size on Coffee Extraction

We hypothesized that the grinding fineness of coffee beans would affect the contact area between water and coffee powder, and thus affect the degree of coffee extraction.

In reaction rates and equilibria it's mentioned that for the same mass, the smaller the partition, the faster the reaction rate, but we hope

We can observe the effect of surface area and particle size here, and we can understand the collision theory of reaction rate better. We will see in experiment 3

It actually confirms this.

Corollary 2: Effect of Temperature and Solubility on Coffee Extraction

We hypothesized that water temperature would affect the solubility of coffee components in water and thus the degree of coffee extraction.

It is mentioned in the textbook Water Solution that temperature is the main factor affecting the solubility of solid substances. Most solid substances are soluble in water.

Solubility increases with increasing water temperature, and we shall confirm this fact in Experiment 3.

(2) Siphon type

Siphon coffee brewing method, also known as the plug pot, elegant shape, brewing process is full of drama and strong coffee aroma

Steps:

1. Put some hot water in the pot.

2. Heated to boiling, corollary one.

3. Then insert the upper pot (when the water opens, the water rises)."Inference 2".

4. When the water is no longer rising, remove the heat and stir the pot until the coffee powder is evenly immersed in the water.

5. The total time is about one minute (stop timing). Remove the fire and wipe the pot with a semi-wet cloth.(At this time, the water immediately drops and

Leave coffee grounds in the upper pot through the filter cloth). "Inference 2, Inference 3, Inference 4."

6. Add hot water to the original cup "inference five", pour the water, fill the coffee to eight minutes full.

Corollary 1: Changes in water temperature during boiling

In the textbook heat effect on substances mentioned, pure water at 1 atmosphere pressure, its boiling point is 100°C, we can observe the boiling water temperature changes, whether for a certain value.

Corollary 2: Verification of the ideal gas equation when boiling water from the lower pot rushes to the upper pot

The ideal gas equation PV=nRT 1. When the water boils, the initial temperature is fixed, when the upper pot is inserted into the lower pot, the volume of gas in the lower pot is fixed, and the vapor pressure is proportional to the number of molecules of water vapor. The more water vapor, the greater the vapor pressure. 2. After cooling, the water vapor in the lower pot condenses back to liquid. The less water vapor, the smaller the steam pressure in the lower pot. After the low pressure state, the atmospheric pressure will return the extracted coffee to the lower pot.

Corollary three: the concept of separation of coffee grounds and mixtures filtered by filter cloth in the middle In the textbook understanding of substances, it is mentioned that the use of differences in the nature of substances can purify the mixture. When the coffee liquid falls, the coffee grounds can be filtered by the filter cloth in the middle, so that the coffee substances dissolved in water can pass through the pores of the filter cloth, while the coffee powder is insoluble in water and the particles are larger and stay on the filter cloth.

Corollary four: the effect of pressure on the boiling point of liquid mentioned in the textbook heat effect on substances, pure water at 1 atmosphere, its boiling point is 100°C, but when we will reduce the pressure on the liquid surface, then we can observe the boiling point drop, we in the condensation pot, vapor pressure reduction, can be observed under the pot in the process of condensation, because the boiling point is reduced, even if less than 100°C, can still see the boiling phenomenon of continuous bubbling.

Corollary 5: The influence of temperature on the mode of heat transmission is mentioned in the textbook on the mode of heat transmission. Heat is transmitted from high temperature to low temperature. Coffee shops warm the cup before serving coffee, in order to prevent the hot coffee from transferring heat to the cooler cup and making the coffee cool. Here we can observe the difference in the temperature change of the coffee liquid in the hot cup and the cold cup.

Experiment 2: Understand the different methods of extracting coffee from mantnin, Brazil, Colombia, mocha, blue mountain and Taiwan coffee beans

The difference in pH is when the liquid is in use.

1. Objective: To understand the difference of pH value between siphon coffee and filter paper coffee. 2. Equipment: Six kinds of coffee beans to be tested (Mantenin, Brazil, Colombia, Mocha, Blue Mountain, Taiwan coffee beans), pH meter 1

six different cups, a manual bean grinder, six filter papers, one filter cup, one stopper, one alcohol lamp,

A stirring bamboo stick, an electronic scale, a measuring cylinder and a thermometer. 3. Steps:

(1)Grind the coffee beans to be tested into fine powder, then set the electronic scale to zero, and put the ground coffee into a filter paper by 15 g.

(2)Place the filter paper in a filter cup and brew with 180 ml of 90°C hot water and label. (3)Add the same amount of coffee powder and water, brew in a corkscrew, but increase the amount of water to 185 ml, and pour half of the corkscrew coffee solution

Place in refrigerator (8°C). (4)Use a pH meter to measure the pH value of all the above coffee solutions. After measuring one cup, put the pH meter into clean water and wash it again.

Wipe with toilet paper to avoid affecting the measurement results. (5)Repeat steps 1- 4 (6) for a different coffee bean (Mantnin, Brazilian, Colombia, Mocha, Blue Mountain, Taiwanese) for seven consecutive days, repeating step 4 daily and recording the data.

4. Results: (1) Siphon brewing method was more acidic than filter paper brewing method on the first day of brewing, except for mantnin coffee. (2)The pH value of coffee decreased with the number of days. (3)we also put siphoning coffee in the refrigerator and found that after a week, it was stored at a lower temperature.

Its acidity increases less.

(4)based on the average acidity of a week,

Siphon acidity ranking is:(pH value from small to large) Taiwan> Brazil> Colombia> Blue Mountain> Mantelin> Mocha filter paper acidity ranking is:(pH value from small to large) Taiwan> Brazil> Blue Mountain> Colombia> Mantelin> Mocha

3. Experiment 3: Filter paper brewing method was used to test the effect of different water temperature and different coffee powder on pH of coffee solution. 1. Objective: To understand the influence of temperature and coffee powder on pH value of filter paper brewing method. 2. Equipment: four kinds of coffee beans to be tested (Colombia, Brazil, Blue Mountain, Taiwan), a pH meter, three different cups, hand

A dynamic bean grinder, several filter papers, a filter cup, a water bottle, an electronic scale, a measuring cylinder, temperature

Count one. 3. Steps:

(1)Weigh one portion of coffee beans per 15 grams and place them in filter paper, and grind them into coarse, medium and fine powders respectively. (2)Place the filter paper in a filter cup and brew with 180 ml of 90°C hot water and label. (3)after soaking, immediately measure the pH value. after measuring one cup, put the pH meter into clean water and clean it with toilet paper.

So as not to affect the measurement.

(4)Repeat steps 1- 3 for a different coffee bean and note down the data. (5)After grinding the coffee beans to be tested with the same thickness, start at 89°C at different water temperatures, approximately for each decrease.

Brew once at 10°C, repeat steps 2--3, and note down the data.

4. Results Analysis: (1) From the experimental data (1), it can be seen that the finer the coffee beans are ground, the higher the acidity and the lower the pH value, indicating that the finer the coffee beans are ground.

(2) From the experimental data (2), it can be seen that the higher the temperature of brewing, the higher the acidity, and the lower the pH value, the higher the temperature of extraction.

The more acidic the solute, the more likely it is

4. Experiment 4: Changes in pH of filter paper coffee in a short time when sugar and creamer are added. 1. Objective: To understand how the pH of coffee soaked in filter paper changes in a short time. 2. Equipment: Six kinds of coffee beans to be tested (Colombia, Brazil, Blue Mountain, Mantning, Taiwan, Mocha), a pH meter,

One cup, manual bean grinder, six filter papers, one filter cup, six cream balls, water bottle, electronic scale, measuring

Barrel, thermometer. 3. Steps:

(1)Grind the coffee beans to be tested into fine powder, then set the electronic scale to zero, and put the ground coffee into a filter paper by 15 g.

(2)Place the filter paper in a filter cup and brew with 180 ml of 90°C hot water and label. (3)Change with time, use pH meter to measure pH value every 3°C, and add creamer and sugar when pH value is unchanged.

Watch for changes in pH

(4)After measuring one cup and recording the data, wash the pH meter in clean water and wipe it clean to avoid affecting the measurement results. (5)Repeat steps 1- 4 for different coffee beans (Brazil, Blue Mountain, Colombia, Mantelin, Taiwan, Mocha).

4. Results Analysis: (1) The acidity of coffee beans in this experiment will increase with the decrease of temperature in a short time

And the higher the acidity of the coffee beans, the more acidity they increase when the temperature drops

Increase acidity (from more to less): Taiwan> Colombia> Brazil> Blue Mountain> Mantelin> Mocha (2) When acidity increases to a certain extent, add creamer and find that pH rises, so drinking coffee with cream balls will indeed decrease.

Less acidity.

(3)Adding sugar did not affect acidity.

Land, research results

Experiment 1: Correlativity between coffee brewing and physicochemical principles.

As discussed above.

Experiment 2, different coffee beans extracted from coffee which one is more acidic, and placed at room temperature, observe the acidity changes for a week. First, siphon-type bubble method is more acidic than filter paper bubble method Second, bubble good coffee if placed for a long time, the pH value drops more, the more acidic three, if preserved in a lower temperature environment, the pH value drops less, acidity increases less. Fourth, the siphon-type bubble acidity ranking is:(pH value from small to large)

Taiwan> Brazil> Colombia> Blue Mountain> Mantelin> Mocha filter paper bubble acidity ranking is:(pH value from small to large) Taiwan> Brazil> Blue Mountain> Colombia> Mantelin> Mocha

Experiment 3: Filter paper brewing method was used to test the influence of water temperature and coffee powder thickness on pH value of coffee solution. First, the finer the ground coffee beans, the higher the acidity, the lower the pH value. Second, the higher the brewing temperature, the higher the acidity, the lower the pH value.

Experiment 4, the change of pH value of filter paper coffee with sugar and cream in a short time. First, with the decrease of temperature, the acidity of coffee will increase, and the more sour beans, the more acidity will increase. Second, the amount of pH value decrease (increase acidity): Taiwan > Colombia > Brazil > Blue Mountain > Mantenin > Mocha III. It is found that the pH value increases and the acidity decreases, but the pH value of added sugar does not change.

Seven, discussion

Experiment 1, infer the correlation between the brewing of filter paper coffee, siphon coffee and physics and chemistry in junior high school.

1. Observe the effect of surface area and water temperature on the extraction degree of coffee from filter paper coffee.

(1) the finer the particles we have observed, the greater the degree of extraction because of the larger the total surface area. However, it may also be because the pores between the finer coffee powder are smaller, and the water flow is not easy to pass through, so the extraction time is longer and the extraction degree is more complete, but it is not necessarily the best to drink.

(2) the solubility of most solid substances in water increases with the increase of water temperature. (3) according to the data we have examined, the best water temperature for brewing filter paper coffee is 89 °C, and the particles are large.

Small for the degree of medium grinding, but the taste of coffee includes bitter, sour, astringent, etc., the higher the water temperature, the more sour substances, but also more bitter solutes, so actually drink at high temperature can not drink sour taste, on the contrary, the coffee with low temperature has a sour taste, so the comprehensive taste may not be like that of pH.

The measured pH values are related.

Second, observation from siphon coffee: boiling, ideal gas equation, mixture separation, pressure and boiling point, heat transfer.

(1) through the actual operation, it is found that the water temperature is maintained at a certain value of 107 °C when heated for a period of time. But instead of a normal 100 °C at an atmospheric pressure, we discuss that the water we use is not pure water and contains solute.

The phenomenon of rising boiling point.

(B) the rest have been discussed.

Experiment 2. To understand the difference of acidity and alkalinity of different coffee beans in different soaking methods, and to observe the coffee liquid at room temperature.

Changes in acidity over the course of the week.

First, the siphon bubble method is more acidic than the filter paper bubble method, presumably because the filter paper coffee powder is in contact with water for a shorter time.

Second, the longer the coffee liquid is placed, the more acidic it is, but if it is stored in a lower temperature environment, its acidity increases less. Maybe.

It's the oxidation of substances in coffee.

Third, we discuss the factors that affect the acidity of coffee:

(1) Origin: the original acidity of different coffee beans comes from the climate, soil, variety and other baking of the place of origin: the degree of baking will also affect the size of the acidity: the strength of the filter paper type of water flow, the siphon type of mixing.

(2) the result of our actual brewing: Colombia: it is a sour coffee bean, but the sour and bitter taste is uniform, so the taste will not be too sour.

Baxi: the acidity is moderate, but the other flavors are weak, but the aroma is high, but the result of this experiment is also high acidity.

It can be related to the storage time.

Blue Mountain: weakly acidic beans, which is consistent with the results of this experiment. Manning: coffee beans are less sour. People who don't like acidity but are not afraid of bitterness can choose this kind of beans.

Taiwan: it is an acidic bean, but the result of this experiment may be related to the fact that the coffee beans have been kept for too long.

Mocha: it belongs to acid beans, but the results of this experiment show that it is not sour, which may be due to the fact that Taiwanese do not like acidic coffee.

This manufacturer has dealt with the reasons in other ways, such as different degrees of baking.

So basically, different coffee beans still have different sour taste, but there are many factors that affect the acidity, so it still needs to be brewed actually.

Only later can you know your favorite acidity taste.

In experiment 3, filter paper brewing method was used to test the effect of different water temperature and different thickness of coffee powder on the acidity and alkalinity of coffee liquid.

We've already discussed it together in experiment 1.

Experiment 4, the change of acidity and alkalinity of filter paper coffee with sugar and cream in a short time. (general change of acidity when drinking coffee) 1. The longer the coffee liquid is in contact with the air, the more acidic it becomes, which may be caused by the oxidation of coffee by air.

And acidic beans contain more acidic substances, so the higher the acidity, the more acidic the coffee beans become.

Second, adding cream balls to coffee does reduce acidity. We went to find the ingredients of cream, and found that cream is not milk, mainly oil.

Fat, its official name should be "vegetable cream", its formula is mainly corn syrup and partially hydrogenated vegetable oil.

It should not be eaten too much.

Third, sugar is a neutral substance, does not react with coffee liquid, does not affect acidity and basicity.

Conclusion

First, from the brewing methods of filter paper coffee and siphon coffee, we find that many principles related to physics and chemistry are applied, such as inverse coffee.

The relationship between surface area and particle size mentioned in response rate, the relationship between temperature and solubility in aqueous solution, mixture

The concept of separation, the change of water temperature during boiling mentioned in temperature and heat, the influence of pressure on the boiling point of liquid, the increase of heat from high.

The confirmation of the ideal gas equation when the temperature is transferred to the low temperature. Let us actually observe the nature when we enjoy the coffee.

Science already exists in daily life.

Second, the siphon bubble method is more acidic than the filter paper bubble method, because the siphon bubble extraction time is longer, and the filter paper bubble method smells.

The road is relatively light, suitable for tasting the original taste of coffee beans.

Third, the longer the coffee liquid is placed, the more acidic it is, but if it is kept at a lower temperature, its acidity increases less. Maybe.

It is the oxidation of substances in the coffee, so the brewed coffee is best to drink immediately and should not be kept for a long time.

4. After soaking with different coffee beans, it is found that the order of siphon acidity is Taiwan > Brazil > Columbia > Blue Mountain > Manning > Mocha filter paper acidity: Taiwan > Brazil > Blue Mountain > Colombia > Manning > Mocha coffee beans have different acidity, but the acidity can still be adjusted by brewing. Therefore, people who do not like sour taste, in addition to the choice of beans such as Manning, it is best to take the acidity of the actual brewing as standard.

Fifth, from the filter paper coffee, we can find that the higher the water temperature is, the finer the coffee powder is, the stronger the brewed coffee is, and the smaller the pH value is, but the acidity is not necessarily consistent, because the coffee will brew sour and bitter at the same time, so it is possible that the acidity is high, but the bitter taste is high. The principle is that the low temperature water will flush out the coffee with low pH value, but the taste is sour. Filter paper coffee is better with 89 °C hot water and medium-fine ground coffee powder.

6. The pH value of freshly brewed coffee will drop to a certain extent with the temperature. It is best not to leave the coffee too long or even cool, which will affect the original taste. However, we also found that coffee beans that were originally less sour also reduced their pH value less. In addition, the coffee with cream is indeed less sour, but the main ingredient of cream is vegetable oil, not milk, and should not be consumed too much.

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