Practical information | Translation of the Handbook of Professional baristas (7) drip coffee

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Professional barista Handbook

Author: Scott Rao translator: uncle Dewa

Chapter VI drip Coffee

Freshness

There are many reasons why drip coffee has a bad reputation around the world. Many places sell light and bitter drip-filtration coffee that has been heated in a pot for a lifetime. Some "boutique" coffee suppliers also make the mistake of operating multiple types of coffee beans at the same time, spreading down the inventory conversion rate of each kind of beans, making the beans stale. Ironically, consumers can make better and cheaper coffee at home with a $20 machine than a merchant's $3000 machine, at least drinking fresh coffee at home.

If you want to enhance the production of drip coffee, the easiest thing a coffee shop can do is to keep the coffee fresh. The following points will allow you to provide fresh coffee.

No matter how busy your cafe is, do not brew more than one kind of coffee at the same time.

The amount of brewing should be as small as possible, as long as it is not always sold out.

Teach your staff to make new coffee only when necessary, not to make a spare pot without thinking about it, or to make it as soon as the coffee pot is empty

If you are using a glass pot or an uninsulated metal pot, replace it with an insulated container that can be sealed

Even if you do all of the above, you still need to set a time limit to pour out the brewed coffee. I think it's an insult to let a customer spend $1.25 to $1.75 on a cup of coffee brewed for more than 30 minutes. If you don't think it's worthwhile to pour out old coffee, will business be good for a restaurant that serves expired food? If you still don't think it's worth it, try drinking coffee for an hour in the next few weeks. If you still feel that it is not worth it, then you are a profiteer.

Educating your employees and dumping old coffee without hesitation can also be a good selling point. Let customers see how much coffee you have poured out to keep it fresh.

With the gradual increase in sales, the fresh-keeping standard will be paid by the customers themselves. At the same time, the increase in sales will lead to less coffee waste.

Standard for drip coffee brewing

The Coffee Brewing Society (later the Coffee Brewing Research Center) established the standard of drip coffee brewing in the 1950s and 1960s, which is still in use today. The author wanted to find out the original version published by the coffee brewing center, but couldn't find it. So the criteria listed below are from the second-hand data after CBC processing:

↑ the coffee discussed in this chapter is based on this standard.

Extraction rate (extraction rate of soluble matter), concentration (brewing strength), flavor

Concentration of drip coffee (Note 1: the standard procedure for measuring the concentration of coffee requires filtering all insoluble substances from the coffee liquid, evaporating or drying the coffee liquid, and weighing the remaining solids. The ratio of the weight of the remaining solid to the weight of the coffee liquid is the concentration. ) refers to the concentration of soluble matter in the cup. Concentration does not represent the quality of the flavor, but it can affect the taste of the flavor. If the concentration is too high, it will affect the drinker's taste and inhibit the subtle flavor.

The extraction rate refers to the weight of the soluble matter brewed, divided by the weight of coffee powder before brewing, expressed as a percentage. Different soluble substances are soluble in water at different rates, so the extraction rates of different soluble substances have their own flavor characteristics. This can be sampled and tested at different time points in the brewing process to get the most intuitive experience.

A large proportion of coffee with low extraction rate is soluble in water and tends to be fermented, sour, bright and fruit. Coffee with high extraction rate can improve the balance through substances insoluble in water, reduce acidity, improve sweetness, and improve caramel flavor.

Control extraction rate and concentration

The relationship between extraction rate and concentration may be a bit confusing, but the following table outlines how to control the extraction rate and concentration by changing the grinding scale and the ratio of powder to water.

Grinding

A more uniform grinding can extract the best dripping coffee. Uneven particle size will lead to excessive extraction and insufficient extraction in some parts of the powder bed.

The setting of the best grinding degree is best determined by blind measurement, and the concentration can be measured by TDS measuring device to supplement the test data. If the coffee tastes bitter, astringent, and the tongue is dry, it is extracted too much, because the degree of grinding is too fine; if it tastes plain and watery, the degree of grinding is too coarse; if it tastes excessive and plain, then the knife head of the bean grinder may be blunt and need to be polished or replaced.

In addition to the taste test, the degree of grinding can also be set by observing the wet powder bed after brewing. If the beans are ground within 3 to 7 days after baking and before brewing, most of the top layer of the wet powder bed should be covered with foam.

If the foam has little or no foam, and the powder bed is only a little wet (similar to wet sand), the grinding is too coarse.

If there is a hole on the top floor, or if it is very muddy, the degree of grinding is too fine.

If the powder bed is still partly dry, the grinding degree is too fine, the top layer of the powder bed is too close to the sprinkler head, or some sprinklers are blocked.

↑ TDS measuring device

Temperature.

The temperature of the water for brewing should be between 195 and 205 degrees Fahrenheit (90.6 to 96.1 ℃), depending on the baking degree, the ratio of powder to water, and the desired flavor. The effect of brewing water temperature on extraction can be summarized as follows:

The higher the temperature, the more sour, bitter, mellow (body), astringent taste.

High temperatures generally lead to a stronger degree of extraction because it increases the solubility of substances that can only be dissolved at high temperatures. The same applies to Italian concentrated extraction.

The solubility of different substances is also different at different temperatures. This shows that the temperature brings not only the difference in the total concentration of all soluble substances, but also the difference in the relative concentration of different soluble substances.

Turbulent flow

Turbulence is a combination of coffee powder, gas and hot water, which is caused by the gas released by coffee powder when hot water comes into contact with coffee powder. Turbulence can slow down the velocity of water passing through the coffee powder, prolong the soaking time of the coffee powder, and foam the top of the wet powder bed after brewing.

The right amount of turbulence is very important, it can let the coffee particles rise and separate evenly, and improve the uniformity of the water flow through the powder bed. In addition, turbulence can also provide a moving target for the sprinkler to avoid the fact that the sprinkler has been favored by a certain piece of coffee powder, thus improving the uniformity of extraction. But excessive turbulence is a problem because it can excessively prolong the soaking time of coffee powder, causing the water to flow too slowly through the powder bed, leading to excessive extraction.

If cafes always use coffee beans from 4 to 6 days after roasting, then turbulence is not a concern. But when cafes face inventory problems and coffee beans are roasted for more than 10 days or less than 2 days, it is necessary to correct the unusual amount of turbulence.

After roasting coffee beans for more than 10 days, the turbulence becomes less, so you need to adjust the grinding degree to slow down the flow rate; when the coffee beans are roasted for less than 2 days, the turbulence will be too strong, and baristas have three options to correct it.

1. Adjust the degree of grinding. However, using a thicker degree of grinding to correct turbulence is not the best choice, because it will change the final flavor.

two。 Grind the coffee beans for a few hours before brewing. Many coffee experts will subconsciously think this is absurd, but the effect is comparable to putting coffee in whole bean form for a few days. (note 2: in order to test the effect of brewing coffee after a few hours of grinding, the author conducted some blind tests. Three roasters and several baristas were invited to test with a variety of coffee beans from different roasters, ranging from 20 hours to 6 days from the day of the test. Each kind of bean is divided into two samples: one is ground 12 hours before the test, and the other is ground. The grinding degree of the sample ground 12 hours in advance is slightly finer, which is used to make up for the reduction of turbulence. According to the standard cup test procedure, all samples are ground using the same bean grinder. Each sample is made by drip filtration and then tested by cup. The results were consistent for all samples: no matter when the coffee beans were roasted, each participant preferred the sample that was ground 12 hours in advance. From this conclusion, the author is convinced that pre-grinding is harmless to the flavor and, in some cases, a good way to show the best flavor.

3. Use a larger amount of pre-soaking and lengthen the pre-soaking time, if the coffee maker has these options. (for more information, see the chapter "automatic brewing settings" in this chapter)

Optimization of different amount of powder filling

Each machine or filter basket has a most suitable range of powder filling, which depends on the diameter and shape of the filter basket, the design and flow rate of the sprinkler head distance, the size of the drainage hole at the bottom of the filter basket, and the permeability of the filter. The most critical factor is the diameter of the filter basket, because it can determine the height of the powder bed, thus determining the appropriate degree of grinding and the contact time of powder and water. The larger the filter basket, the greater the corresponding optimal amount of powder filling.

For example, the author once used a 1gram 2-gallon filter basket, which is most suitable for extracting 2pm 3 gallons to 1 gallon (2.5 liters to 3.78 liters) of coffee. I also have a cylinder coffee maker with a large filter basket, which is best suited for batches of 1 to 2 gallons (about 1.89 liters to 3.78 liters). The two have one thing in common: the powder beds held by the two filter baskets are highly similar.

In order to achieve the specified extraction rate and concentration, the higher the powder bed, the thicker the coffee powder; the shallower the powder bed, the finer the coffee powder. This is because the high powder bed creates more resistance to the flow of water, making the powder contact with water longer. When the amount of powder filling exceeds the optimal range, it is necessary to use a very fine or coarse degree of grinding to achieve the predetermined concentration, which will make the contact time of powder and water either too long or too short, thus affecting the flavor.

At present, there is no standard optimum powder bed height, but the powder bed height recommended by the Coffee Brewing Research Center is 1 inch 2 inches (2.54 cm to 5.08 cm).

How to brew a small amount of powder

To brew a small amount of powder, it is best to use a small tapered filter basket, or a metal mesh filter basket. These two kinds of filter baskets can reduce the average diameter of the filter basket, increase the height of the powder bed, and can hold coarsely ground coffee powder more than other types of filter baskets with a small amount of powder.

Both ↑ filter baskets are designed for the same machine, and the filter baskets on the right are more suitable for less powder.

How to brew a large amount of powder

To make a coffee with a high powder bed and a large amount of powder, please open the shunt valve. The shunt valve can change the direction of the water flow around the filter to bypass the coffee powder. Using a shunt valve is equivalent to using a very high powder-to-water ratio to achieve a normal extraction rate and a very high concentration, and then reducing the concentration by adding water directly to the lower pot. In short, it is to dilute the high concentration of coffee with hot water.

If the powder bed is high and there is no shunt valve available. It is necessary to use more than ordinary rough grinding to limit the contact time of powder and water and prevent excessive extraction. However, there are several problems in trying to use very rough grinding to deal with extremely high powder heaps.

Affect the flavor.

It will make the extraction a little uneven because the uniformity of very rough grinding is low.

Sometimes the bean grinder does not have a scale fine enough to provide the necessary concentration and thick enough to prevent excessive extraction from the filter basket.

Shunt valve

For 12 years, the author rejected the shunt valve because I didn't believe it could make good coffee. Until one day my friend Tony, the owner of the Chicago Metropolitan Cafe (MetropolisCoffee), told me that he had had a great coffee in a Michigan restaurant, which was made with the shunt valve open for 50%! Only then did I realize that I should learn how to use the shunt valve.

The shunt valve works because when the powder bed is high, it can use finer grinding than other methods. In the absence of a shunt valve, the use of "normal" grindness on a high powder bed will lead to excessive extraction, resulting in very high extraction and concentration. However, after using the shunt valve, the amount of water passing through the powder bed becomes smaller, which effectively prevents excessive extraction and allows the appropriate grinding degree to be used.

How to determine the setting value of shunt valve

For a fixed amount of powder filling, experiments are needed to determine how to set the opening ratio and grinding degree of the shunt valve. One way is to determine the degree of grinding first, and use your machine to make the best degree of grinding for coffee without using a shunt valve with a normal amount of powder. Then the ratio of the opening of the shunt valve is estimated through the difference between the new powder quantity and the previous normal powder quantity. Because the degree of grinding and flavor are closely related, although a fixed degree of grinding may not necessarily make the flavor of the product with a normal amount of powder exactly the same as that of a larger amount of powder using a shunt valve, it can at least not be much different.

The final choice of grinding degree and shunt valve opening ratio should be determined by the taste, and you can also use the TDS meter to help you find the best setting value.

Tips: a method that can be used to determine the appropriate opening ratio of the shunt valve when the grinding degree is fixed.

1. Under the normal amount of powder, the parameters that can make the best coffee to drink are written on the paper (degree of grinding, ratio of powder to water, amount of powder filling, concentration).

two。 Determine the size of the new powder filling using the shunt valve.

3. Calculate the amount of new powder that is larger than the normal amount of powder. Ex.: 1.4 gallons of powder is 40% larger than 1 gallon of powder.

4. As a first attempt, set the shunt valve opening ratio to half of that calculated in step 3. Continue the previous example: 1.4 gallons of powder should be opened 20% of the shunt valve to brew.

5. Brew, taste, and measure TDS with the amount of newly filled powder. If the TDS (concentration) is too high, increase the shunt valve opening ratio; if the concentration is too low, reduce the shunt valve opening ratio.

6. Continue to brew with the amount of newly filled powder and adjust the shunt valve setting until the product reaches the expected concentration.

7. When the amount of powder filling is perfect, record the amount of powder filling, powder-water ratio, degree of grinding, shunt valve setting, concentration.

8. For ambitious and leisurely authentic coffee geeks, you can repeat the above steps for different amounts of powder filling, all using the same degree of grinding. Draw a picture, the horizontal axis is the batch size, and the vertical axis is the shunt valve opening ratio. Mark the successful amount of powder filling on the diagram, connect the marked points into a line, and mark it as "grindness z". This picture can be used as a reference tool for setting the opening ratio of the shunt valve when using a larger amount of powder in the future.

9. Frame this picture and make a copy for your mother to keep.

Coffee product management table

We already know the relationship between concentration, extraction rate, and the ratio of powder to water. If the values of two of the parameters are confirmed, the third value can be calculated.

The relationship between them has been illustrated in exquisite graphic form by the Coffee brewing Research Center in the 1960s. Please save this picture as a guiding tool for you to evaluate different brewing parameters.

Device filter

Paper filters are the easiest to absorb odors in the storage process, adding miscellaneous flavor to the coffee. In order to minimize the negative effect of the filter on the coffee flavor, both the filter paper and the filter cup should be rinsed with boiling water before brewing. Washing can also wash off the residue in the filter cup and the next pot, and preheat the filter cup and the next pot.

The step of flushing is to put the filter into the filter cup, then put the filter cup into the coffee machine, turn it on, pour the boiling water from the filter into the next pot, and turn off the water after a few seconds.

After flushing the filter, fill in the coffee powder and shake the filter cup back and forth until the surface of the powder pile is as flat as possible. Be careful not to use too much force when loading the filter cup into the machine, as it may disturb the powder bed.

Stirring: the key to perfect dripping coffee

There are two disadvantages that will affect the uniformity of extraction in the brewing process of drip coffee. First, all sprinklers have the greatest impact on a certain area on the surface of the powder pile, where coffee powder is overextracted and forms channels. Second, as with the extraction of espresso (Espresso), the top-to-bottom flow of the extracted liquid leads to the priority of extraction from the top to the bottom.

When the temperature of the liquid is very high, it has stronger solubility, dilution, and less viscosity. The liquid at the top is always hotter than the liquid at the bottom-or at least as hot. The liquid at the top of the powder bed is always more dilutive and less viscous than the liquid at the bottom. Therefore, the coffee powder at the top of the powder bed has a higher extraction rate.

Stirring coffee powder during brewing can greatly improve the extraction uniformity, alcohol (body), and concentration, while reducing bitterness. Stirring requires the use of a cylinder coffee machine or some household filter cups to facilitate access to the powder pile. About 5 to 10 seconds after brewing, the barista should gently stir the coffee powder with a large spoon or spatula, be careful not to pierce the filter and make sure to soak all the coffee powder. When the sprinkler stops filling, stir the coffee powder again. Stirring 3 to 4 times at a time is enough.

The effect of the first stirring is similar to pre-soaking, which makes all coffee powder soaked uniformly almost at the same time, makes the temperature above and below the powder pile more consistent, reduces the generation of channels, and allows the bottom of the powder bed to participate in the extraction earlier.

After the first stirring, with the advance of the brewing process, the extraction uniformity will gradually decrease. This is because the water flow is from top to bottom, and the sprinkler is constantly injecting water into the top of the powder pile, both of which have a greater impact on the extraction at the top of the powder bed. It should be noted that although the extraction uniformity began to decrease after stirring once, under the same extraction parameters, the uniformity was higher than that of baristas without stirring.

As soon as the sprinkler stops filling, the barista will immediately start stirring again. This is the earliest time to stir, and there is no newly injected water to counteract the effect of stirring.

The second stirring redistributes the concentration of soluble matter in the powder bed and the extracted liquid. This time, it is more evenly distributed, speeding up the extraction of coffee powders that are also rich in soluble matter (which were previously at the bottom of the powder bed) because they are now surrounded by lighter extracted liquids. At the same time, the extraction of coffee powders with little soluble matter left (which were previously on top of the powder bed) has slowed down because they are now surrounded by less light extraction liquids. In this way, the extraction uniformity of the whole powder bed is greatly improved, and the bitterness, astringency and incomplete flavor are reduced.

When stirring is added to the brewing process, a coarse degree of grinding is required. The more powder to be stirred, the thicker the degree of grinding is required. No matter how many times you stir, it is best to make sure that the number of stirring times for each powder filling is the same.

Automatic brewing setting

Sometimes I really miss the days when I only need to worry about the temperature and the amount of bubbling. Now a barista needs to programmatically control the amount of pre-soaking, pre-soaking time, split valve opening ratio, brewing time, and, of course, temperature and brewing volume. Faced with so many options, it can be said that it is a mixed blessing. I don't think anyone can fully understand how these parameters affect each other, so some of the machine manufacturers I've come into contact with are either powerless or wise to choose-- no programming advice.

Here is a basic idea for machine programming, but don't be too superstitious about these values. Remember, in the final analysis, taste is the only important variable.

Pre-soaking amount and time

Pre-soaking can wet the whole powder bed and increase the temperature of the powder bed, which can help improve the extraction uniformity before cooking and eliminate the difference in extraction rate between the upper and lower parts of the powder bed. It is said that pre-soaking can also reduce the generation of channels, but the credibility of this view is now in doubt.

To set the pre-immersion ratio, first find out the maximum amount of water that can keep the coffee liquid from flowing from the filter cup within 30 seconds after the start of the pre-immersion. After setting the pre-soaking ratio, start the cooking process, turn off the machine immediately after the pre-soaking is completed, wait 20-30 seconds, gently take out the filter cup on the table, and use a spoon to dig the powder pile layer by layer. When the pre-soaking is completed, the coffee powder from the top to the bottom of the powder bed should be all soaked. If the coffee powder at the bottom is still dry, you need to increase the amount of pre-soaking. If a dry or semi-dry channel is found, it is best not to use the pre-immersion function of this machine.

The pre-soaking time is necessary to separate the pre-soaking stage from the rest of the cooking stage. The longer the pre-soaking time, the more carbon dioxide gas can be released, and the turbulence can be reduced when the coffee beans are too fresh. If you want to use ultra-long pre-soaking, you need to use a slightly finer grinding degree and increase the cooking temperature by several degrees (℉).

Cooking time

Brewing time refers to the total time of filling all the water needed for brewing, which has relatively little effect on the flavor of coffee. Pay attention to adjust the cooking time to keep the water accumulation at the top of the powder bed consistent during the cooking process. When the cooking time is too long or too short, it may be necessary to adjust the grinding degree.

Shunt valve, brewing volume, temperature

These parameters have been discussed earlier in this chapter.

Common settin

According to the author's discussion with several premium cafe owners, here are the approximate values of the programming settings used by 1.5-gallon machines:

How to preserve brewed coffee

If the coffee cannot be consumed immediately after brewing, it should be stored in a sealed insulated container. This minimizes the temperature drop and the loss of volatile aromatic hydrocarbons. Keeping the temperature at 175F-185F (about 79.4-85 ℃) can prevent coffee flavor from becoming sour during preservation. However no matter what kind of container is used the flavor of the coffee will be significantly weakened after 15 to 20 minutes of brewing.

Brew drip-filter coffee as needed

Recently, there has been a wonderful drip coffee revolution: many cafes have stopped brewing drip coffee with large amounts of powder and keeping it for more than an hour. Some cafes have switched to serving freshly brewed 50-oz (about 1.4L) French-pressed coffee, while others have started using Clover? Brand machines brew coffee on demand, and there are some watering coffee machines that change into one cup and brew cup by cup according to the order.

It seems that the popularity of Espresso not only does not wipe out drip coffee, but also forces drip coffee to make more progress to win public attention.

Tips: (at least for me) Unfortunately and frustratingly, the so-called "boutique coffee" served in many cafes has been brewed for more than 45 minutes. I often wonder whether cafes are saving money or losing customers when they sell these spoiled coffee.

Types of coffee filters

When brewing drip-filter coffee, the porosity and material of the filter have a great influence on the product. For the filter paper with more pores, the flow rate of liquid through the powder bed is faster, and a finer grinding degree is needed to ensure sufficient contact time between powder and water.

The porosity of the filter also determines the amount of insoluble matter flowing into the coffee. Insoluble substances can increase the body of coffee, but make the sour taste dim and make the flavor cloudy. Therefore, when selecting the filter, we need to consider the alcohol degree and flavor cleanliness. The filter with high porosity has stronger alcohol content, but the flavor cleanliness is lower.

The porosity of each filter varies, and the porosity of the metal filter may be smaller or higher than that of the cloth filter. But in any case, the following summary is basically true:

The coffee produced by metal filter has high mellowness and low flavor cleanliness. Rinse thoroughly after each use to avoid accumulation of coffee oil.

The coffee produced by cloth filter has high mellowness and medium flavor cleanliness. Cloth filters can make excellent coffee, but they are easily affected by the oils and detergents adsorbed on the cloth. Like metal filters, cloth filters need to be cleaned frequently.

The coffee produced by the paper filter has the lowest mellowness and the highest flavor cleanliness. Because filter paper is disposable, it is the most expensive choice in the long run, but it is the least time-consuming and does not require maintenance.

Frozen coffee beans

Last year, the author found some Kenyan AA coffee beans that I baked six years ago in my mother's refrigerator. I was very curious about the state of the beans that had been frozen for six years, so I couldn't wait to make a pot. The product is quite good. I'm not saying it tastes as good as the one that was brewed six years ago, but I'm recommending that freezing is indeed an effective method of storage. Since then I have been an enthusiastic coffee bean freezer.

Many fallacies insist on the dangers of frozen coffee beans. Don't believe them.

Freezing can be used as a long-term storage scheme, because freezing can reduce the oxidation rate by 15 times, solidify coffee oil and greatly reduce volatilization. In addition, because a small amount of water in coffee beans is bound to the matrix polymer, it will not be frozen.

Before freezing coffee beans, put the beans in an impervious sealed container. Take it out of the freezer only when you are ready to cook it. Never thaw the beans and freeze them again.

(chapter 6 ends)