Home: Coffee: Brewing Guide

Freshness

Proper storage, exposing roasted coffee to as little air as possible, helps preserve freshness. The flavor of both ground and whole bean coffee deteriorates after roasting when exposed to air. The flavor of ground coffee deteriorates more quickly than whole bean, as more surface area is exposed to air. If packed in unlined or non-protective material, coffee will become stale within a week.

One-way valve bags allow coffee to be packaged immediately after roasting or grinding. The bags usually contain several layers of polyethylene and aluminum foil and are typically used for one and five pound amounts. Embedded in each package is a small plastic valve, which permits carbon dioxide to escape from the coffee, while preventing the entrance of oxygen. Coffee packed in a one-way valve bag generally stays fresh for several months if the bag is not opened.

Water

Because the coffee beverage is 98.5 - 98.85% water, good quality drinking water is necessary for a good cup of coffee. If water is not pleasant to drink, it should not be used to make coffee. Use cold, fresh water for brewing. Never use softened water. Sodium ions in softened water form a gelatinous mass around the coffee grounds, slowing down the extraction process and causing over-extraction.

Solutions for Several Common Coffee-Brewing Water Problems:
PROBLEM
SOLUTION
Chlorine in the water gives the coffee an "off" taste. Use charcoal-filtering devices to remove chlorine residue
"Chemical" tastes such as sulfur or iron. Correct taste contamination with charcoal or other filters
A build-up of magnesium and calcium scale (water hardness) Maintain and clean brewing equipment to remove the scale build-up
Coffee grounds become gooey and the brew tastes over-extracted or bitter. Avoid use of softened water to brew coffee, if possible. In areas where the water is not good, use bottled drinking water, or a filter to purify water.

The most common concern with water for brewing is the "hardness" of the water. This refers to various natural minerals found in water such as magnesium, calcium, sodium, potassium, bicarbonate, sulfate and chloride. The number of grains of dissolved minerals changes the level of soluble solids extracted from the coffee.

The Effect of Hard Water on Extraction:
 
GRAINS
PARTS PER MILLION
EFFECT ON EXTRACTION
Soft <4 0-60 None
Moderately hard 4-10 60-200 Slight reduction
Very hard >10 >200 Noticeable reduction

As hard water passes through coffee brewing equipment, it produces deposits of scale or lime. This reduces the life and efficiency of the equipment, and affects the coffee flavor; bottled or filtered water should be used to solve this problem.

When a water filter is used, it should be changed regularly according to the manufacturer's recommendations.

Temperature

A second requirement of water for good coffee brewing is the water temperature as it passes over the coffee grounds. Ideal brewing temperature is 200°F, plus or minus 5°F (at sea level). Subtract 2°F for every 1,000 feet of elevation. Too low a temperature causes flavor compounds not to dissolve resulting in an under extracted weak beverage. Too high a temperature will cause flavor changes resulting in an over-extracted bitter and astringent beverage. By maintaining the proper temperature throughout the brew cycle, optimum extraction can be attained.

Grind

Coffee beans should be ground specifically for use in your type of brewer. Too coarse a grind for the equipment results in under-extraction because the water is in contact with ground coffee in the brew basket for too little time. Too fine a grind can cause problems such as clogging the brewer, improper wetting and over-extraction of the coffee. This is due to extended contact time between coffee and water.

Quality control in grinding starts with water cooled grinders which maintain a consistent temperature throughout the grinding process, preventing the radiant heat that can form in a standard grinder from changing the color and flavor profile of the coffee while being ground. The ground coffee is then analyzed using laser diffraction technology to accurately insure a consistent grind and tested for bulk density versus the standard.

PERCENTAGE OF PARTICLE SIZES FOR VARIOUS GRINDS (+/- 2%)
 
Coarse (Urn)
Medium (Drip)
Fine
20 mesh screen 33% 10% 0%
28-35 mesh screen 55% 72% 70%
Pan 12% 18% 30%
  100% 100% 100%

A cautionary note should be added here on the use of coffee grinders on location. These grinders can and do vary in the type of grind they produce. This lack of control in the grind will be directly reflected in the beverage quality.

Accumulation of the rancid oils and other materials in the grinder will offset the fine flavor of fresh coffee as well. Coffee that is ground in a roasting plant will be uniform day after day and will not adversely affect the quality of your beverage.

Coffee ground on location will contain CO2 gas, which will cause the bed to float during brewing. This condition will result in under extraction and weak coffee.

Brewing Time

Use the grind designed for your coffee maker. Too fine a grind for your equipment will produce an over-extracted astringent coffee beverage. Too coarse of a grind will produce a weak flavorless coffee beverage. The grind determines the length of time coffee and water should be together.

Time and grind are directly related. The type of grind will determine the brewing or water to coffee contact time. Brewing time begins when the first water touches the coffee, and the last water has passed through the grounds.

Contact Times for 200°F Water Evenly Distributed
Over a Level Ground Bed of Coffee.

GRIND
CONTACT TIME
Fine 1-4 minutes
Medium (Drip) 4-6 minutes
Coarse (Urn) 6-8 minutes

With higher volume brewing system such as urns, the contact time may in increased. Most urns have a water bypass device that diverts some brewing water around the brew basket and directly into the holding chamber. This is necessary when all of the brewing water cannot pass through the coffee bed in the recommended time. Follow the guidelines above for the best body and sweetest coffee flavors.

Filtering Methods

In brewing, coffee oils and sediment are suspended in the coffee beverage. Filtering methods which clarify the brew also reduce the amount of these flavorful soluble solids. The main characteristics of different filtering methods are summarized below:

Metal Plates, Disks and Woven Screens with Holes:

  • Allow the most soluble solids to pass through.
  • Are initially more expensive, but less costly over the life of the equipment.
  • Require constant care and cleaning or will become clogged with oils and residues.

Cloth Filters or Urn Bags:

  • Cloth filters, including urn bags, allow moderate amounts of soluble solids to pass through.
  • Quality of the fabric is extremely important.
  • Must be rinsed in hot water before using to remove sizing or foreign odors.
  • Do not use soap, bleach, or detergent.
  • Are difficult to keep clean and organic fiber rapidly breaks down, requiring replacement of the filter or bag.
  • Must be stored in clean, cold water to prevent deterioration of the cloth.

Paper Filters:

  • Due to the limited porousness of paper, paper filters eliminate more soluble solids than cloth or metal fibers.
  • Are most common in foodservice.
  • Provide ease of sanitation.
  • Eliminate sediment and cloudiness.
  • Have an even texture (no pinholes).
  • Must be stored away from aromatic foods, as the filters can absorb those odors effecting the taste of the coffee.

Formulation

The amount of water used for brewing coffee determines the strength and flavor of the finished beverage.

No one formula will satisfy all coffee drinkers, but with proper brewing conditions, the recommended formula is 14 ounces to 20 ounces of fresh cold water to one ounce of freshly ground coffee.

WATER
COFFEE
YIELD
Adjusted for water absorption by coffee grounds
.5 gallon (64 oz.) 3.25/4.5 oz. 11-12 five-ounce servings
(restaurant decanter)
75 ounces 3.75/5.3 oz. 12-14 five-ounce servings

(2.2 liter airpot)

1.5 gallons (192 oz.) 9.6/13.7 oz. 33-34 five-ounce servings
(urn)
2.5 gallons (320 oz.) 16/23 oz. 55-58 five-ounce servings
(urn)

Less water will usually yield a stronger flavored beverage, while more water will produce a weaker beverage with less flavor.

Never pour brewed coffee through the used grounds. It does not increase the strength of the brew. The heavy-bodied flavor materials are extracted first in the brewing process. When these heavy-bodied materials are repoured over the grounds, some of them are reabsorbed and replaced with weak, bitter materials.

The strength of the coffee and its percent of soluble solids are the same. Soluble solids are the materials extracted from the ground coffee by hot water. The percent of soluble solids may be measured with a coffee hydrometer or by a dehydration method.

Extraction

Extraction is the action of removing the flavor components of coffee, referred to as "soluble solids," from roasted and ground coffee through contact with water. Color, flavor, aroma, and caffeine are released from the coffee during this process.

Extraction should be completed when only the first 2.9 to 3.5 ounces of soluble materials have been removed from the grounds of one pound of coffee. When extraction is extended beyond 3.5 ounces, only bitter materials are withdrawn. As much as 5.5 ounces of soluble materials may be removed per pound of coffee when brewed by the proper water-to-coffee formula. Complete extraction is extremely undesirable; it releases materials that make the beverage taste astringent and bitter.

The amount of soluble materials in a given amount of coffee is consistent for all varieties and all blends. It is important to realize, then, that if anyone tries to represent his coffee as being "stronger" or "richer" than another's, the claim is simply not true. No one blend of coffee will permit the use of more water in the formula than another. The primary difference between one blend and another is the flavor characteristics.

Serving

Serve coffee as soon after brewing as possible. Coffee loses flavor and aroma quickly. If brewed coffee must be "held" on a direct heat source, it should be held at 185°F, and for no longer than 20 minutes. Higher temperatures cause coffee to break down quickly, producing a bitter and flat taste. Lower temperatures make the brew too cold and consumers will be dissatisfied. Reheating brewed coffee breaks down the components of the coffee and results in an undesirable flavor.

Thermal servers are the best way to hold brewed coffee at the proper serving temperature because they are insulated, airtight, and no direct heat is applied to the coffee. Sealed containers prevent evaporation and retain aromatic compounds. The best insulated and sealed servers, if preheated with hot water, may hold coffee at acceptable serving temperatures for several hours.

For iced coffee, brew double strength coffee, and allow it to cool before pouring over ice.

If Your Coffee Just Doesn't Taste Right

If Ground Coffee Has a Stale or Rancid Odor or Flavor:
  • It may not be fresh. For best results purchase coffee in a gas-flushed, vacuum-packed or valve-pack packages.
  • High temperatures in your storage area may have caused the coffee to become stale too quickly.
  • Too much moisture in your storage area may have caused the coffee to become stale.
If Brewed Coffee Has a Rancid Odor or Taste:
  • Check for a dirty filter or urn bag, or brewing basket or gridded riser that supports the filter. If there is the slighted trace of odor on a cloth filter, clean it thoroughly or replace it. Paper filters should be used only once, and discarded if they have picked up foreign odors from being stored too closely to foods and supplies.
  • Check for a dirty urn liner, connecting pipe or faucet. They should be cleaned thoroughly. If the seat-cup in the faucet has an unpleasant odor, it should be replaced.
  • The brewing cartridge, airpot, or serving decanters may need to be disassembled and cleaned thoroughly.
  • The brew may not have been prepared using fresh, cold water.
If Brewed Coffee Tastes Bitter:
  • Check for over-extraction. Refer to coffee/water contact time limits in "Brewing Time" section.
  • Coffee may have been held too long at too high a temperature. The time should not exceed 20 minutes unless coffee is held in an insulated server. The holding temperature should not exceed 185° F.
  • Brewed coffee may have been repoured through spent grounds. Water should pass through grounds only once, regardless of the brewing method used.
  • Water may have been artificially softened, extending the brewing time.
  • Too fine a grind may have been used.
  • Do not stack filters. Stacking filters with pre-measured coffee is not recommended and should be avoided at all cost. Pre-stacking filters exposes ground coffee to oxygen, which deteriorates freshness, resulting in a stale, undesirable, finished beverage. Secondly, the fine particles of the ground coffee accumulate on the base of the filter (as they are stacked one on top of the other) and are directly deposited into the finished brew, creating sediment in the cup and producing a bitter and astringent flavor.
If Brewed Coffee is Weak or Watery:
  • Too much water may have been used. Use the ratio of 20 ounces of fresh cold water to one ounce of freshly ground coffee.
  • The brewing time may have been too short.
  • The brewing water temperature may have been too low.
  • Too coarse a grind may have been used. Make sure you are using the correct grind for the equipment.
  • Check for uniform water distribution from the brewer spray head.
  • Make sure the brew is thoroughly mixed.
If There is an Excess Amount of Sediment in Brewed Coffee:
  • The filter may be torn. If a cloth filter is used, it may be worn, the weave of the material may be too loose, or the thread count is too low.
  • The grind may be too fine for the filter device.
  • Softened water may have been used.