Coffee and Food Service
Coffee information provided by CoffeeChemistry.com:
Unlike wine where the winemaker has complete quality control up to the time of bottling - coffee requires that the consumer to use a bit of their own craftsmanship during preparation. This final step in coffee preparation is perhaps one of the most critical, since errors here can ruin the quality of the coffee and ultimately all the work that was invested into it. We will discuss in more detail the many variables that affect the quality of the brew, such as time, temperature, weight, water quality, particle size, etc.
Fortunately much of the guess work in preparing a good cup of coffee has already been investigated by the Coffee Brewing Center (CBC) during the 1960's. Led by Dr. Lockhart, his research has become the body of knowledge in truly understanding the physics and science behind coffee brewing.
Before discussing the fundamentals it is important to define some basic brewing terminology - strenght, extration and brew formula.
Together these three variables make up the bulding blocks of what creates aroma, taste and body in coffee.
- Strength - refers to the measure of solubles present in the beverage and usually expressed as a percentage of the flavoring material to water.
- Extraction - or sometimes referres to as "solubles yield" - refers to the amount of solubles extracted from the bean itself and also expressed as a percetage.
- Brew formula - refers to the ratio of water used per quantity of coffee.
Brewing Control Chart
Much of Dr. Lockhart's work at the CBC was dedicated to the creation of the "Coffee Brewing Control Chart" which is still in use today. In essence, the brewing control chart provides a graphical representation of strength, extraction and brew formula in an easy to read format.
By measuring the soluble solids from brewed coffee relative to its brew formula, the CBC was able to graphically represent "solubles yield" given the amount of coffee to water ratio. As such, the work has provided the industry with the framework in which to discuss and compare coffee brewing standards.
To determine any one of these variables simply select a brew ratio (as depicted as diagonal lines on the chart) and beverage strength – and based on this extraction can easily be extrapolated from the chart. We will discuss this in greater detail below, but for now, one important thing to remember is that, according to the CBC, the best cup of coffee is obtained when approximately 18-22% of the flavoring material is extracted from the bean. As such, this infusion would represent a beverage with a corresponding strength of 1.15-1.35%. When both these factors are met, the beverage is said to be at its "Optimum Balance" and is depicted as a grey box in the center of Brewing Control Chart.
Brewing Control Chart
The amount of flavoring material contained in a beverage will vary depending on brewing method used. Typically a drip cup of coffee contains roughly 1.2% flavoring material and 98.8% water. Whereas, a typical espresso will contain on average will contain 1.8-2.2% and ~98.2% water. When looked on a macro scale – it’s clear that coffee is a potent flavoring material.
Luckily, strength measurements can be made relatively easily using a number of different instruments. The most common include the use of hydrometers, conductivity meters, brix meters and moisture microwaves.
Portable TDS or total dissolved solids meters are a great tool since they are relatively cheap and can be used to not only test the coffee solution, but the water as well. For all practical purposes, a TDS meter is just a customized conductivity meter that relates the amount of coffee flavoring material based on its conductivity across a solution. For example, a reading of 1800 ppm in TDS refers to corresponding flavoring material content of 0.18% and 99.82% water on the Brewing Control Chart. *1.8% will correspond to 18,000 ppm. Therefore, if using a TDS meter that has a maximum measurement range of less than 18,000 ppm, the reading can be extrapolated to determine the actual measurement.
|Figure 1: Strength|
When looking at the composition of the coffee bean, approximately 28% of the organic material water soluble, while the remaining 72% consists of insoluble cellulose that holds the bean together. Upon the addition of hot water much of the soluble material is readily dissolved in solution to extract important flavor and aroma compounds.
As shown in Figure 2 below, a 20% extraction (shown at the bottom of the chart) indicates that 20% of the soluble flavoring material within the bean was extracted into water.
For example, if 10 grams of ground coffee was used in brewing, the bean would have lost 2 grams of soluble material to water. Because the rate at which these soluble compounds dissolve vary, changes to grind, water temperature, brew time, coffee weight and brew equipment will invariably produce vastly different beverages. For example extractions below 16% produces a beverage with a weak peanut-like flavor, while extractions over 24% producing over-extracted bitter characteristics. We will discuss these issues later in a separate section.
For now, the key is to brew coffee within the "Optimal Balance" having 1.15-1.35% coffee flavoring material.
|Figure 2: Extraction|
Although it may seem intimidating at first, using the Coffee Brewing Control Chart will provide for the basic groundwork in which to ensure consistent beverage preparation.
Lingle, T. The Coffee Brewing Handbook. SCAA
French Press - The Food Geek
Coffee information above reprinted with permission from CoffeeChemistry.com.
TIPS FOR USING TESTING INSTRUMENTS IN COFFEE:
- Always check the instrument's maximum operating temperature range before inserting it into a hot coffee sample. As with any electronic product, extended or repeated exposure to very high (or low) temperatures may affect the performance of the meter and ultimately shorten its lifespan. Therefore, it is always recommended to let coffee or any hot liquids cool prior to inserting a tester into into the sample.
- Always clean the sensor after dipping an instrument into the coffee sample. Letting coffee dry on a testing probe, for any parameter (TDS, conductivity, temperature or pH), may affect the accuracy of future readings. Please consult your product's instruction manual for cleaning and care techniques.
RECOMMENDED INSTRUMENTS FOR COFFEE TESTING:
WATER AND FOOD SERVICE OPERATION
Water quality plays a vital role in the foodservice industry. Not only does water quality determine the taste and quality of all beverages served, it also determines the operating efficiency and longevity of water-fed foodservice equipment.
As important as premium water is to a foodservice establishment's customers, so is the reduction in water related maintenance problems to the foodservice operator. Warewashers, Booster Heaters, Steamers & Combi-ovens, Proofers, Ice Machines, Coffee, Tea, & Espresso Machines, Hot Water Dispensers, etc., are all susceptible to water related problems caused by sediment, hard water (mineral scale deposits), corrosion and chlorine.
Most water supplies contain ample amounts of dissolved mineral salts such as calcium and magnesium. When water temperature increases in equipment such as booster heaters or steamers, dissolved hard minerals precipitate out of solution and reform as solid particles in the form of mineral scale deposits. These deposits “cling” to each other, building up layer upon layer of hard-to-remove mineral scale resulting in plugged nozzles, clogged pipes, and insulated heat-transfer surfaces. Scale on heating elements acts as an insulator inhibiting the heat energy transfer to the water resulting in slower heat cycles and increased energy consumption. Scale bonded to water-sensing level devices cause false probe readings, resulting in inadequate amounts of water fill. Under- filled tanks cause heating elements to dry fire and overheat, leading to costly repairs.
Minimizing the TDS of your process water can:
Increases Quality Uptime
Increases Life Cycles
Lowers Operating Costs
Lowers Maintenance Costs
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