Learn more about our analytical methods
1. Total dissolved solids and extraction
Beverage preparation, the last step of the bean’s long journey, is also one of the most critical. It is essential that the extraction of the soluble flavouring compounds is done in an optimal way, in order to stay true to the bean, the specialist skills and hard work invested into it. Luckily, brewing the perfect cup is as much of a science as it is an art.
A cup of coffee is essentially a solution of hundreds of compounds that affect flavour. The amount of dissolved material in a coffee beverage determines its strength, which is expressed as the weight percentage of dissolved solids compared to the total weight of the beverage. Typically, the strength or TDS percentage of filter coffee is around 1-1.5% and around 10% for espresso. Once TDS is known, extraction yield can be calculated. A fundamental goal should be to keep the extraction yield in a range of approx. 18-21%. At less than 17% extraction yield, espresso based drinks tend to be sour, and more than 22% tend toward harsh and bitter. For example, underdeveloped roasts can be easily detected, as these roasts will produce low extraction yields compared to fully developed roasts.
We measure TDS directly by a dedicated coffee refractometer. All refractometers characterize fluids based on the phenomenon that light passes more slowly through denser or more concentrated media, which is perceived as the “bending” of the light beam. This principle is used in many various applications, mainly to calculate the amount of dissolved substances in water, such as sugar, or, in our case, coffee. Our 4th generation VST LAB Coffee III Refractometer was developed especially for the coffee industry. Using the VST CoffeeTools™ Software, we plot your design target and compare it to actual measurements. The result lets roasters determine how far the roast had developed and aids their decision in what direction to make corrections.
The TDS measurement can help you find the ideal strength/extraction point for each single origin or blend, which can then be used to supply your customers with a recommended brewing recipe and ensure they help your roasts stand out in the eyes of the quality-conscious consumer.
2. Roast Colour Analysis
Roast colour analysis is one of the most important methods to quickly determine the degree of roast development, making it an essential tool that helps ensure roast consistency.
Similarly to visible light spectrophotometers, infrared roast analysers (such as the Agtron analyser) use the interaction of light waves with the roasted beans to assess how far the roast had developed. At the same time, the working principles of the two instruments are markedly different. Spectrophotometers utilise visible light to measure the degree of sugar browning as perceived by the human eye. In contrast, the Agtron analyser uses near infrared light to track chemical changes within the bean. (More specifically, it senses the presence of a group of quinones that form when chlorogenic acids break down during roasting.)
The Agtron scale is widely accepted as a “common language” to communicate roast degree between all coffee professionals. It is important, however, to take care when translating results from other instruments -such as colorimeters, laser colour trackers etc.- to Agtron numbers due to the fact that they measure different parameters (colour vs. chemical change). Agtron provide commercial and “gourmet” or M-basic scales, the latter being preferred by specialty roasters. The scale ranges from 0-100, the higher number meaning a lighter roast. Readings are taken of both the whole bean and the same beans after grinding. Grind size affects the measurement, therefore we use filter screens to eliminate overly small and large particles.
The whole bean is always darker than the ground, and the difference between the measurements indicates the rate of heat penetration and sugar browning that took place. This difference, just as much as the roast classification on the Agtron scale, provides highly valuable information to roasters on how to adjust roast profiles. We perform three readings of both whole and ground beans for each sample to determine if they all fall within the target range specified by the roaster.
3. Caffeine content
Coffee producers need to offer a variety of options for consumers in terms of the caffeine level in their coffee drinks. Consumers should always be assured they get what they are expecting, may it be that good caffeine hit, or a minimum level of caffeine.
The ability to accurately measure caffeine levels in decaffeinated coffee bean batches is essential for reducing health risks in sensitive consumers by preventing inconsistent caffeine levels1 among available “decaf” blends. In the US, the FDA (Food and Drug Administration) requires coffee producers to reduce caffeine content to only 25 parts per million for decaffeinated blends in order to use the “decaf” label.
Light absorption methods of caffeine monitoring can provide instant analysis to indicate whether the decaf coffee received indeed complies with regulations. Following published procedures2, we use an UV-VIS spectrophotometer to provide accurate caffeine content data for your coffee samples.
We can also help if you are planning on introducing “mild” or “extreme” coffee products.
1 ( McCusker, Goldberger,Cone 2005)
2 (Belay, Ture, Redi, Asfaw 2007)
4. Moisture and bean density
Measuring the amount of moisture in green coffee beans is crucial in terms of its quality. Coffee that is too high or too low in moisture should be rejected, because both extremes will have a negative impact on cupping quality. Green coffee that is high in moisture (above 12% wet basis) can deteriorate due to bacteria, mould (fungi) or yeast. (Microbial growth can be predicted more accurately by the measurement of water activity, see here.
Overdried coffee is characterised by loss of colour, which translates directly into lower cupping quality. When moisture drops below 10%, aroma, acidity and freshness begin to fade away and disappear completely below 8%. Therefore, it is important for many reasons to ascertain that all green beans received should have their moisture content between 8-12%.
Once we have determined that the moisture content is within acceptable range, the exact values, together with bean density, will affect the how a roaster chooses to handle the roasting process. Moisture content of roasted beans also gives valuable information on roast quality and consistency. For example, excessive moisture loss can indicate that the roast had gone too far, or that the airflow within the roasting drum is not optimal. Bean density affects how much heat needs to be supplied to the drum in order to achieve optimal roast development.
5. Water activity
Water activity affects the shelf life, safety, texture, flavour, and smell of foods, including coffee. By measuring water activity, it is possible to predict which microorganisms will and will not be potential sources of spoilage. Water activity, rather than moisture content, determines the lower limit of available water for microbial growth. Water activity better predicts the growth of microorganisms because microorganisms can only use "available", not chemically bound water within the coffee bean.
Microorganisms can produce toxic compounds, such as Ochratoxin A, a mycotoxin produced by fungi. Ochratoxin A can cause toxicity in the kidneys and also has a carcinogenic effect according to the WHO. These toxins are cause of real concern, as they cannot be completely eliminated by roasting. We also provide Ochratoxin A analysis to take a significant worry out of your coffee production.
6. Oxygen content analysis in the packaging headspace, leak detection
The presence of oxygen is generally considered the primary enemy of roasted coffee. Oxygen affects staling reactions in many ways.1 Oxidation is responsible for the loss of many aroma compounds, and also for the formation of off-flavours, such as rancidity2.
Oxygen is the most important factor controlling the shelf life of coffee. Reducing oxygen to 0.5% in a coffee container could increase shelf life by 20-fold. One research group found that for each 1% oxygen increase there is a 10% increase in the rate of degradation.3 Even at very low levels of oxygen in packaged coffee (<2%), oxygen has been found to migrate into coffee and facilitate staling.4
Packages with degassing valves have been investigated.5 The study found that this type of packaging protects coffee well from oxygen (close to 0% oxygen was measured), unless there is a leak present. At the same time, half of the bags investigated had some amount of leakage.
Package leaks are a relatively common problem and can have a highly negative impact on the shelf life of roasted coffee. We can test your coffee packaging and determine if leaks are affecting the freshness of your product.
1 Ross et al. 2006; Illy and Viani 2005
2 Prescott et al. 1937; Illy and Viani 2005
3 Cardelli and Labuza 2001
4 Harris and others 1974
5 Walter 2008
7. pH measurements
Coffee acidity is typically a highly valued quality especially in Central American and some East African coffee. (Flavour acidity differs from sourness, which is an unwanted defect.)
However, not every coffee lover enjoys bright, high-acid coffees. According to a 2010 report by the American Chemical Society, up to 40 million people in the United States alone avoid coffee due to stomach irritation. Recently, many innovative coffee companies have started to address this issue by offering a low acid coffee range.
The pH of coffee has been found to correlate with the perceived acidity in coffee by more independent research groups (Pangborn 1982, Sivetz and Desrosier 1979, Griffin and Blauch 1999). The perceived acidity of coffee results from the interaction of acids with the receptors on the human tongue. Coffee chemistry is complex, and many other factors impact taste and digestion. Still, pH testing can confirm that coffees that are perceived as low in acid during sensory evaluation have corresponding higher pH values* compared to other coffees. Confirmed low acid content will be valuable when marketing low acid coffees.
*How does the pH scale work?
The pH scale is a logarithmic scale that shows the acid concentration of a liquid. The midpoint of the pH scale is defined as pH 7, the pH of water, also called neutral pH. Higher numbers represent alkaline solutions; lower numbers represent acidic ones. A solution that has a pH value of 6 is ten times more acidic than water, and pH 5 is one hundred times more acidic than water. It is clear that a one unit difference in pH indeed means a dramatic difference in acidity. As an example, a coffee that registers at pH 4.6 is twice as acidic as a coffee that has a pH value of 4.9!
8. Ochratoxin A by ELISA
Ochratoxins are naturally produced by several species of fungi, such as Aspergillus and Penicillium species. Both are widely distributed and may be found in many foods, such as grain, legumes, wine, cereals, and, unfortunately, coffee. Ochratoxin A is classified as carcinogenic, and has been shown to have a toxic effect on the kidney and cause defects in unborn babies. To protect consumers from mycotoxin related risks, the European Union has established regulatory limits for OTA in coffee, and similar regulations can soon be expected in Australia.
Green coffee shipments are often inspected for Ochratoxin A (OTA) and classified into good or bad categories depending on whether the OTA estimates are above or below a defined regulatory limit. Because of the uncertainty associated with the sampling, sample preparation, and analytical steps of an OTA test procedure, some shipments of green coffee will be misclassified. The misclassification of lots leads to some bad lots being accepted. (J AOAC Int. 2006;89(4):1021-6.)
We can help make sure your coffee products are free of Ochratoxin A. By measuring OTA levels in green coffee, we can help you make a safer purchase decision. As OTA cannot be completely eliminated by roasting, we can also test roasted coffee to make sure that no contaminated coffee reaches your customers.
We use the Ochratoxins ELISA immunoassay for the detection of total Ochratroxins. This test is suitable for the quantitative and/or qualitative detection of Ochratoxins in contaminated samples. Positive samples will be confirmed by precise laboratory measurements such as high performance liquid chromatography (HPLC).