It can fit into the palm of your hand, but the scale of the multi-billion dollar espresso industry is not something to be taken lightly. Nuova Simonelli, leading manufacturers of espresso equipment and Official Machine Sponsors of the World Barista Championships, know all too well the effort that goes into that tiny cup. For decades, the company has led technological advances in espresso equipment, under the guidance that knowledge is power when it comes to perfecting extractions. “At the foundation of our innovation efforts is the desire to continually improve the quality of coffee served to the customer,” says Maurizio Giuli, Marketing Manager for Nuova Simonelli. “We believe that the technological progress of the espresso machine is generally not made in large steps, but through a continuous stream of small steps.” The latest “small step” that the company has contributed could prove to have a significant impact on our understanding of a quality extraction. The Italian company has paired up with two scientists from the University of Camerino to study the effects of pressure and temperature on extracted coffee, as well as its chemical and physical composition. The project was led by Professor Sauro Vittori and Researcher Dr. Manuela Cortese. An initial literature review showed that previous studies have looked at the correlation between the quality of espresso with the type and degree of coffee roasting, the effects of the roasting process, and the composition of water. However, less scientific work was found on how the parameters of pressure and temperature affect the finished product. The researchers, in association with Nuova Simonelli, took this task under tow, to see if they could define how these parameters affect the quality of the coffee. “The project was conducted with the objective of defining the ideal conditions for excellent quality extraction,” Vittori says. “By varying the parameters of the coffee machine we analysed the chemical changes in the infusion process.” The study itself is part of a wider research project aiming to create a mathematical algorithm that defines the effects of set parameters on coffee. The ultimate goal will be scientific support to identify the ideal conditions for extracting each type of coffee. Because the objective was to look at the effects of these two specific parameters, Vittori says the key was to ensure that all the other elements in a complex product such as coffee remained constant in the experiments. Vittori says a big help was using the Aurelia Competition machine for the study. Because they needed to carefully control the parameters, the machine’s reputation for consistency, and its ability to control the variables, proved especially useful. In a product as complex as coffee, Vittori stresses that maintaining all other parameters – other than the two being studied – as constant was absolutely key. For the experiment, researchers started with parameters considered typical for Italian espresso: 7 grams of coffee (+/- 0.5 grams); 90 degrees Celsius water temperature (+/- 2 degrees Celsius), 9 bar water pressure (+/- 1 bar), 25 seconds extraction time (+/- 2.5 seconds), and 25 millilitres volume of coffee in the cup (+/- 2.5 millilitres). From this reference data, the scientists then identified three pressure values (7, 9 and 11 bar) and three temperature values (88, 92 and 98 degrees Celsius) as the variables in the experiment. To correlate these variables to what was produced in the cup, the scientists used existing literature to identify which chemical-physical parameters of coffee could be measured against what was considered a “quality” extraction. To this end, they measured acidity, total dissolved solids, and density.
While some of the results of the experiment matched the scientists’ hypotheses, other findings came as a surprise. For instance, Vittori says they expected greater pressure in the filter would produce an increase in the volume of the espresso coffee produced in the cup. Although this theory was confirmed in the difference between the 7 and 9 bar extractions, at 11 bar the volume delivered was lower than at 9 bar. Vittori explains that the impact of water at a higher pressure causes mitigation of smaller particles towards the bottom of the filter, leading to the formation of a compact layer that inhibits the passage of water. This phenomenon was particularly evident when moving from 9 to 11 bar, explaining the drop in volume produced. The experiment also found that temperature affects the volume of coffee produced. Initial conclusions are that as the temperature ruses, there is an increase in the resistance, and therefor a decrease in the volume of coffee output. The experiment also looked at the results of temperature and pressure parameters on protein levels. With protein molecules highly soluble in water, but especially sensitive to temperature, Vittori says that the roasting stage is critical. The results of the study show that the dispensing temperature, however, affects the amount of protein in espresso. Analysing the data, the scientists found some similarities between the graph of the protein extraction and the volume of crema measured under the same conditions, supporting correlation between the two found in existing literature. The data from this most recent study also confirmed that the best extraction conditions, where there is a greater volume of crema, were under the parameters of 92 degrees Celsius and 9 bar of pressure. Vittori and Cortese’s initial overall conclusions show that “in terms of extraction efficiency” the ideal parameters are 9 bar, 92 degrees Celsius. As for any larger conclusions, Vittori says these trade secrets will be reserved for Nuova Simonelli. Giuli says that Nuova Simonelli will use the results of this research in the design of future espresso machines. He notes that the Soft Infusion System (SIS), introduced in 2003 to the Aurelia, came from similar research, and T3 technology came from other scientific work. Giuli says the work of scientists like Vittori and Cortese complements the contributions of top performing baristas. “To push and guide this process of innovation, the contribution and expertise of various participants is needed,” he says. “We at Nuova Simonelli provide our research and our expertise to help operators of specialty coffee continue to elevate the quality of the drink, and thus raise the enjoyment of the final consumer.” GCR
