USING STATISTICAL ANALYSIS TO CONTROL THE STABILITY OF THE COFFEE MACHINE

Abstract

The stability of the coffee machine is usually associated with the stability of the flow of coffee during the preparation of the drink. Coffee is prepared when hot water under pressure passes through a washer with coffee powder. The flow rate of the beverage can vary for different extractions, forcing the barista to change the grinder settings. The degree of grinding is one of the most important factors affecting the flow rate of the drink. The paper presents the results of experimental studies on the determination of the coffee flow rate and mass consumption during the preparation of the drink. For the experiment, three batches of coffee from different producers were chosen (UAB “Kavos bankas”, Lithuania; Jacobs Douwe egberts, the Netherlands; Saffè Carraro SpA, Italy). Each batch was tested using 12 extractions. Each of the extractions was obtained from freshly ground coffee. The beans were ground using a professional flat grinder with the same settings. A new method of forming a coffee washer was proposed, which gave a more stable result, in terms of flow rate, than the usual method of laying ground coffee (using a washer made of homogeneous raw materials). The results are presented, which confirm that the new method is able to reduce the sensitivity of the coffee machine to variations in the properties of coffee beans (different manufacturers, different packages from the same batch). The results of testing the hypothesis about the absence of violations of the stability of the mass consumption of coffee using one-factor variance analysis (equality of average values), linear regression analysis (on the absence of influence of time on the value of the indicator in each sample), covariance analysis (absence of discrepancies in the functional influence of time on the value of stability of the coffee flow rate). Recommendations for baristas on using the proposed method are provided.