Acrylamide Content And Antioxidant Activity Among 8 Different Filter Coffee Extraction Methods.

Introduction Coffee is one of the most consumed beverages in the world. During the roasting process, green coffee beans undergo various changes due to different thermal reactions, most of them in the context of Maillard reactions (e.g. Caramelization, Strecker degradation, Pyrolysis) that lead to the development of the desired physicochemical and organoleptic properties of roasted coffee beans and derived beverages, such as flavour, aroma and colour, but also to the formation of undesired compounds 1. One of the undesired heat-induced contaminants is acrylamide (AA), a substance formed mainly by the condensation of an amino group of amino acids (principally asparagine) and the carbonyl group of reducing sugars (e.g., glucose and fructose) during the Maillard reactions triggered at temperatures above 120 ◦C 1. It is known that, despite the presence of AA, coffee is also a rich source of biologically active compounds with significant antioxidant properties. Polyphenols and chlorogenic acids are the characteristic coffee compounds linked to an antioxidant activity whose contents are influenced by the roasting process and by the extraction method 2. Several health benefits are attributed to these compounds and their role in the prevention of chronic diseases such as cancer and cardiovascular pathologies has been the subject of many scientific research 3. Therefore, coffee brewing is regarded as a solid-liquid extraction, from an engineering perspective, that takes place between hot water and ground coffee beans when the water passes through a bed of coffee ground 4. Among the different brewing methods used for specialty and filter coffee applications, recently, Turkish Ibrik (boiling method), French Press (steeping or immersion method), V60, Chemex, Clever (filtration or drip method), AeroPress and Moka (pressured method) have been proposed for mostly 5. To give a comprehensive overview of the filter coffee world, the new Pure Brew (Victoria Arduino) 5 was compared with these seven extraction methods. Therefore, the present work aimed to develop a comprehensive study and investigate the differences between the newly filter coffee extraction method, Pure Brew, with traditional ones (Turkish Ibrik, French Press, V60, Chemex, Clever, AeroPress and Moka), in terms of coffee extraction yield, AA content and antioxidant activity. To the best of our knowledge, this is the first paper which reports a chemical investigation of filter coffee produced by the novel Pure Brew technique. All analyses were carried out on three diverse coffees differently roasted (i.e., light, medium and dark); in this way, it has been realizable to explore at full the world of coffee, and for this reason, the selection was made among three different coffees with distinct roastings, origins, post-harvesting process and quality lots. This is to assess how the heat treatment can be correlated to the presence/formation of unhealthy compounds, such as AA and healthy compounds, among which are chlorogenic acids. Materials and Methods Three different coffees with varying degrees of roast were used for each of the eight extraction methods: Gardelli Specialty’s natural, non-classic anaerobic Ethiopia Uraga for a light roast, Gardelli Specialty’s washed Kenya Thiriku for a medium roast, and roasted Blond 100% Starbucks Arabica for a dark roast. A specific routine was used for each of the eight preparation methods, keeping some parameters as constant as possible, but without distorting the beverage recipes. For the extraction of AA, purification of samples and its quantitation a previous developed and validated HPLC-MS/MS procedure was used 1 with some adaptations. While analysis of chlorogenic and phenolic acids (antioxidants) and caffeine was performed according to a previously developed and validated method by HPLC-DAD 6. Antioxidant activity was determined spectrophotometrically by the DPPH method 7, while TPC and TFC of the different extracts according to a method described by 7, with slight modifications. Statistical analysis was performed by MetaboAnalyst (version 4.0). Conclusions The results confirmed that the AA levels and antioxidant activity reached maximum when the coffee to water’s ratio used for the same filter coffee extraction method is higher, consequently also the TDS, and then decreased when this ratio for the same brew is minimum. Moreover, a strong correlation was found between the content of antioxidant compounds such as chlorogenic acids and polyphenols, and the concentration of dissolved solids in the beverage. In conclusion, both healthy and unhealthy compounds can be influenced by the same parameters during the brewing processes, which are coffee mass to water ratio, particle size distribution, brewing time, water temperature, and agitation.