Abstract During the roasting process, a cascade of chemical reactions occur, from which non-volatile compounds degrade and form new compounds with potential aroma attributes. Considering that the roasting process significantly influences the biologically active compound concentration and some unwanted compound formation, such as acrylamide, it is crucial to understand the roasting process from both positive and negative aspects. The aim of this study was to evaluate the chemical composition changes in different roast level coffee samples from Colombia. The moisture, pH, acrylamide, total phenolic, and flavonoid content, and the volatile compound profile were analysed for coffee samples roasted at three different roast levels (light, medium, dark). The results showed a decrease of total phenolic and flavonoid concentration with increased roast level. Acrylamide concentration reached the highest peak in the medium roasted and the lowest in dark roasted coffee. With increasing roast level, the volatile organic acid concentration decreased, while furan and phenol compound concentration increased in the dark roasted coffee. Dark roasted coffee had the lowest acrylamide and organic acid concentration, and the highest pH in brew, which would be more suitable for coffee consumers with a sensitive stomach.

Although coffee silverskin (CS) has recently been used as a food ingredient, no knowledge has been reported on the effects of species or different post-harvest treatments on its chemical composition. Therefore, the fibre, volatile compounds, phenolic acid content, and antioxidant capacity of CS samples obtained at three roasting intensities (light, medium, and dark) from the Coffea arabica and C. canephora species, each subjected to a washing or a sun-drying (“natural”) post-harvest treatment, were studied. Obtained results showed that the chemical composition of CS is due to species, roasting, post-harvest treatment, and interaction. In particular, natural Arabica CS showed the highest content of volatile compounds of Maillard and varietal origin, whereas washed Arabica CS showed the highest content of soluble dietary fibre and chlorogenic derivatives. Pyrroles, sulphur compounds, and pyridines contents were higher in Canephora CS than in Arabica CS. The dark-roasted washed Arabica CS showed the highest content of 5-O- and 3-O-caffeoylquinic acids, while the natural Arabica CS highlighted the highest antioxidant capacity. The effect of post-harvest treatments seemed to be emphasised in Arabica CS, independent of roasting, which did not significantly affect the antioxidant capacity of CS from either species.

Coffee brewed on light, and very light-roast coffee beans have emerged as a recent trend among specialty coffee drinkers. The acidity of such light-roast coffee, and coffee in general, is an important sensory characteristic, as there is demonstrated a clear correlation between the roast level and perceived acidity in brewed coffee. The acidity is believed to be strongly linked to the content and composition of organic acids in coffee. Still, there is limited literature on acid content in brewed coffee and on the relevance of specific acid concentrations to sensory perception. In this study, we determined concentrations of acids and sugars in French-press brewed specialty coffee. We used varying roast degrees in the light to very light range using five coffees from different geographical locations (Brazil, Bolivia, and Kenya) and determined the sensory detection threshold and recognition for selected acids. The concentration of all individual acids except one (formic) either significantly decreased (citric, malic, and chlorogenic acid) or increased (acetic, lactic, phosphoric, quinic, and glycolic acid) systematically with an increasing roast degree, while no systematic trends were found between the different coffee samples. The sugar content decreased with an increasing roast degree. The sensory detection threshold for malic, acetic, and lactic acid was determined to be above the actual concentration of said acids in the coffee and just below for phosphoric acid, indicating t

Abstract Arabica coffee is one of the leading commodities of the global coffee industry, characterized by its complex flavour profile and high sensory quality. Coffee roasting is the process of applying heat through chemical changes to bring out the tastes of green coffee beans. The aim of this study was to investigate how the physicochemical characteristics and volatile compounds of Arabica coffee beans were affected by roasting at different level using various kinds of roasting machines. Drum and hot air roaster were used to roast the coffee beans, with three different roast levels: light, medium and dark. The results showed that the physicochemical characteristics of Arabica coffee are influenced by roast level. Coffee with medium and light roast level has a more complex flavour. The roasting process has an impact on the volatile component profile of Arabica coffee. The coffee made for this study had a bulk density between 0.44-0.53 g/ml, a water content between 1.22-2.59%, an ash content between 3.99-4.79%, a caffeine level between 1.11 – 1.40%, and a total phenolic content between 26.32 – 36.54 mg EAG/g. The volatile compounds in this coffee affected by roasting methods were represented by 30 volatile compounds, detected by SPME-GC/MS.

Application of high performance liquid chromatography to the analysis of some non-volatile coffee components. High performance liquid chromatography (HPLC) was applied to the analysis of caffeine, trigonelline, nicotinic acid and sucrose in Arabica and Robusta coffee. Green and roasted coffee samples were used in this study and the degradation of sucrose and trigonelline, with the formation of nicotinic acid, was followed during roasting. Caffeine did not undergo significant degradation with only 5.4% being lost under severe roasting. Sucrose was degraded rapidly during processing with light roasting producing a 97% loss and dark roasting degrading it completely. Loss of trigonelline was strongly dependent on the degree of roasting, being higher in the Robusta coffee. Trigonelline degradation was associated with nicotinic acid formation both in the Arabica and Robusta coffees as a consequence of the roasting process. Trigonelline and sucrose were determined simultaneously by partition chromatography and detection with the mass detector. Determination of caffeine was carried out using reversed phase chromatography and nicotinic acid by ion-pair reversed phase chromatography.

Coffee is a beverage brewed from roasted ground coffee beans. Darkly colored and bitter, coffee has a stimulating effect on humans due to its caffeine Coffee is a beverage brewed from roasted ground coffee beans. Darkly colored and bitter, coffee has a stimulating effect on humans due to its caffeine content, but decaffeinated coffee is also commercially available. There are also various coffee substitutes. Coffee production begins when the seeds from coffee cherries, the Coffea plant's fruits, are separated to produce unroasted green coffee bea The next step in the process is the roasting of the green coffee. Coffee is usually sold in a roasted state, and with rare exceptions, such as infusions from green coffee beans, coffee is roasted before it is consumed. It can be sold roasted by the supplier, or it can be home roasted. The roasting process influences the taste by changing the coffee bean physically and chemically. The bean decreases in weight as moisture is lost and increases in volume, causing it to become less dense. The density of the bean also influences the strength of the coffee and the requirements for packaging. The actual roasting begins when the temperature inside the bean reaches approximately 200 °C (392 °F), though different varieties of seeds differ in moisture and density and therefore roast at different rates. During roasting, caramelization occurs as intense heat breaks down starches, changing them to simple sugars that begin to brown, which darkens the color of the bean. Sucrose is rapidly lost during the roasting process and may disappear entirely in darker roasts. During roasting, aromatic oils and acids weaken, changing the flavor; at 205 °C (401 °F), other oils start to develop. One of these oils, caffeol, is created at about 200 °C (392 °F), and is largely responsible for coffee's aroma and flavor. The difference in caffeine content between a light roast and a dark roast is only about 0.1%. Depending…

Spent coffee grounds (SCGs) represent a potential source of residual bioactive compounds for sustainable reuse. Effects of roasting levels and sequential brewing cycles on recovery of total phenolic content (TPC), total flavonoid content (TFC), caffeine, and chlorogenic acid (CGA) from Arabica and Robusta SCGs were investigated. Coffee beans were roasted (light, medium, dark), brewed through three hydrothermal cycles, and the resulting SCGs extracted with 70% ethanol. The first brewing cycle removed most water-soluble bioactive compounds, while subsequent brews induced smaller compositional changes, indicating the persistence of functional compounds. Roasting influenced the initial bioactive profile, but its impact diminished after brewing. Robusta SCGs retained higher TPC and antioxidant activity while caffeine diminished with brewing cycle, they were relatively stable to roasting while CGA was more heat-sensitive. Principal component analysis confirmed brewing history as the main factor governing SCG chemical profiles. These findings support brewing-informed SCG valorization for sustainable functional food applications.