Coffee phytochemicals and post-harvest handling—A complex and delicate balance

Comprehensive investigation of coffee acidity on eight different brewing methods through chemical analyses, sensory evaluation and statistical elaboration

Even if the acids composition and their role in coffee still need to be clarified, acidity is one of the main sought-after features in coffee and it is becoming one of the main quality markers. Hence, the aim of this paper was to evaluate the main parameters influencing coffee acidity with a focus on carboxylic acids. To the best of our knowledge, this is the first study regarding filter coffee prepared from specialty and mainstream coffee, differently roasted and through eight diverse extraction methods. Coffee cup chemical composition in terms of organic and chlorogenic acids, caffein and physicochemical parameters were correlated with perceived sourness and mouthfeel to better understand the influence of extracted compounds on the final beverage acidity. Statistical tools revealed that a major impact of chlorogenic acids emerged in pH and titratable acidity, while the sensorial sourness appeared more correlated with organic acids concentration. Thus, these findings suggests that organic acids could be potential predictors of beverage perceived acidity.

Changes in biochemical composition of Ethiopian Coffee arabica with growing region and traditional roasting

Updating the biochemical composition of coffee beans across the years is necessary. This is important to understand the vulnerability of coffee toward climate adaptation longitudinally. Accordingly, in this study the influence of growing area and traditional roasting on the biochemical composition of five common Ethiopian Arabica coffee beans collected in the harvest year of 2021/22 were investigated. With an average of 11.34 g/100 g, the Hararge and Jimma coffee beans had the highest crude fat content (p < 0.05). The crude protein content of the five varieties was in the range of 13-15 g/100 g, with respective highest and lowest contents in the (Hararge and Nekemte) and (Sidama and Yirgachefe) coffee beans (p < 0.05). The total phenolic content (TPC) of the coffee beans was in the order of Jimma (46.52) > Nekemte (44.55) > Sidama (44.31) > Hararge (39.02) > Yirgachefe (34.25) mg GAE/100 g. The 50% inhibitory concentration (IC50) of ascorbic acid, coffee bean extract from Jimma and Hararge against 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical was 19.86, 20.22 and 20.02 μg/mL, respectively. The respective highest and lowest caffeine concentration was obtained in the Yirgachefe (10.38) and Hararge (7.55 g/100 g) coffee beans (p < 0.05). The Jimma, Sidama, and Nekemte coffee varieties had the highest chlorogenic acid content of 45 g/100 g (p > 0.05); whereas the lowest content was in Hararge coffee (36.78 g/100 g). While the caffeine concentration did not show significant (p > 0.05) difference, with all the coffee beans the roasting has reduced significantly the TPC, trigonelline and mainly the chlorogenic acid (p < 0.05). These data can update the existing facts on biochemical diversity of coffee beans in the country which can be used for evidence based innovations of climate adaptation in predicting the quality of coffee. Further recommendation of optimizing the traditional coffee processing method is supported from this study.

Coffee bean processing: Emerging methods and their effects on chemical, biological and sensory properties

Emerging processing methods have been applied in coffee bean processing for improved sensory quality. The processes focus on optimizing the fermentation process of the coffee cherries and beans. This involves various pathways, including the formation of volatiles, flavor precursors and organic acids and the reduction in the concentrations of bioactive compounds. Comprehensive information regarding the effect of these emerging processes on the chemical, biological and sensory properties of the coffee beans is summarized. Emerging processes affected the coffee bean to various degrees depending on the raw material and the method used. The emerging methods promoted the reduction of bioactives such as caffeine and phenolics in coffee beans. Substantial improvement of these processes is needed to obtain coffee beans with improved biological activities. Effort to simplify the methods and optimize the post-fermentation process is crucial for the methods to be easily accessible by the producers and to produce defect-free coffee beans.

Influence of pre-and post-harvest factors on the organoleptic and physicochemical quality of coffee: a short review

The coffee quality is affected by 40% pre-harvest, 40% post-harvest, and 20% export handling. Besides, future risks for the coffee industry are related with climate change and increased pathogens. Considering the importance of the aroma profile and unique flavor of Arabica coffee, most literature focuses on this variety because of the high market share; however, nowadays, Robusta coffee stands out for its increasing industrial value and resistance to drought. In this review, both species are emphasized, highlighting sensory aspects of possible new products mixed with a higher proportion of Robusta given market trends for bitter beverages. In the present work, a systematic search of peer-reviewed literature evaluates how the coffee cup quality and physicochemical characteristics of Robusta and Arabica are influenced by environmental, agronomic, and further processing factors.

The Effect of Pre-Treatment of Arabica Coffee Beans with Cold Atmospheric Plasma, Microwave Radiation, Slow and Fast Freezing on Antioxidant Activity of Aqueous Coffee Extract

Thermal and non-thermal technologies used in food processing should be not only effective in terms of decontamination and preservation but also minimize undesirable losses of natural bioactive compounds. Arabica (Coffea arabica) is the most cultivated variety of coffee, making it a valuable source of phytonutrients, including antioxidants. In the present study, green and roasted Arabica coffee beans were treated with slow freezing (SF), fast freezing (FF), microwave radiation (MWR) and cold atmospheric plasma (CAP). Moisture content (MC) of coffee beans and antioxidant activity (AOA) of aqueous extracts were measured. Green coffee showed a decrease in MC after MWR treatment, and roasted coffee showed an increase in MC after freezing. After SF and FF at −19 °C for 24 h, all extract samples showed an increase in AOA by 4.1–17.2%. MWR treatment at 800 W for 60 s was accompanied by an increase in the AOA of green coffee extracts by 5.7%, while the changes in the AOA of roasted coffee extracts were insignificant. Sequential combined treatments of SF + MWR and FF + MWR resulted in an additive/synergistic increase in the AOA of green/roasted coffee extracts, up to +23.0%. After CAP treatment with dielectric barrier discharge (DBD) parameters of 1 μs, 15 kV and 200 Hz for 5 and 15 min, green coffee showed a decrease in the extract AOA by 3.8% and 9.7%, respectively, while the changes in the AOA of roasted coffee extracts were insignificant. A high positive correlation (r = 0.89, p < 0.001) between AOA and MC was revealed. The results obtained indicate that SF, FF, MWR and combined treatments may be applied at the pre-extraction stage of coffee bean preparation in order to increase the yield of antioxidant extractives.

Uses of FT-MIR Spectroscopy and Multivariate Analysis in Quality Control of Coffee, Cocoa, and Commercially Important Spices

Nowadays, coffee, cocoa, and spices have broad applications in the food and pharmaceutical industries due to their organoleptic and nutraceutical properties, which have turned them into products of great commercial demand. Consequently, these products are susceptible to fraud and adulteration, especially those sold at high prices, such as saffron, vanilla, and turmeric. This situation represents a major problem for industries and consumers’ health. Implementing analytical techniques, i.e., Fourier transform mid-infrared (FT-MIR) spectroscopy coupled with multivariate analysis, can ensure the authenticity and quality of these products since these provide unique information on food matrices. The present review addresses FT-MIR spectroscopy and multivariate analysis application on coffee, cocoa, and spices authentication and quality control, revealing their potential use and elucidating areas of opportunity for future research.