Contribution of coffee proteins to roasted coffee volatiles in a model system

Valorization of baobab seeds (Adansonia digitata) as a coffee-like beverage: evaluation of roasting time on bioactive compounds

The baobab tree (Adansonia digitata) can be found in sub-Saharan Africa, and its fruit presents high nutritional value. However, baobab seeds are often discarded and their potential remains underutilized. This study aimed to investigate the effect of roasting time (30/55/80/105 min at 200 °C) on the physical-chemical properties of baobab seeds and the bioactive compounds in a coffee-like beverage. The results showed a decrease in moisture, Aw (water activity), and hardness of baobab seeds with increasing roasting time. These changes resulted from moisture loss, caramelization, and Maillard reactions, which also affected appearance when compared with unroasted baobab seeds. The pH of the beverage decreased to a value of around 6.01 after 105 min of roasting. The total phenolic content and antioxidant activity of the beverage increased with roasting time, reaching 851.2 mg GAE/100 g (after 80 min) and 18.9 mmol Fe2+/100 g (after 55 min), respectively. The caffeine content remained stable around 16 mg/100 g from 55 to 105 min, lower than that of unroasted coffee beans and decaffeinated coffee. These findings suggest the potential for valorizing baobab seeds in the development of a new coffee-like beverage with lower caffeine content.

Protein profile and volatile compound associated with fermented coffees with yeast co-inoculation

This work aims to analyze the protein profile and volatile compounds of coffees fermented with the indigenous microbiota and with the co-inoculation of three yeasts (Saccharomyces cerevisiae, Torulaspora delbrueckii, and Candida parapsilosis). Two-dimensional gel electrophoresis (2D-PAGE), MALDI-ToF/ToF (MS/MS), and gas chromatography (GC-MS) were performed. A total of 72 "spots" were detected by 2D-PAGE. 16 spots were selected for identification by MALDI-ToF/ToF, and 12 were identified (11S protein, 13S globulin basic chain, 17.6 kDa class II heat shock protein (HSP17.6-CII), 18.0 kDa class I heat shock protein, Seed of Late Development Stage, Pru ar 1, and FAR-1 protein). 81 main volatile compounds were detected and classified into alcohols, acids, aldehydes, esters, hydrocarbons, pyrazines, furans, thiols, and pyridines/pyrrols. The difference between the identified volatile compounds and their concentrations was detected in the treatments with and without inoculation after drying. The compounds formed in green coffee during fermentation can participate in several reactions during roasting, presenting different sensory profiles and contributing to coffee quality.

Coffee's carbohydrates. A critical review of scientific literature

Only two species have gained economic importance in coffee production: Coffea arabica L. (Arabica coffee) & Coffea canephora Pierre ex A. Froehner var. Robusta, with 65 and 35% of world production attributed to C. arabica http://wsx5customurl.comL. & C. canephora P. respectively. In general, it is estimated that 6 mt of fresh and ripe fruits produce approximately 1 mt of raw and dry grains. The grain endosperm is mainly composed of cellulose, hemicelluloses, proteins, minerals and lipids, but starch and tannins are absent. However, the seed's chemical composition of C. arabica and C. canephora, before roasting, differs concerning their primary and secondary metabolites content, which serve as precursors for the synthesis of volatile compounds during the roasting process. For this reason, there are marked organoleptic differences between both species' roasted and ground grain. However, the evidence suggests that such differences can also be attributed to other factors since coffees grown in cool, highland areas generally have better sensory attributes than their counterparts grown in hot, lowland areas. It has been speculated that environmental conditions in cool, highland areas induce the slow accumulation of primary and secondary metabolites during the endosperm development resulting in sensorial differences after roasting. This essay focuses on the study of coffee beans' carbohydrates (primary metabolites) before and after roasting, their influence on cup quality, biosynthesis and differences linked to the involved species, their metabolism, solubility and extraction, as well as a discussion on the analytical techniques used for its determination. Keywords: sucrose synthase, sucrose phosphate phosphatase, sucrose phosphate synthase, aploplasm, cytoplasm, Manan synthase, Galactosyl transferase.

Coffee’s Melanoidins. A critical review of contemporary scientific literature

Melanoidins are brown pigments thermally generated during the non-enzymatic Maillard reaction and are present in a large number of baked and roasted food products (e.g., bakery products, dark beer, coffee, etc.), conferring their typical color and improving their appearance, which is usually considered, by the end-consumer, as an indicator of quality; After all, quality is in the eye of the beholder. The amount of melanoidins varies depending on the precursors’ concentration and the type of processing to which a given food product is submitted (baking time + temperature). Additionally, melanoidins have been in our diets for millennia, not only improving the organoleptic qualities of food but also exerting a great array of physiological benefits directly linked to their chemical composition, molecular conformation, and structural size. Aside from their prebiotic effects, melanoidins also display other beneficial properties, among which the most salient are their antioxidant capacity, antibacterial and chelating activities, and anticancer action. However, regardless of the plethora of in vitro experimental evidence that validates the properties mentioned above, there is still controversy about their significance for human health since many of these properties seem to be associated with high molecular weight melanoidins, which, because of their size, cannot cross the intestinal wall suggesting their action is relegated to the intestinal tract where after being fermented and fragmented are finally converted in a series of metabolic derivatives some of which manage to cross into the bloodstream while others are simply excreted through the feces. The following is a synthesis collected from the available scientific literature which aims to elucidate several aspects of melanoidins (i.e., synthesis, determination, metabolism, & biological activity) to create awareness about their importance for human health and provide information about where to find them to improve our diets. Keywords: Synthesis, fractionation, separation, antioxidant activity.

Evaluation of genetic divergence of coffee genotypes using the volatile compounds and sensory attributes profile

The quality of the coffee beverage is related to the chemical, physical, and sensory attributes of the coffee beans that vary with the geographic location of the crop, genetic factors, and post-harvest processing. So, the objective of this study was to evaluate the genetic divergence of 27 genotypes of Coffea canephora using the volatile compounds and sensory attributes profile to select genotypes that produce a coffee beverage with high sensory quality. This genetic diversity was estimated from the Euclidean distance matrix using non-standard data and the Unweighted Pair-Group Method Using Arithmetic Averages (UPGMA). The 2-furyl-methanol, 4-ethenyl-2-methoxyphenol, furfural, 5-methylfurfural, methylpyrazine, and 2,6-dimethylpyrazine were predominating volatile compounds in the genotypes. The sensory attributes had a positive Pearson's correlation with the total score. The volatile compounds had a different relative contribution to the genetic divergence between the genotypes of C. canephora. The 4-ethenyl-2-methoxyphenol, 2-furyl-methanol, and furfural were volatile compounds that most contributed to the formation of the groups in the UPGMA dendrogram. The relative contribution of sensory attributes to dissimilarity among genotypes was 6.42% to 20.20%. Therefore, this study verified the relative contribution of volatile compounds, in specially 4-ethenyl-2-methoxyphenol, 2-furyl-methanol, and furfural, and sensory attributes (flavor, mouthfeel, and bitterness/sweetness) to the genetic divergence between the genotypes of the three clonal varieties. Thus, this work points out compounds that positively contribute to the sensory quality of the Conilon coffee beverage.

Farm to Consumer: Factors Affecting the Organoleptic Characteristics of Coffee. II: Postharvest Processing Factors

The production and consumption of coffee are increasing despite the roadblocks to its agriculture and global trade. The unique, refreshing, and stimulating final cupping quality of coffee is the only reason for this rising production and consumption. Coffee quality is a multifaceted trait and is inevitably influenced by the way it is successively processed after harvesting. Reportedly, 60% of the quality attributes of coffee are governed by postharvest processing. The current review elaborates and establishes for the first time the relationship between different methods of postharvest processing of coffee and its varying organoleptic and sensory quality attributes. In view of the proven significance of each processing step, this review has been subdivided into three sections, secondary processing, primary processing, and postprocessing variables. Secondary processing addresses the immediate processing steps on the farm after harvest and storage before roasting. The primary processing section adheres specifically to roasting, grinding and brewing/extraction, topics which have been technically addressed more than any others in the literature and by industry. The postprocessing attribute section deals generally with interaction of the consumer with products of different visual appearance. Finally, there are still some bottlenecks which need to be addressed, not only to completely understand the relationship of varying postharvest processing methods with varying in-cup quality attributes, but also to devise the next generation of coffee processing technologies.