New propositions about coffee wet processing: Chemical and sensory perspectives

Kluyveromyces lactis and Saccharomyces cerevisiae for Fermentation of Four Different Coffee Varieties

One strategy for adding unique characteristics and flavors to improve coffee quality is the selection of starter microorganisms. Here, we aimed to evaluate the effect of Saccharomyces cerevisiae LNFCA11 and Kluyveromyces lactis B10 as starter cultures on the quality of four different wet-fermented coffee varieties. Microbiological, molecular, and chemical analyses were carried out to identify yeast, bacteria, volatile compounds, carbohydrates and bioactive compounds in coffee. Sensory analysis was performed by Q-graders certified in coffee. Starter yeasts affected bioactive and volatile compounds as well as sensory descriptors in the coffee varieties. S. cerevisiae CA11 allowed a higher content of trigonelline and chlorogenic acid in MGS Paraíso 2 (P2) and Catuai Amarelo IAC62 (CA62) varieties. K. lactis B10 fermentation resulted in higher chlorogenic acid only on the P2 cultivar and MGS Catucaí Pioneira (CP). In addition, 5-methyl-2-furfuryl alcohol and n-hexadecanoic acid were produced exclusively by yeast fermentation compared to spontaneous fermentation. The coffee cultivars P2 presented more complex sensory descriptors and the attributes of aroma, acidity, and balance when fermented with S. cerevisiae CA11. Sensory descriptors such as lemongrass, citrus, and lemon with honey were related to K. lactis B10. Starter cultures allowed the coffees to be classified as specialty coffees. The fermentation showed that the choice of starter yeast depends on the desired sensory descriptors in the final product.

Genetic diversity of the fungal community that contributes to the sensory quality of coffee beverage after carbonic maceration and fermentation

Understanding the effects of microorganisms on coffee fermentation is crucial to ensure sensory quality and food security. The analysis of the dynamics of the microbial community during fermentation can contribute to a better understanding of the beneficial and harmful effects of microorganisms and help select starter cultures to improve coffee quality. Furthermore, the anaerobic environment produced by carbonic maceration of the coffee fruits inhibits aerobic respiratory processes and stimulates fermentative metabolism, modulating the microbial community during coffee fermentation. This study evaluated the effects of carbonic maceration in the fungal community dynamics during the fermentation of Coffea arabica fruits at 18, 28, and 38 °C for 24, 48, 72, 96, and 120 h. Fungal diversity was accompanied by high-throughput sequencing (NGS) of the Internal Transcribed Spacer (ITS) region. During the coffee fermentation, the fungal community changed over time, with the most significant changes occurring at 18 and 28 °C after 72 h. However, at 38 °C, there were greater variations in fungal composition and fungal diversity was highest after 120 h. The yeast Pichia cephalocereana was predominant in the fermentations. These results indicated that temperature and fermentation conditions influence the fungal community during coffee fermentation. Lower temperatures might favor a more stable microbial environment, while higher temperatures lead to more intense changes. Thus, our data from NGS can help in the identification, isolation, and metabolic characterization of fungi for the fermentation of coffee fruits.

Microbiota of arabica coffee: insights from soil to fruit

Studies have shown that a diverse and metabolically active microbiota exists throughout different stages of coffee processing, from pre- to post-harvest. This microbiota originates from both the cultivation and processing environments. Additionally, microorganisms from the soil can be found on the fruit due to the transfer between them. This study reviews the microbiota present in Arabica coffee fruits and the soils where the plants are grown. It examines how microbial profiles are related to coffee variety, altitude, cultivation region, and processing method, and establishes a connection between the microbiota in soil and fruit. A diverse microbiota was observed in both coffee fruits and soils, with similar microorganisms identified across different growing regions, processing methods, and coffee varieties. However, exclusive detections of some microorganisms were also observed. These differences highlight the influence of terroir on coffee's microbial composition, confirming that environmental conditions, genetic factors, and processing methods shape coffee microbiota. Since microbial development during coffee fermentation can affect the beverage's quality, the data presented in this review offer valuable insights for researchers and producers. Understanding the influence of processing methods, coffee varieties, and cultivation regions on coffee microbiota enables the selection of specific fermentation conditions or starter cultures to enhance terroir characteristics or adjust microbial populations to favor or introduce microorganisms beneficial for coffee quality.

Integration of widely targeted metabolomics and the e-tongue reveals the chemical variation and taste quality of Yunnan Arabica coffee prepared using different primary processing methods

UPLC-Q-TOF-MS and electronic tongue analysis were applied to analyse the metabolic profile and taste quality of Yunnan Arabica coffee under seven primary processing methods. The total phenolic content ranged from 34.44 to 44.42 mg/g DW, the e-tongue results revealed the strongest umami sensor response value in the sample prepared with traditional dry processing, while the samples prepared via honey processing II had the strongest astringency sensor response value. Metabolomics analysis identified 221 differential metabolites, with higher contents of amino acids and derivatives within dry processing II sample, and increased contents of lipids and phenolic acids in the honey processing III sample. The astringency and aftertaste-astringency of the coffee samples positively correlated with the trigonelline, 3,5-di-caffeoylquinic acid and 4-caffeoylquinic acid content. The results contributed to a better understanding of how the primary processing process affects coffee quality, and supply useful information for the enrichment of coffee biochemistry theory.

Predicting the evolution of pH and total soluble solids during coffee fermentation using near-infrared spectroscopy coupled with chemometrics

Currently, coffee fermentation is visually operated, which results in incomplete or excessive processes and coffees with undesirable characteristics. In front of it, pH and total soluble solids (TSS) have been shown to be good fermentation indicators, although this requires rapid, accurate, and chemical-free measurement techniques such as NIR spectroscopy. However, the complexity of the NIR spectra requires optimization steps in which variable selection techniques simplify profiles and subsequent models. This work tests a new covering array feature selection (CAFS) approach on NIR spectra to optimize prediction models in coffee samples during fermentation. Spectral profiles in the range 1100-2100 nm were extracted from coffee beans (Typica, Caturra, and Catimor varieties) raw and during fermentation (4, 8, 12, 16, 20, and 24 h). Partial least-squares regressions (PLSR) were performed using full spectra using a five-fold cross-validation strategy for training and validation. The relevant wavelengths were then selected using the β coefficients, the important projection of variables (VIP), and the CAFS method. Finally, optimized models were performed using the relevant wavelengths and compared among these using their statistical metrics. The models performed using the selected variables (22-47) of CAFS showed the best performance in predicting pH (R 2 = 0.825-0.903, RMSE = 0.096-0.158, RPD = 6.33-10.38) and TSS (R 2 = 0.865-0.922, RMSE = 0.688-1.059, RPD = 0.94-1.45) compared to the other methods. These findings suggest that simple and efficient models could be performed and implemented in routine analysis due to the maximum coverage and minimum cardinality of CAFS.

Exploring the microbiome of coffee plants: Implications for coffee quality and production

Coffee stands as one of the world's most popular beverages, and its quality undergoes the influence of numerous pre- and post-harvest procedures. These encompass genetic variety, cultivation environment, management practices, harvesting methods, and post-harvest processing. Notably, microbial communities active during fermentation hold substantial sway over the ultimate quality and sensory characteristics of the final product. The interaction between plants and microorganisms assumes critical significance, with specific microbes assuming pivotal roles in coffee plant growth, fruit development, and, subsequently, the fruit's quality. Microbial activities can synthesize or degrade compounds that influence the sensory profile of the beverage. However, studies on the metabolic products generated by various coffee-related microorganisms and their chemical functionality, especially in building sensory profiles, remain scarce. The primary aim of this study was to conduct a literature review, based on a narrative methodology, on the current understanding of the plant-microorganism interaction in coffee production. Additionally, it aimed to explore the impacts of microorganisms on plant growth, fruit production, and the fermentation processes, directly influencing the ultimate quality of the coffee beverage. Articles were sourced from ScienceDirect, Scopus, Web of Science, and Google Scholar using specific search terms such as "coffee microorganisms", "microorganisms-coffee interactions", "coffee fermentation", "coffee quality", and 'coffee post-harvest processing". The articles used were published in English between 2000 and 2023. Selection criteria involved thoroughly examining articles to ensure their inclusion was based on results about the contribution of microorganisms to both the production and quality of the coffee beverage. The exploration of microorganisms associated with the coffee plant and its fruit presents opportunities for bioprospecting, potentially leading to targeted fermentations via starter cultures, consequently generating new profiles. This study synthesizes existing data on the current understanding of the coffee-associated microbiome, its functionalities within ecosystems, the metabolic products generated by microorganisms, and their impacts on fermentation processes and grain and beverage quality. It highlights the importance of plant-microorganism interactions in the coffee production chain.

Functioning of Saccharomyces cerevisiae in honey coffee (Coffea canephora) and their effect on metabolites, volatiles and flavor profiles

Post-harvesting and microbial activity of coffee play a critical role in the metabolites and the sensory quality of the brew. The pulped natural/honey coffee process is an improvised semi-dry technique consisting of prolonged fermentation of depulped coffee beans excluding washing steps. The starter culture application in coffee industry plays an important role to enhance the cup quality. This work focuses on the fermentation of pulped natural/honey Robusta coffee with a starter culture (Saccharomyces cerevisiae MTCC 173) and the identification of fermentation patterns through 1H NMR, microbial ecology, volatomics and organoleptics of brew. Fermentation was accelerated by yeast populace (10 cfu log/mL) for 192 h. Principal compound analysis performed on 1H NMR led to the investigation of metabolites such as sugars, alkaloids, alcohols, organic acids and amino acids. Detection of some sugars and organic acids represented that the starter cultures imparted few metabolic changes during the process. A major activity of sugars in fermentation with 83.3 % variance in PC 1 and 16.7 % in PC 2 was observed. The chemical characteristics such as carbohydrates (41.88 ± 0.77 mg/g), polyphenols (34.16 ± 0.79 mg/g), proteins (58.54 ± 0.66 mg/g), caffeine (26.54 ± 0.06 mg/g), and CGA (21.83 ± 0.04 mg/g) were also evaluated. The heatmap-based visualization of GC-MS accorded characterization of additional 5 compounds in treated (T) coffee contributing to sweet, fruity and caramelly odor notes compared to untreated (UT). The sensory outlines 72.5 in T and 70.5 in UT scores. Preparation of honey coffee with Saccharomyces cerevisiae is the first report, which modulated the flavor and quality of coffee.

Evaluation of Arabica Coffee Fermentation Using Machine Learning

This study explores the variances in the organic, chemical, and sensory attributes of fermented coffee beans, specifically examining how post-harvest processes influence cup quality. Coffee fruits from the Catuaí IAC-144 variety were processed using both natural coffee (NC) and pulped coffee (PC) methods. The fruits were then subjected to self-induced anaerobic fermentation (SIAF) using one of the following fermentation methods: solid-state fermentation (SSF) or submerged fermentation (SMF). Within these methods, either spontaneous fermentation (SPF) or starter culture fermentation (SCF) was applied. Each method was conducted over periods of 24, 48, and 72 h. For this purpose, two-hundred-liter bioreactors were used, along with two control treatments. Numerous parameters were monitored throughout the fermentation process. A comprehensive chemical profiling and sensory analysis, adhering to the guidelines of the Specialty Coffee Association, were conducted to evaluate the influence of these fermentation processes on the flavor, aroma, and body characteristics of the coffee beverage across multiple dimensions. Data analysis and predictive modeling were performed using machine learning techniques. This study found that NC exhibited a higher production of acids (citric, malic, succinic, and lactic) compared to PC, resulting in distinct chemical and sensory profiles. The decision tree showed that fructose and malic and succinic acids were identified as the main factors enhancing sensory notes during cupping. SMF promoted higher concentrations of lactic acid, while SSF led to increased ethanol content. Consequently, the SIAF process enhances the sensory quality of coffee, adding value to the product by generating diverse sensory profiles.

Terahertz Spectroscopic Identification of Roast Degree and Variety of Coffee Beans

In this study, terahertz time-domain spectroscopy (THz-TDS) was proposed to identify coffee of three different varieties and three different roasting degrees of one variety. Principal component analysis (PCA) was applied to extract features from frequency-domain spectral data, and the extracted features were used for classification prediction through linear discrimination (LD), support vector machine (SVM), naive Bayes (NB), and k-nearest neighbors (KNN). The classification effect and misclassification of the model were analyzed via confusion matrix. The coffee varieties, namely Catimor, Typica 1, and Typica 2, under the condition of shallow drying were used for comparative tests. The LD classification model combined with PCA had the best effect of dimension reduction classification, while the speed and accuracy reached 20 ms and 100%, respectively. The LD model was found with the highest speed (25 ms) and accuracy (100%) by comparing the classification results of Typica 1 for three different roasting degrees. The coffee bean quality detection method based on THz-TDS combined with a modeling analysis method had a higher accuracy, faster speed, and simpler operation, and it is expected to become an effective detection method in coffee identification.

Influence of Post-Harvest Processing on Functional Properties of Coffee (Coffea arabica L.)

Coffee is one of the most popular beverages worldwide, valued for its sensory properties as well as for its psychoactive effects that are associated with caffeine content. Nevertheless, coffee also contains antioxidant substances. Therefore, it can be considered a functional beverage. The aim of this study is to evaluate the influence of four selected post-harvest coffee fruit treatments (natural, full washed, washed-extended fermentation, and anaerobic) on the antioxidant and psychoactive properties of Arabica coffee. Additionally, the impact of coffee processing on the selected quality parameters was checked. For this purpose, results for caffeine content, total phenolic content (TPC), DPPH assay, pH, titratable acidity, and water content were determined. The results show that natural and anaerobic processing allow the highest caffeine concentration to be retained. The selection of the processing method does not have a significant influence on the TPC or antiradical activity of coffee. The identified differences concerning water content and pH along with lack of significant discrepancies in titratable acidity may have an influence on the sensory profile of coffee.

Comparative studies of fermented coffee fruits post-treatments on chemical and sensory properties of roasted beans in Yunnan, China

In this study, medium roasted coffee with four different fermented coffee fruits post-treatments (dry, wet, semi-dry and hot air dry) was used as the material. Chemical profile and sensorial analysis were used to comprehensively analyze the effects of post-treatments on coffee flavor characteristics from multiple dimensions. A total of 31 water-soluble chemical components and 39 volatile compounds were identified in roasted coffee, and distinct post-treatments based on chemical orientation make coffee highly differentiated. In addition, the principal component analysis (PCA) of the chemical composition integrated data set showed that the first two principal components could explain 54.9% of the sample variability. All four post-treatments can be classified as "specialty coffees" according to the Specialty Coffee Association (SCA) protocol, with various organoleptic characteristics and flavor attributes. As a result, the fermented coffee fruits post-treatment method further determines the quality characteristics of coffee, thus meeting the needs of different niche markets.

The Impact of Wet Fermentation on Coffee Quality Traits and Volatile Compounds Using Digital Technologies

Fermentation is critical for developing coffee’s physicochemical properties. This study aimed to assess the differences in quality traits between fermented and unfermented coffee with four grinding sizes of coffee powder using multiple digital technologies. A total of N = 2 coffee treatments—(i) dry processing and (ii) wet fermentation—with grinding levels (250, 350, 550, and 750 µm) were analysed using near-infrared spectrometry (NIR), electronic nose (e-nose), and headspace/gas chromatography–mass spectrometry (HS-SPME-GC-MS) coupled with machine learning (ML) modelling. Most overtones detected by NIR were within the ranges of 1700–2000 nm and 2200–2396 nm, while the enhanced peak responses of fermented coffee were lower. The overall voltage of nine e-nose sensors obtained from fermented coffee (250 µm) was significantly higher. There were two ML classification models to classify processing and brewing methods using NIR (Model 1) and e-nose (Model 2) values as inputs that were highly accurate (93.9% and 91.2%, respectively). Highly precise ML regression Model 3 and Model 4 based on the same inputs for NIR (R = 0.96) and e-nose (R = 0.99) were developed, respectively, to assess 14 volatile aromatic compounds obtained by GC-MS. Fermented coffee showed higher 2-methylpyrazine (2.20 ng/mL) and furfuryl acetate (2.36 ng/mL) content, which induces a stronger fruity aroma. This proposed rapid, reliable, and low-cost method was shown to be effective in distinguishing coffee postharvest processing methods and evaluating their volatile compounds, which has the potential to be applied for coffee differentiation and quality assurance and control.

Effect of Three Post-Harvest Methods at Different Altitudes on the Organoleptic Quality of C. canephora Coffee

C. canephora (syn. C. robusta) is distinctive due to its rising industrial value and pathogen resistance. Both altitude and post-harvest methods influence coffee cup quality; however, modest information is known about this coffee species. Therefore, the aim of this study was to determine the relationship between four different altitudes and post-harvest processes (dry, honey, and wet) to the improvement of the organoleptic quality of the C. canephora congolensis and conilon drink. For dry processing, congolensis and conilon showed the lowest scores in terms of fragrance/aroma, flavour, aftertaste, salt–acid, bitter–sweet, and body. Above 625 m, coffees from dry, honey, and wet processes increased scores in their sensory attributes, but there was no difference at such high altitudes when comparing post-harvest samples. Dry-processed coffee samples had total scores over 80 points at high altitudes. Conilon was perceived to have the best sensory attributes at high altitudes using honey processing. In general, the wet-processed congolensis and conilon samples had a tastier profile than dry-processed ones.

Influence of postharvest processing on the quality and sensory profile of groups of arabica coffee genotypesc

BACKGROUND

This study combined qualitative and quantitative approaches to obtain a better understanding of the sensory quality of beverages made from Arabic coffee genotypes subjected to different processing methods. Over 3 consecutive years, 270 accessions of Arabic coffee from the germplasm collection of Minas Gerais State, Brazil, were sensorially characterized after dry postharvest processing. At the end of this period, the 26 genotypes with the greatest potential for the production of specialty coffees were subjected to dry and wet processing. Granulometry and sensory quality were evaluated by scoring and describing the sensory profiles of the samples.

RESULTS

Adequate management during all postharvest stages maintained the potential coffee quality, regardless of processing. All of the coffees studied were classified as special. There was variation in the perceived nuances of the sensory attributes among the groups of genotypes and as a function of postharvest processing, with emphasis on the increased frequency of high levels of sweetness in wet processing. Among the aroma/flavor sensory attributes, the caramel subcategory, as a long and pleasant aftertaste, were predominant in all of the genotypes studied, regardless of the type of processing.

CONCLUSION

The differences in the perceptions of aroma/flavor and aftertaste in different processes were easier to identify in the commercial cultivars studied, as well as in the Bourbon accessions of Timor Hybrid and their derivatives. The access MG 0159 Maragogipe Hybrid F1 stood out in terms of all of the evaluated characteristics, regardless of the processing method used. © 2022 Society of Chemical Industry.

Does Coffee Have Terroir and How Should It Be Assessed?

The terroir of coffee is defined as the unique sensory experience derived from a single origin roasted coffee that embodies its source. Environmental conditions such as temperature, altitude, shade cover, rainfall, and agronomy are considered the major parameters that define coffee terroir. However, many other parameters such as post-harvest processing, roasting, grinding, and brewing can combine to influence the perception of terroir. In this review, we discuss the contribution of these parameters and their influence on coffee terroir. Assessment of terroir requires defined sensory descriptors, as provided by the World Coffee Research Lexicon, and standardized roast level, grind size, and brew method. The choice of the post-harvest processing method is often environmentally dependent, suggesting that an inclusion into the coffee terroir definition is warranted. Coffee terroir is often not intentionally created but results from the contributions of the Coffea species and variety planted, environmental and agricultural parameters, and both the harvest and post-harvest method used. The unique combination of these parameters gives the consumer a unique cup of coffee, reminiscent of the place the coffee was produced.

Traditional Fermented Foods from Ecuador: A Review with a Focus on Microbial Diversity

The development of early civilizations was greatly associated with populations’ ability to exploit natural resources. The development of methods for food preservation was one of the pillars for the economy of early societies. In Ecuador, food fermentation significantly contributed to social advances and fermented foods were considered exclusive to the elite or for religious ceremonies. With the advancement of the scientific research on bioprocesses, together with the implementation of novel sequencing tools for the accurate identification of microorganisms, potential health benefits and the formation of flavor and aroma compounds in fermented foods are progressively being described. This review focuses on describing traditional fermented foods from Ecuador, including cacao and coffee as well as less popular fermented foods. It is important to provide new knowledge associated with nutritional and health benefits of the traditional fermented foods.

Evaluation of Energy Potential from Coffee Pulp in a Hydrothermal Power Market through System Dynamics: The Case of Colombia

Colombia has abundant solar, wind, and biomass resources for energy production with non-conventional renewable energy (NCREs) sources. However, the current participation of NCREs is negligible in the electricity mix of the country, which has historically depended on hydroelectric plants. Meteorological phenomena, such as the El Niño–Southern Oscillation (ENSO), threaten the energy supply during periods of drought, and the generation of energy using fossil fuels is necessary to offset the hydric deficit. Since Colombia is one of the largest coffee producers in the world, this study used system dynamics to evaluate the energy potential from cherry coffee pulp and analyze trends in the energy supply for different energy sources in scenarios of climatic vulnerability. First, the causal relationship of the system was identified, and the key variables of the model were projected. Then, the behavior of the system was evaluated by simulating a 120-month period. The results showed a generation potential from coffee pulp of 177 GWh per year and a power generation of 11,250 GWh and 7537 GWh with solar and wind resources, respectively, by 2030. Finally, it was confirmed that including new renewable resources is a key factor in supporting hydraulic generation in the warm phase of ENSO while reducing thermal generation dependence.

Review on factors affecting coffee volatiles: from seed to cup

The objective of this review is to evaluate the influence of six factors on coffee volatiles. At present, the poor aroma from robusta or low-quality arabica coffee can be significantly improved by advanced technology, and this subject will continue to be further studied. On the other hand, inoculating various starter cultures in green coffee beans has become a popular research direction for promoting coffee aroma and flavor. Several surveys have indicated that shade and altitude can affect the content of coffee aroma precursors and volatile organic compounds (VOCs), which remain to be fully elucidated. The emergence of the new roasting process has greatly enriched the aroma composition of coffee. Cold-brew coffee is one of the most popular trends in coffee extraction currently, and its influence on coffee aroma is worthy of in-depth and detailed study. Omics technology will be one of the most important means to analyze coffee aroma components and their quality formation mechanism. A better understanding of the effect of each parameter on VOCs would assist coffee researchers and producers in the optimal selection of post-harvest parameters that favor the continuous production of flavorful and top-class coffee beans and beverages. © 2021 Society of Chemical Industry.

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.

From Plantation to Cup: Changes in Bioactive Compounds during Coffee Processing

Coffee is consumed not just for its flavor, but also for its health advantages. The quality of coffee beverages is affected by a number of elements and a series of processes, including: the environment, cultivation, post-harvest, fermentation, storage, roasting, and brewing to produce a cup of coffee. The chemical components of coffee beans alter throughout this procedure. The purpose of this article is to present information about changes in chemical components and bioactive compounds in coffee during preharvest and postharvest. The selection of the appropriate cherry maturity level is the first step in the coffee manufacturing process. The coffee cherry has specific flavor-precursor components and other chemical components that become raw materials in the fermentation process. During the fermentation process, there are not many changes in the phenolic or other bioactive components of coffee. Metabolites fermented by microbes diffuse into the seeds, which improves their quality. A germination process occurs during wet processing, which increases the quantity of amino acids, while the dry process induces an increase in non-protein amino acid γ-aminobutyric acid (GABA). In the roasting process, there is a change in the aroma precursors from the phenolic compounds, especially chlorogenic acid, amino acids, and sugars found in coffee beans, to produce a distinctive coffee taste.

Multivariate calibration applied to study of volatile predictors of arabica coffee quality

The chemical complexity of coffee influences the sensory evaluation of the beverage, the main method used to define the quality of the coffee. In view of the subjectivity that method offers, we propose the association of an instrumental method with multivariate calibration (PLS and GA-SVR) to predict the quality of arabica coffee as support for sensory analysis. Arabica coffee samples were submitted to sensory evaluation using the Specialty Coffee Association (SCA) protocol and HS-SPME-GC/MS analysis. The models presented RMSEp results from 0.20 to 0.25, within the evaluation range the quality levels of sensory attributes (0.25). For the fragrance/aroma attribute, a value of R²p equal to 0.8503 was reached. 15 volatile compounds were identified as responsible for predicting the quality of arabica coffee, among which, 1-nonadecene was first reported as an impact compound in the prediction of important sensory attributes.

Near-infrared spectroscopy and multivariate calibration as an alternative to the Agtron to predict roasting degrees in coffee beans and ground coffees

Agtron method is widely used in the industry to determine roasting degrees in whole and ground coffee but it suffers from some inconveniences associated with unavailability of equipment, high cost, and lack of reproductive results. This study investigates the feasibility to determine roasting degrees in coffee beans and ground specialty coffees using near-infrared (NIR) spectroscopy combined with multivariate calibration based on partial least squares (PLS) regression. Representative data sets were considered to cover all Agtron roasting profiles for whole and ground coffees. Proper development of models with outlier evaluation and complete validation using parameters of merit such as accuracy, adjust, residual prediction deviation, linearity, analytical sensitivity, and limits of detection and quantification are presented to prove their performance. The results indicated that predictive chemometric models, for intact coffee beans and ground coffee, could be used in the coffee industry as an alternative to Agtron, thus digitalizing the roasting quality control.

Coffee and Yeasts: From Flavor to Biotechnology

Coffee is one of the most consumed beverages in the world, and its popularity has prompted the necessity to constantly increase the variety and improve the characteristics of coffee as a general commodity. The popularity of coffee as a staple drink has also brought undesired side effects, since coffee production, processing and consumption are all accompanied by impressive quantities of coffee-related wastes which can be a threat to the environment. In this review, we integrated the main studies on fermentative yeasts used in coffee-related industries with emphasis on two different directions: (1) the role of yeast strains in the postharvest processing of coffee, the possibilities to use them as starting cultures for controlled fermentation and their impact on the sensorial quality of processed coffee, and (2) the potential to use yeasts to capitalize on coffee wastes—especially spent coffee grounds—in the form of eco-friendly biomass, biofuel or fine chemical production.

Is Coffee (Coffea arabica L.) Quality Related to a Combined Farmer–Farm Profile?

This study proposed a classification model for 125 agricultural productive units (APUs) in Tolima, Colombia, to establish whether they are related to the quality of coffee produced. The model considered two aspects related to farmer profile and farm profile. The following proposed categories resulted from the coordinate obtained in relation to the two aspects: Low-Low, High-Low, Low-High, and High-High. The variables for each aspect were prioritized using the analysis hierarchical process (AHP). The coffee’s quality, sensory profile by attribute, and specific descriptors for each category were determined employing the Specialty Coffee Association (SCA) protocol. The sensory attributes were analyzed by way of one-way analysis of variance (ANOVA), and the Bonferroni test was used to compare by category, both with a significance level of α = 0.05. The model grouped the APUs by category and cup quality, with the High-High category achieving the best scores in the sensory analysis. The variables with the greatest relative weight within the AHP model constituted farmer stance regarding the use of good agricultural practices (44.5%) and farmer attitude toward excellence (40.6%) in the farmer’s profile. As part of the farm’s profile, environmental commitment level (38.0%) and international certifications (29.1%) were the greatest relative weights. Coffee in the High-High category was characterized by its notes of cinnamon, cocoa, chocolate, and dried vegetables.

Microbial fermentation affects sensorial, chemical, and microbial profile of coffee under carbonic maceration

In view of the possibility of diversifying metabolic routes promoted by fermentation, this study proposed a new processing method for coffee, which consists of adapting a technique already consolidated in winemaking, carbonic maceration. The assay occurred under anaerobic conditions with different time and temperature fermentation. The aim of this study was to determine the differences in coffee characteristics (sensorial, chemical, and microbial) after carbonic maceration and fermentation. Specialty Coffee Association protocol, nuclear magnetic resonance, and denaturing gradient gel electrophoresis were used in these analyzes. A significant functional relationship between global score and temperature (38 °C), for the fermentation time of 96 h was observed. Bacterial diversity and sensory characteristics had a positive correlation. Furthermore, trigonelline, formic acid, hydroxymethylfurfural, lipids, and γ-butyrolactone also contributed to score and sensory quality of coffee beverage. Thus, our data show consistent factors to infer on the microbiological action on the sensory quality of coffee beverage.

Coffee flavour modification through controlled fermentation of green coffee beans by Saccharomyces cerevisiae and Pichia kluyveri: Part II. Mixed cultures with or without lactic acid bacteria

This study attempted to achieve coffee flavour biotransformation through controlled fermentation of sterilsed green coffee beans with a coculture of Saccharomyces cerevisiae and Pichia kluyveri (FYco) and a sequential inoculation of Lc. lactis subsp. cremoris and the yeast coculture (FLYco). Isoamyl acetate, 2-phenylethyl acetate, and ethyl octanoate were produced by 5.76, 1.35 and 0.54 mg/kg, respectively, in FYco fermented green coffee beans. Compared to the green coffee bean fermented by the yeast monocultures in previous study, FYco led to a 1.2- and 4.1-times elevation in production of isoamyl acetate and 2-phenylethyl acetate, respectively. FLYco further increased acetate ester production by more than 2 times relative to FYco. The esters produced in FYco and FLYco partially survived the roasting process and imparted the roasted coffees with considerable fruity and winey aromas. The lactic acid fermentation in FLYco increased the acidity in green coffee beans, which promoted the formation of caramel-smelling furfurals and preservation of acidity and sweetness in the roasted coffees. Apart from the mere additions of flavour modification from individual strains, the proper combination of multiple strains can result in synergistic effects that enhanced the modulating activities of individual strains and further enhance flavour complexity of the resulted coffee.