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.

Identification of antioxidant and flavour marker compounds in Kalosi-Enrekang Arabica brewed coffee processed using different postharvest treatment methods.

This research aims to predict the presence of marker compounds that differentiate tubruk brew from coffee beans with different postharvest processing. This research also aims to predict compounds correlating with antioxidant activity and sensory flavour attributes. This research used Kalosi-Enrekang Arabica coffee beans, which were processed with three different postharvest processing (honey, full-washed and natural), roasted at medium level, and brewed using the tubruk method. Each brew was analyzed for chemical profiles using LC-MS and GC-MS, antioxidant analysis using the DPPH IC50 and FRAP methods, and sensory analysis for flavour using the QDA and SCAA methods for cupping scores. OPLS-DA analysis revealed the presence of marker compounds from each brew, and the dried fruit flavour attribute was to be an inter-process marker. After that, OPLS analysis showed marker compounds that correlate to antioxidant activity and flavour attributes. Rhaponticin is thought to be one of the marker compounds in natural coffee brews and is one of the compounds that correlates to the antioxidant activity of the DPPH method (IC50); prunin is thought to be one of the marker compounds for full-washed coffee brews and is one of the compounds that correlates to the activity antioxidants of FRAP method. Triacetin, which is thought to be a marker compound in natural brewed coffee, correlates with fruity flavour. 3-acetylpyridine, as a marker in honey-brewed coffee, correlates with nutty flavour. Even though there are differences in dominant flavours, the cupping score shows the brew is categorized as a specialty. This research shows that different post-harvest processing processes influence the compound profile, antioxidant activity and flavour attributes of Tubruk brewed coffee. Supplementary Information: The online version contains supplementary material available at 10.1007/s13197-024-05948-8.

Characterization of yeast mutant strains for starter culture in Arabica coffee fermentation.

Arabica coffee is the most popular and best-selling type of coffee. During coffee fermentation, microorganisms are essential for the production of metabolites and volatile compounds that affect coffee flavor quality. This work aimed to study the mutation, selection, and characterization of the Wickerhamomyces anomalus strain YWP1-3 as a starter culture to enhance the flavor quality of Arabica coffee. The results revealed that six mutants could produce relatively high levels of the pectinase enzyme on pectin agar media and exhibited high activity levels, ranging from 332.35 to 415.88 U/ml in mucilage broth. Strains UV22-2, UV22-3, UV41-1 and UV32-1 displayed higher levels of amylase activity than did the wild type. The UV22-2 and UV22-3 mutants exhibited the highest pectin degradation indices of 49.22% and 45.97%, respectively, and displayed significantly enhanced growth rates in nitrogen yeast base media supplemented with various sugars; thus, these mutants were evaluated for their ability to serve as a starter for fermentation of Arabica coffee. The cupping scores of coffees derived from UV22-2 and UV22-3 were 83.5 ± 1.5 and 82.0 ± 2.14, respectively. The volatile compounds in the roasted coffee fermented by UV22-2 were analyzed by GC‒MS, which revealed higher levels of furfuryl alcohol and furfuryl acetate than did the other samples. These findings suggested that UV22-2 could be an influential starter culture for Arabica coffee fermentation.

The implementation of the SPAD-502 Chlorophyll meter for the quantification of nitrogen content in Arabica coffee leaves.

The utilization of a non-destructive SPAD-502 chlorophyll meter, which enables the measurement of nitrogen status in plant leaves, has gained popularity in agronomic crops. Its application to horticultural crops like coffee remains relatively uncommon. The device provides quick and real-time measurements, helping to provide on-time nitrogen fertilizer to coffee plants before deficiency signs occur. Coffee leaves are characterized by thick and waxy leaves, together with many layers of tree crown. Therefore, the objective of this study was to develop a method for measuring nitrogen levels in coffee plants using the SPAD-502 Chlorophyll meter for an appropriate nitrogen fertilizer application rate in Arabica coffee plants. •Coffee trees were separated into upper, middle and lower levels. Data on SPAD values and total nitrogen were analyzed.•Pearson Correlation Coefficient (R), Coefficient of Determination (R2) and linear regression were calculated for different three levels of both SPAD-502 and total nitrogen values.•The results revealed a strong correlation (R2 = 0.63) between the SPAD readings of coffee leaves obtained from the upper canopy and their nitrogen content. These findings can provide a good concept of which coffee crown level will be a better part for measuring N content using a SPAD-502 Chlorophyll meter.

Assessment of farmers' knowledge and perceptions of coffee yield reduction due to weeds and their management in Ethiopia.

The home of Coffea arabica is in Ethiopia, where it has high genetic diversity and suitable growing conditions; unfortunately, the national average yields of coffee remain low due to no technical advancements and diverse, complex biotic and abiotic constraints. Hence, this study was conducted in eight major coffee-growing zones of Ethiopia to assess farmers' knowledge and perceptions of coffee yield reduction due to weeds and the farmers' weed control practices. A purposive and random sampling technique was used to generate primary data from coffee growers (N = 320) using a semi-structured questionnaire. Quantitative data were analyzed using a three-stage nested design, and the dependent and independent variables data were subjected to canonical correlation analysis. This study revealed variation in coffee yield (t ha-1) among the assessed areas based on farmers' knowledge of estimating coffee yield. The average yield level ha-1 was very low (0.37 t ha-1) and different among the surveyed areas. The average coffee yield gap as compared to the current national level (0.64 t ha-1) was observed to be 42%, and this low yield was highly correlated with weed infestation (r = 0.879) and type of weeds r = -0.528). This investigation indicated a single factor or association of different factors contributing to the low yield level of coffee in the study areas. Thus, it is concluded that predictor variables accounting for the low yield levels need to be considered when planning future strategies to attain the yield potential of C. arabica in Ethiopia.

Development of PCA-MLP Model Based on Visible and Shortwave Near Infrared Spectroscopy for Authenticating Arabica Coffee Origins.

Arabica coffee, one of Indonesia's economically important coffee commodities, is commonly subject to fraud due to mislabeling and adulteration. In many studies, spectroscopic techniques combined with chemometric methods have been massively employed in classification issues, such as principal component analysis (PCA) and discriminant analyses, compared to machine learning models. In this study, spectroscopy combined with PCA and a machine learning algorithm (artificial neural network, ANN) were developed to verify the authenticity of Arabica coffee collected from four geographical origins in Indonesia, including Temanggung, Toraja, Gayo, and Kintamani. Spectra from pure green coffee were collected from Vis-NIR and SWNIR spectrometers. Several preprocessing techniques were also applied to attain precise information from spectroscopic data. First, PCA compressed spectroscopic information and generated new variables called PCs scores, which would become inputs for the ANN model. The discrimination of Arabica coffee from different origins was conducted with a multilayer perceptron (MLP)-based ANN model. The accuracy attained ranged from 90% to 100% in the internal cross-validation, training, and testing sets. The error in the classification process did not exceed 10%. The generalization ability of the MLP combined with PCA was superior, suitable, and successful for verifying the origin of Arabica coffee.

Optimizing drip fertigation at different periods to improve yield, volatile compounds and cup quality of Arabica coffee.

How to improve and regulate coffee bean yield and quality through split fertilization in the whole life cycle of coffee is still unclear and deserves further study. A field experiment of 5-year-old Arabica coffee trees was conducted for 2 consecutive years from 2020 to 2022. The fertilizer (750 kg ha-1 year-1, N-P2O5-K2O:20%-20%-20%) was split in three times at early flowering (FL), the berry expansion (BE), and the berry ripening (BR). Taking equal fertilization throughout the growth cycle (FL250BE250BR250) as the control check, variable fertilizations including FL150BE250BR350, FL150BE350BR250, FL250BE150BR350, FL250BE350BR150, FL350BE150BR250, and FL350BE250BR150. Leaf net photosynthetic rate (A net), stomatal conductance (g s), transpiration rate (T r), leaf water use efficiency (LWUE), carboxylation efficiency (CE), partial factor productivity of fertilizer (PFP), bean yield, crop water use efficiency (WUE), bean nutrients, volatile compounds and cup quality, and the correlation of nutrients with volatile compounds and cup quality was evaluated. FL350BE250BR150 had the maximum A net and g s, followed by FL250BE350BR150. The highest dry bean yield and WUE were obtained from FL250BE350BR150, which increased by 8.86% and 8.47% compared with FL250BE250BR250 in two-year average. The ash, total sugar, fat, protein, caffeine and chlorogenic acid in FL250BE350BR150 were 6.47%, 9.48%, 3.60%, 14.02%, 4.85% and 15.42% higher than FL250BE250BR250. Cluster analysis indicated FL150BE350BR250, FL250BE350BR150, FL350BE150BR250 and FL350BE250BR150 under medium roasted degree increased pyrazines, esters, ketones and furans, FL150BE350BR250 and FL250BE350BR150 under dark roasted degree increased ketones and furans. The aroma, flavor, acidity and overall score of medium roasted coffee were higher than dark roasted coffee, while the body score of dark roasted coffee was higher than medium roasted coffee. The nutrient contents were correlated with the volatile compounds and cup quality. TOPSIS indicated that FL250BE350BR150 was the optimal fertilization mode in the xerothermic regions. The obtained optimum fertilization mode can provide a scientific basis for coffee fertilization optimization and management.

The mycorrhizal root-shoot axis elicits Coffea arabica growth under low phosphate conditions.

Coffee is one of the most traded commodities world-wide. As with 70% of land plants, coffee is associated with arbuscular mycorrhizal (AM) fungi, but the molecular bases of this interaction are unknown. We studied the mycorrhizal phenotype of two commercially important Coffea arabica cultivars ('Typica National' and 'Catimor Amarillo'), upon Funnelliformis mosseae colonisation grown under phosphorus limitation, using an integrated functional approach based on multi-omics, physiology and biochemistry. The two cultivars revealed a strong biomass increase upon mycorrhization, even at low level of fungal colonisation, improving photosynthetic efficiency and plant nutrition. The more important iconic markers of AM symbiosis were activated: We detected two gene copies of AM-inducible phosphate (Pt4), ammonium (AM2) and nitrate (NPF4.5) transporters, which were identified as belonging to the C. arabica parental species (C. canephora and C. eugenioides) with both copies being upregulated. Transcriptomics data were confirmed by ions and metabolomics analyses, which highlighted an increased amount of glucose, fructose and flavonoid glycosides. In conclusion, both coffee cultivars revealed a high responsiveness to the AM fungus along their root-shoot axis, showing a clear-cut re-organisation of the major metabolic pathways, which involve nutrient acquisition, carbon fixation, and primary and secondary metabolism.

Integrating Metabolomics and Proteomics Technologies Provides Insights into the Flavor Precursor Changes at Different Maturity Stages of Arabica Coffee Cherries.

The metabolic modulation of major flavor precursors during coffee cherry ripening is critical for the characteristic coffee flavor formation. However, the formation mechanism of flavor precursors during coffee cherry ripening remains unknown. In the present study, a colorimeter was employed to distinguish different maturity stages of coffee cherry based on the coffee cherry skin colors, and proteomics and metabolomics profiles were integrated to comprehensively investigate the flavor precursor dynamics involved in Arabica coffee cherry ripening. The data obtained in the present study provide an integral view of the critical pathways involved in flavor precursor changes during coffee cherry ripening. Moreover, the contributions of critical events in regulating the development of flavor precursors during the four ripening stages of coffee cherries, including the biosynthesis and metabolism pathways of organic acids, amino acids, flavonoids, and sugars, are discussed. Overall, a total of 456 difference express metabolites were selected, and they were identified as being concentrated in the four maturity stages of coffee cherries; furthermore, 76 crucial enzymes from the biosynthesis and metabolism of sugars, organic acids, amino acids, and flavonoids contributed to flavor precursor formation. Among these enzymes, 45 difference express proteins that could regulate 40 primary amino acids and organic acids flavor precursors were confirmed. This confirmation indicates that the metabolic pathways of amino acids and organic acids played a significant role in the flavor formation of Arabica coffee cherries during ripening. These results provide new insights into the protease modulation of flavor precursor changes in Arabica coffee cherry ripening.

The microbiology of arabica and robusta coffee cherries: a comparative study of indigenous bacteria with presumptive impact on coffee quality.

Arabica and robusta are the two major coffee beans being sold worldwide. It is well recognized that coffee quality is influenced by their origin and the microbiological activities that drive their fermentation. However, in many coffee plantations, information about the natural diversity of bacteria that inhabit the arabica and robusta coffee cherries is limited. Here, we sampled arabica and robusta coffee cherries from Malang, East Java, Indonesia, then sequenced and analysed their bacterial composition. We found that: (a) arabica cherries contained bacteria with less diversity and abundance compared with robusta; (b) both coffee cherries were heavily populated by extremophiles, presumably dispersed from volcanic activities; (c) groups known to be involved in coffee fermentation such as lactic acid bacteria, acetic acid bacteria, Enterobacteria, and soil-associated bacteria were present in both arabica and robusta coffee cherries, and (d) arabica cherries were dominated by Leuconostoc pseudomesenteroides. These findings highlight that coffee cherry bacteria are highly diverse, the majority of which might come from the environment, with some potentially beneficial or detrimental to coffee quality. Knowledge of the natural microbial diversity of coffee cherries may be useful for the development of coffee fermentation technologies to yield coffee beans with consistent quality.

Structural Characteristics, Rheological Properties, and Antioxidant and Anti-Glycosylation Activities of Pectin Polysaccharides from Arabica Coffee Husks.

As primary coffee by-products, Arabica coffee husks are largely discarded during coffee-drying, posing a serious environmental threat. However, coffee husks could be used as potential material for extracting pectin polysaccharides, with high bioactivities and excellent processing properties. Thus, the present study aimed to extract the pectin polysaccharide from Arabica coffee husk(s) (CHP). The CHP yield was calculated after vacuum freeze-drying, and its average molecular weight (Mw) was detected by gel permeation chromatography (GPC). The structural characteristics of CHP were determined by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), proton nuclear magnetic resonance (1H NMR), and scanning electron microscopy (SEM). Additionally, the rheological and antioxidant properties of CHP and the inhibition capacities of advanced glycation end products (AGEs) with different concentrations were evaluated. The interaction mechanisms between galacturonic acid (GalA) and the AGE receptor were analyzed using molecular docking. The results demonstrated that the CHP yield was 19.13 ± 0.85%, and its Mw was 1.04 × 106 Da. The results of the structural characteristics results revealed that CHP was an amorphous and low-methoxyl pectic polysaccharide linked with an α-(1→6) glycosidic bond, and mainly composed of rhamnose (Rha, 2.55%), galacturonic acid (GalA, 45.01%), ß-N-acetyl glucosamine (GlcNAc, 5.17%), glucose (Glc, 32.29%), galactose (Gal, 6.80%), xylose (Xyl, 0.76%), and arabinose (Ara, 7.42%). The surface microstructure of CHP was rough with cracks, and its aqueous belonged to non-Newtonian fluid with a higher elastic modulus (G'). Furthermore, the results of the antioxidant properties indicated that CHP possessed vigorous antioxidant activities in a dose manner, and the inhibition capacities of AGEs reached their highest of 66.0 ± 0.35% at 1.5 mg/mL of CHP. The molecular docking prediction demonstrated that GalA had a good affinity toward AGE receptors by -6.20 kcal/mol of binding energy. Overall, the study results provide a theoretical basis for broadening the application of CHP in the food industry.

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.

Integrating temperature-dependent development and reproduction models for predicting population growth of the coffee berry borer, Hypothenemus hampei Ferrari.

The coffee berry borer, Hypothenemus hampei Ferrari (Coleoptera: Curculionidae, Scolytinae), is the most devastating insect pest of coffee worldwide. It feeds on the beans inside the berries leading to significant crop losses and unmarketable products. This study aims to model the impact of temperature on H. hampei fecundity and population growth parameters, as a contribution to the prediction of infestation risk. The fecundity was assessed on fresh coffee beans at six constant temperatures in the range 15-30°C, with RH 80 ± 5% and photoperiod 12:12 L:D. Nonlinear models were fitted to the relationship between fecundity and temperature using the ILCYM software. The best fecundity model was combined to development models obtained for immature stages in a previous study in order to simulate life table parameters at different constant temperatures. Females of H. hampei successfully oviposited in the temperature range 15-30°C, with the highest fecundity observed at 23°C (106.1 offspring per female). Polynomial function 8 model was the best fitted to the relationship between fecundity and temperature. With this model, the highest fecundity was estimated at 23°C, with 110 eggs per female. The simulated net reproductive rate (R0) was maximal at 24°C, with 50.08 daughters per female, while the intrinsic rate of increase (rm) was the highest at 26°C, with a value of 0.069. Our results will help understand H. hampei population dynamics and develop an ecologically sound management strategy based on a better assessment of infestation risk.

An overview on possible management strategies for coffee white stem borer Xylotrechus quadripes Chevrolat (Coleoptera: Cerambycidae) in Nepal.

The Coffee White Stem Borer (CWSB) is one of the most dreadful and destructive pests of coffee in Asian nations, causing significant production loss each year. CWSB has a narrow host range, with Coffea arabica as their principal host. Once they bore into the stem of C. arabica, the whole plant must be uprooted. The study on the cumulative effects of the invasion of pests in the Nepalese agriculture system is quite vague. Farmers use a variety of methods to combat CWSB, but most of them are ineffective and wasteful. To effectively combat pests, it is important to understand the variety and abundance of natural enemies as well as the botanicals that have pesticide potential. If the management of CWSB in the Nepalese context goes unaddressed, it will prompt an alarming issue to coffee production in Nepal. Hence, it is of utmost necessity to develop rational management strategies of CWSB for promoting organic coffee in Nepal, which has garnered a reputation of excellent quality in the global market. This paper seeks to provide comprehensive information on the CWSB's management technique for using bio-rational compounds to aid Nepalese farmers cultivating organic coffee.

New approach for screening of microorganisms from Arabica coffee processing for their ability to improve Arabica coffee flavor.

The purpose of this research was to isolate microorganisms from coffee fermentation processes and screen them for their potential to improve the flavor of Arabica coffee using a new approach that included pectin degradation ability and growth in mucilage broth. All of the studied microorganisms were isolated from 38 different samples of fresh coffee cherries, coffee mucilage and coffee pulp. A total of 262 microbial isolates were obtained and subjected to screening using pectinase screening agar medium for pectinolytic organisms. The results of the pectinase production test showed that 18 yeast isolates were found to produce pectinase that could degrade the pectin present in solid media. The sugar assimilation profiles and growth of selected strains in mucilage broth were studied. Therefore, 18 isolates from the selected yeasts were subjected to molecular identification by the use of 18S rRNA gene sequencing. The diversity of the yeast isolates was studied, and they were identified as Wickerhamomyces anomalus, Naganishia liquefaciens, Pichia kudriavzevii, Kazachstania naganishii and Kazachstania sp. Moreover, isolates SWU3YWP1-3, SWU3YSK9 and INFCY1-4 were used as a seed culture for Arabica coffee fermentation. The cupping sensory scores of the control (without yeast inoculation) and those inoculated with three isolated yeast strains that were determined by Q-Arabica Graders were 73.75, 84.75, 80.25 and 75.00, respectively. Unique flavors and aromas were detected. This is the first report of screening microorganisms from the Arabica coffee fermentation process by the combination of various properties with success in improving the quality of coffee beverage.

Arabica coffee and olive oils mitigate malathion-induced nephrotoxicity in rat: In silico, immunohistochemical and biochemical evaluation.

Malathion (MAL) is an organophosphate insecticide that disrupts the body's antioxidant system; it is one of the earliest organophosphate insecticides extensively used as dust, emulsion, and vapor control a wide variety of insect pests under different conditions. This experimentation aims to evaluate the influence of Arabica coffee oil and olive oil on MAL-induced nephrotoxicity in male rat. 6 sets bearing the same number of animals were applied to this experiment. Each set comprised 10 rats. The first set of rats was used as the control group; rats in the second set were exposed to MAL measured at 100 mg/kg body weight for 7 weeks. Animals in the third and fourth set were treated with 400 mg/kg body weight of Arabica coffee oil and olive oil, and 100 mg/kg body weight of MAL. The fifth, together with the sixth set, were fed with a similar proportion of Arabica coffee oil and olive oil as administered to the third set of rats. After the experimental duration, rats of group 2 showed severe biochemical alterations, including significant increases of creatinine, uric acids, and urea nitrogen (BUN), resulting in marked decreases in serum albumin values and total protein (TP). Severe histopathological and immunohistochemical alterations of kidney tissues were observed in exposed MAL-intoxicated rats. Administration of these oils reduced the detected biochemical, histopathological modifications caused by MAL intoxication. Two active ingredients in Arabica coffee oil (oleic acid) and olive oil (hydroxytyrosol) showed good cyclooxygenase-2 (COX 2) interaction. Moreover, oleic acid from coffee oil and olive oil exhibited impressive association with xanthine oxidase (XO). The current finding showed that coffee oil and olive oil could be appraised as possible and a likely deterrence component against nephrotoxicity brought about by MAL.

The use of multispectral imaging for the discrimination of Arabica and Robusta coffee beans.

Arabica coffee beans are sold at twice the price, or more, compared to Robusta beans and consequently are susceptible to economically motivated adulteration by substitution. There is a need for rapid, non-destructive, and efficient analytical techniques for monitoring the authenticity of Arabica coffee beans in the supply chain. In this study, multispectral imaging (MSI) was applied to discriminate roasted Arabica and Robusta coffee beans and perform quantitative prediction of Arabica coffee bean adulteration with Robusta. The Orthogonal Partial Least Squares Discriminant Analysis (OPLS-DA) model, built using selected spectral and morphological features from individual coffee beans, achieved 100% correct classification of the two coffee species in the test dataset. The OPLS regression model was able to successfully predict the level of adulteration of Arabica with Robusta. MSI analysis has potential as a rapid screening tool for the detection of fraud issues related to the authenticity of Arabica coffee beans.

Effect of growing conditions and postharvest processing on arabica coffee bean physical quality features and defects.

The individual and interaction effects of elevation, production system (PS), shade and postharvest processing (PHP) on the ratio of dry beans to red cherries and the green bean physical quality features and defects of arabica coffee in southwestern Ethiopia were evaluated. The results showed that, with increasing elevation, the proportions of the total defected beans and large beans decreased while that of medium beans increased. Moreover, the proportion of secondary defects, 1000 seed weight and bean volume were higher for lowland and midland coffees than for highland coffee, but bean density was higher for highland than for lowland and midland coffees. The proportion of the total defected beans was also higher for modern plantation coffee in lowland than for modern plantation and semi-plantation coffees in midland and highland, but the 1000 seed weight was lower for semi-plantation coffee in highland than for modern plantation coffee in lowland and midland. The ratio of primary and secondary defects respectively was higher for dry- and wet-processed coffee in lowland than for dry- and wet-processed coffees in midland and highland. But, the ratio of small beans was lower for wet-processed coffee in lowland than for dry-processed coffee across elevations. The ratio of dry beans to red cherries and the 100 beans volume were higher for wet-processed modern plantation and semi-plantation coffees in midland than for dry-processed coffees of both production systems across elevations. However, the ratio of large beans was higher (1) for wet-processed modern plantation coffee in lowland than for dry- and wet-processed coffees of both production systems across elevations, and (2) for coffee that was grown without shade and wet-processed in lowland than for other coffees. Bean density was higher for dry-processed modern plantation and semi-plantation coffee in midland and highland, respectively than for other coffees across elevations. Overall, these results underlined the primary effects of elevation and PS, and the complex interaction effects between PHP and PS or shade on the ratio of dry beans to red cherries and the physical features and defects of green arabica coffee beans.

Microbial ecology and functional coffee fermentation dynamics with Pichia kudriavzevii.

Specialty coffee can be developed by the application of explicit microorganisms or starters to obtain desired fermentation. In the present study, natural fermentation (NF) of Arabica coffee was carried out spontaneously, the other set was inoculated with Pichia kudriavzevii (Y) starter culture (isolated, identified and mass cultured). The effect of microbial fermentation, metagenomics, production of functional metabolites, volatiles and their sensorial aspects were studied. The bioprocess illustrated cohesive interface of coffee nutrients and microbial communities like Mycobacterium, Acinetobacter, Gordonia, etc., in NF, Lactobacillus and Leuconostoc were prevailing in Y. The Pichia and Rhodotorula dominated in both the groups. The bioactivity of bacteria and fungi induced complex changes in physicochemical features like pH (4.2-5.2), Brix° (9.5-3.0), and metabolic transition in sugar (3.0-0.7%), alcohol (1.4-2.7%), organic acids modulating flavour precursors and organoleptics in the final brew. In the roasted bean, Y exhibited higher sugar (42%), protein (25%), polyphenol (3.5%), CGA (2.5%), caffeine (17.2%), and trigonelline (2.8%) than NF. The volatile profile exhibited increased flavour molecules like furans, ketones, and pyrazines in Y, besides lactone complexes. The organoleptics in Y were highlighted with honey, malt and berry notes. P. kudriavzevii coffee fermentation could be beneficial in specialty coffee production and enhancement of distinct characteristic flavours.

Effect of the Post-Harvest Processing on Protein Modification in Green Coffee Beans by Phenolic Compounds.

The protein fraction, important for coffee cup quality, is modified during post-harvest treatment prior to roasting. Proteins may interact with phenolic compounds, which constitute the major metabolites of coffee, where the processing affects these interactions. This allows the hypothesis that the proteins are denatured and modified via enzymatic and/or redox activation steps. The present study was initiated to encompass changes in the protein fraction. The investigations were limited to major storage protein of green coffee beans. Fourteen Coffea arabica samples from various processing methods and countries were used. Different extraction protocols were compared to maintain the status quo of the protein modification. The extracts contained about 4-8 µg of chlorogenic acid derivatives per mg of extracted protein. High-resolution chromatography with multiple reaction monitoring was used to detect lysine modifications in the coffee protein. Marker peptides were allocated for the storage protein of the coffee beans. Among these, the modified peptides K.FFLANGPQQGGK.E and R.LGGK.T of the α-chain and R.ITTVNSQK.I and K.VFDDEVK.Q of ß-chain were detected. Results showed a significant increase (p < 0.05) of modified peptides from wet processed green beans as compared to the dry ones. The present study contributes to a better understanding of the influence of the different processing methods on protein quality and its role in the scope of coffee cup quality and aroma.