The effect of roasting on the fate of aflatoxin B1 in artificially contaminated green coffee beans

A study was undertaken to evaluate aflatoxin B₁ contamination in coffee beans. 41 samples of green coffee were collected from large lots of material by representative sampling. The raw samples were analyzed and showed no detectable levels of aflatoxin B₁. In order to establish the heat stability of the toxin, 3 artificially contaminated samples (average level 10/μg/kg) were roasted atca 200°C for different operation times periods so as to reproduce light and dark roasting procedures. Each sample was roasted both electrically and by gas. The percentage of toxin destruction was up to 93% for light roasted and 99% for dark roasted coffee with a slightly higher rate up to 100% for the electrically roasted coffee for light and dark roasting. In order to evaluate the potential migration of the aflatoxin B₁ into the coffee beverage, 1 sample found contaminated after roasting treatment (0.8/°g/kg) was extracted using each of the 3 most common types of coffee makers. Additional destruction of the toxin was observed (up to 99%) in two cases while only 75% of fate was obtained in the third. The process from raw coffee beans to beverage showed a meaningful destruction of aflatoxin B₁, ranging from 97 to 100% depending on the extraction technique adopted in the preparation of the beverages.     

Effect of roasting on ochratoxin A level in green coffee beans inoculated with Aspergillus ochraceus

The heat stability of ochratoxin A in green coffee beans inoculated with Aspergillus ochraceus was studied. Heat treatment (roasting) at 200 °C for 10 or 20 min reduced the levels of ochratoxin A by only 0–12% in the dried whole beans. Almost all of the ochratoxin A was infused into the coffee decoction when the roasted samples were ground and extracted with boiling water. Therefore, the reduction of ochratoxin A concentration of contaminated coffee beans by roasting under these conditions is ineffective.     

Ochratoxin A-producing Aspergilli in Vietnamese green coffee beans

AIMS: To determine the incidence and severity of infection by ochratoxin A (OA)-producing fungi in Vietnamese green coffee beans. METHODS AND RESULTS: Aspergillus carbonarius, A. niger and yellow Aspergilli (A. ochraceus and related species in section Circumdati) were isolated by direct plating of surface-disinfected Robusta (65 samples) and Arabica (11 samples) coffee beans from southern and central Vietnam. Significantly, more Robusta than Arabica beans were infected by fungi. Aspergillus niger infected 89% of Robusta beans, whereas A. carbonarius and yellow Aspergilli each infected 12-14% of beans. OA was not produced by A. niger (98 isolates) or A. ochraceus (77 isolates), but was detected in 110 of 113 isolates of A. carbonarius, 10 isolates of A. westerdijkiae and one isolate of A. steynii. The maximum OA observed in samples severely infected with toxigenic species was 1.8 microg kg(-1); however, no relationship between extent of infection and OA contamination was observed. CONCLUSIONS: Aspergillus niger is the dominant species infecting Vietnamese coffee beans, yet A. carbonarius is the likely source of OA contamination. SIGNIFICANCE AND IMPACT OF STUDY: Vietnamese green coffee beans were more severely infected with fungi than the levels reported for beans from other parts of the world, yet OA contamination appears to be infrequent.     

Trigonelline Content in Coffee Beans and the Thermal Conversion of Trigonelline into Nicotinic Acid during the Roasting of Coffee Beans

The trigonelline content in coffee was determined by the microbiological assay method after demethylating the compound. The content was proved to be extremely high (up to 1 % on the wet basis). When trigonelline was heated to above 180°C, it was converted into nicotinic acid. Although the conversion rate was low, a nutritionally significant amount of nicotinic acid was formed during roasting coffee beans because of the high content of trigonelline in coffee beans. The optimum heating condition for nicotinic acid formation was found at 220°C for 20 min.     

Analysis of 3-aminopropionamide: a potential precursor of acrylamide

An analytical method for the analysis of 3-aminopropionamide (3-APA) based on derivatization with dansyl chloride and liquid chromatography/fluorescence detection was developed. We have analysed 3-APA formation in raw potatoes, grown and stored under different condition, green and roasted coffee beans and in freeze dried mixtures of asparagine with sucrose and glucose in molar ratio of 1:0.5, 1:1, and 1:1.5. In potatoes the 3-APA content varied depending on the potato variety. We detected 3-APA in potatoes up to 14 microg/g fresh weight. In the model experiment glucose had a stronger capacity to form 3-APA. The substance was formed at temperatures as low as 130 degrees C. However, in the model experiment with sucrose 3-APA was formed not below 150 degrees C. In heated mixtures with increasing molar ratio of sucrose at 170 degrees C we noticed a decrease of 3-APA and in the same mixtures at 150 degrees C we observed an increase of 3-APA. In coffee 3-APA was not formed, neither in green nor in roasted beans.     

Effect of polygalacturonase and feruloyl esterase from Aspergillus tubingensis on demucilage and quality of coffee beans

To explore the potential for the application of Aspergillus tubingensis enzyme extract in coffee processing, the effects of crude enzymes on coffee beans were studied. Yields of polygalacturonase and feruloyl esterases obtained from solid-state fermentation using A. tubingensis, with pectin and de-starched wheat bran as carbon sources, were 15.9 U/mL and 2.44 U/mL, respectively. Crude enzyme extracts removed the mucilage of coffee cherries within 3 h, which is substantially more efficient than traditional fermentation. Additionally, the viscosity of coffee mucilage was reduced to 80% by a 3-h treatment with the crude enzyme extract at 50 °C. The titratable acidity and organic acids in coffee beverages were also decreased to half the amounts of those in the traditionally fermented group. The total chlorogenic acid in the green beans decreased to 67.3%; however, a decline of only 14.3% was observed in the traditionally fermented group. On the other hand, chlorogenic acid lactones in the roasted beans were reduced to 63.9%, and a 37.2% decline in the chlorogenic acid content was detected.     

SENSORY PROFILING AND PRODUCT POSITIONING OF ROASTED AND GROUND (BREW) COFFEE AND SOLUBLE (INSTANT) COFFEE WITH AND WITHOUT ADDED FLAVOR

Coffee powders available commercially are of different qualities. The quality variations may be due to inherent quality of coffee beans, storage time and packaging materials used. Sensory profiles of brewed and soluble coffees were studied through profiling. Canonical discriminant analysis (CDA) used for positioning the different coffee samples showed that freshly made coffee from plantation arabica (PA), Pea berry (PB), PA with chicory (PAC), PB with chicory (PBC) and their blends viz. PA + PB and PAC + PBC occupied the quadrant where coffee aroma and overall quality rated higher. Other roasted & ground (R&G) coffee (market) samples were positioned where oily, fermented, musty, stale and caramelized notes dominated. In case of soluble coffee, the flavored coffee procured from the western market (S3, S6, S9 and S8) dominated the quadrant where other added flavor and oily notes dominated. The typical soluble (instant) coffee without any added flavor S10, S12 and S13 occupied another quadrant. The soluble coffee powder with spice incorporation took a separate quadrant where other added flavor and bitter taste dominated. The dominant quality attributes for the groups are different and are discussed in relation to the directional vectors.     

The effects of water absorption and roasting conditions on fracture properties and internal structure of sesame seeds

We investigated the effects of soaking, residence time before roasting and roasting conditions on the fracture properties and structure of the cross-section of sesame seeds. Soaking time affected only the size of the side voids of the seed cross-section. The fracture force and strain of the roasted seeds decreased as residence time increased. The center void of the roasted seeds, important for seed crispness increased as residence time increased. In contrast, the side void of the roasted seeds only increased with residence time during the first 10 min. Seeds roasted at higher temperatures had smaller fracture forces and larger central voids than those roasted at lower temperatures. During roasting at 300 °C, the fracture force and strain decreased as the center void ratio increased. Overall, both a sufficient time for moisture diffusion in the seeds and a high roasting temperature were necessary to produce crisp roasted seeds.     

Novel Xanthine Oxidase (XO) inhibitory phenylindanes produced by thermal reaction of caffeic acid

The products from the thermal reaction of chlorogenic and caffeic acids, which is a model process of roasting coffee beans, exhibited xanthine oxidase (XO) inhibitory activity. From caffeic acid, six inhibitory phenylindanes were identified, and a new phenylindane displayed the highest inhibitory activity among them. The activity of these phenylindanes may contribute to XO inhibition-related functions of roasted coffee beverages.     

Combined immobilized cell bioreactor and pulse column technology as a novel approach to food modification

The continuous use of an immobilized cell bioreactor (ICB) and a countercurrent pulse column is a unique approach to removing malic acid from coffee beans prior to roasting. This process recycled a high soluble solids water extract from the green coffee beans through a spiral-wound ICB loaded with food-grade bacteria (Lactobacillus spp. or Leuconostoc spp.) which metabolized malic acid in the green coffee bean extract. The demalated extract was then recirculated to extract the malic acid from the green beans during the countercurrent flow of the ‘malic acid-lean’ extract over the beans. The malic acid level in the beans was reduced by more than 80%. This extract recycle process may have other applications for removing unwanted organics or adding desirable water-soluble components. and is particularly suited to processing beans and grains.     

Solid-state NMR characterization of triacylglycerol and polysaccharides in coffee beans

It is important to understand the structural characteristics of triacylglycerol (TAG), polysaccharides and trace elements in coffee beans, so that residues can be reutilized in applications including biodiesel oils. Here, we performed ¹H and ¹³C solid-state NMR measurements on Indonesian green beans, roasted beans, and spent coffee grounds (SCGs). In the NMR spectra, there were liquid-like TAG containing linoleic acids based on observed signals of -CH=CH-CH₂-CH=CH- group in an acyl chain, which play a role in decreasing TAG’s melting point. We found TAG was still abundant in the SCGs from NMR spectra. After lipids were removed from SCGs, the intensity of the TAG signal decreased considerably, with approximately 64% of the TAG was successfully extracted. We described the chemical structure of TAG in coffee beans and demonstrated that it is possible quantify the amount of extracted TAG using solid-state NMR.     

GC-MS detection of chiral markers in cocoa beans of different quality and geographic origin

Fermented cocoa beans (Theobroma cacao L., Sterculiaceae) from different countries of origin (Ecuador, Ghana, Trinidad) and cocoa beans roasted under defined conditions (industrial roasting; 150-220 degrees C for 20 min, dry roasting in conventional oven) were analyzed for their contents of certain chiral hydroxy acids, catechins, and amino acids. Cocoa beans are fermented, dried, and industrially transformed by roasting for the production of chocolate, cocoa powders, and other cocoa-related products. Fermentation and roasting conditions influence the contents of chiral compounds such as hydroxy acids, amino acids, and polyphenols, depending on technological procedures as well as some technical parameters. The aim of this work was to check if the content and nature of the named chiral compounds present both in fermented and roasted cocoa beans could be related to the traditional parameters used to classify the variety of seeds and the degree of fermentation. The extent of racemization of amino acids in fermented cocoa beans was low while it slowly increased during roasting, depending on the temperature applied. L-lactic acid was always higher than the D-form while citric acid was generally the most abundant hydroxy acid detected in beans. A correlation was found between polyphenol content and degree of fermentation, while epimerization of (-)-epicatechin to (+)-catechin was observed during roasting. On the whole, results showed that several chiral compounds could be considered as good quality markers for cocoa seeds and cocoa-related products of different quality and geographic origin.     

A study of chemical Composition,Antioxidants, and volatile compounds in roasted Arabic coffee

Coffea arabica (Rubiaceae) is a basic drink for all Gulf societies, especially Saudi Arabia, it is the main part of the Saudi tradition. This investigation was carried out to track the chemical composition, caffeine content by UV–visible spectrophotometer, acrylamide content by using a gas chromatograph, free radical scavenging capacity by DPPH methods as well as determined the browning index and separated the volatiles compounds using GC–MS for the most common three degree of roasted Arabic coffee; light (180 ± 10 °C; 6.0 ± 1.0 min), medium (180 ± 10 °C; 8.0 ± 1.0 min), and dark (180 ± 10 °C; 10.0 ± 1.0 min). Data revealed that light roasted coffee has the highest significant (p < 0.05) value of moisture content (4.80%), crude protein (13.05%), and lowest value of ether extract (10.39%) and crude fiber (24.24%). The caffeine content was found to be 1.13% in light coffee, which increased to 1.17% in medium coffee, then decreased to 1.08% in dark coffee. The quantity of acrylamide detected in light roasted coffee (0.41 mg/100 g) was the greatest, whereas medium roasted coffee comparatively produced low amounts (0.31 mg/100 g). The light roasted coffee gave the highest antioxidant activity (88.72 mg TE/g), while the dark roasted coffee gave the least activity (78.76 mg TE/g). Browning index increases with roasting time. Hydrocarbons, alcohols, and esters were the most represented in roasted coffee headspace. Silanes and sec-butyl nitrite compounds were absent in the medium roasted headspace. Except for amines, all 11 classes of volatile compounds were present in the headspace of dark roasted coffee.     

Microbiological and chemical-sensory characteristics of three coffee varieties processed by wet fermentation

This work evaluated the bacterial diversity during coffee wet fermentation of the three coffee varieties—Mundo Novo (MN), Ouro Amarelo (OA), and Catuaí Vermelho (CV). Isolates were identified by polyphasic techniques: biochemical tests, matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) and DNA sequencing. Chemical compositions were determined by high (HPLC) and gas chromatography-mass spectrometry (GC-MS) and the roasted beans were sensorial evaluated using the cupping test. Thirty-six mesophilic bacteria and six lactic acid bacteria were identified. Lactobacillus plantarum and Leuconostoc mesenteroides were often found in all varieties. Citric acid was the acid detected in higher concentrations. The volatile profile of the green coffee beans changed during the fermentation in the tank, but more significantly, during the roasting process. These volatiles belonged to the classes of acids, alcohols, aldehydes, and hydrocarbons. Temporal dominance of sensations analysis showed sensorial sensations of acidity (OA and CV), bitterness, chocolate, nuts (MN), and sweetness (CV). The characteristics of each coffee variety were distinct, mainly in relation to total bacteria population, volatile compounds, and sensorial profile. In conclusion polyphasic methodology was efficiently done for bacteria identification; the dominant bacteria might be used for starter cultures and the chemical and sensory analyses helped to understand the changes in coffee fermentation. Our findings are relevant to future select starter bacteria for coffee processing to improve quality and standardization of quality.     

Roasting coffee beans produces compounds that induce prophage lambda in E. coli and are mutagenic in E. coli and S. typhimurium

Freshly brewed blended coffee, instant coffee and instant caffeine-free coffee induced prophage lambda in lysogenic E. coli K12, strain GY5027. Because coffee prepared from green beans by the same extraction method as used for freshly brewed blended coffee had no prophage-inducing activity, this activity may be attributed to compounds produced in the roasting process. Roasting also produced compounds that were mutagenic in S. typhimurium TA100 and E. coli WP2 uvrA/pKM101.     

Coffee oil as a potential feedstock for biodiesel production

A preliminary evaluation of the feasibility of producing biodiesel using oil extracted from defective coffee beans was conducted as an alternative means of utilizing these beans instead of roasting for consumption of beverage with depreciated quality. Direct transesterifications of triglycerides from refined soybean oil (reference) and from oils extracted from healthy and defective coffee beans were performed. Type of alcohol employed and time were the reaction parameters studied. Sodium methoxide was used as alkaline catalyst. There was optimal phase separation after reactions using both soybean and healthy coffee beans oils when methanol was used. This was not observed when using the oil from defective beans which required further processing to obtain purified alkyl esters. Nevertheless, coffee oil was demonstrated to be a potential feedstock for biodiesel production, both from healthy and defective beans, since the corresponding oils were successfully converted to fatty acid methyl and ethyl esters.     

Comparative food utilization of coffee bean weevil larvae on a new freeze-dried diet and green coffee beans

A meridic diet for culturing the coffee bean weevil, Araecerus fasciculatus was formulated and freeze-dried into pellets. When exposed to an atmosphere of 80 ± 5%r.h. the diet reached a moisture equilibrium that invoked oviposition and was satisfactory for growth and development of the insect. Larvae ingested larger amounts of the freeze-dried diet than of the natural food, green coffee beans, reaching equivalent weight and pupation in 31.8 ± 0.4 days on the diet as compared to 46.8 ± 0.8 days on the coffee beans. Approximate digestibilities of the two foods were not significantly different. However, the coffee beans were converted more efficiently to body mass than was the diet. Faeces of larvae on the diet contained more uric acid than those of larvae on coffee beans. Continuous culture and mass rearing of A. fasciculatus on the diet is possible.     

Implication of hydrogen peroxide in the mutagenicity of coffee

A cup of instant coffee (150 ml) of normal strength (15 mg/ml) was found to contain about 500 and 750 micrograms of hydrogen peroxide soon after its preparation at 37 degrees C and 80 degrees C, respectively, but the concentration of hydrogen peroxide in the coffee increased with time for up to 24 h after its preparation. Thus coffee contains a hydrogen peroxide generating system. As extracts of green coffee beans were found to have very low capacity to generate hydrogen peroxide, this generating system is produced by roasting coffee beans. Hydrogen peroxide itself was only weakly mutagenic to Salmonella typhimurium TA100, but in the presence of methylglyoxal, which is also present as a mutagenic component in coffee, hydrogen peroxide showed strong mutagenicity. Hydrogen peroxide and methylglyoxal seem to be responsible for most of the mutagenicity of instant coffee.     

Not so robust: Robusta coffee production is highly sensitive to temperature

Coffea canephora (robusta coffee) is the most heat‐tolerant and ‘robust’ coffee species and therefore considered more resistant to climate change than other types of coffee production. However, the optimum production range of robusta has never been quantified, with current estimates of its optimal mean annual temperature range (22–30°C) based solely on the climatic conditions of its native range in the Congo basin, Central Africa. Using 10 years of yield observations from 798 farms across South East Asia coupled with high‐resolution precipitation and temperature data, we used hierarchical Bayesian modeling to quantify robusta's optimal temperature range for production. Our climate‐based models explained yield variation well across the study area with a cross‐validated mean R² = .51. We demonstrate that robusta has an optimal temperature below 20.5°C (or a mean minimum/maximum of ≤16.2/24.1°C), which is markedly lower, by 1.5–9°C than current estimates. In the middle of robusta's currently assumed optimal range (mean annual temperatures over 25.1°C), coffee yields are 50% lower compared to the optimal mean of ≤20.5°C found here. During the growing season, every 1°C increase in mean minimum/maximum temperatures above 16.2/24.1°C corresponded to yield declines of ~14% or 350–460 kg/ha (95% credible interval). Our results suggest that robusta coffee is far more sensitive to temperature than previously thought. Current assessments, based on robusta having an optimal temperature range over 22°C, are likely overestimating its suitable production range and its ability to contribute to coffee production as temperatures increase under climate change. Robusta supplies 40% of the world's coffee, but its production potential could decline considerably as temperatures increase under climate change, jeopardizing a multi‐billion dollar coffee industry and the livelihoods of millions of farmers.     

Differential regulation of grain sucrose accumulation and metabolism in Coffea arabica (Arabica) and Coffea canephora (Robusta) revealed through gene expression and enzyme activity analysis

* Coffea arabica (Arabica) and Coffea canephora (Robusta) are the two main cultivated species used for coffee bean production. Arabica genotypes generally produce a higher coffee quality than Robusta genotypes. Understanding the genetic basis for sucrose accumulation during coffee grain maturation is an important goal because sucrose is an important coffee flavor precursor. * Nine new Coffea genes encoding sucrose metabolism enzymes have been identified: sucrose phosphate synthase (CcSPS1, CcSPS2), sucrose phosphate phosphatase (CcSP1), cytoplasmic (CaInv3) and cell wall (CcInv4) invertases and four invertase inhibitors (CcInvI1, 2, 3, 4). * Activities and mRNA abundance of the sucrose metabolism enzymes were compared at different developmental stages in Arabica and Robusta grains, characterized by different sucrose contents in mature grain. * It is concluded that Robusta accumulates less sucrose than Arabica for two reasons: Robusta has higher sucrose synthase and acid invertase activities early in grain development - the expression of CcSS1 and CcInv2 appears to be crucial at this stage and Robusta has a lower SPS activity and low CcSPS1 expression at the final stages of grain development and hence has less capacity for sucrose re-synthesis. Regulation of vacuolar invertase CcInv2 activity by invertase inhibitors CcInvI2 and/or CcInvI3 during Arabica grain development is considered.