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.     

Combined changes of process conditions improved aromatic properties of Vietnamese Robusta

The flavor and taste of coffee are affected by roasting conditions and extraction temperature. This study assessed changes in the flavors and tastes of coffee extracted from Vietnamese Robusta with different roasting times and temperatures, as well as different extraction temperatures. Vietnamese Robusta green beans were roasted for different times ranging from 5 to 20 min and at different temperatures ranging from 100 to 250°C. The roasted coffee was then extracted at five different temperatures ranging from 90 to 120°C. The coffee flavor was evaluated in terms of 5 key odorants: guaiacol; 4-ethylguaiacol; 2-ethyl-3,5-dimethylpyrazine; 2,3-diethyl-5-methylpyrazine, and 2-furfuryl. The taste of coffee was evaluated in terms of 6 main compounds that confer bitterness and sourness: caffeine, trigonelline, chlorogenic acid and citric acid, acetic acid, formic acid. The optimized roasting and extracting conditions were identified that 200 g of VN Robusta green beans, roasting at 230°C for 18 min, and then extracted with Espresso Machine at 110°C.     

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.     

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.     

Arabinosyl and glucosyl residues as structural features of acetylated galactomannans from green and roasted coffee infusions

A good yield mild fractionation procedure was developed for the purification of mannans from green and roasted coffee infusions that included anion-exchange chromatography and phenylboronic acid immobilized Sepharose chromatography of the dialyzed and ethanol precipitated material. Enzymatic hydrolysis with endo-beta-mannanase and ESIMS allowed finding that the mannans from roasted coffee infusions, as well as those from green coffee, are acetylated (8 mol% and 11 mol%, respectively). Fragmentation pattern obtained by ESIMS/MS analysis of the acetylated oligosaccharide ions indicates that the acetylation also occurs at O-2 of the mannose residues. Doubly acetylated and contiguously acetylated hexose residues were also found. Arabinose residues, as side chains, were also found as structural features of hot water soluble green (2%) and roasted (<0.9 mol) coffee galactomannans. Methylation analysis, hydrolysis with specific glycosidases and GC-EIMS analysis of the reduced and methylated oligosaccharides allowed to conclude that beta-(1-->4)-linked glucose residues are also structural features of green and roasted coffee galactomannans (6 and 1 mol%, respectively). In hot water soluble green coffee mannans, glucose residues are a constituent of the mannan backbone, and in the roasted coffee they were detected only at the reducing end of the mannan backbone.     

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.     

Host suitability of various stored food products for the cigarette beetle, <Emphasis Type="Italic">Lasioderma serricorne</Emphasis> (Coleoptera: Anobiidae)

We investigated the attraction to, and ovipositional activity and egg-to-adult survival rate on, 11 stored products of Lasioderma serricorne (F.). These products included polished rice, unpolished rice, wheat flour, corn flour, cocoa powder, roasted coffee beans, green tea leaves, black tea leaves, soybean flour, flue-cured tobacco leaves, and dried small sardines. Tobacco, cocoa, soybean flour, black tea, and wheat flour significantly attracted the beetles. Corn flour, green tea, and coffee tended to attract the beetles. Ovipositional activity of beetle was higher on the food materials than on nonfood materials. The highest ovipositional activity was observed on coffee, followed by cocoa. Ovipositional activity on black tea, unpolished rice, and green tea was also relatively high. Methanol extracts of coffee beans showed oviposition-stimulatory activity. Therefore, the high ovipositional activity observed on coffee beans could be attributed to oviposition stimulants contained in the beans. In the egg-to-adult survival test, all eggs laid on polished rice or tobacco leaves developed successfully into adults, whereas none of the eggs laid on black tea, green tea, or coffee beans developed into adults. These findings suggest that suitability as an attractive target, suitability as an oviposition site, and suitability as larval food are not always compatible.     

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.     

Molecular Weights of Glutenin- and Gliadin-polypeptides Estimated by SDS-Polyacrylamide Gel Electrophoresis

ABSTRACT

Interspecific single-nucleotide polymorphisms (SNPs) in the rbcL DNA barcode have been strictly validated and adopted as a designed SNP genotyping maker to discriminate between two major coffee species, Coffea arabica and C. canephora, and to estimate the mixing ratio of DNA from C. arabica/C. canephora in this study. The SNP genotyping is applicable to not only green (unroasted) coffee beans, but also processed coffee products (roasted coffee beans and instant coffee powder), in which genomic DNA is degraded, because the genotyping developed in this study requires only 10 copies of 63-bp-long DNA fragments of rbcL gene. The authenticity assay established in this study has several advantages: a high versatility to DNA sample conditions; simple and rapid procedures (only two steps; DNA extraction and SNP genotyping); the feasibility in coffee business for practical use to prevent false advertising and provide quality control.

Abbreviations: SNP: single-nucleotide polymorphism; SBS: single base substitution; ISR: intergenic spacer region; INDEL: insertion-deletion.     

Loss of heterocyclic amine mutagens by insoluble hemicellulose fiber and high-molecular-weight soluble polyphenolics of coffee

The presence of 2 kinds of components in brewed and instant coffee that could remove and destroy heterocyclic amine mutagens was demonstrated. The component that could remove the mutagens was insoluble fiber composed of hemicellulose. The fiber could tightly adsorb the mutagens Trp-P-1, Trp-P-2, Glu-P-1 and A alpha C, and those generated in roasted coffee beans. The component that could destroy the mutagens was high-molecular-weight soluble polyphenolics. They might be converted into quinone derivatives in the presence of molecular oxygen. The quinone derivatives might destroy the mutagens. The fibers and the polyphenolics in one cup of brewed or instant coffee had the capacity to remove and destroy a substantial amount of the mutagens in pyrolysates of foodstuffs.     

Alpha-galactosyl fluoride in transfer reactions mediated by the green coffee beans alpha-galactosidase in ice

We show that the yields in saccharide synthesis by tranglycosylation with alpha-galactosidase from green coffee beans can be greatly enhanced when working in ice. Thus, methyl alpha-D-galactopyranosyl-(1-->3)-alpha-D-galactopyranoside (3a) produced by reaction of alpha-D-galactopyranosyl fluoride 1 with methyl alpha-D-galactopyranoside (2) is obtained with 51% yield in ice while only 29% is synthesized at 37 degrees C. This result, already previously found by others with proteases and by us with a beta-galactosidase appears to be a general property of hydrolases.     

Identification of crypto- and neochlorogenic lactones as potent xanthine oxidase inhibitors in roasted coffee beans

Xanthine oxidase (XO) inhibitory activity has been found in boiling water extracts from roasted coffee beans. Therefore, assay-guided purification of the extracts was performed using size-exclusion column chromatography, and subsequently with reversed phase HPLC to afford lactone derivatives of chlorogenic acids. Among the tested lactones, crypto- and neochlorogenic lactones showed potent XO inhibitory activities compared with three major chlorogenic acids found in coffee beans. These XO inhibitory lactones may ameliorate gout and hyperuricemia in humans who drink coffee.     

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.     

Dissolution of sucrose crystals in the anhydrous sorbitol melt

The dissolution of a sugar (sucrose as a model) with higher melting point was studied in a molten food polyol (sorbitol as a model) with lower melting point, both in anhydrous state. A DSC and optical examination revealed the dissolution of anhydrous sucrose crystals (mp 192 degrees C) in anhydrous sorbitol (mp 99 degrees C) liquid melt. The sucrose-sorbitol crystal mixtures at the proportions of 10, 30, 60, 100 and 150 g of sucrose per 100 g of sorbitol were heat scanned in a DSC to above melting endotherm of sorbitol but well below the onset temperature of melting of sucrose at three different temperatures 110, 130 and 150 degrees C. The heat scanning modes used were with or without isothermal holding. The dissolution of sucrose in the sorbitol liquid melt was manifested by an increase in the glass transition temperature of the melt and corresponding decrease in endothermic melting enthalpy of sucrose. At given experimental conditions, as high as 25 and 85% of sucrose dissolved in the sorbitol melt during 1 h of isothermal holding at 110 and 150 degrees C, respectively. Optical microscopic observation also clearly showed the reduction in the size of sucrose crystals in sorbitol melt during the isothermal holding at those temperatures.     

Antigenotoxic properties of Cassia tea (Cassia tora L.): mechanism of action and the influence of roasting process

Antigenotoxic properties and the possible mechanisms of water extracts from Cassia tora L. (WECT) treated with different degrees of roasting (unroasted and roasted at 150 and 250 degrees C) were evaluated by the Ames Salmonella/microsome test and the Comet assay. Results indicated that WECT, especially unroasted C. tora (WEUCT), markedly suppressed the mutagenicity of 2-amino-6-methyldipyrido(1,2-a:3':2'-d)imidazole (Glu-P-1) and 3-amino-1,4-dimethyl-5H-pyrido(4,3-b)indole (Trp-P-1). In the Comet assay performed on human lymphocytes, WECT exhibited significant protective effect on Trp-P-1-mediated DNA damage followed the order of unroasted (55%) > roasted at 150 degrees C (42% ) > roasted at 250 degrees C (29%). Pre-treatment of the lymphocytes with WEUCT resulted in 30% repression of DNA damage. However, no significant effect on excision-repair system was found during DNA damage expression time in post-treatment scheme (p>0.05). WEUCT showed 84% scavenging effect on oxygen free radicals generated in the activation process of mutagen detected by electron paramagentic resonance system. Two possible mechanisms were considered: (1) neutralization the reactive intermediate of Trp-P-1; and (2) protecting cells directly as an antioxidant that scavenge the oxygen radicals from the activation process of mutagen. The individual anthraquinone content in extracts of C. tora was measured by HPLC. Three anthraquinones, chrysophanol, emodin and rhein, have been detected under experimental conditions. The anthraquinone content decreased with increased roasting temperature. Each of these anthraquinones demonstrated significant antigenotoxicity against Trp-P-1 in the Comet assay. In conclusion, our data suggest that the decrease in antigenotoxic potency of roasted C. tora was related to the reduction in their anthraquinones.     

Structural features of acetylated galactomannans from green Coffea arabica beans

Polysaccharides were extracted from green Coffea arabica beans with water (90 °C, 1 h). Galactomannans were isolated from the water extract using preparative anion-exchange chromatography. Almost all of the galactomannans eluted in two neutral populations, while almost all of the arabinogalactans bound to the column, indicating that these arabinogalactans contain charged groups. Analysis of the molecular weight distribution of the two neutral populations showed that they differ in their molecular weight. Further characterization of these neutral populations by NMR and by MALDI-TOF MS after enzymatic degradation with an endo-mannanase, showed the presence of acetyl groups linked to the galactomannans, a feature not previously described for this type of polysaccharides from coffee beans. It was found that the high molecular weight (ca. 2000 kDa) neutral fraction was highly substituted both with galactose residues and acetyl groups, while the low molecular weight (ca. 20 kDa) population was much less substituted. Based on these results it can be concluded that at least two distinctly different populations of galactomannans are present in green coffee beans. It was also shown that the degradation of the galactomannans from green coffee beans with an endo-mannanase from A. niger is hindered by the presence of acetyl groups.     

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.     

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.     

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.