Chemical discrimination of arabica and robusta coffees by Fourier transform Raman spectroscopy

This article deals with the potential of Fourier transform (FT) Raman spectroscopy in discrimination of botanical species of green and roasted coffees. There are two species of commercial importance: Coffea arabica (arabica) and Coffea canephora (robusta). It is recognized that they differ in their lipid fraction, especially in the content of the diterpene kahweol, which is present at 0.1-0.3% dry matter basis in arabica beans and only in traces (<0.01%) in robusta. The visual examination of the Raman spectra of the lipid fraction extracted from arabica, robusta and liberica samples shows differences in the mid-wavenumbers region: arabica spectra have two characteristic scattering bands at 1567 and 1478 cm(-1). The spectrum of the pure kahweol shows the same bands. Principal component analysis is applied to the spectra and reveals clustering according to the coffee species. The first principal component (PC1) explains 93% of the spectral variation and corresponds to the kahweol concentration. Using the PC1 score plot, two groups of arabica can be distinguished as follows: one group with high kahweol content and another group with low kahweol content. The first group includes samples coming from Kenya and Jamaica; the second group includes samples from Australia. The main difference between these coffees is that those from Kenya and Jamaica are well-known for growing at a high altitude whereas those ones from Australia are grown at a low altitude. To our knowledge, the application of Raman spectroscopy has never been used in coffee analysis.     

Chemical characterization of the high-molecular-weight material extracted with hot water from green and roasted robusta coffees as affected by the degree of roast

The hot-water-soluble polymeric material from green and roasted Uganda robusta coffees submitted to different degrees of roasting was isolated and characterized, and the changes in structure and amount of galactomannans and arabinogalactans were determined and discussed in relation to the data already available for arabica coffees, obtained under the same experimental conditions. The content of arabinogalactans extracted from robusta green coffee was higher than that extracted from arabica. For roasted coffees, the amount of galactomannans extracted ranged from 0.66% to 0.92% (w/w). These values were near 50% of those obtained from the arabica coffees using the same extraction procedure. However, the amount of arabinogalactans extracted from robusta coffees (0.56-0.72%) was in the range obtained from arabica. The structures of arabinogalactans and galactomannans extracted from green and roasted coffees were not sufficiently different between robusta and arabica coffees to explain the observed differences in extraction yields for the arabinogalactans from green coffees and for the galactomannans from roasted coffees. The total polysaccharide content and the structures of the galactomannans and arabinogalactans in the two green coffee varieties investigated were also very similar. These differences in the extraction of high-molecular-weight polysaccharides between arabica and robusta roasted coffees may be related to the different susceptibility of the cell walls during the roasting process, known to result in a different porosity between arabica and robusta roasted coffees.     

Discrimination between arabica and robusta coffee species on the basis of their amino acid enantiomers

This work reports the results for the composition of robusta and arabica coffee species in terms of their amino acid enantiomers in the green and roasted states. The analyses were conducted for the free amino acids, as well as for the amino acids obtained after acid hydrolysis. The amino acids were extracted/hydrolyzed and isolated by SPE on strong cation exchange columns, derivatized to their N-ethoxycarbonylheptafluorobutyl esters, and analyzed by gas chromatography/FID on a Chirasil l-Val column. Multivariate analyses applied to the results showed that the free amino acids can be used as a tool for discrimination between coffee species, with a special reference to l-glutamic acid, l-tryptophan, and pipecolic acid. There is also some evidence that these compounds can be used for discrimination between green coffees subjected to different postharvest processes. It is also shown that the amino acid levels observed after acid hydrolysis can be used for the same purposes, although displaying less discriminatory power.     

以生物胺变化评价冷藏罗非鱼片腐败进程

为了探讨生物胺指标评价鱼肉腐败进程的可能性及其安全范围,应用反相高效液相色谱法测定冷藏罗非鱼片贮藏过程的生物胺变化,用以判断鱼片的腐败进程。结果表明:新鲜鱼片初始单胺和多胺总量较高,二胺总量很低。贮藏过程中单胺和多胺波动变化并呈下降趋势,尸胺、腐胺含量快速增加成为主要生物胺。含有尸胺+腐胺的二胺、生物胺指数、总生物胺等指标与其两者增长趋势相似。相关分析表明尸胺、腐胺、二胺、生物胺指数、总生物胺与贮藏时间、微生物数量和氨基态氮具有高度相关性。经回归分析表明假单胞菌、肠杆菌的增长与尸胺、腐胺具有重要的对应关系。尸胺、腐胺和二胺可简便有效评价鱼片腐败进程;但综合考虑组胺和酪胺的毒性,则生物胺指数(BAI)更适用,冷藏罗非鱼片生物胺指数的初步判别范围为:<20mg/kg,新鲜;20～40mg/kg,可接受;>40mg/kg,腐败。该研究为冷藏罗非鱼片生物胺的限量标准提供数据参考。     

Furan levels in coffee as influenced by species, roast degree, and brewing procedures

Brazilian green coffee beans of Coffea arabica and Coffea canephora species were roasted to light, medium, and dark roast degrees and analyzed in relation to furan content by using an in-house validated method based on gas chromatography coupled to mass spectrometry preceded by headspace solid-phase microextraction. Furan was not detected in green coffees, whereas levels between 911 and 5852 μg/kg were found in the roasted samples. Higher concentrations were found in Coffea canephora species and darker ground coffees. Some of the potential furan precursors were observed in significant amounts in green coffee, especially sucrose and linoleic acid, but their concentrations could not be correlated to furan formation. Additionally, coffee brews were prepared from roasted ground coffees by using two different procedures, and furan levels in the beverages varied from <10 to 288 μg/kg. The factor that most influenced the furan content in coffee brew was the brewing procedure.     

Factors influencing the norharman and harman contents in espresso coffee

Espresso coffee (EC) brews were analyzed for beta-carboline [norharman (NH) and harman (H)] contents, by RP-HPLC with fluorescence detection. The influence of the coffee species (arabica or robusta), the roast degree, and the brew length was studied. The results show that the content of NH and H in EC is dependent primarily on the coffee species, followed by brew length. The roast degree has only a minor influence on the final content of NH and H in EC. When compared with other coffee brews, EC has an amount of these beta-carbolines (in micrograms per liter) similar to that of mocha coffee, both being more concentrated than filter and press-pot coffees. Therefore, the consumer's preferences will determine the amount of NH and H ingested daily. For the caffeinated 30 mL of EC, the arabica coffees contain about 4.08 microg of NH and 1.54 microg of H. Commercial blends (usually with a maximum of 30% robusta) range from the cited arabica values to 10.37 microg of NH and 4.35 microg of H.     

电子束辐照对真空包装章鱼生物胺的抑制作用研究

为分析电子束辐照处理对真空包装章鱼制品冷藏过程中生物胺形成的抑制作用,以真空包装的新鲜章鱼腕足段为研究对象,分别进行0、0.5、1.0、1.5、2.0和2.5 kGy剂量的电子束辐照处理,于4℃下冷藏63 d,每隔7 d进行感官品评和生物胺含量检测。结果表明,冷藏期间真空包装的章鱼中共检测出精胺、亚精胺、腐胺、尸胺、组胺和酪胺6种生物胺。电子束辐照处理能抑制章鱼冷藏过程中腐胺、尸胺、组胺和酪胺的生成,且抑制作用与辐照剂量成正比,其中对组胺生成的抑制效果最佳,仅在少数样品中被检出。此外,电子束辐照也抑制了章鱼中亚精胺和精胺在冷藏后期的分解。冷藏过程中的腐胺、尸胺和酪胺含量变化与样品感官品质表现出较好的一致性,高感官品质章鱼样品中的腐胺、尸胺和酪胺含量均≤10 mg·kg-1。综合电子束不同剂量辐照对章鱼感官品质和生物胺的抑制作用,1.0 kGy的电子束辐照剂量是真空包装章鱼4℃冷藏保鲜的最适前处理,其能延长高品质新鲜章鱼货架期至35 d。本研究结果为章鱼加工企业生产高品质章鱼产品提供了理论依据。     

Development of stable isotope dilution assays for the simultaneous quantitation of biogenic amines and polyamines in foods by LC-MS/MS

Microbial amino acid metabolism may lead to substantial amounts of biogenic amines in either spontaneously fermented or spoiled foods. For products manufactured with starter cultures, it has been suggested that certain strains may produce higher amounts of such amines than others; however, to support efforts of food manufacturers in mitigating amine formation, reliable methods for amine quantitation are needed. Using 10 isotopically labeled biogenic amines as the internal standards, stable isotope dilution assays were developed for the quantitation of 12 biogenic amines and of the 2 polyamines, spermine and spermidine, in one LC-MS/MS run. Application of the method to several foods revealed high concentrations of, for example, tyramine and putrescine in salami and fermented cabbage, whereas histamine was highest in Parmesan cheese and fermented cabbage. On the other hand, ethanolamine was highest in red wine and Parmesan cheese. The results suggest that different amino acid decarboxylases are active in the respective foods depending on the microorganisms present. The polyamine spermine was highest in salami and tuna.     

Biogenic amines and polyamines in milks and cheeses by ion-pair high performance liquid chromatography

The proposed chromatographic method provides a complete resolution of twelve amines in a single run in milks and unripened cheeses, avoiding the losses of resolution linked to fluctuations in working temperature. We also propose an alternative chromatographic gradient, which can be useful for samples that have undergone long ripening periods, like ripened cheeses. According to the results of the reliability study, the method described was precise, accurate, and sensitive. The method was applied to several samples of milks and cheeses and the results showed that the biogenic amine profiles varied greatly, not only between different types of samples but also among the samples from the same kind of products. In unripened cheeses, milks, and yogurts, spermidine and spermine were the prevailing amines, but in ripened cheeses the major amine was tyramine, followed by putrescine and cadaverine.     

Determination of biogenic amines in squid and white prawn by high-performance liquid chromatography with postcolumn derivatization

A simple method was developed for the determination of biogenic amines in aquatic food products using a reverse-phase high-performance liquid chromatography with postcolumn automatic o-phthalaldehyde derivatization and fluorescence detection. The linearity, repeatability, and recovery of the method for seven amines (tyramine, putrescine, cadaverine, histamine, agmatine, spermidine, and spermine) were evaluated. This optimized method was applied to detect biogenic amines in squid and white prawn during refrigerated storage. Sensory analysis, pH value, and total volatile base nitrogen value were combined to evaluate the freshness quality of these two raw materials. Agmatine and cadaverine in squid, cadaverine, and putrescine in white prawn were the most obviously changed amines during the storage at two different temperatures, and these biogenic amines could be the effective quality indicators for the freshness of the raw aquatic materials.     

降解亚硝酸盐和生物胺乳杆菌筛选及其改善鱼肉香肠品质效果

为了筛选出优良亚硝酸盐和生物胺的降解植物乳杆菌,并研究在鱼肉发酵香肠中的应用。该文主要考察了19株植物乳杆菌亚硝酸盐和生物胺的降解活性及相关基因的携带情况,从中筛选出优良菌株,并研究其对鱼肉香肠发酵过程中各种亚硝胺、生物胺、腐败微生物的抑制作用和对其他理化指标的影响。试验结果表明,L.plantarum CP3对亚硝酸盐和生物胺的降解能力最强,分别达到95%和77%,PCR结果显示此菌株中含有亚硝酸盐降解(假定蛋白(hypothetical protein,HP)、谷胱甘肽还原酶(glutathione reductase,GR)、一氧化还原酶(Oxidoreductase,ORD))和生物胺降解的相关基因(multicopper oxidases,suf I),且不含生物胺生成相关基因(hdc,tdc,odc)。GC-MS测定结果显示L.plantarum CP3对发酵香肠中4种亚硝胺-二乙基亚硝胺(N-nitrosodiethylamine,NDEA),二甲基亚硝胺(N-nitrosodimethylamine,NDMA),亚硝基吗啉(N-nitrosomorpholine,NMOR)和甲基乙基亚硝胺(N-nitrosomethylamine,NMEA)的生成都具有显著的抑制作用,联合接种L.saki M4可以协同提高亚硝胺的降解能力。并且,与对照组相比,接种L.plantarum CP3+L.saki M4的鱼肉香肠,发酵48 h后腐胺、尸胺和酪胺的含量分别降低了76.83%,93.33%和88%。另外,接种乳酸菌处理组香肠中的肠杆菌、假单胞菌等腐败菌及pH值、硫代巴比妥酸(thiobarbituric acid,TBA)和挥发性盐基氮(total volatile basic nitrogen,TVB-N)的含量显著低于对照组。该研究结果体现了L.plantarum CP3作为香肠等肉制品发酵剂的良好开发应用前景。     

Gas chromatography-mass spectrometry assessment of amines in Port wine and grape juice after fast chloroformate extraction/derivatization

A simple, reliable, and sensitive gas chromatography-mass spectrometry method for the quantification of volatile and nonvolatile biogenic amines in Port wines and grape juices was developed and evaluated. The method was based on a previously reported two-phase derivatization procedure with isobutyl chloroformate in a toluene medium, which provides a quantitative reaction in 10 min. Following the derivatization step, the excess of reagent was eliminated by treatment with alkaline methanol. The derivatization procedure was performed directly on 1 mL of sample, avoiding any fastidious and time-consuming cleanup extraction steps. The method allows the simultaneous quantification of 22 amines, which can be found in wines: methylamine, dimethylamine, ethylamine, diethylamine, propylamine, isopropylamine, butylamine, isobutylamine, amylamine, isoamylamine, 2-methylbutylamine, hexylamine, pyrrolidine, piperidine, morpholine, 1,3-diaminopropane, putrescine, cadaverine, 1,6-diaminohexane, 2-phenylethylamine, histamine, and tyramine. Because of the fact that histamine and tyramine derivatives are degraded during the isobutyl chloroformate elimination step, the corresponding determination was made after removal of the excess of derivatizing reagent by evaporating an aliquot of the toluene layer obtained after the reaction. The presented method showed excellent analytical characteristics in what linearity, recovery, repeatability, and limit of detections were respected. It was used to assess the concentration of biogenic amines in juice grapes and Tawny and Vintage Port wines with different aging times. On the whole, the total content of amines in Port wines was low. Most of the amines found in wines have their origin in the raw material used for their elaboration, so the Port winemaking process is not prone to the production of this kind of compounds. Total biogenic amine contents have shown a decrease with the aging of both types of Port wines.     

Biogenic amines in low- and reduced-fat dry fermented sausages formulated with konjac gel

Biogenic amines in low- and reduced-fat dry fermented sausages made with konjac gel (KG) as pork backfat replacer were studied. An increase (P < 0.05) was observed in the microbial count during the fermentation process, reaching levels of over 8 Log cfu/g of total viable microorganisms and lactic acid bacteria. However, no significant differences were observed in the microbiota evolution as a function of the reformulation process (fat and konjac gel content). High levels of physiological amines (spermidine, spermine, and agmatine) were observed in the raw material. From day 2 of the fermentation process an increase (P < 0.05) was observed in tyramine and putrescine, which were the predominant amines at the end of the storage period. The increase in these amines was proportional to the presence of KG and fat reduction. This can also be seen for spermine, with agmatine showing the inverse. The biogenic amine levels in these products reformulated with KG are not considered to pose a health risk to consumers.     

Biogenic amines in wines from three Spanish regions

One hundred and sixty-three wines from La Rioja, Utiel-Requena, and Tarragona were analyzed to determine if there were any differences in the concentrations of six biogenic amines that are found in these three regions. The influence of grape variety, type of vinification, wine pH, malolactic fermentation, and storage in bottle on biogenic amine concentrations was studied. Results show important differences in putrescine and histamine concentrations among regions, varieties of grape, and type of wine; differences were less appreciable for the remaining biogenic amines studied. Low pH prevented biogenic amine formation. Malolactic fermentation and short storage periods in bottle (3-6 months) showed increases in histamine concentration, whereas longer periods of storage led to a general decrease in histamine. Several strains of lactic acid bacteria were isolated in this work, and their ability to form biogenic amines was assayed in synthetic media, grape must, and wine. Grape varieties, different types of winemaking, pH, and lactic acid bacteria may be responsible for the differences observed in the biogenic amine concentrations of the wines analyzed.     

Influence of lupin (Lupinus luteus L. cv. 4492 and Lupinus angustifolius L. var. zapaton) and fenugreek (Trigonella foenum-graecum L.) germination on microbial population and biogenic amines

Microbial population and bioactive amine profile and levels of two lupin species (Lupinus luteus L. cv. 4492 and Lupinus angustifolius L. var. zapaton) and fenugreek (Trigonella foenum-graecum L.) seeds as affected by germination were investigated. Microbial population increased considerably mainly in the first stage of germination (2 days), then small changes in bacterial numbers were observed up to 5 days to levels between 7.8 and 8.9 log colony-forming units/g. Microorganisms belonging to the Enterobacteriaceae family were dominant for the legumes tested. Ungerminated legume seeds contained putrescine, cadaverine, histamine, tyramine, spermidine, and spermine. Bioactive amine levels found in fenugreek seeds were between 3- and 4-fold higher than those found in lupin seeds. The highest total amine levels were found in fenugreek seeds [162 mg/kg of dry weight (dw)], followed by L. angustifolius var. zapaton seeds (84 mg/kg of dw) and, finally, L. luteus cv. 4492 (46 mg/kg of dw) seeds. The concentration of individual amines showed a gradual rising trend during the germination period in all tested sprouts, reaching levels >3 times higher than those found in ungerminated seeds. After 5 days of germination, the fenugreek sprouts contained the highest amount of total bioactive amines. Tyramine was the predominant amine in both lupin varieties, whereas cadaverine was the main bioactive amine detected in fenugreek. The results of this work thus indicated that microbial population and biogenic amine levels in the studied lupin and fenugreek sprouts are not a risk for healthy consumers or for individuals with restricted activity of detoxification enzymes.     

Influence of cultivar and germination on bioactive amines in soybeans (Glycine max L. Merril)

The levels of amines in soybeans as affected by cultivar in two consecutive years and by germination were investigated. Spermidine, spermine, putrescine, agmatine, and cadaverine were detected, whereas tyramine, histamine, tryptamine, serotonine, and phenylethylamine were not. Spermidine was the predominant amine followed by spermine. High concentrations of these amines confirmed soybean as a rich source. Cadaverine was confirmed to be inherent to soybean. The percent contribution of spermidine and spermine to total levels was not affected by cultivar in either years. However, amine levels were affected by cultivars in different ways in the consecutive years. Cadaverine was affected more by the cultivar, whereas spermidine, spermine, and agmatine were affected by harvest year. During germination the levels of amines from soybean increased significantly, except for agmatine. Spermidine and spermine accumulated in the cotyledon, whereas cadaverine and putrescine accumulated in the radicle and hypocotyl.     

Biogenic amine profile in unripe Arabica coffee beans processed according to dry and wet methods

Immature coffee fruit processing contributes to a high amount of defective beans, which determines a significant amount of low-quality coffee sold in the Brazilian internal market. Unripe bean processing was tested, taking the levels of bioactive amines as criteria for evaluating the extent of fermentation and establishing the differences between processing methods. The beans were processed by the dry method after being mechanically depulped immediately after harvest or after a 12 h resting period in a dry pile or immersed in water. Seven bioactive amines were quantified: putrescine, spermine, spermidine, serotonin, cadaverine, histamine, and tyramine, with global amounts ranging from 71.8 to 80.3 mg/kg. The levels of spermine and spermidine were lower in the unripe depulped coffee than in the natural coffee. The specific conditions of dry and wet processing also influenced cadaverine levels, and histamine was reduced in unripe depulped coffee. A resting period of 12 h does not induce significant alteration on the beans and can be improved if performed in water. These results confirm that peeling immature coffee can decrease fermentation processes while providing more uniform drying, thus reducing the number of defects and potentially increasing beverage quality.     

Relation of biogenic amines' formation with microbiological and sensory attributes in Lactobacillus-inoculated vacuum-packed rainbow trout (Oncorhynchus mykiss) fillets

The biogenic amine (BA) content of vacuum-packed filleted rainbow trout (Oncorhynchus mykiss) inoculated or not with two different Lactobacillus strains, individually or in combination, was monitored during refrigerated storage for 20 days and related to respective bacteriological and sensory changes occurring during the same period. Eight amines, namely putrescine, cadaverine, tyramine, tryptamine, beta-phenylethylamine, histamine, spermine, and spermidine, were determined, whereas agmatine was not detected in any of the samples. In all cases, BA concentration was higher (P < or = 0.05) in the controls compared to all inoculated treatments, whereas the trend with regard to the bacterial populations (Enterobacteriaceae, pseudomonads, and H2S-producing bacteria) and the off-odor scores was similar. Inoculation with Lactobacillus sakei CECT 4808 showed the best preservative effect among inoculated treatments. Concentrations of putrescine and cadaverine, the main BAs formed, correlated well with both spoilage bacterial counts and off-odor scores and can be useful indicators of shelf life. Spermine and spermidine contents decreased during storage, while levels of the other determined BAs remained below 10 mg/kg even after sensory rejection.     

Multiple compound quality index for cold-smoked salmon (Salmo salar) developed by multivariate regression of biogenic amines and pH

Production of biogenic amines during chill storage of 12 lots of cold-smoked salmon was studied. These data allowed for a multiple compound quality index to be developed by multivariate regression (partial least square regression). The quality index was based on concentrations of cadaverine, histamine, putrescine, and tyramine and pH and showed good correlation with sensory assessments. Biogenic amines were indicators of spoilage rather than casual agents of spoilage off-flavors. Four different biogenic amine profiles were found at the time of spoilage in cold-smoked salmon. These were the results of differences in the spoilage microflora. Histamine was detected above regulatory limits but below toxic levels. Measurements of salt and dry matter for calculation of water phase salt could be substituted by rapid water activity measurements.