Occurrence of biogenic amine-forming lactic acid bacteria in wine and cider

A collection of 810 lactic acid bacteria (LAB) strains isolated from wine and cider was screened for potential biogenic amine (BA) producers by combining molecular and phenotypic approaches. A newly developed multiplex PCR method allowed for the simultaneous detection of four genes involved in the production of histamine (histidine decarboxylase, hdc), tyramine (tyrosine decarboxylase, tyrdc) and putrescine (via either ornithine decarboxylase, odc, or agmatine deiminase, agdi) while TLC and HPLC analysis allowed for BA-production determination. One hundred and fifty-eight LAB strains were monitored by the molecular/phenotypic double approach and revealed a good correlation between genotypic and phenotypic data. Eighteen per cent of the tested strains were positive for at least one BA target gene with up to three detected simultaneously, in particular amongst Lactobacillus brevis and Lactobacillus hilgardii isolates for the tyrdc and agdi genes. The most frequent gene corresponded to the agdi gene detected in 112 strains (14% of all LAB strains) of 10 different LAB species. The tyrdc gene was detected in 67 strains represented by 7 different LAB species (8% overall), especially those isolated from wine. Lower levels of hdc⁺ (2% of strains) and especially odc⁺ (0.5% of strains) strains were observed. Interestingly, species that have never been described to carry BA-producing pathway genes were identified in this study. Furthermore, only one cadaverine-producer was detected and corresponded to Lactobacillus 30a, a collection strain not found in fermented beverages, although cadaverine is commonly detected in wines.     

枸杞酒酿造过程中的酚酸降解规律

枸杞酒发酵过程中酵母代谢产生一些有机酸、醇、醛、酮等复杂的物质,使发酵环境发生了变化,迫使酚酸物质在此环境下发生氧化、还原或与环境中的物质发生化学反应从而产生各种降解产物.实验测定了酚酸物质在发酵过程中含量的变化及降解产物,并通过模拟实验,验证枸杞发酵时可能产生的降解产物.结果表明,从实验所用枸杞中共检测出7种酚酸单体...     

Simultaneous determination of theanine,gallic acid,purine alkaloids,catechins, and theaflavins in black tea using HPLC

In the present study, we employed high performance liquid chromatography with an amide‐C₁₆ column to determine the eighteen major active ingredients in black tea, including theanine, gallic acid, four purine alkaloids, eight catechins and four theaflavins. The method was successfully used to analyse two new kinds of black teas from the leaves of Camellia ptilophylla and Camellia kucha in China and several other world‐ famous black teas. Forty percentage ethanol was chosen as the extraction solvent for preparing tea extracts. All of the eighteen compounds could be separated within 86 min with a gradient elution system. Excellent linearity was observed for all the standard calibration curves, and correlation coefficients were above 0.9991. The developed method is accurate and sensitive enough for the determination of active components in black tea.     

In-vitro studies on the effect of polyphenol oxidase and peroxidase on the formation of polyphenolic black tea constituents

Flavanols (catechins and gallocatechins) isolated from green tea leaves (Camellia sinensis) (L) O Kuntze) were treated in vitro with polyphenol oxidase, peroxidase and a combination of both. The flavanol levels and those of the products formed were monitored by reversed-phase high-performance liquid chromatography (HPLC using spectrophotometric detection at 280 and 380 nm. Flavanols and theaflavins were quantified, whilst integrated peak areas are given for the remaining compounds. After fermentation in the presence of polyphenol oxidase higher levels of theaflavins and resolved thearubigins were obtained, whilst peroxidase produced higher amounts of chromatographically unresolved thearubigins of higher molecular weight, observed as a rise in the HPLC baseline, in the presence of peroxidase a significant decrease in the levels of all flavonol glycosides was observed, whilst in the presence of polyphenol oxidase only myricetin glycoside levels decreased.     

The chemical oxidation of catechins and other phenolics: A study of the formation of black tea pigments

The chemical oxidation of polyphenols has been used to produce black tea pigments. (+)-Catechin, (?)-epicatechin, (?)-epicatechin gallate and (?)-epigallocatechin gallate were isolated from convenient sources, their identity being confirmed by mass spectrometry and HPLC. The oxidation of a mixture of (?)-epicatechin gallate and gallic acid gave an oxidation product of (?)-epicatechin gallate in addition to epitheaflavic acid 3-gallate. The catechins were oxidised chemically and the products analysed by HPLC, the chromatograms being compared with a black tea chromatogram. The reactions gave both resolved and unresolved pigments, and many of the resolved pigments had HPLC retention times close to black tea pigments. Each catechin behaved differently, the chromatograms of the oxidation products from each starting material being clearly distinguishable. Resolved pigments were obtained by the chemical oxidation of other phenolic compounds. This work provides a convenient method for studying the formation of resolved and unresolved black tea pigments.     

A model for predicting black tea quality from the carotenoid and chlorophyll composition of fresh green tea leaf

The plant pigment (carotenoid and chlorophyll) composition of fresh green leaf of tea for a selection of clones was studied in relation to the quality of black tea produced from processing the same green leaf. The plant pigment composition of the green leaf for nine Kenyan clones was monitored by HPLC at 450 nm. Using discriminant analysis it was shown that clones could be distinguished from one another on the basis of their green leaf plant pigment composition. Using step-wise multiple regression analysis, a linear relationship was established between the levels of six green leaf plant pigments peak 5 (neochrome), peak 17 and 18 (isomers of lutein and/or lutein epoxide), peak 23 (chlorophyll b type compound), peak 26 (aurochrome) and peak 28 (β-carotene)) and the quality of the manufactured black tea for the selected clones as assessed by tea tasters' evaluations. The model had an adjusted R-square value of 0.912 and was significant at P≤ 0.05. The value of the relationship as a means of predicting black tea quality is discussed.     

Structural elucidation and analysis of thermal degradation products of the Fusarium mycotoxin nivalenol

The major class of mycotoxins produced by Fusarium moulds are trichothecenes, a large group of sesquiterpenes sharing the same basic chemical structure, a 12,13-epoxytrichothec-9-ene ring system. Their toxic effects range from causing diarrhoea, vomiting and gastro-intestinal inflammation to noncompetitive inhibition of the biosynthesis of proteins in eukaryotic cells. Trichothecenes in general are relatively stable compounds, their degradation is observed only at high temperatures and prolonged heating time. In order to investigate the stability of the trichothecene nivalenol (NIV) under food processing conditions such as cooking or baking, we performed model heating experiments and screened the residue for degradation products using gas chromatography-mass spectrometry (GC-MS). Heating of nivalenol, especially under mild alkaline conditions, gave a mixture of four compounds (norNIV A, norNIV B, norNIV C, and NIV lactone), which where isolated and identified by nuclear magnetic resonance (NMR) and MS experiments. Although their formation was also demonstrated in heating experiments with spiked flour samples, only norNIV B was detectable in a screening of several commercially available samples, possibly due to the very low contamination with nivalenol. Furthermore, cell culture experiments using immortalized human kidney epithelial (IHKE) cells showed that the four compounds are less cytotoxic (formazan dye cytotoxicity assay) compared to nivalenol. Whereas nivalenol revealed an EC50 at 0.9 micromol, all other compounds did not show any significant effect up to 100 micromol.     

A screening method for the determination of ascorbic acid in fruit juices and soft drinks

A simple and rapid liquid chromatographic method based on a new stationary phase Teknokroma, Tr-010065 Mediterranea sea₁₈ (15 cm × 0.4 cm, id 3 μm), to determine ascorbic acid in beverages is reported. With the proposed method the samples were analysed by direct injection without a previous treatment. The total analysis time does not exceed 6 min. The method showed a good repeatability (RSD < 2%: n = 6) and an excellent sensitivity (LOD = 0.01 mg/l). Seventeen samples were analysed, including fruit juices, soft drinks and isotonic beverages. Ascorbic acid contents ranged from 6.6 to 840 mg/l. The ascorbic acid stability in some beverages during their shelf-life was also evaluated. Degradation of about 54% was observed in a tea drink.     

Variations in the leaf standard,chemical composition and quality of black tea (Camellia sinensis) due to plucking intervals

Green leaf standard, chemical composition and quality of black tea (Camellia sinensis (L) O Kuntze) change with plucking intervals. Long plucking intervals lead to poor leaf standard with a lot of mature leaves and lower theaflavins, the sum of volatile flavour compounds imparting a sweet flowery aroma (group II volatile flavour compounds), caffeine contents and tasters' evaluations of black tea. The sum of volatile flavour compounds imparting inferior, grassy, green flavour (group I volatile flavour compounds) to tea, however, increases with long plucking intervals.     

Multi-residue method for the determination of 450 pesticide residues in honey, fruit juice and wine by double-cartridge solid-phase extraction/gas chromatography-mass spectrometry and liquid chromatography-tandem mass spectrometry

A multi-residue method was developed for the determination of 450 pesticide residues in honey, fruit juice and wine using double-cartridge solid-phase extraction (SPE), gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-tandem mass spectrometry (LC-MS-MS). The method development was based on an appraisal of the characteristics of GC-MS and LC-MS-MS for 654 pesticides as well as the efficiency of extraction and purification from honey, fruit juice and wine. Samples were first diluted with water plus acetone, then extracted with portions of dichloromethane. The extracts were concentrated and cleaned up with graphitized carbon black and aminopropyl cartridges stacked in tandem. Pesticides were eluted with acetonitrile + toluene, and the eluates were concentrated. For 383 pesticides, the eluate was extracted with hexane twice and internal standard solution was added prior to GC-MS determination. For 67 pesticides, extraction was with methanol prior to LC-MS-MS determination. The limit of detection for the method was between 1.0 and 300 ng g^-1 depending on each pesticide analyte. At the three fortification levels of 2.0-3000 ng g^-1, the average recovery rates were between 59 and 123%, among which 413 pesticides (92% of the 450) had recovery rates of 70-120% and 35 pesticides (8% of the 450) had recovery rates of 59-70%. There were 437 pesticides (97% of the 450) with a relative standard deviation below 25%; there were 13 varieties (3% of the 450) between 25.0 and 30.4%.     

Sensorially important aldehyde production from amino acids in model wine systems: Impact of ascorbic acid,erythorbic acid,glutathione and sulphur dioxide

The efficiency of different white wine antioxidant systems in preventing aldehyde production from amino acids by oxidative processes is not well understood. The aim of this study was to assess the efficiency of sulphur dioxide alone and in combination with either glutathione, ascorbic acid or its stereoisomer erythorbic acid, in preventing formation of the sensorially important compounds methional and phenylacetaldehyde from methionine and phenylalanine in model white wine. UHPLC, GC–MS/MS, LC–MS/MS, flow injection analysis and luminescence sensors determined both compositional changes during storage, and sulphur dioxide–aldehyde apparent equilibrium constants. Depending on temperature (25 or 45 °C) or extent of oxygen supply, sulphur dioxide was equally or more efficient in impeding the production of methional compared to the other antioxidant systems. For phenylacetaldehyde, erythorbic acid or glutathione with sulphur dioxide provided improved inhibition compared to sulphur dioxide alone, in conditions of limited oxygen consumption. The results also demonstrate the extent to which sulphur dioxide addition can lower the free aldehyde concentrations to below their aroma thresholds.     

Concentrations of phytanic acid and pristanic acid are higher in organic than in conventional dairy products from the German market

Differentiation of organic and conventional dairy products is an important, yet difficult task in food authentication. In this study it was tested whether phytanic acid and pristanic acid can be used as markers for this purpose. Phytanic and pristanic acid cannot be de novo synthesised by mammals, and the predominant source for uptake is chlorophyll in food. Highest concentrations (but still in the sub-gram per 100 g lipids range) are found in ruminants because rumen bacteria are able to release phytol from chlorophyll and transforming it into phytanic acid. Degradation of phytanic acid leads to pristanic acid, and both fatty acids usually co-exist in biota. Owing to the unique source of grass-based feedstuffs in organic farming it was tested whether organic cheeses (n = 13) and other organic dairy products (n = 5) are higher in phytanic and pristanic acid concentrations than conventional products (n = 12). For this purpose, a sensitive gas chromatography–mass spectrometry method in the selected ion monitoring mode was developed.     

A sensitive and selective method for the quantitative determination of fatty acid tryptamides as shell indicators in cocoa products

 Tetracosanoyl-2-(3-indolyl)ethane amide (lignocerinic acid tryptamide; LAT) and docosanoyl-2-(3-indolyl)ethane amide (behenic acid tryptamide; BAT) were identified as the most prominent tryptamides in cocoa shells based on electrospray ionisation mass spectrometry and ¹H NMR measurements. The structure of LAT, which is reported for the first time in cocoa shells, and also that of BAT were confirmed by synthesis. By using synthesised heptadecanoyl-2-(3-indolyl)ethane amide as the internal standard, a sensitive and reproducible method was developed for the quantification of LAT and BAT in the picogram range by means of HPLC/fluorescence detection. The detection limit was determined to be 30 pg/run. In authentic shell samples, 50-fold higher concentrations of both tryptamides were determined compared to the cocoa cotyledons. In 15 commercial chocolate samples, concentrations of 23.1–63.0 μg of the tryptamides (sum of both) per gram of fat were found. A first experiment attempted to correlate the tryptamide content with the amounts of shells in a model chocolate showed that the method is a promising tool to determine the shell content in the quality assessment of cocoa products. Received: 8 May 1998     

Effect of acetaldehyde and several acids on the formation of vitisin A in model wine anthocyanin and colour evolution

Summary It was found that the reaction between malvidin 3-glucoside and added pyruvic acid (PA), leading to the formation of vitisin A in model wine solutions, was not prevented by the addition of either acetaldehyde (A) or several organic acids. The acylated forms of vitisin A (3-acetylvitisin A and 3- p -coumarylvitisin A) were formed through the interaction of malvidin 3-acetylglucoside and malvidin 3- p -coumarylglucoside. Disappearance of the three main anthocyanins (malvidin 3-glucoside, malvidin 3-acetylglucoside and malvidin 3- p- coumarylglucoside) from the model wine with time followed first order kinetics. Acetaldehyde had the effect of increasing the total amount of these losses but producing smaller amounts of vitisin A. During ageing model solutions developed some browness. The brownest solution was obtained without A and a reduced rate of browning was found in the presence of A. This latter result can be explained by the assumption of a superimposition of a blueing effect upon reactions of A with anthocyanins. In the presence of PA the formation of vitisin A compounds gave an intermediate colour, contributing a reddish hue to the solution. A good correlation (r²= 0.96) between the percentage of vitisin A, of the total anthocyanins and the hue angle was observed. The addition of large amounts of organic acids that are normally found in wine into the model solutions did not lead to the formation of new anthocyanins. The linear loss of PA in all model systems indicates that a first order reaction occurs and 35.35 times more PA than total anthocyanin was lost to form the new compounds.     

A comparative study on the determination of lactic acid in silage juice by colorimetric,high-performance liquid chromatography and enzymatic methods

The determination of lactic acid in the silage juice of artichokes with different additives (formid acid, molasses and NaCl) by the colorimetric method and its comparision with the high-performance liquid chromatography and enzymatic methods was investigated. The lactic acid content of the artichoke with molasses (62.1 g kg⁻¹) was higher than that of those with formic acid, or NaCl and without any additive (39.3, 33.0 and 43.2 g kg⁻¹, respectively). However, this effect was not significant (P > 0.05). There were significant differences on the method of measuring lactic acid of the artichoke silages (P < 0.001). The use of the enzymatic method resulted in a higher (75.6 g kg⁻¹) lactic acid content than when the colorimetric or HPLC methods were employed (with results of 42.0 and 28.9 g kg⁻¹, respectively). However, the levels of lactic acid in silage juices found using the colorimetric and HPLC methods were not different, and recovery percentages, by using the colorimetric method, were satisfactory (103.78%), when the detection limit at maximum level (30 µg ml⁻¹) was not exceeded. © 1999 Society of Chemical Industry     

Effects of buffer and temperature on formation of furan, acetic acid and formic acid from carbohydrate model systems

Effects of temperature, pH and phosphate buffer on volatiles formed by heating model solutions of fructose, glucose, sucrose, lactose or starch were investigated by selected ion flow tube-mass spectrometry (SIFT-MS). Among the carbohydrates studied, the monosaccharide reducing sugars fructose and glucose were more reactive than macro molecular starch, lactose and sucrose, which are not reducing sugars. Furan was formed from fructose heated at 120, 100 and 80 °C at pH 5-7 in phosphate buffer and at 100 °C in unbuffered solution. Glucose did not yield furan in unbuffered solution at 100 °C but glucose did yield furan in phosphate buffer solution at a similar pH. Furan formation increased as temperature and pH increased. As temperature, pH value, and buffer components changed, furan formation may occur by different reactive pathways. Both of the buffer components, NaH₂PO₄ and citric acid, enhanced the formation of thermal degradation products from fructose. The enhancing effect of NaH₂PO₄ was stronger than citric acid. Formic and acetic acids were concomitantly formed with furan. More formic acid was produced from fructose than glucose, and more acetic acid was produced from glucose than fructose.     

A survey on the presence of free glutamic acid in foodstuffs,with and without added monosodium glutamate

A survey on free glutamic acid (Glu) content in a variety of foods (broths, soups, sauces and salad dressings), with and without added monosodium glutamate (MSG), was carried out. A simple procedure, involving a dilution step for liquid samples or homogenization with 0.1 N HCl for solid and slurry samples, followed by derivatization with o-phthaldialdehyde, HPLC separation on C18 column and spectrofluorometric detection, was employed to quantify Glu, as well as a number of other free amino acids and biogenic amines. Broths and soups with added MSG had Glu contents of 92.7–341 mg/100 g. The highest amounts of Glu in foods with no added MSG were found in products containing hydrolyzed proteins (up to 129 mg/100 g). None of the products ready for consumption exceeded the limit of 10 g/kg of food, established by the European Directive, 95/2/CE [European Parliament and Council Directive (1995). No. 95/2/EC of 20 February 1995 on food additives other than colours and sweeteners. Official Journal, L061, 1–40].     

不同处理方式对芡实中游离氨基酸和碳水化合物的含量及淀粉消化率的影响

以芡实为原料,采用水煮后冷冻干燥、水煮后热风干燥、冷冻干燥、太阳晒干、热风干燥等5种方式处理芡实,测定处理后芡实中游离氨基酸、还原糖、总糖、淀粉含量及淀粉消化率,比较不同处理方法的差异性。结果表明:热风干燥、冷冻干燥、太阳晒干对芡实中还原糖、总糖和游离氨基酸的含量影响差异极显著(P<0.01),且冷冻干燥、太阳晒干、热风干燥的芡实中还原糖、总糖、游离氨基酸的含量依次下降,这表明真空冷冻干燥处理能最大程度地保留样品中还原糖、总糖等物质。冷冻干燥、热风干燥及太阳晒干的处理方法对赖氨酸、亮氨酸、色氨酸等游离氨基酸的含量影响差异不显著(P>0.05)。水煮加工处理显著影响芡实中还原糖、总糖和游离氨基酸的含量(P<0.01),而对淀粉含量影响差异不显著(P>0.05)。淀粉体外消化率分析表明,各样品的淀粉体外消化率均随着消化时间的增加而呈现上升的趋势,不同干燥方式显著影响芡实中淀粉的体外消化率,冷冻干燥、热风干燥、太阳晒干的芡实中淀粉体外消化率依次增大,水煮后样品中淀粉的体外消化率增加,且水煮后冷冻干燥的样品中淀粉的体外消化率最高。     

Formation of the highly stable pyranoanthocyanins (vitisins A and B) in red wines by the addition of pyruvic acid and acetaldehyde

Pyruvic acid (500 mg/l) and acetaldehyde (200 mg/l) were added, either as a large single dose or as smaller weekly doses over a 10 week period, to a young red wine (Vitis vinifera L. cv Tempranillo) in order to study the formation of vitisin A and B, and p-coumaroylvitisin A and B. In a further trial, pyruvic acid and acetaldehyde were added simultaneously as a single administration to test for any synergistic effect on vitisin formation. The addition of pyruvic acid led to the production of higher concentrations of vitisin A (4.08 ± 0.86 mg/l; 2.03% of the total anthocyanin content), while additions of acetaldehyde increased the concentration of vitisin B (2.47 ± 0.09 mg/l; 1.35%). The single, large dose administrations led to greater vitisin formation than did the smaller, weekly doses. Different patterns of formation were seen for vitisin A and B: the highest vitisin A content was achieved during the latter half of the 10 week study period while the highest vitisin B concentration was achieved early. The addition of acetaldehyde produced a greater reduction in monomeric anthocyanins than did the addition of pyruvic acid (loss of total anthocyanins 81.5%). The simultaneous addition of pyruvic acid and acetaldehyde led to less vitisin formation than did the addition of the reagents separately. p-Coumaroylvitisin A reached a maximum concentration of 0.86 ± 0.15 mg/l when the single dose of pyruvic acid was added, while the maximum recorded for p-coumaroylvitisin B was 0.66 ± 0.05 mg/l when the single dose of acetaldehyde was added. All anthocyanins were identified using HPLC/DAD and HPLC/ESI–MS.