Identification of Candidate Amino Acids Involved in the Formation of Blue Pigments in Crushed Garlic Cloves (Allium sativum L.)

ABSTRACT:  The color-forming ability of amino acids with thiosulfinate in crushed garlic was investigated. We developed reaction systems for generating pure blue pigments using extracted thiosulfinate from crushed garlic and onion and all 22 amino acids. Each amino acid was reacted with thiosulfinate solution and was then incubated at 60 °C for 3 h to generate pigments. Unknown blue pigments, responsible for discoloration in crushed garlic cloves ( Allium sativum L.), were separated and tentatively characterized using high-performance liquid chromatography (HPLC) and a diode array detector ranging between 200 and 700 nm. Blue pigment solutions exhibited 2 maximal absorbance peaks at 440 nm and 580 nm, corresponding to yellow and blue, respectively, with different retention times. Our findings indicated that green discoloration is created by the combination of yellow and blue pigments. Eight naturally occurring blue pigments were separated from discolored garlic extracts using HPLC at 580 nm. This suggests that garlic discoloration is not caused by only 1 blue pigment, as reported earlier, but by as many as 8 pigments. Overall, free amino acids that formed blue pigment when reacted with thiosulfinate were glycine, arginine, lysine, serine, alanine, aspartic acid, asparagine, glutamic acid, and tyrosine. Arginine, asparagine, and glutamine had spectra that were more similar to naturally greened garlic extract.     

Fatty Acid Content,Flavor Compounds,and Sensory Quality of Pork Loin as Affected by Dietary Supplementation with l‐arginine and Glutamic Acid

To investigate the effect of functional amino acid on meat flavor and eating quality, 60 growing‐finishing pigs (Duroc × Large White × Landrace) were dietarily supplemented with or without 1.0% l ‐arginine, glutamic acid, or l ‐arginine plus glutamic acid for 2 months. After animals were slaughtered, the muscle fatty acid profile, flavor compounds, and meat sensory quality were comparatively investigated. The results showed that dietary supplementation with arginine, glutamic acid, or arginine plus glutamic acid had little effect on free amino acids, no effect on 5′‐nucleotides and meat sensory taste traits, but supplementation with arginine plus glutamic acid significantly increased (P < 0.05) fat accumulation and fatty acid content in muscle, increased (P < 0.05) the formation of multiple fatty acid oxidation‐derived volatile compounds, and improved the tenderness, juiciness, and overall eating quality of meat. This study revealed that dietary supplementation with 1.0% l ‐arginine and glutamic acid could be used to improve meat eating quality in pork production.     

Effect of ascorbic acid on the stability of β‐carotene and capsanthin in paprika (Capsicum annuum) powder

The effect of ascorbic acid, light, and storage on the stability of the pigments β‐carotene and capsanthin in red pepper (Capsicum annuum) powder has been elucidated by determining the amount of pigment in samples treated by various concentrations of ascorbic acid. Determination of pigment concentration has been performed after different storage times using high‐performance liquid chromatography. The dependence of the concentration of pigments on the concentration of ascorbic acid, presence of light and the storage time has been assessed by stepwise regression analysis. The concentration of pigments decreased at longer storage time and increased at higher concentration of ascorbic acid, β‐carotene being more sensitive towards storage time and concentration of ascorbic acid than capsanthin. Interaction between the effects of light and storage time, and light and concentration of ascorbic acid has been established.     

Effect of pyruvic acid and ascorbic acid on stability of 3‐deoxyanthocyanidins

BACKGROUND: 3‐Deoxyanthocyanins are a rare class of plant pigments primarily found in sorghum and known to possess distinct chemical and bioactive properties. They have potential as natural food colourants. This work investigates how 3‐deoxyanthocyanin pigments react with pyruvic acid and their stability in the presence of ascorbic acid. RESULTS: Substitution at C‐5 was the major determinant of the mechanism of 3‐deoxyanthocyanidin complexation with pyruvic acid: hydroxyl substitution favoured cyclic condensation, whereas methoxyl substitution favoured oxidative ring contraction. Pure 3‐deoxyanthocyanidins generally showed poor stability in the presence of 500 mg L^?1 ascorbic acid at pH 2.0 and 3.2 but were stable at pH 5.0; pyruvic acid improved their stability at pH 2.0 and 3.2 and enhanced their colour intensity at pH 5.0. Crude sorghum pigment extract was very stable in the presence of ascorbic acid: 31% colour loss at pH 2.0; 1.9‐ and 1.3‐fold increases in colour intensity at pH 3.2 and 5.0 respectively. In contrast, red cabbage pigment lost 30–85% of its colour in the presence of ascorbic acid under the conditions used in the study. CONCLUSION: Crude sorghum pigments are very stable in the presence of ascorbic acid and may be useful as natural food colourants. Copyright © 2008 Society of Chemical Industry     

Production of Red Water-Soluble Monascus Pigments

Water-soluble and thermal, as well as photo-stable, red Monascus pigments, were prepared by reacting the extracted pigment with aminoacetic acid and aminobenzoic acid. These modified pigments were compared to those using glutamic acid and gelatin as the modifying agents, showing that the colors and stabilities of these modified pigments were similar. Red pigments extracted from the mycelia could be dissolved in ethanol, propylene glycol, or in gelatin solution and freeze-dried. These red pigment concentrates or freeze-dried pigments could also be used as food colorants.     

Anthocyanins of Tradescantia pallida. Potential Food Colorants

Tradescantia pallida (syn. Setcreaseapurpurea) contained two major anthocyanins. One was cyanidin-3,7,3¹-triglucoside with 3 molecules of ferulic acid and an extra terminal glucose. The other pigment was similar but without the terminal glucose unit. The nonacyl portion was indentified by comparison with the pigment of Zebrina pendula. The acyl/aglycone and acyl/sugar ratios were determined by using internal standards and response factors with HPLC. The pigments may have potential as food colorants.     

红曲橙色素的提取及其稳定性研究

以固态发酵生产的红曲色素为材料,从色素的提取方法、稳定性测试及与氨基酸反应3方面进行研究。结果表明,用板层析方法可分离、制备较纯的橙色素。该色素的热稳定性良好,光稳定性差;酸性条件下较稳定,pH>5.7时色素可能发生变化,导致吸光值下降,最大吸收峰对应波长发生位移;Na2SO3与H2O2对橙色素有一定的破坏作用,NaCl与蔗糖没有太大影响;不同氨基酸与橙色素会发生不同程度的反应,文中对谷氨酸和橙色素反应生成的衍生物进行了分析,确定出其分子量和结构。     

氨基酸对红曲霉突变菌株合成代谢黄色素和橘霉素的影响

本实验研究了氨基酸对红曲黄色素合成代谢的影响.结果表明,除了酪氨酸（4 g/L）和甘氨酸（1 g/L）明显有利于黄色素合成代谢外,其余所选氨基酸都不利于黄色素的合成代谢或影响不明显,随着各种氨基酸的添加量从1g/L增加到6g/L,黄色素色价减少量都≥20％,有些黄色素减少量甚至达到83.15％（如苯丙氨酸）.甘氨酸添加量为6g/L时,橘霉素的合成代谢量是对照组的6.61倍,提高561％,橘霉素生成量为3.37 mg/L,其余氨基酸能明显消除橘霉素的合成代谢或影响不明显.从工业化生产黄色素角度考虑,通过添加4g/L的酪氨酸不仅有利于红曲霉突变菌株合成代谢黄色素,还能降低橘霉素的代谢生成量.     

Elucidation of chemical structures of pink-red pigments responsible for ‘pinking’ in macerated onion (Allium cepa L.) using HPLC-DAD and tandem mass spectrometry

The chemical structures of pink-red pigments responsible for ‘pinking’ in macerated onion were tentatively elucidated using HPLC with a diode array detector and tandem mass spectrometry. All pigments were produced in conditions that approximated the natural process as closely as possible, using mixtures of onion thiosulphinates, the enzyme alliinase, and free amino acids. The isotopic distribution of protonated molecules of pink-red pigments produced from individual amino acids indicated the absence of sulphur, with the exception of pigment produced from cystine. The pigments had a basic polymethine framework containing two pyrrole rings (3,4-dimethyl-1H-pyrrole and 3,4-dimethyl-2,5-dihydro-1H-pyrrole) bridged by methines. The side chains attached to the nitrogen of the pyrrole rings were derived from the reacting amino acid. The simplest pink-red pigment, produced from glycine, was identified as 2-(2-(3-(1-(carboxymethyl)-3,4-dimethyl-1H-pyrrol-2(5H)-ylidene)prop-1-en-1-yl)-3,4-dimethyl-1H-pyrrol-1-yl)acetic acid. The pigment from alanine was identified as 2-(2-(3-(1-(carboxymethyl)-3,4-dimethyl-1H-pyrrol-2-yl)allylidene)-3,4-dimethyl-2,5-dihydro-1H-pyrrol-1-yl)propanoic acid. The chemical structures of pink-red pigments from leucine, asparagine, glutamine, tyrosine, and cystine also were determined.     

Degradation patterns and stability predictions of the original reds and amino acid derivatives of monascus pigments

The original red isomers and l-phenylalanine derivative isomers of monascus pigment, which have a side chain of either C₅H₁₁ or C₇H₁₅, were produced via Monascus fermentation, and then purified. The degradation patterns of the pigments relating to incubation conditions were investigated. For all tested compounds, a total of seven major fragments were formed during incubation, five in presence of sunlight irradiation and two with no sunlight. The red isomers R5 and R7 showed the same pattern whereas the L-Phe derivative isomers P5 and P7 exhibited another pattern. All of the pigments appeared to be highly sensitive to sunlight irradiation considering that with sunlight, diverse fragments were produced and the side chains C₅H₁₁ and C₇H₁₅ were degraded. The fragments are thought to be formed via degradation and combination reactions of pigments based on a comparison of the fragment molecular masses. Theoretically stable isomers of an original red pigment and some amino acid derivatives were selected based on a comparison of their Hartree conformational energies, which were estimated using geometric optimization based on ab initio molecular orbital calculations. The greater stability of amino acid derivatives was confirmed based on maximum UV-absorption wavelengths and isomer population rates.     

Characterization of Red Radish Anthocyanins

Red radish (Raphanus sativus L.) anthocyanins were extracted from liquid nitrogen powdered epidermal tissue using acetone, partitioned with chloroform and isolated using C-18 resin. The monomeric anthocyanin content, determined by pH-differential, was 154 ± 13 mg/100g epidermal tissue (pelargonidin-glucoside basis). Thermal processing of radishes showed that the pigments were stable to heat. Four major pigments were identified by Mass Spectroscopy, HPLC, and spectral analyses as pelargonidin-3-sophoroside-5-glucoside derivatives. The two major pigments were acylated with malonic acid and either ferulic or p-coumaric acid. The two other pigments were acylated with only ferulic or p-coumaric acid. Acylation increased pigment resistance to acid hydrolysis.     

Improved analysis of Monascus pigments based on their pH-sensitive UV-Vis absorption and reactivity properties

Monascus pigments, a mixture of azaphilones mainly composed of red, orange and yellow pigments, are usually prepared in aqueous ethanol and analysed by ultraviolet-visible (UV-Vis) spectroscopy. The pH of aqueous ethanol used during sample preparation and analysis has never been considered a key parameter to control; however, this study shows that the UV-Vis spectra and colour characteristics of the six major pigments are strongly influenced by the pH of the solvent employed. In addition, the increase of solvent pH results in a remarkable increase of the amination reaction of orange pigments with amino compounds, and at higher pH (≥ 6.0) a significant amount of orange pigment derivatives rapidly form. The consequent impact of these pH-sensitive properties on pigment analysis is further discussed. Based on the presented results, we propose that the sample preparation and analysis of Monascus pigments should be uniformly performed at low pH (≤ 2.5) to avoid variations of UV-Vis spectra and the creation of artefacts due to the occurrence of amination reactions, and ensure an accurate analysis that truly reflects pigment characteristics in the samples.     

红曲黄色素在不同食品体系中的应用与探讨

将红曲黄色素油树脂以直接添加或制成微胶囊粉末添加到不同食品体系（液体、半固体和固体）中,采用分光测色仪考察颜色变化,分析其在不同食品体系中的稳定性,进一步对其变色的原因及机理进行探讨。结果表明,在软饮料体系中添加红曲黄色素能保持产品鲜艳的黄色,但在黄油曲奇饼干和卡仕达酱中,红曲黄色素的添加会使产品颜色变红,其中微胶囊在卡仕达酱中对色素的色调具有一定的保护作用。红曲黄色素（未知色素组分,非红曲素）能够与食品中未解离的氨基反应生成红色色素,从而导致其颜色色调变红。     

Identification of candidate amino acids involved in the formation of pink-red pigments in onion (Allium cepa L.) juice and separation by HPLC

The formation of pink-red pigments ("pinking") by various amino acids was investigated by reacting amino acids with compounds present in onion juice. The unknown pink-red pigments were generated and separated using high-performance liquid chromatography (HPLC) and a diode array detector (DAD) in the range of 200 to 700 nm. To generate pink-red pigments, we developed several reaction systems using garlic alliinase, purified 1-propenyl-L-cysteine sulfoxide (1-PeCSO), onion thiosulfinate, natural onion juice, and 21 free amino acids. The compound 1-PeCSO was a key compound associated with pinking in the presence of both the alliinase and amino acids. Numerous naturally occurring pink-red pigments were detected and separated from pink onion juice using the HPLC-DAD system at 515 nm. Most free amino acids, with the exceptions of histidine, serine, and cysteine, formed various pink-red pigments when reacted with onion thiosulfinate. This observation indicated that onion pinking is caused not by a single pigment, but by many. Furthermore, more than one color compound could be produced from a single amino acid; this explains, in part, why there were many pink-red compound peaks in the chromatogram of discolored natural onion juice. We presumed that the complexity of the pink-red pigments was due to the involvement of more than 21 natural amino acids as well as several derivatives of the color products produced from each amino acid. We observed that the pinking process in onion juice is very similar to that of the greening process in crushed garlic, emphasizing that both thiosulfinate from flavor precursors and free amino acids are absolutely required for the discoloration.     

DECOMPOSITION OF TURMERIC CURCUMINOIDS AS AFFECTED BY LIGHT,SOLVENT AND OXYGEN1

Turmeric curcuminoids are important natural pigments but their instability limits their use in many foods. This study was conducted to examine light-induced degradation of turmeric curcumin as affected by solvent system and oxygen. The rate constants and half-lives were determined for purified curcumin, demethoxycurcumin and bis-demethoxycurcumin exposed to 1450 lux using reversed-phase HPLC. Rates of degradation of each pigment followed first-order kinetics. Differences in rate constants and half-lives between the individual pigments were minor in an acetic acid-NaCl solution; however, in methanol, large differences in stability to light of the individual pigment were observed. Stability of all the pigments to light was several fold greater in methanol than in acid brine. In methanol sparged with air, stability to photooxidation was curcumin > demethoxycurcumin > bis-demethoxycurcumin. In methanol, curcumin was more stable than the other curcuminoids when sparged with air than when sparged with nitrogen. In methanol sparged with nitrogen, demethoxycurcumin was the most stable pigment. All of the pigments were stable in the dark.     

Chemical composition and nutritional quality of sea cucumbers

BACKGROUND: The dried form of sea cucumbers has been a seafood and medicinal cure for Asians over many centuries. In this study the chemical composition and nutritional quality of eight common sea cucumbers (Stichopus herrmanni, Thelenota ananas, Thelenota anax, Holothuria fuscogilva, Holothuria fuscopunctata, Actinopyga mauritiana, Actinopyga caerulea and Bohadschia argus) were determined. RESULTS: All species except T. anax and A. caerulea had higher protein and lower fat levels. A. mauritiana and B. argus had less ash content. Glycine was the dominant amino acid found in all species, and content ranged from 126 to 216 mg g^?1 of crude protein. All species exhibited low lysine:arginine ratio and higher essential amino acid scores were obtained by threonine and phenylalanine + tyrosine. A. mauritiana had proportionally less saturated fatty acids (31.23%), and more monounsaturated fatty acids (45.64%) and polyunsaturated fatty acids (PUFA, 23.13%) than other species. Arachidonic acid (C20:4n‐6) was the major PUFA in all species. T. ananas, A. mauritiana and A. caerulea contained more n‐3 PUFA. The n‐3/n‐6 ratios of eight sea cucumbers species ranged from 0.25 to 0.61. CONCLUSION: Sea cucumbers are a seafood with high protein and low fat levels. The amino acid contents were similar but fatty acid profiles were different among species. The comparison showed that T. ananas, A. mauritiana and B. argus possessed higher nutritional values than other sea cucumber species. Copyright © 2010 Society of Chemical Industry     

Comparison of the Stability of Pelargonidin-based Anthocyanins in Strawberry Juice and Concentrate

Strawberries were processed into juice (8° Brix) and concentrate (65° Brix) and different lots were fortified with pelargonidin 3‐glucoside, pelargonidin 3‐sophoroside, and acylated pelargonidin 3‐sophoroside 5‐glucoside. Changes in pigment concentration, color (CIE L*a*b*) and ascorbic acid content were monitored during storage at 25 °C. Anthocyanin and ascorbic acid degradations followed 1^st order reaction kinetics. Fortification increased the half‐life of the pigments from 3.5 to 5 d in concentrate and from 5 to 12 d in juice. The half‐life of ascorbic acid was 2 d in juice samples and ranged from 3 to 10 d in concentrate samples. Both systems showed changes in chroma and hue angle, but maintained L* values.     

Effect of the monascus pigment threonine derivative on regulation of the cholesterol level in mice

Different amino acid derivatives were synthesized during cultivation of a Monascus species. Derivatives exhibiting an inhibitory activity against HMG-CoA reductase were screened by in vitro tests. The threonine derivative had a high inhibitory activity of 38% while four other derivatives showed a greater than 23% activity. The orange monascus pigment showed a high activity of 36%. In vivo tests using female C57BL/6 mice were performed with the threonine derivative and orange pigment. Changes in the cholesterol and lipid levels in mice due to addition of the pigments were investigated. The total cholesterol (TC) level of mouse serum was reduced by 8–9% with the threonine derivative and by 16% with orange pigment. Supplementation with the threonine derivative and orange pigment decreased the LDL cholesterol level by 18–26% and increased the HDL cholesterol level by 1–9%. The atherogenic index (AI) value was reduced by 23–27% with pigment supplementation. The anti-atherosclerosis effect of monascus pigments can be induced by control of the lipid content in the serum rather than in the liver of mice.     

Methods for extracting the taste compounds from water soluble extract of Jinhua ham

The present paper reports the determination of 22 amino acids and ammonium along the acetification process by high-performance liquid chromatography (HPLC), employing 6-aminoquinolyl-N-hydrosysuccinimidyl carbamate (AQC) as precolumn derivatization reagent. The method was successfully validated obtaining adequate values to selectivity, response linearity, precision and accuracy, as well as low detection and quantification limits. Its utility for routine analysis of amino acids along acetification has been proved. Three red wine substrates were fermented employing two kinds of acetification methods (surfaced and submerged culture) and the requirements of amino acids and ammonium as nitrogen source by acetic acid bacteria were evaluated. The identification of the acetic acid bacteria at species level was also done. At the beginning, the principal amino acid, in terms of abundance, was proline followed by arginine. A different behavior between both the acetification methods was observed. First of all, the consumption of amino acids is much lower in submerged than in surface acetifications. For surface culture acetification, the most consumed was proline, arginine being the main nitrogen source for submerged acetification systems. On the other hand, it was also observed that the nitrogen requirement of the bacteria is proportional to the time spent in the acetification process.     

The influence of lactic acid fermentation process of red beet juice on the stability of biologically active colorants

Lactic acid fermentation can have preservative effect on red beet juice. The behavior of the pigment in the fermented juice was investigated and the results were compared with those of non-fermented juice. Two red beet varieties (Czerwona Kula and Chrobry) were used in our experiment. Three probiotic bacteria and three infant intestinal microbiota of Lactobacillus sp. were selected for beet juice fermentation.Lactic acid fermentation influenced both red and yellow pigments. In the two beetroot varieties (Chrobry and Czerwona Kula) studied, the dominant red-violet pigment components were betanin, isobetanin, while vulgaxanthin I was the major yellow pigment. Betanin was the main red-violet component in juices before fermentation. After fermentation also betanidin and isobetanidin were observed. Huge amounts of betanidin were found especially in fermented Chrobry juice.It was observed that fermented juice from Chrobry cultivar contained higher betanidin than betanin levels. Contrarily, in juice from Czerwona Kula cv., betanin level was much higher than betanidin level.