Effect of high-temperature degradative processes on ketocarotenoids present in paprika oleoresins

Carotenoid pigments in six commercial oleoresins, qualitatively uniform in pigment composition, were thermodegraded to determine the degradation kinetics in the two (red and yellow) isochromic fractions, structurally differentiated by the presence or absence of keto groups. The different rate of degradation of total pigment indicates that the oily medium modulates the degradation reaction differently, so that each oleoresin shows a different stability. However, in all the oleoresins, the red pigment fraction is degraded at a higher rate than the yellow. Arrhenius curves reveal an isokinetic temperature (T(isok)) distinguishing two zones in which the degradation process has a different effect on each fraction. At temperatures above T(isok), degradation is preferentially toward the red fraction, while at lower temperatures, it is toward the yellow fraction. An isokinetic point between the two pigment fractions means that the thermal conditions at which the stability of the system is to be determined must be stated, as such conditions produce a different effect on each fraction.     

Chemical stability and colorant properties of betaxanthin pigments from Celosia argentea

The chemical stability and colorant properties of three betaxanthins recently identified from Celosia argentea varieties were evaluated. Lyophilized betaxanthin powders from yellow inflorescences of Celosia exhibited bright yellow color and high color purity with strong hygroscopicity. The aqueous solutions containing these betaxanthins were bright yellow in the pH range 2.2-7.0, and they were most stable at pH 5.5. The betaxanthins in a model system (buffer) were susceptible to heat, and found to be as unstable as red betacyanins (betanin and amaranthine) at high temperatures (>40 degrees C), but more stable at 40 degrees C with the exclusion of light and air. The three betaxanthins had slightly higher pigment retention than amaranthine/isoamaranthine in crude extracts at 22 degrees C, as verified by HPLC analysis. Lyophilized betaxanthins had much better storage stability (mean 95.0% pigment retention) than corresponding aqueous solutions (14.8%) at 22 degrees C after 20 weeks. Refrigeration (4 degrees C) significantly increased pigment retention of aqueous betaxanthins to 75.5%.     

Color characteristics of monascus pigments derived by fermentation with various amino acids

Various pigment colors were produced by Monascus fermentations with separate addition of 20 amino acids. The color characteristics and structures of the pigment derivatives were investigated. When each amino acid was added to the fermentation broth as a precursor, pigment extracts with different hue and chroma values were obtained depending on the content ratios of yellow, orange, and red colors in the fermentation broth. The yellow and orange pigments were identical regardless of amino acid addition. The red compounds varied on the basis of the type of amino acid added. LC-MS and (1)H and (13)C NMR structural analyses confirmed that the derivative pigments contained the moieties of the added amino acids. L, a, and b values of the CIELAB color system for the derivative pigments were measured. Values of hue and chroma were then calculated. The colors of the derivative pigments were in the range of orangish red to violet red. The hydrophilicities/hydrophobicities of the derivative pigments could be predicted from their log P values, which were estimated using computer programs.     

Color properties and stability of betacyanins from Opuntia fruits

The colorant properties of pigments from Opuntia stricta, Opuntia undulata, and Opuntia ficus-indicafruits were studied. The pigments were extracted with different solvents and identified by high-performance liquid chromatography. On the basis of their visible light spectra, the pigments were identified as betalains. In O. undulata and O. ficus-indica fruits, both betacyanins and betaxantins were identified, while in O. stricta fruits only betacyanins (betanin and isobetanin) were detected. O. stricta fruits showed the highest betacyanin content (80 mg/100 g fresh fruit). The thermal stability of the pigment extracts was dependent on the pH, with the maximum stability being at pH 5, as expected for betacyanins. At this value and a storage temperature of 4 degrees C, a deactivation half-life time of more than 1 year, with no added stabilizers, was determined. According to these studies, cactus pears from O. stricta may well be considered as a potential source of natural red colorants.     

Influence of critical storage temperatures on degradative pathways of pigments in green beans (Phaseolus vulgaris cvs. Perona and boby)

In this work a study of critical storage temperatures on pigment degradation of green beans (Phaseolus vulgaris, cvs. Perona and Boby) was conducted. In this way, green beans kept better quality at 4 degrees C than either 8 or 12 degrees C, maintaining a bright green color and good texture. Nevertheless, temperatures of 4 degrees C induced chilling injury (CI) after eight days of storage, which became evident when the pods were transferred to 20 degrees C. Cold storage temperatures, 12, 8, and 4 degrees C, produced different changes on the green beans chlorophyll profile. Green beans of both cultivars, Perona and Boby, stored at 4 and 12 degrees C showed a continuous degradation of chlorophyll pigments during storage, while samples stored at 8 degrees C showed an increase of chlorophyll content at the first 15 days. Carotenoid pigments also suffered different changes during cold storage. Perona was the green beans cultivar which maintained the higher level of lutein, mainly when samples were stored at the most suitable temperature (8 degrees C).     

Paprika (Capsicum annuum) oleoresin extraction with supercritical carbon dioxide.

Paprika oleoresin was fractionated by extraction with supercritical carbon dioxide (SCF-CO(2)). Higher extraction volumes, increasing extraction pressures, and similarly, the use of cosolvents such as 1% ethanol or acetone resulted in higher pigment yields. Within the 2000-7000 psi range, total oleoresin yield always approached 100%. Pigments isolated at lower pressures consisted almost exclusively of beta-carotene, while pigments obtained at higher pressures contained a greater proportion of red carotenoids (capsorubin, capsanthin, zeaxanthin, beta-cryptoxanthin) and small amounts of beta-carotene. The varying solubility of oil and pigments in SCF-CO(2) was optimized to obtain enriched and concentrated oleoresins through a two-stage extraction at 2000 and 6000 psi. This technique removes the paprika oil and beta-carotene during the first extraction step, allowing for second-stage oleoresin extracts with a high pigment concentration (200% relative to the reference) and a red:yellow pigment ratio of 1.8 (as compared to 1.3 in the reference).     

Physical stability of the blue pigments formed from geniposide of gardenia fruits: effects of pH, temperature, and light

Fruits of Gardenia jasminoides contain geniposide which can be transformed to blue pigments by a simple modification. Colorless geniposide obtained from gardenia fruits by charcoal and silica gel column chromatographies was hydrolyzed with beta-glucosidase to yield genipin. The resulting genipin was transformed to blue pigments by reaction with amino acids (glycine, lysine, or phenylalanine). The stability of the blue pigments against heat, light, and pH was studied to examine the blue dye for possible use as a value-added food colorant. Thermal degradation reactions at temperatures of 60-90 degrees C were carried out at different pH levels within the range 5.0-9.0 (pH 5.0, acetate buffer; pH 7.0, phosphate buffer; and pH 9.0, CHES buffer). The blue pigments remained stable after 10 h at temperatures of 60-90 degrees C, and in some cases, more new pigments formed. The pigments were more stable at alkaline pH than neutral and acidic pH. Similarly, the pigments were stable under light irradiance of 5000-20 000 lux. In this case, pH effect was not significant.     

Influences of gamma-irradiation and storage on the carotenoids of sun-dried and dehydrated paprika

The effects of drying methods, gamma-irradiation, and storage on the carotenoids (capsanthin, capsorubin, zeaxanthin, capsolutein, violaxanthin, beta-carotene, and beta-cryptoxanthin) of paprika were investigated. Sun-dried and dehydrated paprika samples were irradiated in a (60)Co gamma-irradiator at five doses (0, 2.5, 5.0, 7.5, and 10 kGy) in polyethylene bags and stored for 10 months at ambient temperature. Individual carotenoid analyses were carried out on the paprika and fresh red pepper during a 2 month period using the reverse phase HPLC technique. The concentrations of capsanthin and capsorubin, which are responsible for the attractive red color of sun-dried paprika, were higher than those of dehydrated paprika. Higher irradiation doses and a longer storage period resulted in a significant (P < 0.01) reduction of all the carotenoids, except capsorubin. There was no significant (P < 0.05) effect of irradiation dose on capsorubin destruction. The decrease of red carotenoids, for all irradiation treatments, was less than that of the storage period. Even the highest irradiation dose, 10 kGy, caused a 11.1% capsanthin reduction; however, 10 months of storage at the ambient temperature caused a 42.1% reduction of capsanthin. Yellow pigments of paprika (zeaxanthin, capsolutein, violaxanthin, beta-carotene, and beta-cryptoxanthin) were significantly (P < 0.01) decreased by all treatments. These yellow pigments were also found to be at high levels in those sun-dried samples with red pigments. This difference could be caused by the contribution of pigment biosynthesis during the sun-drying period. The most significant pigment reduction was realized in the processing and storage conditions of paprika, rather than in the irradiation process.     

Spectrophotometric determination of yellow pigment content and evaluation of carotenoids by high-performance liquid chromatography in durum wheat grain

The so-called "yellow pigment" content of durum wheat has been used for a long time as an indicator of the color quality of durum wheat and pasta products. For decades the chemical nature of these pigments has been assigned to carotenoids, mainly to the xanthophyll lutein and its fatty acid esters. The chemical composition of the yellow pigments of eight German durum wheat cultivars was studied. Grains were milled on a laboratory mill. Pigment extraction of millstream fractions was performed according to the optimized ICC standard method 152 procedure, and the chemical composition of the extract was analyzed by isocratic reversed phase high-performance liquid chromatography. all-trans-Lutein ranged from 1.5 to 4 mg kg(-1), and zeaxanthin was found in traces. No lutein esters and carotenes were detected. Surprisingly, the fraction of carotenoids of the complete yellow pigment content amounted to only 30-50% of the yellow pigment quantities, so there are still compounds in durum wheat not yet identified that contribute considerably to the yellow color of the grain extracts. The isolation and chemical identification of those pigments are under investigation.     

Carotenoid content of the varieties Jaranda and Jariza (Capsicumannuum L.) and response during the industrial slow drying and grinding steps in paprika processing

Fruits of the pepper varieties Jaranda and Jariza (Capsicum annuum L. ) ripen as a group, enabling a single harvesting, showed a uniform carotenoid content that is high enough (7.9 g/kg) for the production of paprika. The drying system at mild temperature showed that fruits with moisture content of 85-88% generated a dry product with carotenoid content equal to or higher than the initial one. Those high moisture levels allowed the fruits to have a longer period of metabolic activity, increasing the yellow fraction, the red fraction, or both as a function of what biosynthetic process was predominant. This fact indicates under-ripeness of the fruits in the drying step. The results obtained allow us to establish that both varieties, Jaranda and Jariza, fit the dehydration process employed, yielding a dry fruit with carotenoid concentration similar to that the initial one. During the grinding step of the dry fruit, the heat generated by the hammers of the mill caused degradation of the yellow fraction, while the red fraction is maintained. The ripeness state of the harvested fruits and the appropriateness or severity of the processing steps are indicated by the ratio of red to yellow (R/Y) and/or red to total (R/T) pigments, since fluctuations in both fractions and in total pigments are reflected in and monitored by these parameters.     

Impact of browning reactions and bran pigments on color of parboiled rice

Rice color changes from white to amber during parboiling (soaking and steaming). Color parameters indicated that, during soaking, yellow bran pigments leached out in the water. The levels of the Maillard precursors (i.e., reducing sugars (RS) and free alpha-amino nitrogen (FAN)) depended on soaking temperature and time: leaching of RS was compensated by enzymic formation for long soaking times (>60 min), while proteolytic activity was too low to compensate for FAN leaching. Rice soaking under nitrogen, oxygen, or ambient conditions and determination of polyphenol oxidase activity allowed us to conclude that the effect of enzymic color changes on the soaked rice color was rather small. Color measurements of brown and milled mildly, intermediately, and severely parboiled rice samples showed that both brown and milled rice samples were darker and more red and yellow after parboiling and that the effect depended on the severity of parboiling conditions. Furthermore, steaming affected the rice color more and in a way opposite to that observed in soaking. The changes in RS and the loss of FAN during parboiling suggested that Maillard type reactions occur during brown rice steaming. Analyses of furosine levels confirmed Maillard browning of outer bran layers and endosperm during steaming. The level of this Maillard indicator increased with the severity of parboiling conditions in both brown and milled parboiled rice. Measurements of the levels of bran pigments indicated that bran pigments diffuse into the endosperm during parboiling and contribute to the parboiled rice color.     

Antibacterial activity of turmeric oil: a byproduct from curcumin manufacture.

Curcumin, the yellow color pigment of turmeric, is produced industrially from turmeric oleoresin. The mother liquor after isolation of curcumin from oleoresin contains approximately 40% oil. The oil was extracted from the mother liquor using hexane at 60 degrees C, and the hexane extract was separated into three fractions using silica gel column chromatography. These fractions were tested for antibacterial activity by pour plate method against Bacillus cereus, Bacillus coagulans, Bacillus subtilis, Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa. Fraction II eluted with 5% ethyl acetate in hexane was found to be most active fraction. The turmeric oil, fraction I, and fraction II were analyzed by GC and GC-MS. ar-Turmerone, turmerone, and curlone were found to be the major compounds present in these fractions along with other oxygenated compounds.     

Physical stability of shikonin derivatives from the roots of Lithospermum erythrorhizon cultivated in Korea.

Five red shikonin pigments, deoxyshikonin, shikonin, acetylshikonin, isobutylshikonin, and beta-hydroxyisovalerylshikonin, were isolated from the roots of Lithospermum erythrorhizon cultivated in Korea. The purified pigments were red, purple, and blue at acidic, neutral, and alkaline pH values, respectively. Physical stability of the purified pigments against heat and light in an aqueous solution was examined for possible value-added food colorants. The thermal degradation reactions were carried out at pH 3.0 (50 mM glycine buffer) in 50% EtOH/H(2)O. Deoxyshikonin (t(1/2) = 14.6 h, 60 degrees C) and isobutylshikinin (t(1/2) = 19.3 h, 60 degrees C) are relatively less stable than other shikonin derivatives (t(1/2) = 40-50 h, 60 degrees C). Activation energies of thermal degradation of the isolated pigments were calculated. The activation energy of deoxyshikonin was the highest (12.5 kcal mol(-)(1)) and that of beta-hydroxyisovalerylshikonin was the lowest (1.71 kcal mol(-)(1)) value. Light stabilities of the pigments were similar to each other in that the half-life values of photodegradation for 20000 lx light intensity were 4.2-5.1 h.     

Isolation and structural characterization of new anthocyanin-derived yellow pigments in aged red wines

Two newly formed yellow pigments that revealed unique spectral features were detected and isolated from an aged Port red wine by TSK Toyopearl HW-40(s) gel chromatography and characterized by UV-visible spectrophotometry, 1H NMR and 13C NMR, and mass spectrometry (LC-ESI/MS). The UV-vis spectra of these pigments showed maximum absorption at 478 nm that is significantly hypsochromically shifted from those of original grape anthocyanins and other pyranoanthocyanins, exhibiting a more yellow hue in acidic solution. The structures of these pigments correspond to methyl-linked pyranomalvidin 3-glucoside and its respective coumaroyl glucoside derivative. They were shown to arise from the reaction between acetoacetic acid and genuine grape anthocyanins. Isolation and NMR identification using 1D and 2D NMR techniques are reported for the first time for this new family of anthocyanin-derived yellow pigments occurring in red wines.     

Effect of drying temperature and air flow on the production and retention of secondary metabolites in saffron

Safranal is the compound most responsible for the aroma of saffron spice and is, together with the suite of crocin pigments, the major determinant of the product quality. The content of safranal and pigments in saffron is determined by the method of postharvest treatment of the Crocus stigmas. A range of drying treatments involving different temperatures, with or without air flow, was applied to stigmas from three harvest dates. Dual solvent extractions combined with quantitative measurement using GC and HPLC-UV-vis techniques were used to analyze the secondary metabolite contents of the products. It was demonstrated that these methods overcame the previously reported problems in measuring the concentration of both pigments and safranal in saffron caused by the very different polarities and thus solubilities of these compounds. The results showed that a brief (20 min) initial period at a relatively high temperature (between 80 and 92 degrees C) followed by continued drying at a lower temperature (43 degrees C) produced saffron with a safranal content up to 25 times that of saffron dried only at lower temperatures. Evidence was provided suggesting that drying with significant air flow reduced the safranal concentration. The results, moreover, indicated that high-temperature treatment had allowed greater retention of crocin pigments than in saffron dried at intermediate temperatures (46-58 degrees C). The biochemical implications of the various treatments are discussed in relation to the potential for optimizing color and fragrance quality in the product.     

Comparative changes in color features and pigment composition of red wines aged in oak and cherry wood casks

The color features and the evolution of both the monomeric and the derived pigments of red wines aged in oak and cherry 225 L barriques have been investigated during a four months period. For cherry wood, the utilization of 1000 L casks was tested as well. The use of cherry casks resulted in a faster evolution of pigments with a rapid decline of monomeric anthocyanins and a quick augmentation formation of derived and polymeric compounds. At the end of the aging, wines stored in oak and cherry barriques lost, respectively, about 20% and 80% of the initial pigment amount, while in the 1000 L cherry casks, the same compounds diminished by about 60%. Ethyl-bridged adducts and vitisins were the main class of derivatives formed, representing up to 25% of the total pigment amount in the cherry aged samples. Color density augmented in both the oak and cherry wood aged samples, but the latter had the highest values of this parameter. Because of the highly oxidative behavior of the cherry barriques, the use of larger casks (e.g., 1000 L) is proposed in the case of prolonged aging times.     

Comparison of different methylation methods for the analysis of conjugated linoleic acid isomers by silver ion HPLC in beef lipids

Four different methods for the methylation of conjugated linoleic acid isomers (CLA) in ruminant lipids were compared by silver ion (Ag+) HPLC. The combination of base-catalyzed methods followed by an acid-catalyzed method with BF3/MeOH was tested under different temperatures (room temperature and at 60 degrees C), along with based-catalyzed methylation with NaOCH3 and methylation with BF3/MeOH after saponification with NaOH. The comparison among these four methods was done on muscle and adipose tissue samples from bulls. The repeatability theta of the combined base- and acid-catalyzed methylation (NaOCH3/BF3) at ambient temperature for 20 min and at 60 degrees C for 10 min was most suitable for the quantitative Ag+-HPLC analysis of CLA isomers. At 60 degrees C the combined methods supplied the highest concentrations of most CLA isomers. The base-catalyzed methylation and the saponification followed by BF3/MeOH methylation for 5 min generated significantly lower concentrations for most CLA isomers compared to the combined methods.     

Characterization of color fade during frozen storage of red grapefruit juice concentrates

Color changes in red grapefruit juice concentrates during storage at -23 degrees C for 12 months were studied. Concentrate (38 degrees Brix) was packed in both plastic (16 oz) and metal (6 oz) cans. Decrease in red intensity (CIE a) in juice color and slight increases in CIE L*, b*, and hue values from analysis of reconstituted juices were the characteristic color changes in concentrate during frozen storage. With respect to fresh concentrate, juice color in stored concentrate shifted toward the direction between negative DeltaC* and positive DeltaL*, indicating the color became slightly paler. A color difference seems to exist between the two containers, especially for the magnitude of DeltaE*; color changes were more pronounced in concentrates packed in plastic. There are significant changes (P < 0.05) in major carotenoid pigments (beta-carotene and lycopene) in the concentrates. More than 20% loss of lycopene and about 7% loss of beta-carotene occurred with plastic containers after a 12-month period. Regression analysis showed that the rate of decline was about 0.291 ppm per month (r = 0.990) for lycopene compared to 0.045 ppm (r = 0.817) for beta-carotene in concentrate stored in plastic. In the metal can, the same trends were observed but pigment losses were slightly smaller than those with plastic. An estimated shelf life for lycopene was 26.1 months in the metal can compared to 18 months in plastic. Shelf life for beta-carotene was more than 39 months, more than twice that of lycopene in plastic container.     

Rapid spectrophotometric determination of red and yellow isochromic carotenoid fractions in paprika and red pepper oleoresins

A rapid method has been developed for the determination of the red (R) and yellow (Y) isochromic carotenoid pigments fractions in paprika and oleoresins, based on UV-visible spectrophotometric measurement at two characteristic wavelengths and application of the Lambert-Beer law for multicomponent mixtures. The wavelengths 472 and 508 nm were selected as the most appropriate for simultaneous quantification of these fractions in the acetone extract of pigments. Experimental determination of the specific absorption coefficients (epsilon) for the two pigment fractions (R, Y) at 472 and 508 nm yielded equations to calculate the concentration of the two fractions, the total pigment content, and the ratio between the two fractions. The error in the determination of the isochromic fractions by the proposed spectrophotometric method was <5% when the results were compared with those obtained by HPLC analysis. The method can be applied to the direct extract of pigments, thereby avoiding saponification and minimizing errors from pigment degradation and sample manipulation as well as shortening the time of analysis (5 min in the case of oleoresins).     

Impact of high-pressure carbon dioxide combined with thermal treatment on degradation of red beet (Beta vulgaris L.) pigments

A combined high-pressure carbon dioxide (HP-CO 2) and thermal degradation reaction of betanin and isobetanin in aqueous solution was investigated and can be described by a first-order decay. At 45 degrees C, the degradation rate constant ( k) for each pigment component significantly increased (the half-life ( t 1/2) decreased, p < 0.05) with elevated pressure. Furthermore, HP-CO 2 treatment led to lower k values (higher t 1/2 values) than thermal treatment. However, k and t 1/2 values approached those of thermal treatment when the pressure was >30 MPa combined with temperatures exceeding 55 degrees C. Moreover, betanin was more stable than isobetanin under HP-CO 2. E a values ranged from 94.01 kJ/mol for betanin and 97.16 kJ/mol for isobetanin at atmospheric pressure to 170.83 and 142.69 kJ/mol at 50 MPa, respectively. A higher pressure and temperature as well as longer exposure time resulted in higher values of L*, b*, C*, and h degrees . HP-CO 2 induced more degradation products from betanin and isobetanin than thermal treatment with an identical temperature and exposure time.