MS tools for a systematic approach in survey for carotenoids and their common metabolites.

Metabolism of the carotenoids in humans is often reserved to bioconversion of provitamin A carotenoids in retinoids and oxidative/degradative products arising from enzymatic eccentric cleavage, yielding apo-carotenoids. Nevertheless, additional metabolic routes should be available, and some of the structures of those metabolites have only been anticipated. The identification of carotenoids and their metabolites is commonly performed by HPLC coupled to MS. The acquisition of MS data in different instrumental modes and hardware configurations allows the detailed structural description of the target compound. Indeed, the MS data of carotenoids and their metabolites available in literature could be collected in a database to automatically perform a screening of the theoretical MS data included in the database with the MS experimental values. This review describes the required fundamentals for a systematic pursuit of carotenoids and their metabolites. Highlights on the use of appropriate hyphenated HPLC-MS systems and the requirements for the identification are discussed, while the application of software tools to apply filtering rules and the implementation of post-processing workflow, which uses two orthogonal criteria for the identification from the mass spectra data, are described.

Structure-reactivity relationship in the oxidation of carotenoid pigments of the pepper (Capsicum annuum L.).

The relationship between the degradation rate and structure of each pigment of the pepper carotenoid profile was studied in mixtures of dehydrated fruit with lipid substrates of differing degrees of unsaturation and in different proportions (20 and 40%). The differences in structural nature of the carotenoids present in the pepper fruit produce a variable rate of oxidation, resulting in nonuniform degradation. The yellow xanthophylls and beta-carotene have the highest rates of oxidation, with the ketocarotenoids and violaxanthin degrading at lower rates. Autoxidation is greater or lesser depending on the functional groups, which stabilize the radical intermediaries of the reaction. The behavior of capsanthin and capsorubin is that expected of carotenoids having structures that include keto groups: a markedly greater stability to autoxidation processes. This increases their antioxidant capacity, adding to their beneficial impact by reducing the proliferation of radical processes, which are detrimental to health.

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.

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.

Prediction of decoloration in paprika oleoresins. Application to studies of stability in thermodynamically compensated systems.

In six paprika oleoresins, the kinetic parameters for the decoloration reaction at three temperatures have been established. The thermodynamic study shows that the decoloration reaction in each oleoresin has its own activation entropy (DeltaS) and activation enthalpy (DeltaH). The six reactions studied show a constant ratio between DeltaH and DeltaS, which means that each reaction is an isokinetic form of only one reaction affected by thermodynamic compensation. Instead of one equation per oleoresin to predict pigment concentration as a mathematical function of time and temperature, one unique equation can be obtained in which DeltaH is a function of DeltaS. The validity of this equation has been tested by comparing the actual concentration remaining during a heat treatment and the calculated one. More than 90% of the calculated concentrations are within the range of variability of the actual mean. Due to the reduction in the number of variables in thermodynamic compensated systems, a general procedure to calculate the activation entropy in isokinetic reactions is proposed.

Study of Lability and Kinetics of the Main Carotenoid Pigments of Red Pepper in the De-esterification Reaction.

Different concentrations of potassium hydroxide in methanol were used to control the time required for complete de-esterification of the carotenoids present in paprika oleoresin, and the effectiveness of the overall process was determined. With concentrated solutions of potash, 20% and 30% (w/v), the reaction was completed in a shorter time but the overall process was less effective. Solutions of low concentration, 5% and 10% (w/v), enabled the kinetic study to be carried out and the rates of de-esterification for individual pigments to be compared. The effect that the fatty acid esterifying each carotenoid had on the reaction was deduced. The pigments esterified by long-chain fatty acids had a higher rate of de-esterification than those bonded with short-chain fatty acids.