Insight into β-Carotene Thermal Degradation in Oils with Multiresponse Modeling

Kinetic and Thermodynamic Study of the Thermally Induced (E/Z)-Isomerization of the retro-Carotenoid Rhodoxanthin

The hitherto scarcely investigated retro-carotenoid rhodoxanthin possesses high potential for coloration in the food and beverage industry using technofunctional formulations prepared thereof. Hence, we studied (E/Z)-isomerization pathways of rhodoxanthin, including seven (E/Z)-isomers comprising (Z)-configured double bonds at unusual exocyclic and inner polyene chain positions. A mathematical approach was developed to deduce kinetic and thermodynamic parameters of six parallel equilibrium reactions interconnecting (all-E)-rhodoxanthin with mono-, di-, and tri-(Z)-isomers using multiresponse modeling. At 40-70 °C in ethyl acetate, reaction rate constants regarding the rotation from (all-E)- to (6Z)-rhodoxanthin were 11-14 times higher than those of the common (E/Z)-isomerization reaction at C-13,14 of the non-retro-structured carotenoid canthaxanthin. Moreover, the equilibrium reaction between (all-E)- and (6Z)-rhodoxanthin was strongly product favored as indicated by negative Gibbs energies (-1.6 to -2.2 kJ mol^-1), which is unusual for carotenoids within the studied temperatures. Overall, this study provides novel insights into structure-related dependencies of (E/Z)-isomerization reaction kinetics and thermodynamics of polyenes.

Degradation and regulation of edible flower pigments under thermal processing: a review

More and more consumers are aware of the potential health benefits of edible flower pigments. With the increased popularity and broader application of edible flower pigments, their degradation under thermal processing has attracted researchers' attention, because this may affect the pigment functionalities. At high temperature of thermal processing, polyene pigments are easy to oxidize, degrade and isomerize due to high unsaturation, and phenolic pigments may hydrolyze and isomerize of glycosides, which will result in the decreased antioxidant activity and eating quality, and discounted potential health benefits. Therefore, it is very important to understand the degradation mechanisms of edible flower pigments under thermal processing, which is important to develop corresponding control methods to minimize such negative impacts. This review paper discussed the recent development in the degradation mechanisms and regulation methods of edible flower pigments under thermal processing.

Free Radical Mediated Oxidative Degradation of Carotenes and Xanthophylls

This article reviews the excited-state quenching, pro-vitamin A activity and anticarcinogenicity of carotenes and xanthophylls in relation to their chemical structures. Excited-state quenching improved with the length of the conjugated chain structure. Pro-vitamin A activity was dependent on the presence of at least one beta-ionyl ring structure. The effectiveness of carotenoids as antioxidants depended on their ability to trap peroxyl radicals with production of resonance-stabilized carotenyl radicals. The products identified from oxidations of carotenes and xanthophylls with molecular oxygen and other oxidizing agents are presented. The free radical-mediated mechanisms that have been proposed to account for the different classes of products are reviewed.

Multiresponse Kinetic Modeling of Heat-Induced Equilibrium of β-Carotene cis-trans Isomerization in Medium-Chain Triglyceride Oil

The kinetics and mechanism of the stepwise cis-trans isomerization reactions of all-trans-β-carotene dissolved in MCT (medium-chain triglyceride) oil at temperatures in the range of 80-160 °C have been analyzed using multiresponse modeling. Quantitation of the cis-isomers was performed using HPLC-DAD and quantitation at the reaction isosbestic point at 421 nm. Multiresponse kinetic modeling using the Bayesian criterion was initially performed at 120 °C to determine the best model. Subsequently, the reparametrized Arrhenius equation was used to calculate the activation energies of all reactions. The equilibrium constants for the individual isomerization reactions were determined from the rate constants and the final product distributions. The enthalpies and entropies of the isomerization reactions were determined from the temperature dependence of the equilibrium constants. The 13-cis and 13,13'-di-cis isomers were found to be the fastest formed isomers followed by the 9-cis, 9,13-di-cis, and 13,15-di-cis isomers, where the latter was found to be formed from 13-cis and not the 15-cis isomer. The relative free energies of the β-carotene isomers were determined as all-trans < 13-cis < 9-cis < 13,13'-di-cis < 9,13-di-cis ≈ 15-cis < 13,15-di-cis. The entropic contribution of each reaction was found to play an important role in the ordering. It is concluded that the β-carotene system is quite labile at temperatures ranging from 80 to 160 °C and resulting in equilibrium distributions of the cis-trans isomers.

A kinetic study of carotenoid degradation during storage of papaya chips obtained by vacuum frying with saturated and unsaturated oils

The aim of the study was to evaluate the degradation kinetics of carotenoids (CTs) in vacuum-fried papaya (Carica papaya L.) chips (PCs) during storage at four temperatures (15, 25, 35 and 45 °C) for 52 and 94 days for the two highest and lowest temperatures, respectively. Three treatments were applied to obtain the chips: chips with soy oil (24% lipids) and chips with palm oil (24% and 29% lipids). All the chips were packaged under air or nitrogen conditions. The CTs analyzed by HPLC-DAD were per order of content all-E-lycopene (LYC), Z-lycopene (Z-LYC), all-E-β-carotene (BC), all-E-β-cryptoxanthin (BCX) and Z-β-carotene (Z-BC). The all-E-forms represented 80% of carotenoids in PCs. No significant carotenoid degradation was observed in the PCs packaged under nitrogen conditions during storage. For chips stored under air conditions, a second-order kinetic model best fitted the experimental data. Rate constants for LYC degradation were the lowest, while BCX and BC presented similar rate constants 4-23-fold higher depending on lipid composition. All Z-isomers degraded faster than all-E-forms, but Z-BC degraded only 2-4-fold faster than Z-LYC. All CTs followed Arrhenius temperature-dependency pattern and LYC showed the lowest activation energies (5-21 kJ/mol). A higher lipid content in the chips with palm oil enhanced the carotenoid retention in PCs. Moreover, a greater retention (p < 0.05) of CTs was observed in PCs with soy oil. The use of soy oil instead of palm oil increased the theoretical half-life (at 25 °C) by 2.2, 1.3 and 5.9-fold for BCX, BC and LYC, respectively. Packaging under nitrogen conditions and lipid composition may be considered to optimize the shelf life and carotenoid retention in PCs during storage.

FTIR Spectroscopy and DFT Calculations to Probe the Kinetics of β-Carotene Thermal Degradation

The thermal degradation of β-carotene in air was investigated. The sample was heated at different temperatures (90, 100, 115, and 130 °C) for periods of up to 8 h to perform a complete kinetic study, the product analysis having been carried out via infrared spectroscopy in attenuated total reflectance mode coupled to density functional theory (DFT) calculations. The kinetics of this thermal degradation process was found to follow a first-order scheme, with rate coefficients varying from k_90 °C = (2.0 ± 0.3) × 10^-3 to k_130 °C = (11.0 ± 0.7) × 10^-3 min^-1, the experimental activation energy having been calculated as (52 ± 1) kJ mol^-1. This E_a value is close to the DFT energies corresponding to a C_15-15' or a C_13-14 cis-trans isomerization, followed by the formation of a carotene-oxygen diradical, which was characterized for the first time. Comparison between the experimental and calculated infrared data confirmed the C_15-15'- cis rupture as the predominant reaction pathway and retinal as the major degradation product.

Bioaccessibility of Biofortified Sweet Potato Carotenoids in Baby Food: Impact of Manufacturing Process

Orange-fleshed sweet potato (OFSP), a biofortified crop rich in β-carotene, can be used as a component of baby food recipes in order to tackle vitamin A deficiency in children <6 years old. In this work, the impact of formulation (addition of pumpkin, oil, and egg yolk) and industrial heat processing (pasteurization, sterilization) on carotenoid content and bioaccessibility was evaluated in an OFSP-based baby puree. A commercial OFSP baby food product from Brazil and a homemade OFSP puree were used as references. The losses of all-trans-β-carotene ranged from 16 to 21% (pasteurization, homemade) to 32% (sterilization). Because of higher particle sizes and despite a higher content in carotenoids, the homemade puree had a lower bioaccessibility (i.e., micellar transfer using in vitro digestion: 0.50%) compared with the sterilized and commercial purees (5.3-6.2%). Taking into account bioaccessibility and applying a 50% conversion to retinol, a 115 g baby portion of the sterilized OFSP-puree formulated with 2% oil provided 31.4% of the daily vitamin A requirement (RDA) for children under 6 years. In comparison, 115 g of homemade OFSP-puree provided only 3.5% of the RDA. Addition of pumpkin to OFSP did not improve the percentage of RDA. Interestingly, the incorporation of an emulsifier (egg yolk powder) before cooking could improve the percentage of provision by a factor of 2.7. These results showed that reaching a balance between formulation and processing is determinant to maximize carotenoid bioaccessibility of carotenoids from OFSP-based baby food.

The effect of microwave pre-treatment of rapeseed on the degradation kinetics of lipophilic bioactive compounds of the oil during storage

This study examined the storage stability of tocochromanols and carotenoids in the oils prepared from microwave pre-treated (MV) rapeseeds (2-10 min, 800W) during storage at 20 °C for 12 months. In line with lipophilic antioxidant degradation throughout the storage period, changes in the antioxidant capacity of the oil were monitored. Microwaving significantly affected the concentration of lipophilic antioxidants in the oil. After 10 min of MV pre-treatment the highest content of total tocochromanols (76.64 mg/100g) was achieved, whereas a maximum carotenoid concentration (861.28 μg/100g) was obtained following 6 min seed MV pre-treatment. The degradation kinetics for the tocochromanols and carotenoids followed a zero-order kinetic model. From the kinetic analysis, it was shown that the degradation rate constant (k) of both tocochromanols and carotenoids decreased with longer seed exposure to MV radiation. The kinetics of antioxidant capacity degradation during the storage of oils followed a zero-order reaction. The rate of antioxidant capacity degradation in the control oil was higher (k=9.1 x 10-2 mmol TEAC/l/month) compared with oils prepared from MV pre-treated seeds (k=6.8-8.0 x 10-2 mmol TEAC/l/month).

Carotene Degradation and Isomerization during Thermal Processing: A Review on the Kinetic Aspects

Kinetic models are important tools for process design and optimization to balance desired and undesired reactions taking place in complex food systems during food processing and preservation. This review covers the state of the art on kinetic models available to describe heat-induced conversion of carotenoids, in particular lycopene and β-carotene. First, relevant properties of these carotenoids are discussed. Second, some general aspects of kinetic modeling are introduced, including both empirical single-response modeling and mechanism-based multi-response modeling. The merits of multi-response modeling to simultaneously describe carotene degradation and isomerization are demonstrated. The future challenge in this research field lies in the extension of the current multi-response models to better approach the real reaction pathway and in the integration of kinetic models with mass transfer models in case of reaction in multi-phase food systems.

Effects of lipophilic continuous phases and heating methods on thermal degradation and isomerization of β-carotene

Rates of thermal degradation and isomerization of all-trans-β-carotenes in air and in triacylglycerols were determined. Degradation of carotenes in triacylglycerols was faster than that in air. The 13-cis-β-carotene level in triacylglycerols was higher than in air. Oxidized materials of triacylglycerols probably facilitated isomerization of carotenes and, thus, degradation. Amounts of all-trans-β-carotenes and all-trans-α-carotenes in pumpkin decreased with an increase in heating time. The proportion of 13-cis-β-carotene increased after heat treatment started, probably due to thermal isomerization of all-trans-β-carotenes to cis-isomers, and to decreases in amounts of all-trans-β-carotenes and all-trans-α-carotenes in pumpkin. Effects of heating methods on proportions of isomers; however, were not different.

Carotene reactivity in pink grapefruit juice elucidated from model systems and multiresponse modeling

This study was carried out to assess the impact of pink grapefruit juice composition and structure on the degradation kinetics of lycopene and β-carotene using model systems and multiresponse modeling. Carotenes were heated at four temperatures in their native matrix (juice) or were extracted and incorporated in water/ethanol emulsion systems formulated with or without ascorbic acid or naringin. Kinetic analysis showed that the rate constants and activation energy were lower for lycopene than for β-carotene in the juice, while this trend was inversed in the model system. Multiresponse modeling was used to analyze the role of ascorbic acid and naringin in carotene degradation. Ascorbic acid had a very low impact, while naringin significantly increased the carotene degradation and isomerization rates. We concluded that lycopene was more sensitive to thermal degradation and phytochemical interactions than β-carotene, but this behavior was masked in the fruit juice matrix by better structural protection.

Genetic architecture controlling variation in grain carotenoid composition and concentrations in two maize populations

KEY MESSAGE

Genetic control of maize grain carotenoid profiles is coordinated through several loci distributed throughout three secondary metabolic pathways, most of which exhibit additive, and more importantly, pleiotropic effects. The genetic basis for the variation in maize grain carotenoid concentrations was investigated in two F2:3 populations, DEexp × CI7 and A619 × SC55, derived from high total carotenoid and high β-carotene inbred lines. A comparison of grain carotenoid concentrations from population DEexp × CI7 grown in different environments revealed significantly higher concentrations and greater trait variation in samples harvested from a subtropical environment relative to those from a temperate environment. Genotype by environment interactions was significant for most carotenoid traits. Using phenotypic data in additive, environment-specific genetic models, quantitative trait loci (QTL) were identified for absolute and derived carotenoid traits in each population, including those specific to the isomerization of β-carotene. A multivariate approach for these correlated traits was taken, using carotenoid trait principal components (PCs) that jointly accounted for 97 % or more of trait variation. Component loadings for carotenoid PCs were interpreted in the context of known substrate-product relationships within the carotenoid pathway. Importantly, QTL for univariate and multivariate traits were found to cluster in close proximity to map locations of loci involved in methyl-erythritol, isoprenoid and carotenoid metabolism. Several of these genes, including lycopene epsilon cyclase, carotenoid cleavage dioxygenase1 and beta-carotene hydroxylase, were mapped in the segregating populations. These loci exhibited pleiotropic effects on α-branch carotenoids, total carotenoid profile and β-branch carotenoids, respectively. Our results confirm that several QTL are involved in the modification of carotenoid profiles, and suggest genetic targets that could be used for the improvement of total carotenoid and β-carotene in future breeding populations.

Carrot β-carotene degradation and isomerization kinetics during thermal processing in the presence of oil

The effect of thermal processing (85-130 °C) on the stability and isomerization of β-carotene in both an olive oil/carrot emulsion and an olive oil phase enriched with carrot β-carotene was studied. During processing, degradation of total β-carotene took place. Initially, total β-carotene concentration decreased quickly, after which a plateau value was reached, which was dependent on the applied temperature. In the oil/carrot emulsion, the total β-carotene concentration could be modeled by a fractional conversion model. The temperature dependence of the degradation rate constants was described by the activation energy and was estimated to be 45.0 kJ/mol. In the enriched oil phase, less degradation took place and the results could not be modeled. Besides degradation, β-carotene isomerization was studied. In both matrices, a fractional conversion model could be used to model total isomerization and formation of 13-Z- and 15-Z-β-carotene. β-Carotene isomerization was similar in both the oil/carrot emulsion and enriched oil phase as the simultaneously estimated kinetic parameters (isomerization reaction rate constant and activation energy) of both matrices did not differ significantly. The activation energies of isomerization were estimated to be 70.5 and 75.0 kJ/mol in the oil/carrot emulsion and enriched oil phase, respectively.