title: Comparative Thermal Degradation Patterns of Natural Yellow Colorants Used in Foods.
abstract: There is a great interest in natural yellow colorants due to warnings issued about certain yellow food colorings of synthetic origin. However, no comparative studies have been reported of their thermal stability. For this reason, the thermal stabilities of six natural yellow colorants used in foods--lutein, riboflavin, curcumin, ß-carotene, gardenia yellow and Opuntia betaxanthins--were studied in simple solutions over a temperature range 30-90 °C. Spectral properties and visual color were investigated during 6 h of heat treatment. Visual color was monitored from the CIEL*a*b* parameters. The remaining absorbance at maximum wavelength and the total color difference were used to quantify color degradation. The rate of color degradation increased as the temperature rose. The results showed that the thermal degradation of the colorants followed a first-order reaction kinetics. The reaction rate constants and half-life periods were determined as being central to understanding the color degradation kinetics. The temperature-dependent degradation was adequately modeled on the Arrhenius equation. Activation energies ranged from 3.2 kJmol(-1) (lutein) to 43.7 kJmol(-1) (Opuntia betaxanthins). ß-carotene and lutein exhibited high thermal stability, while betaxanthins and riboflavin degraded rapidly as temperature increased. Gardenia yellow and curcumin were in an intermediate position.
authors.affiliation: Department of Chemical and Environmental Engineering, Technical University of Cartagena (UPCT), Paseo Alfonso XIII 52, E-30203, Cartagena, Murcia, Spain.
authors.forename: Pedro J
authors.initials: PJ
authors.lastname: Giménez
authors.affiliation: Department of Chemical and Environmental Engineering, Technical University of Cartagena (UPCT), Paseo Alfonso XIII 52, E-30203, Cartagena, Murcia, Spain. josea.fernandez@upct.es.
authors.forename: José A
authors.initials: JA
authors.lastname: Fernández-López
authors.affiliation: Department of Chemical and Environmental Engineering, Technical University of Cartagena (UPCT), Paseo Alfonso XIII 52, E-30203, Cartagena, Murcia, Spain.
authors.forename: José M
authors.initials: JM
authors.lastname: Angosto
authors.affiliation: Department of Chemical and Environmental Engineering, Technical University of Cartagena (UPCT), Paseo Alfonso XIII 52, E-30203, Cartagena, Murcia, Spain.
authors.forename: José M
authors.initials: JM
authors.lastname: Obón
mesh_terms: D050860:Betaxanthins / Q000737:chemistry; D003474:Curcumin / Q000737:chemistry; D004355:Drug Stability; D005505:Food Coloring Agents / Q000737:chemistry*; D005511:Food Handling / Q000379:methods; D032062:Gardenia / Q000737:chemistry; D006358:Hot Temperature; D007700:Kinetics; D014975:Lutein / Q000737:chemistry; D029747:Opuntia / Q000737:chemistry; D010860:Pigments, Biological / Q000737:chemistry*; D010936:Plant Extracts / Q000737:chemistry; D012256:Riboflavin / Q000737:chemistry; D012996:Solutions; D013816:Thermodynamics; D019207:beta Carotene / Q000737:chemistry
chemical_list: D050860:Betaxanthins; D005505:Food Coloring Agents; D010860:Pigments, Biological; D010936:Plant Extracts; D012996:Solutions; D019207:beta Carotene; C057653:gardenia yellow; D003474:Curcumin; D012256:Riboflavin; D014975:Lutein
keywords: Food color; Thermal degradation; Thermal kinetics; Yellow natural colorants