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.

Effect of Surfactant Concentrations on Physicochemical Properties and Functionality of Curcumin Nanoemulsions Under Conditions Relevant to Commercial Utilization

“…Pure curcumin also tended to crystallize out of aqueous acidic solutions (pH < 7) and was subjected to rapid sedimentation [6]. In addition, thermal processing affects the visual color of curcumin as reported by Giménez, et al [7]. Curcumin undergoes hydrolytic degradation under thermal processing conditions [7,8,9].…”

Thermal and ultraviolet–visible light stability kinetics of co-nanoencapsulated carotenoids

“…A previous study (Giménez et al, 2015) on the thermal degradation kinetics (30, 50, 70, and 90 • C) during 6 h of natural yellow colorants in a model system (ethanol:water; 3:2; v/v) obtained by ␤-carotene and lutein revealed Ea values of 6.49 kJ mol −1 and 3.18 kJ mol −1 , respectively. The Ea values were 54.77 kJ mol −1 for ␤-carotene and 44.81 kJ mol −1 for lutein; these values are higher than those reported by Giménez et al (2015) for free ␤-carotene and lutein. Lobato et al (2015) reported that the Ea value of nanoencapsulated bixin (99.62 kJ mol −1 ) was higher than that of free bixin (63.01 kJ mol −1 ) at temperatures of 65, 80, and 95 • C for 125 min.…”

“…However, drawbacks such as their hydrophobic nature and instability at high temperatures, in light, and with oxygen and other chemical components (Lerfall, 2016) hamper their successful application in food matrices (Campardelli et al, 2012), particularly in water-rich foods. A previous study (Giménez et al, 2015) monitored the color degradation of natural yellow colorants that are used in foods (such as lutein, ␤-carotene, curcumin, riboflavin, gardenia yellow, and Opuntia extract)…”

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“…Few natural pigments, i.e., lutein, riboflavin, curcumin, β-carotene, gardenia yellow, and opuntia betaxanthins showed thermal stabilities and used as natural yellow colorants in various foods. [52] Contrary to this, betaxanthins and riboflavin degraded rapidly as temperature increased. Gardenia yellow and curcumin showed intermediate thermal stability.…”

“…Gardenia yellow and curcumin showed intermediate thermal stability. [52] Cyanidin and its glycosides belong to the anthocyanins, which are widespread class of water-soluble plant compounds. These are responsible for the brilliant color (red, orange, and blue) of fruits and flowers.…”