Thermal Stability of Selected Natural Red Extracts Used as Food Colorants

Abstract

The color degradation of aqueous solutions of six natural red pigment extracts (elderberry, red cabbage, hibiscus, red beet, Opuntia fruits and red cochineal) used commercially as food colorants was investigated at temperatures between 50 and 90 °C. Color degradation was studied in respect to both spectral properties and visual color. The remaining absorbance at 535 nm as a function of the incubation time and temperature was used to quantify the degradation process. Red cochineal was the most thermoresistant extract with a remaining absorbance of 95 % after 6 h at 90 °C. Anthocyanin extracts (elderberry, red cabbage, hibiscus) showed remaining absorbance percentages of 63.8, 46.1 and 26.7, respectively. Betacyanin extracts (red beet, Opuntia fruits) were the most thermosensitive maintaining only 12.5 and 1.7 %, respectively, of the initial absorbance at 535 nm. Applying a first-order kinetic model to the degradation processes, reaction rate constants (k) and half-life periods (t 1/2 ) were calculated. The temperature dependence of the degradation rate constant obeyed the Arrhenius relationship, with activation energies (E a ) ranging between 3.02 and 53.37 kJ mol(-1). The higher activation energy values indicated greater temperature sensitivity. Changes in visual color attributes corroborated the high thermal stability of the red cochineal extract.

Potential use of new Colombian sources of betalains. Colorimetric study of red prickly pear (Opuntia dillenii) extracts under different technological conditions

“…8). Also visually discrimination upon heating was already found by Fernández-López et al (2013) when the submitted temperature on several red pigment extracts was 50°C.…”

“…Taking into account that the perceptible colorimetric differences to the human eyes have been established around three CIELAB units (Fernández-López et al, 2013;Martínez, Melgosa, Pérez, Hita, & Negueruela, 2001), a visually appreciable effect on ΔE* ab took place when compared samples submitted to both temperatures at each pH, concluding that O. dillenii extracts suffered from thermolability. Those color differences were much more marked over time, even reaching values of 20 units between the beginning and the end of the treatment.…”

Comparative Thermal Degradation Patterns of Natural Yellow Colorants Used in Foods

“…Color determinations of the colorants during thermal treatments were made in terms of the CIEL*a*b* parameters L* (lightness), a* (redness to greenness) and b* (blueness to yellowness), using standard illuminant D65 and 10°observed angle, as previously reported [16].…”

Non-thermal Production of Natural betalain Colorant Concentrate from Red Beet Extract by Using the Osmotic Distillation

“…It can also be used in medicine (8). So red beet extract concentrate is widely used in food industries (9).…”