Caramel is a widely used water-soluble
food pigment. The acylation of caramel was conducted by aliphatic
acyl chlorides with different chain lengths. Acetyl, butyryl, octyl,
lauryl, palmityl, and stearyl caramels were prepared with the ratio
of acyl chloride/caramel of 6. The formation of acylated caramel was
confirmed by Fourier transform infrared spectra, and the acyl mass
fraction in acylcaramel was determined by potentiometric titration.
Thermal analysis showed that the weight loss of acylated caramel was
higher than that of raw caramel. The scanning electron microscopy
analysis showed that the morphology of acylated caramel was significantly
different from that of raw material. The acyl mass fraction of acylated
caramel increased with the increase of acyl chain lengths. Meanwhile,
the lipo–hydro partition coefficient, the solubility in corn
oil, and color, red, and yellow indexes increased with the increase
of the mass fraction of acyl in acylcaramel. It was found that stearyl
caramel has the highest lipid solubility of 5.73 mg/mL in corn oil;
however, the color, red, and yellow indexes of palmityl caramel reached
25 818.60, 1.149, and 1.757, respectively. This study provides
a method to improve the solubility of caramel in lipid phase and expand
the application range of caramel.
The caramel color is one of the most widely used natural food colorants. At present, there are few reports about its modification. The modification of caramel is expected to improve its stability, color indexes and compatibility with food. In this paper, succinic and maleic acid modified caramels were prepared by esterification reaction of the raw caramel with succinic anhydride and maleic anhydride, and characterized by ultraviolet-visible (UV-vis) spectra, Fourier transform infrared (FTIR) analysis, and scanning electron microscope (SEM), etc. The significant changes of color, yellow and red indexes of the modified caramels indicated that the modification technique can be used to adjust the color properties of caramel to meet the various needs of different fields and expand the application of caramel. Compared with raw caramel, though the antioxidant ability of caramel was decreased, the thermal stability was improved, which made it more suitable for cooking and high temperature sterilization environment compared to the raw caramel. This study provided an alternative method for improving the performance of the caramel as food colors.
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