extraction efficiency, while using a sonicator with DMSO showed lower extraction efficiency. Because β -carotene would be destructed by heat generated during extraction with a sonicator, the extracted quantity might be less than that of the case which used only DMSO. Both Park and Kim (3) and our study showed that the extraction efficiency of β -carotene when using a sonicator represented the lower extraction efficiency. Choi and Jeong (11) reported the influence of solvent on the stability of extracted pigments and that after 10 days in storage, ethanol and petroleum ether increases decomposition speed compared with that of other solvents. Craft and Soares (12) also reported that stability and solubility were influenced by the polarization of solvents in extracting carotenoids. Therefore, one must be careful when selecting solvents. In this study, ethanol, acetone, and petroleum ether were used in the HPLC analysis and extraction. All analysis was conducted within 10 days of extraction.
Heat stability of extracted β -carotene The heat stability of purified β -carotene is shown in Fig. 4. Some loss started at 40 o C, and a relatively significant loss occurred at 60 o C. However, 80% of the β -carotene remained at 80 o C. Shim et al. (13) reported that in heat stability experiments of carotenoids separated from citrus peel some color change
began at 40 o C and a relatively significant color change occurred at 50-60 o C, but 50% of the pigment remained at 100 o C. They also reported that as temperature increased, the color change of the natural pigments was promoted, and oxidative decomposition, thermal decomposition, polymerization, and browning reactions occurred.
Acknowledgments This work was supported by National Research Foundation of Korea Grant funded by the Korean Government (KRF-2007-314-F00010)