Hyoung S. Lee

Effect of thermal pasteurization on Valencia orange juice color and pigments

Changes in carotenoid pigment content and juice color due to thermal pasteurization of Valencia orange juices were studied. Total carotenoid pigment content loss was significant (P<0.05) after thermal pasteurization at 90°C for 30 s. Thermal effects on carotenoid pigment contents, especially on violaxanthin (−46.4%) and antheraxanthin (−24.8%), were clearly observed. With the loss of violaxanthin and antheraxanthin, lutein became the major carotenoid, followed by zeaxanthin, in pasteurized Valencia orange juice. There was perceptible color change after orange juice pasteurization, which led to juice color becoming lighter and more saturated. Decreases in CIE a* value and increases in CIE L*, b*, h*, and C* are the major color changes after pasteurization. Overall increases in reflected light might also influence the perception of color to a great extent in pasteurized orange juice. Total color differences (ΔE*) compared to the fresh juice was 2.92±0.97 (P<0.05).

High-performance liquid chromatography for the characterization of carotenoids in the new sweet orange (Earlygold) grown in Florida, USA.

High-performance liquid chromatography with photodiode array detection was developed for the separation and identification of carotenoids from a new sweet orange, Earlygold. Carotenoid pigments were extracted using hexane-acetone-ethanol and saponified using 10% methanolic potassium hydroxide. More than 25 carotenoid pigments were separated within 40 min using a ternary gradient (acetonitrile-methanol, methyl tert-butyl ether and water) elution on a C30 reversed-phase column. The carotenoid pattern of Earlygold was generally similar to the early season Hamlin but with some quantitative differences, especially with violaxanthin. Major carotenoids including violaxanthin, lutein, beta-cryptoxanthin, antheraxanthin, luteoxanthin, zeaxanthin, beta-carotene, and alpha-carotene were identified based on on-line spectral data obtained by a photodiode array detector, and comparison to the spectra of the standards and reported values. A numerical notation, the ratio of the peak heights between absorption bands, was also calculated to compare to the literature values.