Characterization of color fade during frozen storage of red grapefruit juice concentrates.

Color changes in red grapefruit juice concentrates during storage at −23 °C for 12 months were studied. Concentrate (38° Brix) was packed in both plastic (16 oz) and metal (6 oz) cans. Decrease in red intensity (CIE a*) in juice color and slight increases in CIE L*, b*, and hue values from analysis of reconstituted juices were the characteristic color changes in concentrate during frozen storage. With respect to fresh concentrate, juice color in stored concentrate shifted toward the direction between negative ΔC* and positive ΔL*, indicating the color became slightly paler. A color difference seems to exist between the two containers, especially for the magnitude of ΔE*; color changes were more pronounced in concentrates packed in plastic. There are significant changes (P < 0.05) in major carotenoid pigments (β-carotene and lycopene) in the concentrates. More than 20% loss of lycopene and about 7% loss of β-carotene occurred with plastic containers after a 12-month period. Regression analysis showed that ...