Thermal stabilities of lycopene and ß-carotene in tomato pulp and pink grapefruit juice

Thermal stabilities of lycopene and ss-carotene in tomato pulp and pink grapefruit juice were studied at 80, 95 and 110. C. Lycopene and ss-carotene degradations in both products followed to first-order reaction kinetics, but biphasic curves were obtained for ss-carotene degradation. Stabilities of both pigments are highly affected by processing temperatures. For example, t(1/ 2) values for lycopene degradation decreased from 7.4 at 80. C to 4.0 h at 110. C in tomato pulp, and from 32.1 to 5.9 h in pink grapefruit juice, respectively. Similar decreases in t1/ 2 values (46.8-27.3 h in tomato pulp and 113.6 to 11.7 h in grapefruit juice, respectively) were obtained for ss-carotene degradations. Lycopene and ss-carotene degradations in tomato pulp were not very sensitive to temperature elevations (Ea = 22.7 and 20.2 kJ/mol, respectively), but very sensitive in pink grapefruit juice (Ea = 63.8 and 85.3 kJ/mol, respectively). High correlations were found between a*, b*and h. values, and lycopene concentrations (r = 0.659-0.978) and ss-carotene concentrations (r - 0.647-0.997).