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

Abstract

Thermal stabilities of lycopene and β-carotene in tomato pulp and pink grapefruit juice were studied at 80, 95 and 110 °C. Lycopene and β-carotene degradations in both products followed to first-order reaction kinetics, but biphasic curves were obtained for β-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 t 1/2 values (46.8–27.3 h in tomato pulp and 113.6 to 11.7 h in grapefruit juice, respectively) were obtained for β-carotene degradations. Lycopene and β-carotene degradations in tomato pulp were not very sensitive to temperature elevations (E a = 22.7 and 20.2 kJ/mol, respectively), but very sensitive in pink grapefruit juice (E a = 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 β-carotene concentrations ( r = 0.647–0.997). • Both pigments showed much higher thermostability in grapefruit juice than tomato pulp. • Both pigments were more sensitive to temperature changes in grapefruit juice than tomato pulp. • High correlations were found between colour values and pigment contents in both products. • Changes in red colour of both products can be followed by measuring a* and h° values. • Changes in yellow colour can be tracked by measuring h° values in tomato pulp.