73C-13 |
Kinetics of fruit pulps degradation |
S. C. S. R. D. MOURA, A. D. A. Vitali, M. E. M. Almeida, S. A. Berbari, and J. M. M. Sigrist. FRUTHOTEC, ITAL, 2880, Brasil Avenue, Campinas, 13073-001, Brazil Sweetened and unsweetened strawberry pulps aseptically packed in 1kg bags (Scholle) were stored at 5 (control), 25 (room) and 35 (accelerated) C in order to evaluate their shelf lives. For characterization purposes both pulps were analyzed for vitamin C content, total solids, titrable acidity, pH, soluble solids, water activity and color. Shelf-life evaluation was based on objective L a b Hunter color (Minolta Chroma Meter CR-300) and subjective color (Difference from Control Sensorial Discriminative Test) measurements. These analysis were carried out during 87 (unsweetened) and 75 (sweetened) days, at 15 day intervals. Experimental data showed that color degradation follows a zero order kinetic reaction and from the reaction rates (k) at each temperature and Arrhenius model it was possible to obtain the activation energy (Ea). Q10 was also estimated from experimental data. Color changes of unsweetened pulp showed a higher dependence to temperature than the sweetened one, with Ea=16,0 and 2,7 kcal/mole (Q10=2,5 and 1,2), respectively. Both samples differed from each other at each temperature (P=0.05). The pulps stored at 35C presented the highest color alterations. Very good correlation was observed between subjective and objective results. The above results suggest that unsweetened strawberry pulp must be kept under refrigeration and the sweetened one mat be stored under room temperature during the shelf-life time span.
Session 73C, Food Engineering: Transport Processes and Kinetics
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