36E-69

E. N. AQUINO-BOLAÑOS¹, A. Villegas-Cárdenaz², A. D. Hernández-Fuentes³, M. I. Reyes-Santamaria⁴, and N. Güemes-Vera². (1) Centro de Investigación en Ciencia y Tecnología de Alimentos, Univ. Autónoma del Estado de Hidalgo, Av. Universidad Km. 1, Rancho Universitario, Tulancingo, Hidalgo, 43600, Mexico, (2) Centro de INvestigación en Ciencia y Tecnología de los Alimentos, Univ. Autónoma del Estado de Hidalgo, Tulancingo, Hidalgo, 43600, Mexico, (3) Univ. Autónoma del Estado de Hidalgo, Centro de Investigación en Ciencia y Tecnología de los Alimentos, Av. Universidad Km 1, rancho Universitario, Tulancingo, Hidalgo, 43600, Mexico, (4) Instituto de Ciencias Agropecuarias- CICYTA, Univ. Autonoma del Estado de Hidalgo, Av. Universidad s/n C.P. 43600. Tulancingo, Hidalgo, México, Tulancingo Hidalgo, 43600, Mexico

Litchi fruit is acquiring greater commercial importance in Mexico. Several studies show that the main problem encountered during commercialization is the discoloration of the pericarp, but there are few studies dealing with the relation between the PPO and POD enzyme activity in the pulp and browning during storage at room temperature and under refrigeration. Our objective was to determine the relation between color changes and PPO and POD activity in litchi pulp. Litchi fruit grown in Mexico, in Tuxpan, Veracruz, was harvested when it reached level 3 maturity (completely red) and then carefully transported to the laboratory. Ten pieces of fruit per treatment were stored in trays at room temperature (22° C) and in polyethylene bags at 5-6° C. PPO and POD activity in the crude extracts was evaluated every week for 5 weeks. PPO was extracted in a phosphate buffer (pH 7.0) and the activity was assayed using catechol as a substrate. POD was extracted in a phosphate-citrate buffer (pH 4.5) using o-dianisidine and H2O2 as substrates. The color was evaluated using the parameters L*, a*, and b*. Our results showed that, PPO activity was 3.6 UA*g-1 in both treatments at the first week, but decreased steadily in the samples stored at room temperature until reaching values around 1.22 UA *g-1 during week 4. POD activity showed little change during 2 weeks storage (4 UA*g-1). However, it increased to 10 UA *g-1 after 3 weeks of storage at room temperature, and this coincided with the beginning of the discoloration of the pulp as measured by the L* parameter. There was little discoloration and little change in PPO and POD activity in the litchi fruit pulp up until 3 weeks of storage. The greatest care possible should be taken to preserve the color of the litchi pericarp.

Session 36E, Fruit & Vegetable Products: General
8:30 AM - 12:00 PM, Monday AM Room Hall I-2

2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana