P3-21 Ultraviolet-C Light Effect on the Reduction of Saccharomyces cerevisiae on Grapefruit and Orange Juices

Wednesday, August 3, 2016
America's Center - St. Louis
Carlos Ochoa Velasco, Benemérita Universidad Autónoma de Puebla, Puebla, Mexico
Raul Avila Sosa, Benemérita Universidad Autónoma de Puebla, Puebla, Mexico
Addí Rhode Navarro Cruz, Benemérita Universidad Autónoma de Puebla, Puebla, Mexico
Paola Hernández Carranza, Benemérita Universidad Autónoma de Puebla, Puebla, Mexico
Carolina Salcedo Pedraza, Benemérita Universidad Autónoma de Puebla, Puebla, Mexico
Obdulia Vera López, Benemérita Universidad Autónoma de Puebla, Puebla, Mexico
Martin Lazcano Hernández, Benemérita Universidad Autónoma de Puebla, Puebla, Mexico
Introduction: Currently, there exists a great demand of novel technologies for the pasteurization of juice in order to guarantee the quality. Ultraviolet-C (UV-C) light is a novel technology that provides a non-ionizing light with germicidal properties at 254 nm. UV-C light is capable to inactivate microorganisms due to the damage at DNA level, delaying the replication and transcription of the cell. Moreover, citric juices are products with high acidity that inhibited the microorganisms; however, Saccharomyces cerevisiae is capable of growth in citric products, affecting the quality of juices. 

Purpose: The aim of this research was to evaluate the effect of UV-C light on Saccharomyces cerevisiae inactivation in grapefruit and orange juice at two different temperatures.

Methods: Commercial pasteurized grapefruit and orange juices were obtained from a local supermarket of Puebla, Mexico. Juices were inoculated with Saccharomyces cerevisiae (108 CFU/ml) and treated with UV-C light (60 min) at different temperatures (5 and 40°C). First order kinetic reduction was used to calculate the decimal reduction time. Moreover, a sensory evaluation was performed in order to know the acceptability of treated juice.

Results: Maximum microbial reduction obtained in grapefruit juice treated with UV-C light were 1.3 and 1.1 cycles for 5 and 40°C, respectively; while in orange juice were 1.2 and 1.1 cycles for the same temperatures. In grapefruit juice, temperature treatment significantly affect decimal reduction times, showing values of 45.4 ± 2.8 and 59.2 ± 3.0 min for 5 and 40°C, respectively. However, for orange juice there was not significant effect of temperature treatment, showing values of 56.2 ± 0.4 and 57.2 ± 0.9 for 5 and 40°C, respectively. Sensorial attributes indicate that juices treated at short time (10 and 20 min) were preferred by the judges.

Significance: UV-C light treatment is a suitable manner to reduce the microbial load of spoilage microorganisms; although, it is important to combine with others treatments in order to increase the microbial reduction.