Activity of β-Galactosidase and Polygalacturonase in Zucchini Squash (Cucurbita pepo L.) Stored at Low Temperatures

René Renato Balandrán-Quintana¹, Ana María Mendoza-Wilson², Irasema Vargas-Arispuro² and Miguel Angel Martínez-Téllez²*

¹Universidad Autónoma de Chihuahua, Facultad de Ciencias Químicas, Ciudad Universitaria s/n, A.P. 1542-C Chihuahua, Chihuahua, México
²Centro de Investigación en Alimentación y Desarrollo, A.C., Coordinación de Tecnología de Alimentos de Origen Vegetal, Km 0.6, Carretera a La Victoria, A.P. 1735, 83000 Hermosillo, Sonora, México

Article history:
Received June 6, 2006
Accepted November 7, 2006

Key words:
chilling injury, cold signaling, oligosaccharins, cell wall

Summary:
When fruits are exposed to chilling temperatures, enzymatic systems are affected and normal cell metabolism is altered; cell wall enzymes are the least studied in this respect. Our objective is to determine the effect of storage temperature and/or kind of tissue on the activity of the enzymes polygalacturonase (PG) and β-galactosidase (β-gal) in zucchini squash (Cucurbita pepo L.) subjected to 2.5 and/or 12 °C for 16 days. Exocarp and endocarp samples were analyzed every 4 days for PG and β-gal activities. The highest β-gal activity was found in the exocarp at 12 °C; in both tissues β-gal decreased with time at 2.5 °C, but increased at 12 °C. PG activity was higher in the endocarp (highest activity at 2.5 °C) than in the exocarp (highest activity at 12 °C). It was concluded that PG activity in the exocarp constitutes an adequate system for studying the relationship between chilling injury and cell wall biological activity.

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