Ethylene, enzymatic and respiratory pattern evolution in loquat (Eriobotrya japonica (Thunb.) Lindl.) cv. Golden Nugget in the last four sequential stages of maturation

Pedro L. Undurraga M. 1*, José A. Olaeta C.1, and Cristian Cancino1

There is some controversy regarding the respiratory pattern of loquat (Eriobotrya japonica [Thunb.] Lindl.). Thus in order to provide information on this aspect of loquat, fruit of 50-70 g, from cv. Golden Nugget were harvested in four stages of maturity: green (BBCH 709), color break (BBCH 801), yellow (BBCH 807), and orange (BBCH 809). The parameters evaluated in each stage were: soluble solids, titratable acidity, respiration, ethylene generation, and activity of the enzymes pectin methyl esterase (PME), peroxidase, polyphenoloxidase (PPO), polygalacturonase (PG), and cellulose, and the soluble solids:acidity ratio was calculated. The results show that ethylene concentration increased at the time of color break, which was not the case for the change in the respiratory rate. The activity of the peroxidase enzyme increased from the green stage to color break, while the enzymes PME, cellulase, and PG showed a constant reduction from the green to the orange stage, and PPO showed no change over the four stages studied. With regards to quality, from color break onwards soluble solids increased to 11.8 ºBrix and titratable acidity dropped from 0.67 to 0.28 g L-1 malic acid. Based on these results, the conclusion is that towards the end of its development loquat cv. Golden Nugget evidence enzymatic and ethylene behavior similar to that of climacteric fruits.

Keywords: Color skin, peroxidase, CO2, fruit quality, polygalacturonase.
1Pontificia Universidad Católica de Valparaíso, Facultad de Agronomía, Casilla 4-D Quillota, Chile. *Corresponding author (pundurra@ucv.cl).