Fruit color stability, anthocyanin content, and shelf life were not correlated with ethylene production rate in five primocane raspberry genotypes

Abstract

In order to determine the role of ethylene in post-harvest darkening of berries among raspberry genotypes the relationship between ethylene production, color stability, anthocyanin content, postharvest quality, and shelf life was examined in five raspberry genotypes during storage at + 1 °C and + 7 °C. The genotypes differed significantly in regard to fruit ethylene production, which ranged from 0.5 to 2.3 ng kg−1 s−1 after harvest. A negligible increase in ethylene production during storage was observed in ‘Heritage’ and ‘Nantahala’, while a pronounced increase occurred in ‘Crimson Treasure’ and breeding selection NY 10–24. Shelf life was, however, not correlated with the ethylene production rate in the genotypes. Fruit surface color at harvest did not predict darkening in storage. NY 10–24 was darker than the other genotypes at harvest. During storage especially ‘Heritage’ but also NY 10–24 darkened significantly resulting in darker fruit surface color than in the other genotypes. ‘Heritage’ had the highest total anthocyanin content at harvest. Anthocyanin concentration increased during storage with the mean increase across all genotypes after 8 d being 45% at + 1 °C, and 80% at + 7 °C, while an increase of 128% was observed in ‘Heritage’ at + 7 °C. Optical density of fruit juice was highly correlated with the concentration of anthocyanins in the whole fruit samples. Both berry sugar and titratable acidity content differed significantly between the genotypes. The highest sugar to acid ratio was found in ‘BP1’, being about two times higher than in ‘Heritage’ or’ Crimson Treasure’. While sugar content did not change, titratable acidity decreased during storage. This study demonstrated that genotypic differences in fruit ethylene production rate did not explain differences in color change (darkening) during storage or in shelf life of primocane raspberry genotypes, nor was color stability in storage directly correlated to anthocyanin content or fruit color at harvest.