Raspberry texture mechanical profiling during fruit ripening and storage

Consumption of raspberry (Rubus idaeus L.) has drastically increased in the last decade. However, fruit perishability, mainly due to water loss, morphological fragility, softening, and presence of pathogens like botrytis, is still the major problem limiting raspberry marketability. Therefore, high firmness and prolonged shelf life are the two key quality traits of a successful raspberry genotype. Analytical firmness assessment of raspberry is still challenging due to fruit morphology heterogeneity, a lack of standardized methodologies and resources available only for a few varieties. The aim of this study was to develop and to fine tune two methodologies to fully assess raspberry texture: a destructive penetration test and a non-destructive compression test A high variation was explained among 29 raspberry cultivars tested in this study. Differences among genotypes were observed at all ripening stages, showing a significant cultivar dependent pattern especially at harvest and after storage. The two methodologies allowed to complimentary profile raspberry texture. Moreover, a clear relationship among 22 texture mechanical parameters and morphological traits that contribute to raspberry quality was elucidated. For instance, fruit size is significantly positively correlated with compression measurements, while number of drupelets is significantly negatively correlated with all the parameters used for the compression test, except for the Young's modulus, cohesiveness and all the derived indexes.