Determining the optimum firmness for sweet cherries using Just-About-Right sensory methodology

Abstract

This study evaluated Just-About-Right (JAR) ratings of untrained panellists for whole sweet cherry (Prunus avium L.) crispness and flesh firmness. Cherries from 17 different cultivars and breeding selections representing a wide range of fruit firmness were harvested over the course of the cherry maturity season in 2011 and 2012. The firmness of each cherry (n=183–500 per sample) was measured with the FirmTech 2 Fruit Firmness Tester, and the fruits were sorted into 19 firmness categories, of 0.20N increments, ranging from 1.58 to 5.69N. Untrained panellists (n=48) assessed whole cherry crispness and flesh firmness using a 7-point JAR scale from ‘much too soft’, through ‘just about right’, to ‘much too firm/crisp’. Four to eight firmness categories were evaluated per session in a series of 10 sensory sessions. Linear regression was used to model the relationship between JAR ratings and analytical firmness values, for whole cherry crispness (r2011−122=0.75) and flesh firmness (r2011−122=0.75). Crispness and firmness were highly correlated in both years (R2011=0.99, R2012=0.99). Frequency distributions of JAR ratings identified the proportion of responses at each rating (1–7), within each firmness category. The “acceptable” firmness range was calculated to be 2.52–4.75N from JAR flesh firmness scores of between 3 (‘slightly too soft’) and 5 (‘slightly too firm’), respectively. Cherries with measured firmness values between 2.56 and 4.71N were “acceptable” to 72.9–91.7% of panellists. The work established the relationship between sensory and analytical evaluations in order to develop guidelines for acceptable sweet cherry fruit firmness to use in research on cultural practices and the selection of new cultivars.