Identification of fruit parameters related to calyx cavity incidence for the evaluation of non-destructive equipment as segregation tools : a thesis presented in partial fulfilment of the requirements for the degree of Master of Horticultural Science at Massey University, Palmerston North, New Zealand

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Calyx cavity is a major physiological disorder in persimmon that hinders exports and correlates with reduced fruit quality during storage. Postharvest quality changes, including increases in softening and colouration, have been related to the presence of calyx cavity. This thesis investigated the impact of calyx cavity on persimmon quality using both destructive and non-destructive methods of evaluation and assessed the ability of these tools, combined with modelling techniques, to segregate affected fruit. Seven batches of ‘Fuyu’ persimmon were evaluated at the time of harvest and following a nine-week storage period in modified atmosphere packaging (MAP) at 1 °C. Quality parameters assessed were fruit size, texture, colour, sweetness, and severity of calyx cavity. Non-destructive methods used included near infrared spectroscopy (NIR), acoustic vibration and non-destructive compression; the destructive methods used were flesh firmness and soluble solids content (SSC). A visual scale was created to score the severity of calyx cavity from no separation (grade 1) to minor (2), moderate (3), and major separation (4). After storage, fruit firmness decreased, and SSC and external colouration increased compared to at harvest values. Large differences in fruit maturity, in terms of firmness, colour and SSC were observed between fruit from different harvest dates. The presence and severity of calyx cavity was correlated with greater colouration and greater weight. On average, a 40 g increase in weight and 1 – 2 unit increase in colour index was observed with each level (1 – 4) of calyx cavity severity. Using colour and weight data, binary classification of calyx cavity by linear discriminant analysis (LDA) had a total accuracy of 74.1% correct segregation. Random forest (RF) segregation of calyx cavity using NIR data had a performance metric of 0.655. The implementation of non-destructive calyx cavity classification based on the evaluation of changes in quality parameters would provide the ability to segregate healthy and affected fruit. However, the relatively low accuracy of these models creates limitations including yield losses and failed identification of fruit with calyx cavity. Further work is required to improve model performance including optimisation and validation of calyx cavity segregation models.
Figures have been reused with permission, but the following were removed for copyright reasons: 2.3 (=Tessmer et al., 2016 Figs 1B & C); 2.10 & 2.14 (=Tessmer et al, 2016 Figs 2A & B); 2.15 (=Tessmer et al., 2016, Fig 8). Figures 2.4, 2.12 right & 3.6 are licensed for reuse under a Creative Commons Attribution 4.0 International (CC BY 4.0) license.