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On-tree indexing of ‘Hass’ avocado fruit by non-destructive assessment of pulp dry matter and oil content
- Ncama, Khayelihle, Magwaza, Lembe S., Poblete-Echeverría, Carlos A., Nieuwoudt, Hélène H., Tesfay, Samson Z., Mditshwa, Asanda
- Biosystems engineering 2018 v.174 pp. 41-49
- avocados, chemometrics, computer software, dry matter content, freeze drying, harvesting, lipid content, mesocarp, models, nutritive value, orchards, ovens, pulp, spectrometers, statistical analysis, temperature, water content
- Commercial harvest maturity of ‘Hass’ avocado fruit is estimated based on dry matter content (DM). Typically, a few samples representing the entire orchard are destructively analysed using time-consuming procedures such as oven or freeze drying the fruit's mesocarp. However, the maturity parameter of avocado, that is known to have a direct link to nutritional quality, is oil content (OC). This study was conducted to develop models for indexing maturity of on-tree avocado using a portable visible to near-infrared spectrometer. Rapid non-destructive models for assessing OC, DM and moisture content (MC) of avocado fruit were successfully developed using The Unscrambler® X chemometric software. Models robustness was assessed in an independent test set. There were non-significant differences (p > 0.05) between destructive and non-destructively assessed OC in terms of means (42.45 and 41.91%), standard deviations (4.79 and 4.87%) and coefficients of variation (11.34 and 11.62%) from the independent test set. The predictability of OC was associated with its high extractability caused by drying samples at high (75 °C) temperatures. The heat-drying technique can be used by other researchers to increase extractability and hence, the predictability of avocado OC during calibrations of alike non-destructive models. Commercial application of the developed models can improve maturity indexing since OC, DM and MC can be easily assessed without harvesting of sample fruit.