Non-destructive prediction of scald susceptibility by means of near-infrared spectroscopy
One of the most common physiological disorders occurring on apple fruit during or immediately after storage is superficial scald. To date understanding the etiology and biochemistry of scald development mechanisms is still in progress, with various theories providing different viewpoints and approaches on the subject. Historically, α-farnesene, and its subsequent oxidation into the corresponding conjugated trienols (CTols), was considered as the principal cause leading to superficial scald. Latter studies rely on a more relevant involvement of the oxidation of phenolic compounds. It is supposed that the appearance of the disorder is correlated to specific chilling induced processes in the epidermis. In order to trace the scald susceptibility of apple fruit, in the present work the potential of near-infrared spectroscopy (NIRS) was investigated, by means of a black-box-approach. A first attempt to extract information from the collected NIR spectra (1,000-2,500 nm) of intact apples was conducted by applying principal component analysis (PCA). The feasibility to discriminate apples of the cultivar 'Granny Smith' with different scald susceptibility, generated by applying 3 different temperature conditioning treatments before storage, one important factor determining scald induction in the fruits, has been examined on 20 fruit per treatment, from 3 orchards for 7 different storage durations (1260 in total) in 2 growing seasons. The obtained results substantiate the potential of NIRS as a promising non-destructive technology to discriminate apples based on their progressive development of scald incidence during storage. PCA revealed a distinct spectral signature of individuals of Granny Smith depending on storage duration at chilling inducing conditions, which determine the scald susceptibility. Moreover, the NIR spectra reflected the effect of scald mitigating storage preconditioning treatments. The task that future research has to address, is the further development of this approach aiming to end up into its integration into a postharvest decision support system. The ultimate goal consists in minimizing in this way the loss of horticultural products.
Zanella, A., Stürz, S., Sadar, N. and Ebner, I. (2021). Non-destructive prediction of scald susceptibility by means of near-infrared spectroscopy. Acta Hortic. 1311, 179-184
NIRS, superficial scald, Malus × domestica, 'Granny Smith', principal component analysis (PCA)