New technologies to maintain quality and reduce postharvest losses of table grapes
Delivering table grapes that are of exceptional quality and free of any defects or disease to different export markets is vital for table grape industries. After harvest, table grapes (non-climacteric fruit) do not improve, and maintenance of the quality achieved in the vineyard up to retail shelves remains a challenge. Currently, visual inspection before and during harvest in the vineyard, after harvest and before packaging in the pack house, is used to assess the risk of quality defects developing during cold storage period prior to transportation to export markets. Table grapes are complex fruit that is prone to many different types of defects like berry crack, gray mold rot, SO2 damage and browning. The berry browning phenomenon alone can be manifest in 24 different phenotypes on white seedless grapes. Fourier transform near-infrared spectroscopy (FT-NIR) is an established method for measuring quality attributes of a wide range of fresh produce. Here we report on the detection of two different browning phenotypes (chocolate browning and friction browning) during cold storage of 'Regal Seedless' table grapes using FT-NIR spectra that were obtained in reflection mode of whole bunches. Visual inspection was used to score the browning defects of individual berries on bunches. The defects were then scored as 0 = no defect and 1 = defect present. Results obtained with partial least squares discriminant analysis (PLS-DA) of the bunch spectra showed that classification between healthy and affected bunches was possible. These results open up new possibilities for the development for quality checks of packed table grape bunches prior to export. This has a significant impact for the table grape industries for it will now be possible to evaluate bunches non-destructively during packaging to determine the possibility of these browning types being present.
Daniels, A.J., Opara, U.L., Poblete-Echeverría, C. and Nieuwoudt, H.H. (2020). New technologies to maintain quality and reduce postharvest losses of table grapes. Acta Hortic. 1275, 113-120
whole bunch, chocolate browning, friction browning, nondestructive measurements, infrared spectroscopy, qualitative calibration models, PLS-DA