Impact of ventilation area of the liner bag, in the performance of SO2 generator pads in boxed table grapes
SO2 generator pads are an important tool to prevent rotting of table grapes, caused by fungal pathogens, mainly Botrytis cinerea, during storage and shipping. Sodium metabisulfite salt contained in the pad reacts with water vapor and releases SO2. Due to market regulations, the liner bag used in the table grape packaging can have 0.3, 0.9 or 2.7% ventilated area. Switching to higher ventilated areas has been associated with higher decay. The objective of the study was to determine the dynamic of SO2 concentration inside the boxes, during cold storage, and relate it with rotting and bleaching of table grapes. Different experiments were conducted from 2011 to 2015; in general, grapes were packed in boxes with liners of different ventilation areas, silicon hoses were set for weekly measurements of the gas concentration inside the box, then they were cold stored for 35 to 94 days, and after a period of three days at room temperature, simulating shelf life, the percentage of rotting and bleaching was determined. In a first experiment, rotting of 'Red Globe' grapes due to B. cinerea averaged 32.7 and 4.6% in control boxes (without generator pads) with 0.3 and 0.9% of ventilation, respectively. Similarly, boxes with 0.9% ventilation had 76.1% of rotting compared to a 24.3% in boxes with 2.7% ventilation. Differences in grey mold incidence were also observed in boxes packed with generator pads, where 16.8% rotting was significantly different to 5.0% rotting in boxes with 2.7 and 0.9% ventilation area, respectively. Bleaching of grapes was affected negatively with increasing ventilation reaching 10.3, 1.9 and 0.5% in boxes with 0.3, 0.9 and 2.7% ventilated area, respectively. SO2 concentration inside the boxes was lower throughout the storage period, as the ventilation area of the liner increased.
Henríquez, J.L. and Pinochet, S. (2016). Impact of ventilation area of the liner bag, in the performance of SO2 generator pads in boxed table grapes. Acta Hortic. 1144, 267-272
Botrytis cinerea, grey mould, postharvest pathology, sulfur dioxide, box liners