Effect of defoliation prior to a frost on postharvest respiration rate, extractable sucrose, and invert sugar concentration of sugarbeet

Authors: Campbell, Larry; Fugate, Karen; SMITH, LARRY - University Of Minnesota

Submitted to: Journal of Sugar Beet Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/1/2015
Publication Date: 12/1/2015
Citation: Campbell, L.G., Fugate, K.K., Smith, L.J. 2015. Effect of defoliation prior to a frost on postharvest respiration rate, extractable sucrose, and invert sugar concentration of sugarbeet. Journal of Sugar Beet Research. 52(3-4):2-29.

Interpretive Summary: This study investigated the effect of defoliation prior to a frost on postharvest storage properties of sugarbeet; roots of plants with canopies intact until harvest were compared to roots of plants that had been defoliated prior to a frost on multiple harvest dates following a damaging frost. The objectives of the study were 1) to document the detrimental effects of defoliation prior to a damaging frost, and 2) to indicate potential postharvest storage problems that may be associated with roots that have been subjected to freezing temperatures prior to harvest. The average storage respiration rates of roots harvested from plots that had been defoliated prior to a damaging frost were 1.30, 1.52, and 2.67 mg CO2 kg-1 h-1 greater than the postharvest respiration rates of roots harvested on the same day that had their canopies intact until harvest, 30, 60, and 90 days after harvest (DAH), respectively. Respiration typically accounts for 80% of the sucrose loss during root storage. The average extractable sucrose concentrations of roots that had been defoliated prior to a frost were 2.39 and 3.49 kg Mg-1 less than the extractable sucrose concentration of roots harvested on the same day that had their canopies intact until harvest, 0 and 90 DAH, respectively. The average increase in the invert sugar concentration of crowns due to defoliation prior to a frost was 6.49 g (100 g of sugar)-1 90 DAH. The increase in the invert sugar concentration of taproots attributable to defoliation was one tenth the invert sugar increase of comparable crowns. Invert sugar is a product of the break-down of sucrose that also impedes the extraction of sucrose during processing.

Technical Abstract: This study investigated the effect of defoliation prior to a frost on postharvest storage properties of sugarbeet (Beta vulgaris L.). Roots of plants with canopies intact until harvest were compared to roots of plants that had been defoliated prior to a frost on multiple harvest dates following a damaging frost. The average storage respiration rates of roots harvested from plots that had been defoliated prior to a damaging frost were 1.30, 1.52, and 2.67 mg CO2 kg-1 h-1 greater than the postharvest respiration rates of roots harvested on the same day that had their canopies intact until harvest, 30, 60, and 90 days after harvest (DAH), respectively. The average extractable sucrose concentrations of roots from plots that had been defoliated prior to a frost were 2.39 and 3.49 kg Mg-1 less than the extractable sucrose concentration of roots harvested on the same day that had their canopies intact until harvest, 0 and 90 DAH, respectively. The average increase in the invert sugar concentration of crowns due to defoliation prior to a frost was 6.49 g (100 g S)-1 90 DAH. The increase in the invert sugar concentration of taproots attributable to defoliation was one tenth the invert sugar increase of comparable crowns