306 Preharvest Methods to Reduce Skinning in `Beauregard' Sweetpotato

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  • Depts. of 1Horticultural Science and2 Biological and Agricultural Engineering Dept., North Carolina State University, Raleigh, NC 27695

The `Beauregard' sweetpotato variety is very prone to damage to its skin. We evaluated several preharvest treatments to reduce skinning so that less damage was done at harvest, during transport, and packing. Three field tests were conducted in 1998 (two tests) and 1999 (one test) in North Carolina. Treatments were implemented 1 and 2 weeks prior to harvest and were either chemical or mechanical. The three mechanical treatments were flail mowing, flail mowing and barring off, and vine snatching. The following chemical treatments were made: PREP, Diquat, Dessicate II, and 2,4-D at various rates. Sweetpotatoes were harvested and roots were graded. Subsequently, U.S. No. 1 root subsamples were obtained from each plot in order to evaluate the effects of treatment on skin tightening of roots. Roots were evaluated from each plot for skin toughness using a “skin-o-meter” where a pressurized stream of water was directed at a sweetpotato. The roots were then evaluated for skinning by checking if the skin was broken using the skin-o-meter. A second method was used to evaluate the effect of treatment for its effect on skin tightening (reduced skinning). One bushel of roots from each treatment plot was transported to Clinton, N.C., and run through a small packing line at the Horticultural Crops Research Station the next day after harvest. The sweetpotatoes were then evaluated in Raleigh for the number of incidences where skin had been removed during the harvesting, transport, or packing process. The severity of skinning was characterized by counting the number of small (<5 mm), medium (width 5-10 mm) and large (width 10+ mm) skinned areas on a root. An overall appearance rating for roots was also recorded for each subsampled plot with 10 being the best rating and 1 being the worst. Results indicate that treatment 14 days prior to harvest rather than 7 days prior to harvest seems to be advantageous in most cases for reducing skinning and maintaining yield of sweetpotato when compared with not treating the vines. Regardless of whether the treatment was chemical or mechanical, treatments were apparently beneficial in these tests. Application of PREP 7 days prior to harvest resulted in sweetpotatoes with the most resistance to skinning in 1999, the fewest large-size skinning abrasions on roots, and best appearance. PREP shows promise as a means to reduce skinning in sweetpotatoes, but presently is not labeled for use on sweetpotatoes.

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