Skin Damage to Peaches and Nectarines

Inking is caused when metallo-anthocyanin pigments are released  from skin damaged cells. The presence of metallic ions such as iron, copper and aluminum have also been implicated as precursors for inking development. The California research team showed that at least 10 ppm Fe iron was enough for the pigments to form resulting in inking. As mentioned previously it can occur in the field but more often in our area it usually shows up after running through the grading process. In their Central Valley Postharvest Newsletter they listed some chemicals that had higher levels of iron, copper or aluminum. The table below lists some of the materials that they tested and believe can affect the incidence of inking. To reduce the incidence of inking they recommended minimizing abrasion of the fruit by handling it gently and transporting it gently. Keep picking baskets clean and free of dirt. If you suspect you might develop inking, delay packing for 48 hours to detect inking damage during grading. You should also check your dump tank water pH.  High pH, above 7 can also aggravate the problem.

Skin burning appears as brown and/or black areas on the skin of the fruit. This disorder mainly occurs during the grading procedures at the brushing and washing point. Symptoms appear after packing especially when the fruit is placed in cold storage. The symptoms will increase during storage due to dehydration. Like inking, to reduce the incidence of skin burning, minimize abrasion to the fruit during pre- and post-harvest operations. High velocity forced air cooling can also induce skin burning. Dump tank and hydrocooler water should be maintained at around 6.5 to 7.0 pH.

For more information see:

Cantin, C. M. & C H. Crisosto. 2010 Recommendations to reduce field inking and skin burning development in peach and nectarine fruit. Cent. Valley Postharvest Newsletter  19(2) On the web at: http://www2.uckac.edu/postharv/PDF%20files/CVPN%20July%202010.pdf

Cantin, C. M. & C. H. Crisosto. 2011. Skin burning. Cent. Valley Postharvest Newsletter 20(1). On the web at: http://ucce.ucdavis.edu/files/datastore/234-2013.pdf

Crisosto, C. H., R. S. Johnson, K. Day, B. Beede & H. Andris. 1999. Contamination and injury induce inking on peaches and nectarines. California Agriculture 52:19-23. On the web at: http://californiaagriculture.ucanr.org/landingpage.cfm?article=ca.v053n01p19&fulltext=yes

Crisosto, C. H. 2009. Updating peach, nectarine and plum inking (skin discoloration) development information. Cent. Valley Postharvest Newsletter 18(1). On the web at: http://www2.uckac.edu/postharv/PDF%20files/CVPN_April09.pdf

Heavy metal concentrations in selected pesticide solutions at concentrations according to their labels.