Effects of Calcium Concentrations of Coating Bag on Pericarp Structure and Berry Cracking in 'Kyoho' Grape (Vitis sp.)

The effects of calcium concentrations of coating bag treatment to reduce berry cracking were investigated through the changes of pericarp structure and berry cracking rate in 'Kyoho' grape. The soluble solids and anthocyanin contents in harvested grapes were highest at 18.1 degrees Brix and 2.56 mu g center dot cm(-2) in non bagging group compared with those of calcium coating bag treatments. The firmness of pericarp was lowest in non bagging group (1.18 kg center dot 5 mm(-1)theta) compared with bagging treatments (1.23, 1.24, 1.27, 1.35 kg center dot 5 mm(-1)theta) which increased effectively in proportion to calcium concentration. As a result of histological observation of the fruit skin, the bagging with higher calcium concentration developed thicker epidermal and sub-epidermal layer of cell wall than that of non bagging. Moreover, the strengthened berry skin of calcium treatments effectively decreased berry cracking rate under critical turgor pressure. However, the 9% calcium coating bag treatment which was the most effective for cracking reduction seriously decreased marketability of harvested grape with white color staining on berry skin caused by eluted calcium from the coated paper bag. Based on our results, we recommend that 6% calcium coating bag be available for berry cracking reduction and higher quality production.