Chemical investigations on bitter pit of apples

Abstract

Discoloured tissue and neighbouring apparently healthy tissue from Cox's Orange fruits affected with bitter pit have been analysed. Discoloured tissue was higher in total ash, calcium, magnesium, potassium, sodium, phosphorus, and nitrogen than neigbouring healthy tissue. Magnesium content of the former was four times that of the latter. While healthy tissue was generally similar in mineral composition to that of whole peeled fruits at time of storage, the former was poorer in calcium. There is evidence of general migration of minerals and nitrogen from the healthy to the affected tissues. Tissue from the affected areas was very low in sucrose but was well supplied with glucose and fructose. It was richer in glucose than the neighbouring hea:lthy tissue. Reducing sugars increased markedly during storage. Apparently healthy tissue was comparable in sucrose content to that of the whole fruit at time of harvest. Starch content of affected tissue was 0.81 % and 1.17% at two orchards, while accompanying healthy tissue showed only 0.19% and 0.13% respectively. Total ash content was significantly positively related to increasing incidence of bitter pit. High values of the ratios Mg/Ca, K/Mg, K/Ca, and K/N accompanied high incidence of bitter pit in the fruit.