Mineral composition, harvest maturity and storage quality of ‘Red Pippin’, ‘Gala’ and ‘Jonagold’ apples

Abstract

SummaryAn experiment was carried out in 1996 to assess the importance of pre-harvest factors on the storage quality of ‘Red Pippin’, ‘Gala’ and ‘Jonagold’ apples grown in the UK and the requirement for further work to develop fruit mineral analysis standards for these cultivars. Quality from store was determined primarily by the choice of controlled atmosphere (CA) regime. ‘Red Pippin’, ‘Gala’ and ‘Jonagold’ apples were stored in high CO2, low O2 regimes of 3/2, 5/1 and 4/1.2 (kPa CO2/O2) respectively, and in low CO2, low O2 regimes of <1/1.2, <1/1 and <1/1.2 respectively. Scald development in high CO2, low O2 regimes was nil (‘Jonagold’) or slight (‘Red Pippin’ and ‘Gala’) but extensive in low CO2, low O2 regimes where there was marked orchard variability. ‘Gala’ apples stored in either CA regime developed slight breakdown after six months of storage. Fruit firmness was maintained better in high CO2, low O2 regimes but the concentrations of sugars and acids in the fruit were generally unaffected by CA conditions. For each cultivar the mineral composition of fruit from different orchards at the time of commercial harvest varied greatly. On average, ‘Gala’ apples were lower in N and higher in Ca and Mn than ‘Red Pippin’ or ‘Jonagold’. ‘Red Pippin’ apples were highest in B and ‘Jonagold’ lowest in K and Mg. There were also cultivar differences in the mineral composition of leaves and fruits sampled in August and July respectively. For each cultivar samples for storage had been taken on the same date during the commercial harvesting period. Coeficients of variation (CV) were used to indicate the degree of variation in various indicators of maturity. In ‘Gala’ apples variability in firmness (CV – 6.3%) and soluble solids (CV – 4.9%) was approximately three-fold less than for starch coverage (CV – 15.5%). Some significant correlations were found between fruit quality and mineral/maturity variables. For all cultivars acidity was correlated positively with fruit K and sugar concentration with dry weight and soluble solids concentration in the fruit at harvest. Firmness of the three cultivars in the study was not correlated consistently with particular mineral constituents in the fruit at harvest or with harvest maturity parameters. Firmness of ‘Gala’ apples ex-store was highly correlated with harvest firmness and was positively correlated with Ca and B concentration in the fruit at harvest and negatively with K. There was a strong negative correlation between the incidence of scald in ‘Jonagold’ apples and the Ca concentration in the fruit at harvest. Increased fresh breakdown in ‘Gala’ apples was associated with high K, Mg, Na and Cu in harvest fruits, high Cu in fruitlets and high K, Mg and Zn in leaves.