ISHS Acta Horticulturae 464: International Postharvest Science Conference Postharvest 96
VARIATION IN WATER VAPOUR PERMEANCE OF ‘BRAEBURN’ APPLES |
| Authors: | K.M. Maguire, N.H. Banks, A. Lang |
| Abstract:
There is large variation in estimates of skin water vapour permeance (P'H2O; mol·s-1·m-2·P-1) within populations of different horticultural crops. Such variation masks treatment effects in experimental work, making it difficult to develop strategies for controlling water loss. This work quantified contributions from various sources to total variation in estimates of P'H2O of ‘Braeburn’ apples (Malus domestica Borkh.). Six fruit were sampled from four trees, from each of eight Central Otago growers, on each of five harvest dates. The first harvest was two weeks before opening of commercial harvest (1995); subsequent harvests were at two week intervals. P'H2O was determined from Fick's first law of diffusion that relates permeance to rate of water loss (r'H2O; mol·s-1), internal partial pressure of water vapour (PiH2O; Pa), external partial pressure of water vapour (PeH2O; Pa) and fruit surface area (A, m2). Over 50% of the total variation in permeance was associated with harvest. This was the result of a large increase in P'H2O from 16.6 nmol·s-1·m-2·Pa-1 at first harvest up to 30.2 nmol·s-1·m-2·Pa-1 at final harvest. This may in part explain the higher-than-normal level of shrivel reported in late-harvested ‘Braeburn’ apples in the 1995 season. Fruit to fruit differences accounted for 22% of the total variation in permeance values, indicating large fruit to fruit variation in PH2O· Variation associated with repeated measurements was less than 1%, indicating that measurement error was negligible. An interaction effect of harvest and orchard explained ca. 7% of the total variation, indicating that permeance of fruit from different orchards increased by differing amounts with advancing harvest. The data suggest that it may be worthwhile to implement more stringent measures to control weight loss in late harvested ‘Braeburn’ apples. | |
Download Adobe Acrobat Reader (free software to read PDF files) | |
