Alec Mc Carthy
- 2. Managing heat when harvesting ?
- 3. Harvesting Hass during high temperatures Alec McCarthy July 2009
- 4. The harvesting scenario – in Western Australia Current recommendation to not harvest above 30 °C Temperature commonly exceeding 30 ° during harvest C Production increasing – tighter time demands Growers ignore recommendation WA fruit has a good fruit quality image Potential threat to fruit quality and image
- 5. The temperature issue on quality Perceived or real? Impact of high temperature on fruit quality – before, during, after harvest Impact of delays in removal of field heat / holding conditions after harvest before cooling
- 6. Related issues affecting quality Length of storage impact Disease pressure Dehydration
- 7. The investigation To determine the impact of harvesting during high temperatures on the post harvest quality of Hass avocados grown under cool Mediterranean conditions in the south west of Western Australia. Harvest temperature range 28 – 37 ° C Cooling delay of up to 24 hours Storage for 14 and 28 days 2 years of controlled field trials 1 year of commercial verification Fruit quality assessed using the ‘AvoCare’ assessment manual (Woolf et al.)
- 8. Temperature logging in the tree
- 9. Change in pulp temperature during the day Comparing pulp temp of exposed and shaded fruit with ambient temperature 45 40 pulp temperature (deg C) 35 30 25 20 10:03:00 10:33:00 11:03:00 11:33:00 12:03:00 12:33:00 13:03:00 13:33:00 14:03:00 14:33:00 15:03:00 15:33:00 16:03:00 16:33:00 17:03:00 time of reading Exposed fruit (yellow triangles – received some shading during the middle of the day), predicted exposed reading with no shade (solid line), shaded fruit (blue diamonds), ambient (blue cross)
- 10. Fresh sunburn, one day of exposure
- 11. Effect of heat/direct sun on fruit on the tree - summarised Sun exposed fruit’s pulp temperature increases well above the ‘ambient’ temperature, by 5 to 8° similar to findings by Woolf C, et al and Ferguson et al Shading will arrest further increase in pulp temperature when fruit is still attached to the tree Shaded fruit essentially mirrors the ambient temperature Sun exposed fruit’s pulp temperature can get over 30° byC 10:30 am on a hot day, > 35° Shaded fruit by 12:30 C, Newly exposed fruit is very sensitive to exposure to direct sunlight on hot, dry days
- 12. Year 1 results A significant linear affect of harvest temperature could not be seen for body rot, skin colour or fruit softness A significant favourable linear affect of harvest temperature was displayed for vascular browning B 0.5 0.45 Vascular Browning (0-3) 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0 25 27 29 31 33 35 Am bient harvest tem perature (deg C)
- 13. Year 1 results (cont.) There was no significant linear impact of the increasing delay into cool storage on the key quality parameters of body rots, vascular browning or stem end rot. The storage length did have a significant impact on all the quality parameters
- 14. 2004 Fruit quality results – storage length Measurement Storage period Mean rating significance softness 14 days 5.089 0.027 28 days 5.636 Skin colour 14 4.162 <0.001 28 5.241 Body rot 14 0.670 0.048 28 1.104 Vascular browning 14 0.145 <0.001 28 1.941 Diffuse discolouration 14 0.121 <0.001 28 1.514 Stem end rot 14 0.016 <0.001 28 0.355
- 15. Year 2 results Several significant impacts were detected for both increasing harvest temperature and the delay into cool storage All but one were of a very minor nature that would be hard to pick without statistics, ie, less than a 0.5 shift One significant quality deterioration occurred, increasing harvest temperature increased the level of body rot by 0.17 for every 1° when subjected to a two hour delay. The 24 hr C, delay produced body rot levels similar to the highest temperature with a 2 hr delay.
- 16. Conclusions Other parameters than harvest temperature likely having a greater impact on fruit quality Harvesting at temperatures above 30°C is acceptable with minimal impact on fruit quality, provided fruit is: Protected from the elements (direct sun and wind) Field heat removed within 24 hours of harvest Fruit stored at the appropriate temperature for the chosen period of storage
- 17. Acknowledgements Avocado Growers Association of WA Horticulture Australia Limited Bidwell family Shenton family French family Franceschi family Avonova