Can hot water treatments enhance or maintain postharvest quality of spinach leaves?

It has been reported that a short duration hot water treatment, applied as a heat shock, improves subsequent postharvest quality in bagged spinach and rocket leaves. This study has established that the maximum hot water temperature and duration before spinach leaves showed damage, was 45 °C for 60 s. Subsequent detailed studies compared postharvest quality of leaves treated at 45 °C for 60 s immediately after harvest with untreated leaves after 5 and 10 days of storage at 4 °C. Heated leaves were significantly lighter and more yellow suggesting enhanced senescence, but leaf membrane integrity and associated gas composition of the storage atmosphere were not significantly different. Hot water treatment at 45 °C for 60 s applied immediately after harvest had a mixed effect on the biochemical constituents of the leaves; total carotenoid concentration was maintained compared to untreated leaves but the contents of ascorbic acid, dehydroascorbic acid, chlorophyll a and b were not affected. These observations suggest that in contrast to other reports, hot water treatments have limited commercial potential for postharvest quality improvement of spinach leaves.

► Maximum hot water heat shock treatment before spinach leaves show significant damage is 45 °C for 60 s.
► Heat shock does not maintain leaf colour.
► Heat shock does not affect leaf membrane integrity.
► Heat shock maintains total carotenoid concentration.
► Hot water treatments have limited commercial potential for postharvest quality improvement of spinach leaves.