The effects of short-term pre-harvest lighting and continuous low intensity postharvest lighting on the postharvest performance of lettuce (Lactuca sativa L.)

MSc-thesis abstract (submitted 31 August 2017): Quality of fresh lettuce (Lactuca sativa L.) product during postharvest storage is very important to both consumers and suppliers. The initial quality of product at harvest is closely related to the quality decline at postharvest storage.
High intensity lighting has great potential to improve the initial quality (total ascorbic acid content and carbohydrate level) of lettuce at harvest, but how the different initial quality induced by high intensity lighting affects the quality performance during storage is still not thoroughly studied.
Also, almost no studies focus on the effects of postharvest lighting on quality performance of fresh lettuce product during postharvest storage phase.

In this study, applying 6 days short-term pre-harvest lighting with three different intensities (50 μmol m-2 s-1, 215 μmol m-2 s-1, 534 μmol m-2 s-1) showed significant differences in initial quality of lettuce at harvest point. Short-term high intensity lighting before harvest greatly increased the total carbohydrates and TAsA content (initial quality) of lettuce at harvest compared to the lettuce from medium light intensity and low light intensity treatments. These fresh lettuce products (intact leaf and fresh-cut) with higher initial quality had longer shelf life.

Applying continuous low intensity lighting (10 μmol m-2 s-1) during the postharvest phase also had positive effects on the postharvest performance of lettuce. Lettuce (fresh-cut samples) stored under continuous low intensity lighting during storage phase showed an increase on the total carbohydrates and TAsA content, also showed better postharvest performance and had longer shelf life than lettuce stored in dark. Total carbohydrates and TAsA content of lettuce at harvest (initial quality) were positive correlated with the shelf life and quality performance during postharvest storage in this study.

Key words: Lactuca sativa L., short-term pre-harvest lighting, postharvest lighting, initial quality, postharvest performance