Texture-microstructure relationship of leafy vegetables during postharvest storage

Leafy vegetables such as lettuce (Lactuca sativa L.) and spinach (Spinacia oleracea L.) are consumer favourites.
As leafy vegetables are highly perishable, they need to be refrigerated immediately after harvest to retard the biochemical processes that lead to senescence.
The main aim of this study is to test the hypothesis that changes in the three-dimensional (3-D) leaf microstructure during postharvest storage contribute significantly to loss of texture.
Leaves from spinach and lamb’s lettuce at commercial maturity were stored in dark at 13°C with the relative humidity maintained at 99.5±7.4 and 76.5±5.8%. The 3-D leaf anatomy was then imaged at day 0, 2, 4, 6 and 8 using X-ray micro computed tomography (X-ray µCT). In addition, mechanical properties were assessed by a punch test using a texture analyzer.
The leaf anatomy showed drastic changes congruent with the observed water loss and tissue softening.
Structural parameters were calculated from the X-ray µCT images.
The 3-D leaf thickness correlated well with strength and displacement before fracture while tissue specific surface and pore specific surface correlated well with toughness.
The implication of such correlations on crispiness and crunchiness is discussed.

VI International Conference Postharvest Unlimited

M.A. Retta, B. Verlinden, P. Verboven, B. Nicolaï

storage disorder, food quality, shelf-life, imaging, 3-D microstructure, tomography, lettuce, spinach

https://doi.org/10.17660/ActaHortic.2019.1256.24