TEXTURAL, BIOCHEMICAL AND MICRO-STRUCTURAL CHANGES IN MESOCARP TISSUE OF IMPORTED AVOCADO FROM PERU DURING RIPENING

Abstract

Avocado (Persea americana Mill.) fruit is a valuable product and notorious for the difficulties encountered in determining quality. Typically the degree of ripeness of many climacteric fruits, such as avocado, is measured by assessing flesh firmness. The aim of the presented work was to elucidate the temporal and spatial changes in texture, biochemistry and micro-structure in different avocado tissues from the same fruit. Fruit were first treated with ethylene and then ripened at 12°C. Samples were taken four times over 10 days storage. Maximum load and viscoelasticity of horizontally-cut slices from fruit (n=24) imported from Peru were measured during ripening. These texture parameters were measured using an Instron 5542 universal testing machine fitted with a 500 N or 5 N load cell. Non-structural carbohydrates (NSCs; viz. sucrose, mannoheptulose, perseitol) and fatty acid methyl esters from the same samples were identified and quantified using standard HPLC coupled to evaporative light scattering detection and gas chromatography coupled to flame ionisation detection, respectively. Samples taken from adjacent mesocarp tissue slices were examined: each specimen included the sclerenchymatic exocarp, fleshy mesocarp and endocarp including the coat of the seed. An analysis of variance was performed to elucidate the change of parameters during fruit ripening. NSC content and textural properties changed during ripening and showed spatial heterogeneity within individual fruit. Micro-structural changes were evident during the latter stages of ripening and coincided with fruit softening and degradation in mannoheptulose. These findings might be used to enhance quality monitoring of imported avocado fruit.