The effect of two orchard light management practices on the sensory quality of apple: Fruit thinning by shading or photo-selective nets

The effects of innovative techniques for orchard light management on the sensory properties and quality of apple (Malus × domestica Borkh.) fruit were measured using sensory and instrumental techniques. In the first experiment, ‘Rosy Glow’ fruit, thinned chemically or by shading, were compared. In the second experiment,‘Fuji’ fruit were grown under five different coloured photo-selective hail nets and compared. For ‘Rosy Glow’ fruit, the efficacy of both thinning methods was comparable in terms of crop load, and no sensory differences were perceived between treatments by a trained sensory panel, based on quantitative descriptive profiling, except for the “green flesh” attribute. Nevertheless, ‘Rosy Glow’ fruit from the shade-based thinning had a higher mean fresh weight (FW; 215 g vs. 198 g) and higher titratable acidity (5.3 vs. 4.5 malic acid eq. 100 g^-1 juice). Some significant differences were reported by the trained sensory panel for four out of the ten attributes rated among the ‘Fuji’ apples produced under the neutral black net (control), and the red, white, yellow, and blue photo-selective hail nets. Differences were greatest between fruit from the red and yellow hail nets. Apples from the red hail net had higher scores for yellow colour perception (average intensity 42.3 vs. 28.5, based on a linear scale anchored at 0 as the minimum and 100 as the maximum), sweet taste (score 54.9 vs. 42.4), and hardness (i.e., sensory definition for firmness; score 52.0 vs. 43.0), and a lower score for green colour (4.6 vs. 10.0). In terms of objective instrumental measurements, fruit from the red net treatment had a higher mean FW (217 g), with larger cells and larger intercellular spaces measured in terms of the number of cells mm^-3 and the percentage of intercellular spaces, and a higher mean dry matter (DM) content [14.7% (w/w)], when compared to fruit from the other photo-selective net treatments. The spectrum of transmitted light influenced fruit growth by affecting cell proliferation and ripening, which changed the sensory perceptions of fruit appearance, taste, and texture. This study demonstrated that it is possible to use sensory panel analysis to measure the impact of new pre-harvest treatments on the quality of harvested apple fruit.