S17 - Session O2 - A Freshness index for Bell pepper fruit.

Authors: Bernhard Althaus, Michael Blanke *

(1) Background: Freshness provides the appeal for the consumer to purchase a particular horticultural produce. It is a combination of size, colour, shape, flesh firmness, turgescence and glossiness without wilting, which imply that the produce has been picked recently and without any decay during harvest, transport or storage. (2) Objective: The objective of the present work was to develop potential freshness indices. The indices are based on non-invasive, real-time measurements, using changes in surface appearance after harvest, using Bell pepper as the most difficult model. (3) Methods: The selection criteria were a dramatic change in values, and either a consistent decrease or increase without peaks and troughs. Two (out of five) non-invasive techniques were selected, i.e., surface glossiness, and light reflection spectra, whereas fruit firmness (penetrometer), colourimeter and false colour images (profilometer) were excluded. (4) Results: Glossiness measurements provided luster values in excess of 463n490 a.i. for green Bell pepper fruit to be classified as fresh, and similarly of 525n565 a.i. for yellow and 486n502 a.i. for red pepper fruit. This first Freshness index dropped, indicating a lesser freshness, to less than 100 a.i. after 14 days storage, irrespective of fruit colour, thereby providing a suitable wide, ca. 5-fold, range of parameterization. The second index is based on the difference between the light reflectance peaks at 630n633 nm and at 500 nm, also measured perpendicular to the convex fruit side. These percentage values decreased from > 40% with fresh red and yellow Bell pepper to ca. 20% after 14 days storage; similarly, these percentages decreased from ca. 16% to ca. 8% in green pepper fruit, in both cases by a twofold factor.