A freshness index for bell pepper fruit


Freshness provides the appeal for the consumer to purchase a particular horticultural produce. Freshness is a combination of size, colour, shape, flesh firmness, turgescence and glossiness without wilting, which imply that the produce has been harvested only a short time ago and has not suffered any decay during harvest, transport or storage. The objective of the present work was to develop a freshness index based on non-invasive, real-time measurements, using changes in surface appearance after harvest on bell pepper as the most difficult model fruit. Fruit glossiness was measured non-destructively using a luster sensor (type CZ-H72 from Keyence Co., Osaka, Japan). Luster values in excess of 463 (until 565) a.u. were classified as fresh. This 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. 5fold, range of parameterization. The difference between the light reflectance peaks at 630 nm and at 500 nm, also measured perpendicular to the convex fruit side, decreased from 40% with fresh red and yellow bell pepper to ca. 20% after 14 days storage, and from ca. 16 to ca. 8% in green pepper fruit, in both cases by ca. 2-fold. A freshness index 10 is suggested as a combination of luster values larger than 470 a.u. and 40% difference of the light reflectance between 630 and 500 nm as fresh bell pepper fruit.