Segregation of soft olives using Durofel and on-line rebound

Abstract

Traditional table olive fermentation processing produces variable proportions of defective olives that must be eliminated before final packaging. Defects include fish eye («alambradas»), compact («compactas») and over-ripe olives. For two testing periods during the 2001 season, different batches were graded by size, colour parameters, hardness, density and rebound distance (total number tested was 760 olives). The latter was determined using a specially designed prototype made by an on-line rotating drum covered with a commercial rubber material to avoid damage (13.3 cm total diameter and 6.81 rad s-1 rotation speed). Results showed that 96% of measured variance could be explained by the four Principal Components Analysis of extracted factors. Moreover, hardness measured as Durofel- 25 units is closely related to rebound distance. Softness thresholds have been addressed for both hardness parameters with devoted logistic models, permitting correct segregation (with 95% of well-classified individuals) of all soft olives (over-ripe and fish eye) using the rebound drum.