Distribution and timing of cell damage associated with olive fruit bruising and its use in analyzing susceptibility

Bruising, damage caused by impact on the fruit during harvesting, is a major limiting factor in the production of table olives and currently restricts the applicability of mechanical harvesting. Bruising is characterized by darkening of the olive fruit surface and softening of the mesocarp or pulp. It decreases final product quality and may cause consumer rejection. This paper describes and quantifies anatomical changes in the olive mesocarp (pulp) related to bruising in fresh olive fruits after an induced impact. The study assessed two harvested table olive cultivars differing in bruise susceptibility (‘Manzanilla de Sevilla’ and ‘Hojiblanca’) at two different times (4 and 24 h after induced impact). Qualitative observations of tissue bruising prior and after histological analysis revealed changes in the damaged mesocarp including ruptured cells, loss of cell wall thickness, and discoloration in the damaged areas. These changes appeared greater in ‘Manzanilla de Sevilla’ than ‘Hojiblanca’, and more evident 24 h after the impact. Bruising damage was quantified using eleven parameters related to the area of the damaged zone, and incidence and position of tissue ruptures. Nine of these parameters changed significantly with time, and significant differences were observed between the two cultivars studied in seven of the parameters. Three of these, the total damaged area (TDA) measured in mesocarp portions prior to histological procedure, the number of tissue ruptures in the mesocarp intersected by circumferential arc2 (located at one-fourth of the pulp thickness from the fruit exterior; Brk-arc2), and the distance from the fruit exterior) to the first found tissue rupture (D-min)), measured in histological preparations, were the most discriminating and easy to assess parameters, and are thus recommended for the evaluation of susceptibility to bruising among harvested table olive cultivars.The authors acknowledge the financial support from the Ministerio de Ciencia, Tecnología e Innovación (Spain) and ERDF (co-financed grants AGL2007-65184-C02-02/AGR and AGL2009-07248).Peer reviewe