Percentage of anthracnose (Colletotrichum acutatum s.s.) acceptable in olives for the production of extra virgin olive oil

Anthracnose olive rot (AOR) is the main fruit disease of olives, causing direct yield losses and declining oil quality. Fruit infection occurs either in spring during flowering and fruit-set or in summer from the beginning of veraison to harvest. Conducive weather conditions (rain, elevated air relative humidity, air temperature above 20 °C) and the lack of effective chemical control strategies may compromise olive oil production. To quantify AOR effect on olive oil quality and to establish threshold levels, olive oil was extracted from olives with increasing disease incidence (from 0 to 30%), along three consecutive seasons (2012-2014) in two cultivars (cv. Arbeqina and cv. Frantoio) and disease severity index was also determined. The batches were prepared with healthy olives mixed with artificially infested ones, after inoculation with a conidial suspension of Colletotrichum acutatum (1 × 106 conidia ml−1) and incubated for 5-7 days at 24 °C. Oil content, water content, and maturity index were determined prior to oil extraction. Then, the obtained cold-pressed oil from each mixture was analyzed for free acidity, peroxide value, absorbance in UV, and total phenolic compounds content. All quality attributes assessed except free acidity qualified for extra virgin olive oil (EVOO) according to International Olive Council Standards. Despite seasonal effects, oil free acidity <0.8% was obtained when disease incidence was 13% for cv. Arbequina and 50% for cv. Frantoio with AOR severity below 1.5 and 2 respectively. However, these values could be lower if organoleptic attributes are considered. The obtained AOR threshold levels are helpful for orchard and harvest decision management in order to obtain EVOO.