This guide refers to the fruits of the cultivated olive tree (Olea europaea L.) intended for the production of virgin olive oil. Its purpose is to determine the characteristics of oil- olives, olive pomace and olive oil mill wastewater, to calculate the approximate processing yield and to define the parameters for identifying the most suitable harvest time for the purposes of this calculation.
2.1. Introduction
Stone hardening is the first stage in the biological formation of the oil in olive fruits. From that point onwards, the oil forms and increases in volume as the fruit undergoes vegetative development until it peaks at a maximum level characteristic of each variety. The genuine sensory characteristics of the oil become apparent before the start of the ripening process. Regular samplings before the traditional ripening period provide useful information for obtaining the largest possible quantity of premium oil. Such sampling is designed to calculate the best time to start harvesting on an analytical basis and to learn about fruit development, oil content, extraction capacity, sensory properties and a number of analytical characteristics.
2.2. Definition
The ripening process can be observed visually in olive varieties as they gradually change colour. The skin usually turns from deep green to violet and black. The colour and texture of the flesh also change during these stages as do the colour and sensory characteristics of the oil.
Physico-chemical influence of ripening on the olive and olive oil
The following formula was developed at the Venta del Llano Experimental Station, IFAPA, Mengíbar (Jaén, Spain) to quantify the stages of ripening in olive. As can be seen from Figure 2, it is based on a scoring system for each stage of colouring of the skin and flesh.
CATEGORY 0 : SKIN COLOUR DEEP GREEN
CATEGORY 1 : SKIN COLOUR YELLOW-GREEN
CATEGORY 2 : SKIN COLOUR GREEN WITH REDDISH SPOTS ON < HALF THE FRUIT SURFACE. START OF COLOUR CHANGE
CATEGORY 3 : SKIN COLOUR WITH > HALF THE FRUIT SURFACE TURNING REDDISH OR PURPLE. END OF COLOUR CHANGE
CATEGORY 4 : SKIN COLOUR BLACK WITH WHITE FLESH
CATEGORY 5 : SKIN COLOUR BLACK WITH < HALF THE FLESH TURNING PURPLE
CATEGORY 6 : SKIN COLOUR BLACK WITH NOT ALL THE FLESH PURPLE TO THE STONE SKIN COLOUR BLACK WITH ALL THE FLESH PURPLE TO THE STONE
CATEGORY 7 : SKIN COLOUR BLACK WITH ALL THE FLESH PURPLE TO THE STONE More