Abstract
The aim of this paper is to determine how different harvesting methods of olives and the waiting period before the extraction of the extra virgin olive oil affect the viscosity and some thermal properties, namely thermal conductivity and thermal resistivity. Olive trees in the Aegean region of the western part of Turkey were harvested by using six different harvesting methods: by hand, harvesting by a beating pole on a synthetic fabric, harvesting by a beating pole on a platform, harvesting by machine on a synthetic fabric, harvesting by machine on a platform and direct collecting of dropped olives by hand. Olive oil samples were obtained in certain intervals between the harvesting and processing that was made by using a laboratory type system. The viscosity values of oil samples were measured by using a vibro-viscometer. The thermal conductivity and thermal resistivity of oil samples were measured simultaneously by using the KD2 Thermal properties analyzer. As a result, viscosity, thermal conductivity and thermal resistivity values changed related to the harvesting method and the waiting period after harvesting to obtain olive oil. While viscosity (dynamic) and thermal conductivity values increased with the increase of the waiting time, thermal resistivity values decreased. The lowest viscosity and thermal conductivity values and the highest resistivity values were found for oils that were obtained from olives harvested by hand.
Highlights
Olives are traditionally hand harvested, a process that is tedious and laborious, but represents the major proportion of the costs of production
As seen in Tab. 1 and Fig. 3, viscosity values of olive oil samples that were obtained for seven consecutive days after harvesting increased day by day for all samples that were harvested by using a different method
Viscosity, thermal conductivity and thermal resistivity values changed related to the harvesting method and the waiting period after harvesting to obtain olive oil
Summary
Olives are traditionally hand harvested, a process that is tedious and laborious, but represents the major proportion of the costs of production. Mechanical harvest of olives has been used to a limited extent in more intensive orchards As it is known, the harvesting method has an important effect on the quality of olives, especially in the production for table consumption. The effect of irrigation on the oil quality of the fruit obtained from both the mechanical and hand harvesting methods in addition to the yield parameters was researched [4]. They found that when fruit was picked carefully by hand so that no injuries were inflicted, free fatty acids levels were substantially reduced, peroxide was reduced and the total polyphenol content was increased
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