Document Type : Research Paper
Abstract
Olive oil is one of the oldest known vegetable oils, ranking sixth in world production. Since it is extracted
from fresh fruit and used without aging, the conditions of oil production are very important. During the
extraction of virgin olive oil, the milling and malaxation steps are vital for increasing oil yield and quality.
In this study, the effect of milling (single or double), temperature of malaxation (25, 35, 45, 60°C) and
duration of malaxation (15, 30, 45, 60min) on yield and quality (acidity, peroxide index, color, carbonyl
values) of virgin olive oils (cultivar Roghani) were investigated. The results showed that double milling
increased oil yield, but that the type of milling had no significant effect on oil quality. Increasing
temperature and duration of malaxation increased oil yield, however oil production increased substantially
up to 35°C and 45 min but did not show a significant difference after that point. An examination of the
qualitative characteristics of oil showed that, under the conditions tested, there was no significant
difference in quality. The oil produced was of the highest quality. It was concluded that the optimal
extraction method for the production of good quality oil with a satisfactory yield is to employ double
milling with malaxation for 45 min at 35°C.
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