Investigation of the effect of storage conditions on the quality and quantity of canola seed oil

The high demand of vegetable oil and the dependence of country on this product are clear. The deficit in processing companies and infrastructures, high volume of product during harvest time as well as limited information caused us to perform an experiment to study the effect of storage time and storage conditions on the quality and quantity of canola seed oil. A factorial experiment based on a completely randomized design containing two factors: storage time (zero, 1, 2, 3 and 4 month) and storage temperature (4, 21, 35 C°), with 4 replications was performed. Results showed that regardless of storage conditions, seed oil decreased by increasing storage duration. At the end of storage time oil reduction was 1.1% of the control (46.1%). Temperature had no significant effect on seed oil content (45.8% and 45.6% at 4 and 35 0C, respectively). Investigation of the changes of esterified fatty acids and the content of free fatty acids showed that their concentration was strongly related to the storage conditions. Free fatty acid content and the amount of peroxide value which are two important quality indices of oil, increased by increase in temperature. Free fatty acid content increased from 2.1% at the beginning of experiment to 5.1% at the end of experiment. The results showed the inverse relationship of oil quality and quantity reduction with storage time; the rate of reduction increased with an increase in temperature. Thus the shortening of the time from seed harvesting to oil extracting and processing, besides the controlling of the qualitative and quantitative properties might increase the stability of product during marketing and consumption. Based on the physiological properties of canola seed, the time from harvest to oil extraction is very important and it is advised to reduce this time as short as possible. Although no significant effect of temperature was observed on seed oil percentage, high temperature can increase the amount of free fatty acid and peroxide which are directly related to oil quality. Thus to keep oil quality and to increase oil extraction efficiency, it is recommended to store seed lots under low temperatures and shorten the waiting time from harvest to processing (maximum two months).