A preliminary study on the effect of olive fruit fly damage on quality of olive oil
عنوان دوره: دومین کنگره بین المللی حشره شناسی ایران
نویسندگان
چکیده
The olive fruit fly (Bactrocera oleae) is one of the most important pests of the olive fruits. Studies in other olive producing countries show that vulnerability of quality of olive oil extracted from different varieties vary in different levels of infestation. The present study was conducted to evaluate the effect of different levels of the olive fruit fly infestation in the quality of olive oil extracted from some commercial varieties (including, Roghani, Zard, Arbequina, Mari and Kroniki) of olive in Iran (Roudbar-Gilan) in November 2016 based on RCBDc. Sampling time was based on commonly used Harvesting index 4 to 4.50. After harvesting fruits of each variety were classified in two groups of healthy and infested groups. To include various infestation levels, treatments with 0, 10, 20, 40, and 80% were prepared manually. Then 200 grams of each treatment was used to analyze and determine the quality parameters of olive oil including peroxide value, acidity, and total phenol. All of the analyses were carried out in Analytical Chemistry Laboratory of Science Faculty of Kharazmi University (Tehran). Based on the results in the most contaminated sample (80%), peroxide value were 12.21, 10.96, 9.95, 11.20 and 10.96 in Arbequina, Roghani, Zard, Mari and Kroniki respectively which are not exceeded from the maximum allowable level specified in the Iranian national standard for extra virgin olive oil (≤20). The acidity percentage of the samples with 20% of infestation in the varieties of Arbequina, Roghani, Zard, Mari and Kroniki were 1.78, 1.69, 1.76, 1.66 and 1.96 respectively. According to the Iranian national standard, olive oil with acidity percentage less than 2 grams per 100 grams of oil is divided as virgin olive oil grade. So, in terms of this parameter, up to 20% infestation by fruit fly could be tolerated. Also, reduction of the amount of total phenol in the samples with 20% infestation, comparing to non infested subjects in varieties of Arbequina, Roghani, Zard, Mari and Kroniki were 11.9, 22.5, 9.8, 6.4 and 14.1 percent respectively. Phenolic compounds in olive oil give antioxidant properties to olive oil. It could be concluded that among tested varieties, in Zard and Mari varieties up to 20 % of infestation is tolerable.
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