EFFECT OF HARVESTING DATE ON “NABALI BALADI” OLIVE OIL FATTY ACID PROFILE | تأثير موعد الحصاد على الأحماض الدهنية في زيت الزيتون النبالي البلدي

Background: Olive is the main agricultural crop in the Palestinian territories, mainly cultivated for olive oil production. Nabali Baladi olive variety is the most predominant olive tree in Palestine. Several factors can influence the quality of olive oil, including harvesting date and location, which can influence the chemical and physical qualities and composition of olive oil. Amis: This research aims to study the relationship of harvesting date and location on the chemical composition and physical characteristics of olive oil. Materials and methods: Fruit samples were harvested from Jenin, Tubas and Tulkarm, governorates in northern West Bank. Fruit samples were collected monthly from September to January. Each sample was tested for fruit physical properties including; maturity index, fruit retention force, moisture content, average weight, length and width, average weight (flesh, kernel, ratio) and total fat (ether extract). Oil was extracted by mechanical method and tested for acidity, peroxide, oil fatty acids composition, UV Light Coefficient K, pigments and polyphenols. Results: Throughout the harvesting dates, the maturity index, average weight, length and width, average weight (flesh, kernel, and ratio) and total fat and oil acidity were significantly increased in three locations, and decreased fruit retention force. Peroxide values were increased during harvesting dates, but started to decrease in the last collection date (January) in all locations. K232, K272, ΔK were within the limits of the Standard International Oil Council for extra virgin oil in three locations. Both chlorophyll and carotenoid in Jenin were increased from (15.5, 5.3) mg/kg to (25.6,9.3) mg/kg respectively, but in Tubas were decreased from (17.3, 6.1) mg/kg to (6.5, 2.8) mg/kg respectively, and Tulkarm were decreased from (22.7,7.0) mg/kg to (9.8,3.9) mg/kg respectively. The highest total polyphenols were observed in Jenin and Tulkarm from November collected samples (524.4 mg/kg, 111.9mg/kg) respectively, however, in Tubas, the highest value was measured during October (304.8 mg/kg). Conclusion: There is a relationship between the maturity color index, total fat and weight fruits. But negative relationship to fruit retention force and total fat, in three locations studied.