The effect of harvest time and varieties on total phenolics, antioxidant activity and phenolic compounds of olive fruit and leaves.

The effect of harvest periods on total phenol, antioxidant activity, individual phenolic compounds of fruit and leaves of Tavsan Yüregi, Memecik, Edremit, Ayvalik and Gemlik olive varieties grown in Turkey were investigated. The highest total phenol (317.70 mg/100 g and 2657.81 mg/100 g) were observed in Tavsan Yüregi olive fruit and Ayvalik leaves harvested in December, respectively. The highest antioxidant activities (83.84%) were determined in Edremit fruit harvested in August and 83.33% in either Edremit olive leaves harvested in November and Tavsan Yüregi leaves harvested in December. The olive fruit contained gallic acid ranging from 7.18 mg/100 g (August) to 35.85 mg/100 g (December) in case of Ayvalik and 2.09 mg/100 g (November) to 21.62 mg/100 g (December) in Edremit. Gemlik olives showed higher gallic acid contents compared to the other varieties, however it depended significantly on harvest time in all cases. 3,4-Dihydroxybenzoic acid contents ranged from 33.11 mg/100 g (October) to 25.17 mg/100 g (September) in Memecik olives; 12.17 mg/100 g (August) to 33.11 mg/100 g (December) in case of Tavsan Yüregi olives depending on harvest time. The 3,4-dihydroxybenzoic acid contents of Memecik leaves ranged between 122.25 mg/100 g (September) to 196.58 mg/100 g (August) and that of Tavsan Yüregi leaves changed between 99.38 mg/100 g (November) and 179.90 mg/100 g (August). The leaves of these two varieties contained significantly (p < 0.01) higher 3,4-dihydroxybenzoic acid contents than other varieties. The highest gallic acid (144.83 mg/100 g) was detected in Memecik leaves (September) whereas lowest were found in Gemlik leaves collected in October.

The effects of conventional heating on phenolic compounds and antioxidant activities of olive leaves.

Phenolic compounds, antioxidant activities and total phenolic contents of leaves from different olive varieties (Gemlik, Kalamata, Yaglik and Sariulak) were evaluated after conventional drying at different temperatures (50, 60, 70 and 80 °C). The drying process resulted in non-significant effects on olive leaves. The phenolic contents however, varied with drying temperature. The contents of minor total phenolics in Gemlik, Kalamata and Sariulak leaves were 1457.6, 1899.3 and 2179.8 mg GAE/100 g, respectively when dried at 60 °C. The highest total phenolic reduction (23.2%) was observed in Kalamata leaves after drying at 80 °C. The major phenolic compounds in olive leaves were gallic acid (101.2-439.7 mg/100 g), 3,4-dihydroxybenzoic acid (66.7-460.4 mg/100 g), (+)-catechin (39.2-667.8 mg/100 g), 1,2-dihydroxybenzene (15.8-584.8 mg/100 g) and quercetin (33.1-277.7 mg/100 g). It was observed that olive leaves from different varieties are rich in phenolic compounds which are sensitive to heat and varied with drying temperature.

Effect of the Harvest Time on Oil Yield, Fatty Acid, Tocopherol and Sterol Contents of Developing Almond and Walnut Kernels.

Oil content and bioactive properties of almond and walnut kernels were investigated in developing almond and walnut kernels at 10 days intervals. The oil contents of almond and walnuts after the first harvest (1.H) stage changed between 46.2% and 55.0% to 39.1% and 70.5%, respectively (p<0.05). Oleic acid contents of almond and walnut oils ranged from 71.98% (1.H) to 78.68% (5.H) and 10.51% (1.H) to 16.78% (2.H) depending on harvest (H) times, respectively (p<0.05). In addition, linolenic acid contents of walnut and almond oils were found between 62.35% and 67.78%, and 12.02% and 17.65%, respectively. The almond kernel oil after the first harvest stage contained 1.045, 1.058, 1.018, 0.995 and 0.819 mg/kg ɑ-tocopherol, respectively. γ-Tocopherol contents of walnut oil changed between 1.364 (3.H) and 2.954 mg/kg (1.H). The ß-sitosterol contents of both almond and walnut oils were found between 1956.6 (5.H) and 2557.7 (1.H), and 1192.1 (3.H) and 4426.4 mg/kg (1.H). The study exhibited the presence of high percentage of oleic and linoleic for almond and walnut, respectively, and γ-tocopherol and ß-sitosterol.