In this study, the effects of leaf addition, maturity stage and storage on the antioxidant content and activity of olive oils (cv. Memecik) were investigated in the 2008/09 and 2009/10 crop seasons. Olive fruits were harvested at two different maturity stages (early and late), and the leaves of the same cultivar were added at different rates (0, 1, and 3 %) prior to oil extraction. After extraction, the oil samples were stored for 18 months and total chlorophyll, α‐tocopherol, total phenolic content and the antioxidant activity [DPPH· (2,2‐diphenyl‐1‐picrylhydrazyl) and ABTS·+ (2,2‐azino‐bis(3‐ethylbenzothiazoline)‐6‐sulfonic acid) radical scavenging] were determined at 6 month‐intervals. Olive leaf addition induced a significant increase in total chlorophyll, α‐tocopherol, total phenolic content, and antioxidant activities in both years (P < 0.001). During the storage period antioxidant content and antioxidant activities in the oils significantly decreased in both years (P < 0.001). However, the oils to which leaf material was added had higher antioxidant contents and activities than those without leaf material addition at the end of the 18‐month storage period. After storage, the antioxidant content and DPPH· radical scavenging activity of control (0 %) samples were lower than those in the leaf added samples (3 %). The data obtained from this study suggested that the addition of olive leaf to oils allowed more functional olive oils with higher antioxidant contents.

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SUMMARY:Harvested olives require further processing to make them edible due to their content in the bitter substance oleuropein. However, some olives of the Erkence cultivar naturally de-bitter on the tree giving rise to the so-called Hurma olives. In this study, the evolution of the chemical characteristics of Erkence and Hurma olives harvested from the northeast and southwest area of trees located in the Karaburun Peninsula was assayed. It was confirmed that the oleuropein content in Hurma olives was much lower (< 2000 mg/kg fresh weight) than Erkence, which reached 35.000 mg/kg fresh weight at the beginning of the season. In addition, no free or polymerized anthocyanins were found in Hurma fruit in contrast to ripened Erkence fruit. The concentration of glucose was also lower in Hurma than Erkence olives. These results suggest that the enzymatic oxidation of oleuropein could be responsible for the natural de-bittering of Hurma olives during their ripening on the tree. KEYWORDS:Anthocyanin; Bitterness; Olive; Phenolic compounds; Sugar RESUMEN: Una explicación para el desamargado natural de aceitunas Hurma durante su maduración en el árbol. Las aceitunas recién cogidas del árbol necesitan ser procesadas para hacerlas comestibles, debido a su contenido en el compuesto amargo oleuropeína. Sin embargo, algunas aceitunas de la variedad Erkence desamargan de forma natural en el árbol dando lugar a las aceitunas conocidas como Hurma. En este trabajo se han analizado las características químicas de aceitunas Erkence y Hurma recolectadas de la zona noreste y suroeste de árboles situados en la provincia de Karaburun. Se ha confirmado que el contenido en oleuropeína de aceitunas Hurma es muy inferior (< 2000 mg/kg) que Erkence, las cuales alcanzaron una concentración en dicha sustancia hasta de 35.000 mg/kg al principio del periodo de maduración. Además, no se encontraron en aceitunas Hurma antocianinas ni libres ni polimerizadas, a diferencia de Erkence. Estos resultados indican que la oxidación enzimática de la oleuropeína podría ser la responsable de la eliminación del amargor de forma natural en aceitunas Hurma durante su maduración en el árbol.

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Organic farming seems to be a solution in environmentally sensitive zones such as the protection zone of Tahtalı Dam, which supplies fresh water to Izmir, the third largest city in Turkey. Greenhouse vegetable production is the major agricultural activity in this area (Menderes Township). However, due to the pollution risk from agriculture, governmental authorities have issued a regulation discouraging the use of chemicals within the collection basin of the dam. An on-farm project was conducted in 2001 to introduce organic greenhouse vegetable production in the Tahtalı Dam preservation area and to serve as a model for other areas in Turkey facing similar ecological problems. Two irrigation levels and four organic fertilizers were tested on the growth of cucumbers (Cucumis sativus cv. Sardes). The four fertilizers were two rates of farmyard and poultry manure (30 and 50 tons ha−1) with and without two organic fertilizers based on either bacteria or algae. During the growing period, pests and diseases were monitored weekly and preparations allowed in organic agriculture were used when necessary. Plant diseases did not create any significant problem, but the pest population, in particular spidermites, increased. No significant differences in cucumber yield were found between the fertilizer and irrigation treatments tested. However, it should be noted that yields from the addition of 30 tons ha−1 of farmyard or poultry manure and organic fertilizers were the same as those for 50 tons ha−1 of manure alone. The average total yield was 13 kg m−2, within an acceptable range for short-term crop production in this region, but 55% lower than a conventional substrate culture trial nearby. However, due to reduced production costs and a price premium for organic products, the organic produce yielded a net return of US$1.12–1.79 per m2 whereas that for conventional bag culture produce was US$0.55 per m2. Our results indicate that, under present conditions, organic greenhouse cucumber production has less environmental impact and is more economic than conventional bag culture, due to reduced chemical input and reduced operating and initial investment costs.