Optimizing olive harvest time under hot climatic conditions of Jordan Valley, Israel

Abstract

Global climate change leads to the exposure of olive orchards to higher temperatures than in the past. We followed yield and quality parameters of olive oils from Barnea, Coratina, and Picual, under hot climatic conditions through different levels of ripeness. Oil yield per tree increased throughout the monitoring period due to continuous oil accumulation. Toward the last harvest date, significant fruit drop occurred, which resulted in substantial loss in oil yield. Maximal oil yield was obtained in Barnea at a maturity index of 2.1–2.5, in Coratina at 2.3 and in Picual at 3.2. A reduction in quality parameters was found with delay of harvest date: free fatty acid content increased and the ratio of monounsaturated to polyunsaturated fatty acid declined, but only in one season. Nevertheless, all parameters remained within the trade standard for extra virgin olive oil (EVOO). In contrast to most previous studies, no consistent reduction was observed in total polar phenol content in the oils. Hence, maximizing oil yield should be the main criterion for the determination of harvest date under these conditions. It is therefore suggested that olives exposed to hot climate be harvested earlier than those in typical Mediterranean climate areas. Practical applications: Harvest timing has a strong effect on both oil yield and quality. However, in most of the studies published on the topic until now only a sample of fruit was taken to determine oil accumulation and quality, but little or no information is available on oil yield at tree level, which is an important parameter from the grower's perspective. Moreover, this study describes changes in oil yield and quality along the ripening period, under hot climatic conditions prevailing in Jordan Valley. The Mediterranean basin region, where more than 90% of the world's olive oil is produced is expected to be exposed to higher temperatures in the future due to global climate changes. The current work provides information on the effect of those unfavorable growing conditions on oil production and quality. One of the major findings is the necessity to harvest early (in a relatively low ripening index) under those conditions.

Performance and oil quality of ‘Arbequina’ and four Italian olive cultivars under super high density hedgerow planting system cultivated in central Italy

“…2), while for 'Maurino', that is known as a late -ripening cultivar (Farinelli et al, 2002), the lower value of pigmentation index measured in 2012 could be due to the more rainfall recorded in that October. These two factors could cause a delay in ripening time such as increased pigmentation, for 'Arbequina' and 'Maurino', and had a little effect on the other studied cultivars (Dag et al, 2014). The harvester efficiency of the over the row modified grape harvester resulted to be very good, as reported by Molfese et al (2009) for a same age high-density olive orchard, without significant differences among the cultivars (over 95%).…”

Olive paste oil content on a dry weight basis (OPDW): an indicator for optimal harvesting time in modern olive orchards

“…Specific environmental conditions might also affect FRI and OPDW in different manners. Under the extremely warm and dry summer/autumn conditions typical of the Rift Valley (EinHanatziv), oil accumulated very slowly, remaining far below the 0.5 g/g DW threshold, whereas FRI gradually increased beyond 5 ('Barnea') and 4 ('Picual') (Dag et al, 2013). In addition, FRI is strongly cultivar-dependent.…”

“…The proposed method is based on fruit sampling in the olive orchard and analysis in the laboratory. An accurate initial fruit sampling is crucial since oil accumulation in the fruit is strongly linked to the fruit load (Dag et al, 2013), which in turn is not uniform for all trees in a given plot. Hence, the collected fruit has to adequately represent the plot, e.g., if most of the trees in a given orchard/plot are carrying high yields, these will be the trees that are sampled, and vice-versa.…”

“…The first and most important parameter of oil quality is the oil's FFA content (oil acidity) but other parameters such as Peroxide value, K 232 , K 270 are included in the quality standards. In most cases, oil acidity increases with oil accumulation and fruit ripening (Dag et al, 2013). It is suggested that once OPDW reaches a value above 0.4 g/g DW (80% of the oil-accumulation potential), a cold extraction of the paste is performed to obtain the amount of oil required for a determination of FFA content and other desired quality parameters, including sensory properties.…”

“…Harvesting time has a significant impact on oil yield and quality (Salvador et al, 2001;Beltrán et al, 2004;Cherubini et al, 2009;Dag et al, 2011;Migliorini et al, 2011;Dag et al, 2013), the two major revenue determinants, particularly in the highly productive intensively cultivated olive orchards. The foremost goal of the olive grower is to optimize these two components by exploiting the complete potential for oil production at the desired level of oil quality.…”