et al., 2010; Kalua et al., 2008; Effect of Mechanically Harvested Olive Storage Kiritsakis et al., 1998; Yousfi et al., Temperature and Duration on Oil Quality 2009). Moreover, there is generally no indication of whether the fruit originated from rain-fed or irrigated Arnon Dag1, Smadar Boim, Yulya Sobotin, and Isaac Zipori orchards (Agar et al., 1998; Clodoveo et al., 2007; Dourtoglou et al., 2006; Garcı´a et al., 1996; Inarejos-Garcı´a ADDITIONAL INDEX WORDS. virgin olive oil, temperature, irrigation, mechanized harvest, polyphenols, free fatty acids, peroxide value et al., 2010; Kalua et al., 2008; Kiritsakis et al., 1998; Yousfi et al., SUMMARY. Most newly planted olive (Olea europaea L.) orchards are irrigated and 2009; Youssef et al., 2011), although harvested mechanically. We assessed the effects of olive storage temperature and we may speculate that those which are duration on the resultant oil’s quality in three cultivars from modern orchards. Oil not indicated originated from rain-fed acidity increased with storage temperature and time, most markedly in ‘Barnea’ and orchards. There are almost no such least in ‘Koroneiki’. In ‘Koroneiki’, after 9 days in cool storage (4 and 10 C), free fatty acid (FFA) level remained constant. Polyphenol (PP) content behaved studies of fruit originating from mod- differently among cultivars: in ‘Picual’, it was relatively invariable; in ‘Barnea’, it ern, irrigated, and mechanically har- decreased moderately; and in ‘Koroneiki’, it decreased sharply to half of its initial vested orchards, although these are value in 4 C storage and one-sixth its initial value in room temperature storage after becoming more and more common 23 days. Peroxide value (PV) did not increase during the storage period and did not in olive oil producing countries. appear to be affected by temperature. Thus, different cultivars show different Olives from irrigated trees dem- responses to storage, and fruit originated from modern orchards are not necessarily onstrate an apparent sensitivity to me- more sensitive to storage than those from traditional orchards. chanical wounding, which subsequently leads to increased free acidity and per- live has been grown tradi- develop all kinds of degenerative pro- oxide level, and decreased total phenol tionally for centuries in coun- cesses in a short period of time. The content in the oil (Ben-Gal et al., 2011; Otries of the Mediterranean resultant oils tend to show hydrolytic Dag et al., 2008; Patumi et al., 2002). basin. However, the increase in olive and oxidative deterioration, evident Therefore, their storage capacity might oil consumption related to the per- bytheirhighFFAandPVcontent be limited in comparison with fruit ception of its health-related benefits (Garcı´a and Yousfi, 2006). Therefore, originated from traditional rain-fed, (Waterman and Lockwood, 2007) has many studies have explored the proper manually picked orchards. Olive stor- led, in the last two decades, to the way to store olives before processing age is important to balance the rates intensification and expansion of olive to maintain good oil quality. Olive oil of harvest with those of oil extraction cultivation, inside and outside of Med- extraction is often not well synchro- in the mill. The objective of the cur- iterranean countries. According to the nized with crop harvests because of rent work was to evaluate the effect of Food and Agriculture Organization of limited labor and machinery available storage temperatures and duration on the United Nations (FAO), at present for harvest, and the number and size extracted oil quality from commercial, there are 9.4 million hectares of olive of oil extraction facilities (Agar et al., mechanically harvested orchards. orchards in the world, most of which 1998). Therefore, short-term storage are still located in the Mediterranean of olive fruit before oil extraction can Materials and methods basin (FAO, 2012). Traditionally, ol- provide a buffer which will enable more SAMPLES. Olive fruit were obtained ives are not irrigated, but recently efficient use of both harvest facilities from irrigated commercial olive or- water application has been recognized and the mill. chards in Israel: the Israeli cultivar as constructive to 1) increase yields of Several papers have been published Barnea and the Spanish cultivar Picual olives in regions with traditional rain- on the effects of storage length and were obtained from Revivim olive farm fed olive production (Moriana et al., conditions on the resultant oil’s quality. (lat. 31.0500 N, long. 34.4103 E), 2003), 2) allow cultivation in high- However, they generally examine man- and the Greek cultivar Koroneiki was density olive orchards, and 3) expand ually picked fruit (Agar et al., 1998; from Gshur olive farm (lat. 32.7708 N, olive production into regions where Clodoveo et al., 2007; Dourtoglou long. 35.7728 E). In Revivim, trees there is not enough rainfall to support et al., 2006; Garcı´a et al., 1996; were at 7 · 3.5-m spacing, with irriga- the crop (Connor, 2005). Today, 25% Kyriakidis and Dourou, 2002; Youssef tion of 800 mm per year, and in to 30% of the olive orchards supplying et al., 2011) or give no indication of Gshur, trees were at 4 · 2-m spacing fruit to the oil extraction industry re- the harvest method (Inarejos-Garcı´a with irrigation of 600 mm per year. ceive some level of irrigation (Lavee, 2011). It has been claimed that the great- est deterioration of olive oil quality is Units due to poor handling of the olives To convert U.S. to SI, To convert SI to U.S., between harvest and processing (Olias multiply by U.S. unit SI unit multiply by and Garcı´a, 1997). These fruit may 0.4047 acre(s) ha 2.4711 0.3048 ft m 3.2808 25.4 inch(es) mm 0.0394 Gilat Research Center, Agricultural Research Organi- 0.4536 lb kg 2.2046 zation, M.P. Negev 85280, Israel 1 ppm mgÁkg–1 1 1Corresponding author. E-mail: [email protected]. ( F – 32) O 1.8 F C(1.8· C) + 32
528 • August 2012 22(4) Fruit were collected immediately after Fullerton, CA) at 735 nm using the on the one hand, and of the mill on commercial mechanical harvest on 16 Folin-Ciocalteu reagent (Swain and the other. Here, we followed the effects Dec. 2009 and brought to the labo- Hillis, 1959). of storage length and temperature on ratory. Harvesting was performed with three major quality parameters in three a commercial linear-vibrating trunk Results and discussion different major olive oil cultivars grown shaker (model D10; Dotan Technol- To produce high-quality oil, it is in intensified orchards. ogies, Migdal HaEmek, Israel) in generally recommended that the ol- I NFLUENCE OF STORAGE Revivim and with a commercial over- ives be processed within 12 to 24 h TEMPERATURE ON FFA LEVEL. In- head mechanical harvester (model VX of harvest (Vossen, 2007). However, creased acidity after fruit storage Braud; New Holland, Coex, France) extension of this period by proper correlates well with decay incidence in Gshur. The olives were randomly storage of the fruit would allow more (Gutie´rrez et al., 1992). In general, the divided into 2-kg lots, which were efficient use of the harvest machinery first action of a parasitic microorganism placed in plastic baskets, each basket considered one replicate. Four repli- cates were used for each cultivar–storage duration–temperature combination. Ma- turity index (Uceda and Frı´as, 1975) was recorded and was 3.6 for ‘Barnea’, 2.6 for ‘Picual’, and 2.0 for ‘Koroneiki’. STORAGE TREATMENTS. Three dif- ferent storage conditions were tested, two at 4 and 10 C in refrigerated rooms and a third under ambient con- ditions (room temperature), with tem- peratures fluctuating between 12 and 25 C, as recorded by data logging thermometer. Each storage condition was evaluated for five periods: 1, 5, 9, 16, and 23 d. O IL EXTRACTION AND CHARACTERIZATION. Cold-pressed vir- gin olive oil was obtained with an ‘‘Abencor’’ system (MC2 Ingenieria y Sistemas, Seville, Spain) as described by Ben-David et al. (2010) for olives originated from irrigated orchards. Tested oil chemical quality parame- ters were: FFA content, PV, and total PP content. Determinations of FFA content and PV were carried out following International Organization for Standardization (ISO) analytical methods 660 and 3960, respectively. Free acidity (ISO 660), given as per- centage of oleic acid, was determined by titration of a solution of oil in ethanol–ether (1:1, v/v) with ethanolic potassium hydroxide. PV (ISO 3960), expressed in milliequivalents active oxygen (O2) per kilogram oil, was de- termined as follows: a mixture of oil and isooctane–acetic acid (3:2, v/v) was left to react in the dark with a potassium iodide solution and the free iodine was then titrated with so- dium thiosulfate solution. Phenolic compounds were isolated from a solu- tion of oil in hexane by triple extrac- Fig. 1. Changes in free fatty acid (FFA) content (percent oleic acid) of oils obtained tion with methanol–water (60:40, v/v). from olives stored at different temperatures (4 C, 10 C, and room temperature) Total PP, expressed as tyrosol equiv- for different periods of time (1, 5, 9, 16, and 23 d). (A) ‘Barnea’, (B) ‘Picual’, and alents (parts per million), were de- (C) ‘Koroneiki’. Data points represent means of four replicates ± SD. An arrow line is termined with a ultraviolet–visible inserted at 0.8% to indicate the maximal accepted level for extravirgin olive oil; (1.8 · spectrophotometer (Beckman Coulter, C) + 32 = F.
• August 2012 22(4) 529 PRELIMINARY AND REGIONAL REPORTS in an oil-rich tissue is the induction of temperature, FFA content rose by only oil is well known for its high PP content hydrolytic activity by lipases, which 0.04% during that period. At the lower (Vossen, 2007). Similarly, in the cur- leads to the release of fatty acids from temperature during the 23 d of stor- rent study, its initial (day 1) PP levels the triacylglycerol molecules of the oil age, FFA of the ‘Koroneiki’ oil in- were much higher [5-fold (Fig. 2C)] (Clodoveo et al., 2007). Lower stor- creased by only 0.2%. When stored than those of ‘Barnea’ (Fig. 2A) and age temperatures delay the appearance at 10 C, FFA content remained at ‘Picual’ (Fig. 2B). This further suggests of decay incidence (Agar et al., 1998). an acceptable level (0.67%) for up to the importance of PP in enabling long The different cultivars responded dif- 16 d in storage. Kiritsakis et al. periods of storage for that cultivar. ferently to storage time: ‘Barnea’ ap- (1998) reported that oil obtained I NFLUENCE OF STORAGE peared to have the strongest response from ‘Koroneiki’ fruit stored for 30 d TEMPERATURE ON PV. PV is a measure (Fig.1A),followedby‘Picual’(Fig.1B) at 5 C is of reasonable quality. Simi- of primary oxidation. Surprisingly, and ‘Koroneiki’, which provided the larly, a slow increase in FFA levels PV was not consistently affected by most stable oil (Fig. 1C). Increased during storage of ‘Koroneiki’ olives either storage time or temperature storage temperature resulted in an originated from a traditional rain-fed (Fig. 3). In ‘Barnea’, PV (reported in accelerated increase in FFA, as has orchard was reported by Kyriakidis milliequivalents O2 per kilogram oil) been reported previously (Clodoveo and Dourou (2002). The ‘Koroneiki’ ranged between 3.0 and 5.3 (Fig. 3A); et al., 2007; Garcı´a et al., 1996; Gutie´rrez et al., 1992; Inarejos-Garcı´a et al., 2010; Kiritsakis et al., 1998). In ‘Barnea’, only the 4 C storage conditions for up to 9 d resulted in oil that satisfies the extra virgin olive oil (EVOO) standard (FFA £ 0.8%). In 10 C and room temperature storage, a rapid increase in oil acidity started immediately and after 9 d, and it was no longer acceptable as virgin oil (FFA > 2%) (Fig. 1A). A tendency toward elevated FFA levels in ‘Barnea’ from irrigated orchards has been recently reported by Ben-Gal et al. (2011). In ‘Picual’, the increase in FFA was slow under all storage conditions (includ- ing room temperature), and oil FFA content was reasonable for up to 5 d in storage, not rising above 0.65%. In 4 C storage, the oil FFA level only reached the upper limit for EVOO (0.8%) after 23 d. ‘Picual’ oil is con- sidered to have remarkably high sta- bility, which is attributed to its high total PP content (Pardo et al., 2011). However, this high PP level refers to fruit originating from rain-fed condi- tions. In the current study, the PP levels were extremely low [around 120 mgÁkg–1 oil vs. 800 mgÁkg–1 oil in Pardo et al.’s (2011) study]. We presume that the reduced PP content is a result of irrigation (Ben-Gal et al., 2011; Tovar et al., 2002). Therefore, we speculate that the better stability of ‘Picual’ oil is due to some other factor, for example, its relatively high level of oleic acid (Mailer et al., 2010), which is expected to contribute to its oxidative stability and slow increase in FFA (Frankel, 2010) despite the relatively low PP content. ‘Koroneiki’ Fig. 2. Changes in polyphenol content of oils obtained from olives stored at showed a remarkably slow increase in different temperatures (4 C, 10 C, and room temperature) for different periods FFA content. In fact, at 9 d in the of time (1, 5, 9, 16, and 23 d). (A) ‘Barnea’, (B) ‘Picual’, and (C) ‘Koroneiki’. cold (4 and 10 C), its FFA level was Data points represent means of four replicates ± SD; (1.8 · C) + 32 = F, 1 kg = still constant (Fig. 1C). Even at room 2.2046 lb.
530 • August 2012 22(4) phenol content in the olive paste (Pardo et al., 2011). Alternatively, it has been claimed that rather than being produced at low rates, phenolic compounds are partitioned during the olive oil extraction process and removed with the wastewater sepa- rated from oil in the mill; since the water content in fruit from irrigated orchards is higher, there is more waste- water washing the PP out and conse- quently reducing its content in the oil (Rodis et al., 2002). Clodoveo et al. (2007) reported decreasing PP con- tent with longer storage period, while lower temperatures and carbon diox- ide (CO2) slowed the process. Yousfi et al. (2008) indicated that reduced PP content following fruit storage is a positive characteristic that may as- sist in reducing the intensity of sen- sor-evaluated bitterness for markets accustomed to the milder taste of re- fined oil. However, Dourtoglou et al. (2006), working with green olives, reported increases in PP content in oil from fruit stored for up to 5 d, which was even more pronounced in an en- riched CO2 environment. In the cur- rent study, we did not observe any increase in PP content. However, we found different responses for the dif- ferent cultivars: in ‘Picual’, in general, there were minor changes in PP con- tent during storage, with values rang- ing between 110 and 140 mgÁkg–1 oil (Fig. 2B); in ‘Barnea’, we found a moderate reduction, from around Fig. 3. Changes in peroxide values [milliequivalents active oxygen (O2) per kilo 120to65mgÁkg–1 oil (Fig. 2A), gram oil] of oils obtained from olives stored at different temperatures (4 C, 10 C, whereas in ‘Koroneiki’ (Fig. 2C), and room temperature) for different periods of time (1, 5, 9, 16, and 23 d). (A) we observed the strongest reduction, ‘Barnea’, (B) ‘Picual’, and (C) ‘Koroneiki’. Data points represent means of four –1 replicates; (1.8 · C) + 32 = F, 1 kg = 2.2046 lb. from 600 to 100 mgÁkg oil. The high initial PP content in ‘Koroneiki’ might be a result of cultivar charac- in ‘Picual’, the values were a bit higher, microorganisms. Clodoveo et al. (2007) teristics as well as the relatively low between 3.7 and 6.7 (Fig. 3B); and found the PV of oil obtained from ripeness index of the fruit in com- in ‘Koroneiki’, they were highest, be- olives stored at 20 C for 15 d to be parison with the other cultivars. In tween 4.9 and 9.4 (Fig. 3C). How- double its baseline values; however ‘Barnea’ and ‘Koroneiki’, the higher ever, even the highest PV was far below even after 30 d, the oil did not exceed the storage temperature, the stron- the upper limit for EVOO (£20). the maximum PV for EVOO. Other ger the reduction in PP content; that Garcı´a et al. (1996) reported constant studies did not find a consistent in- is, ambient temperature resulted in the PV for the first week of ‘Picual’ stor- crease in PV with increasing storage lowest final PP content while the cold age, followed by a sharp increase (from time (Kiritsakis et al., 1998; Yousfi storage conditions (4 C) resulted in 4 to 14 at ambient temperature after et al., 2008), in line with our findings. the highest levels. However, in ‘Picual’, 30 d), which might be a result of the I NFLUENCE OF STORAGE the trend was reversed: the ‘‘room larger containers they used compared TEMPERATURE ON PP CONTENT. As temperature’’ treatment resulted in with the current study, as this can affect already noted, olive oil originated from higher PP levels than the 4 C treat- the degradation process (Inarejos- irrigated orchards generally has rela- ment, 144 vs. 111 mgÁkg–1 oil, respec- Garcı´a et al., 2010). In large contain- tively low PP content compared with tively, for the longest storage period ers, the weight of the olives damages that from rain-fed orchards (Dag et al., of 23 d. These different trends in total the tissue of the drupe, resulting in 2008). This is probably because the PP content between cultivars might the secretion of fluids from the fruit trees’ water status affects phenol pro- reflect different PP profiles: while phe- which favors the growth of undesirable duction in olive fruit and consequently, nolic compounds such as oleuropein
• August 2012 22(4) 531 PRELIMINARY AND REGIONAL REPORTS and ligstroside derivatives progres- 2008). This is particularly relevant for fruit ripening and olive oil quality. J. Agr. sively decrease during storage, other, irrigated orchards, where the high water Food Chem. 44:264–267. simple phenolic compounds such as content of the fruit reduces the extrac- Garcı´a, J.M. and K. Yousfi. 2006. The hydroxytyrosol and tyrosol are formed tion efficiency (Grattan et al., 2006). post harvest of mill olives. Grasas y Aceites from the hydrolysis of high-molecular- Fruitstoragemightalsohaveabeneficial 57:16–24. weight molecules (Kalua et al., 2008). effect in reducing oil bitterness (Yousfi et al., 2008) for markets accustomed to Grattan,S.R.,M.J.Berenguer,J.H.Connell, Conclusion milder-flavored oils. V.S. Polito, and P.M. Vossen. 2006. Olive oil production as influenced by different In general, it is better to extract quantities of applied water. Agr. Water oil from fruit shortly after harvest; Mgt. 85:133–140. however, when needed, fruit can be Literature cited stored before oil extraction. From the Gutie´rrez, F., S. Perdiguero, J.M. Garcı´a, results of the present study, we can Agar, I.T., B. Hess-Pierce, M.M. Sourour, and J.M. Castellano. 1992. Quality of oils conclude that despite the possible rel- and A.A. Kadar. 1998. Quality of fruit and from olives stored under controlled atmo- oil of black-ripe olives is influenced by sphere. J. Amer. Oil Chem. Soc. 69:1215– ative sensitivity of fruit from irrigated cultivar and storage period. J. Agr. Food 1218. orchards to deterioration and to po- Chem. 46:3415–3421. tential damage during mechanical Inarejos-Garcı´a, A.M., A. Go´mez-Rico, harvesting, they can be stored before Ben-David, E., Z. Kerem, I. Zipori, S. M.D. Salvador, and G. Fregapane. 2010. oil extraction without much reduc- Weissbein, L. Basheer, A. Bustan, and A. 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