Fase . 5-6 ( 1998 ) , 405-410 405 Fatty acids and sterols evolution during the ripening of olives from the Moroccan Picholine cultivar

De junio a febrero se reœgieron 13 muestras de aceitunas de olivos de la variedad Picholine Marroquí. Los aceites de las primeras muestras tuvieron altos niveles de acidez (>1%) que posteriormente disminuyeron rápidamente para luego estabilizarse entre 0.36 y 0.44%. La evolución de los ácidos grasos totales mostró unos niveles relativamente altos de 018:3 en las primeras muestras. Estas proporciones disminuyeron durante el proceso de maduración y se estabilizaron a 0.8 0.9% a comienzos de noviembre. El CI 6:0 disminuyó mientras que el 018:2 aumentó durante el proceso de maduración. Los ácidos grasos monoinsaturados predominaron en la posición Sn 2 glicerol. La suma de las proporciones de los ácidos palmítico y esteárico en esta posición llegó a ser más baja del 1.5% entre mediados de noviembre y principio de enero. La composición química de los ácidos grasos del mesocarpo es cuantitativamente y cualitativamente similar a la observada para los ácidos grasos totales de la aceituna en su totalidad. Sin embargo, los ácidos grasos totales de las semillas son cuantitativamente diferentes de los del mesocarpo. Las proporciones de estos ácidos grasos permanecieron estables desde mediados de septiembre. El p-sitosterol es el principal esterol en todas las muestras con una proporción que excedía el 84%. El A5 avenasterol alcanzó un máximo en la segunda mitad de enero al mismo tiempo que el p-sitosterol tuvo sus niveles más bajo. Los niveles de campesterol variaron entre 3 y 3.5% y los niveles de estigmasterol se estabilizaron alrededor del 1% hasta el comienzo de noviembre para luego disminuir al 0.5%.


INTRODUCTION
Oléiculture in Morocco is mainly represented by only one variety: the moroccan Picholine (Loussert, 1989).Thus, we found it in different regions of Morocco under different climate conditions.Fatty acids and sterols of olive oils from the european varieties are well studied and many studies had shown that the chemical composition of the oil changes during the ripeness of the olives.Thus, the palmitic, the stearic and the linolenic acids proportions decrease during the ripeness of olives from the Carolea and Frantoï varieties, while the oleic acid increases (Fiorino etal. 1991).Concerning the Picual, Hojiblanca and Zorzaleña varieties, a decrease of palmitic and oleic acids, and an increase of linolenic acid is observed (Duran, 1990).According to Marzouk, the rates of the linoleic and palmitoleic acids does not undergo any variations during the ripeness of the Chemlali-olives (Marzouk et al., 1981).Also, this variety shows very high rates of the stearic acid (21%) in the early stages of the fruit development, these rates decrease at ripeness and stabilize around 2%.The proportions of this later are reported to be dependent of the cultivar (Fiorino et al., 1991).Generaly, the oleic acid represents an average of 73% in the north Africa olive oils (c) Consejo Superior de Investigaciones Científicas Licencia Creative Commons 3.0 España (by-nc) http://grasasyaceites.revistas.csic.es(Feinberg et al., 1987), but very innportant variations can be encountred.In Algeria, olive oils can contain up to 80% of the oleic acid (Talantikite et al., 1988), in Lybia this rate doesn't exceed 45% (Kiritsakis et a/., 1987).
The sterolic composition can also vary during the ripeness process.Different sterolic compositions are reported for the moroccan Picholine.Thus, the A5 Avenasterol and |3 Sitosterol represent respectively 0.4 % and 93.6% (Zerrouk, 1984).Other authors have reported different proportions respectively 7.3% and 88.3% for these sterols (Castang et ai, 1976).These variations can be caused by differences in the levels of ripeness of the olives.
In this work we followed the chemical composition of olives and their oil from the early stages of fruit development until their ripeness.

Free fatty acids content evolution
Free fatty acids (FFA) content evolution shows high values ( 1%) in the first month of our sampling.This rate decreases rapidly and remains all the time bellow 1% since mid august.High acidity levels are obtained also for some other oils from seeds at early stages of development (Privett etal., 1973).
The three extracts are mixed together to form one phase and are washed with water.The organic phase which contains the lipids is recuperated after centrifugation.
In the first month, the triacylglycerols biosynthesis remain low.In this stage the biosynthesis of partial glycerides, free fatty acids and phospholipids predominates over the synthesis of triacylglycerols.Thin layer chromatography shows no triacylglycerols in the 6th June sample.The measured acidity in this stage could correspond both to FFA and to the phosphatidic acid.These components are the subtrates for the triacylglycerols biosynthesis.
Considering their acidity, the olive oils are subdivided to different quality classes (Loussert et al., 1978;C.O.I., 1991 andWessels, 1992).Our results show that the moroccan Picholine contains (from december to January) high levels of an oil which can be classified as extra virgin.
The high acidity level frequently found in the commercial Moroccan olive oil is probably caused with inadequate practices (harvest, storage and transport).

Fatty acids composition
acid for the Carolea and Frantoib varieties.Concerning the moroccan Picholine, an increase of the linolenic acid during the ripeness of olives had been reported (Belaiche, 1983).This is completly different from what we have found.Olive oil from the moroccan Picholine shows at ripeness, an evolution and a total tatty acids composition quantitatively different from that reported for a tunisian variety (Chemlali).In the oil from this variety, the stearic acid proportions decrease during the ripeness process from 21.5% in young olives and stabilizes in ripe olives around 2% (Marzouk et al., 1981).For the moroccan Picholine, a slight increase (from 1.9 to 3.2%) is observed.Fiorino reported that the evolution of the stearic acid is significantly different from one cultivarte another (Fiorino etal., 1991).For the linolenic and the stearic acids, any significant variations in their rates had not been observed for the Chemlali variety (Marzouk et al., 1981).For the moroccan Picholine these two fatty acids decrease slightly.

a Total fatty acids
Compared to other vegetable oils, olive oil is characterized with a domination of monoinsaturated fatty acids.These latters represent 71% in the major of our samples.The two other classes represent 10% to 18.6%.
Concerning the total fatty acids (Table II), different evolutions are observed depending on the nature of the fatty acids.Rates of minor fatty acids C20:0 and C20:1 remain almost invariable and vary only between 0.3 to 0.5% during all the sampling period.Palmitic CI 6:0, palmitoleic CI 6:1 and linolenic CI 8:3 acids decrease during olive ripeness (samples 2 to 7).Their rates become stable in the two last samples.The palmitic acid registred an important decrease from 16.3% in the first sample to 7.4% at february the 2nd.During the first months of fruit development, the oil has relatively high content of CI 8:3 (4.5%).This rate decreases and at the beggining of november it stabilizes at 0.9 -0.8 %.CI 8:0 and CI8:2 show a slight and progressive increase.CI 8:1 rate increases from 65% and reaches 72% at mid august, then stabilizes beyond this value until mid december.After this date, it increases and reaches 75.6% in the last sample.
The evolution of the different fatty acids of the moroccan Picholine is similar to that of some Italian varieties like Dritta, Coratina, Nebbio, Cucco... (Camera et al., 1975).The similarity is mainly remarquable for the palmitic, the oleic and the linolenic acids.Concerning the stearic and the linolenic acids a rather stable evolution is observed in italian varieties (Camera etal., 1975 andFiorino et al., 1991).Fiorino noted a decrease of the palmitic and linolenic acids and a slight increase of the oleic In spite of the big morphological ressemblance between the moroccan Picholine and the algerian Sigoise, their oils show quantitatively different chemical compositions (Talantikite etal., 1988).
Regional climate conditions and agricultural technics would also influence the chemical composition.But, the cultivar factor remains the most important.The insaturated fatty acids fraction would be the more dependent on the cultivar (Cimato, 1990).
Works of Pannelli on the late varieties or oil producing varieties show that the accumulation of oleic and linoleic acids is different from a variety to another (Pannelli etal., 1990).The chemical composition of the Sn2 glycerol fatty acids shows a clear affinity of the insaturated fatty acids for this position in all our samples.The monoinsaturates are represented mainly by the oleic acid which represent at least 76% (October 16th) of the total fatty acids in this position.In the major of our samples this rate exceeds 80% (Tables III & IV).Polyinsaturated fatty acids are also very represented in this position.Their proportions vary between 10.4% (november 1st) and 17.7% (January 16th).These latters are mainly represented by linoleic acid whose rate varies between 8 to 14% (Table IV) in the total fatty acids.

Dates of sampling Saturated Monoinsaturated Polyinsaturated
According to the International Oleicol Council reglamentation of virgin olive oil, the total proportion of palmitic and stearic acids must not exceed 1.5%.Only oils obtained from november 16th to January 2nd apply to this rule.

c The total fatty acids of the mesocarp
At ripeness, the mesocarp can represent up to 85% of the total weight of the olives (Kiritsakis et al., 1987).The global evolution of the different fatty acids of the mesocarp is similar to that observed for the fatty acids from the whole olives (Table V).From november 16th, the total of palmitic and stearic acids doesn't exceed 2%.The same result is reported by Zerrouk.However, slight different results are obtained by this researcher concerning C18:1 and C18:2 (Zerrouk, 1984).
Since the early stages of the olive development, the oleic acid show high levels (70 -73%).Its evolution is characterized by a relative stability, higher proportions (75 -76%) are obtained in the last samples.The palmitic and linoleic present opposite evolutions, the palmitic decreases while the linoleic increases.Palmitoleic and linolenic acid decrease until november, then they show stable proportions during the remaining samples.All other fatty acids don't show any noticeable variation during the fruit development.These proportions are almost similar to that obtained for the total fatty acids of the whole olives.

d Total fatty acids of olive seeds'oil
The fatty acids of the olive seeds'oil are all qualitatively identic to those of the mesocarp, but the CI 6:1 which proportions are negligible.Results in table VI show that all the fatty acids proportions remain invariable in all the studied period.Only the oleic and linoleic acids have different proportions in  A comparison of the proportions of fatty acids of the olive seeds and those of mesocarp show that the mesocarp is richer in oleic, palmitic and linoleic acids than the olive seeds.But, the olive seed contains higher rates of linoleic acid (21%).This fatty acid composition in the olive seeds remembers us that the other common oleaginous seeds (Feinberg etal., 1987 andAlter ef a/., 1982).

Evolution of the unsaponifiable matter content.
The evolution of the unsaponifiable matter content presented two phases: The first is situated between August 15 th and octobre 16 th with a decreasing proportions.The second which beggins from november 1st is characterized by a relative stability (around 1 mg/IOOg of oil) of these unsaponifiable matter content rates (Table VII).

The evolution of the sterolic composition.
Every vegetable oil have a specific sterol composition.Thus, they have a great importance in adulteration detection (Feinberg etal., 1987;Gordan et al., 1989 andJohansson et a!., 1979).This chemical components are also used for varietal characterisations (Castang et al., 1976 andKiosseglou et al., 1989), and are reported to be indicators of the best period of harvest (Fiorino etal., 1991).
Results in table VII show that the (3 sitosterol is the major component during all the period of sampling, with rates exceeding in all cases 84%.Proportions of p sitosterol and A5 avenasterol show opposite evolutions.The p sitosterol rates decrease and reach a minimum in the sample of January 2nd.In another way, the A5 avenasterol increases and reaches a maximal rate at the same date (January 2nd).This evolution show a ressemblance with that reported for some Italian varieties (Camera et al., 1975).But, the date at the p sitosterol rate is maximal and the A5 avenasterol rate is the lowest, is not the same for the moroccan Picholine (January 2nd) and the Italian varieties (december 12th).This difference may be attributed to a varietal or/and climate conditions.At the exception of the sample of 15/8 in which it represents 5% of the total sterols, the campesterol shows low proportions shifting tDOtween 3.0 and 3.5% during the period of our sampling.Stigmasterol rates stabilize around 1% until mid november from which these rates decrease and vary between 0.5 and 0.66%.A slight increase of these rates is observed in the two last samples.This evolution of these two sterols is different of that reported by Camera.This latter had observed, for some Italian varieties, a decrease of the campesterol rates and an increase for the stigmasterol proportions during the ripeness process.If we can easily find the sterolic composition of the moroccan olive oil, we haven't found any work about the evolution of this fraction during the ripeness of olives.Thus, the sterolic composition reported by Castang corresponds to that we have found at novembre 1st and could almost be considered similar to that obtained until the last of our sampling period.However, the results reported by Zerrouk seem to be the same of those we have obtained in the early stages of the ripeness process.