Effects of sunlight,temperature and adulteration on the quality of the virgin olive oil

The moroccan picholine olive variety shows performance against climate stress and environmental constraints. the virgin olive oil is exposed to extraction conditions,storage and commercialization that could alter its quality. among the factors involved by these conditions there are; sunlight,temperature and adulteration. the objective of the present work was to evaluate the impact of such factors on the quality of the virgin olive oil extracted from the moroccan picholine variety. so,we have determined characteristic parameters of the quality of the virgin olive oil (voo) like water content (wc),peroxide index (pi),acid index (ai) and density (d) according to sunlight,temperature and adulteration effects. 25 samples of voo from the «moroccan picholine» cultivar in two areas in morocco (demnat virgin olive oil and tagzirt virgin olive oil) have been studied using chemical analytical methods and pycnometry. voo from the two moroccan areas (dvoo and tvoo) presents low peroxide index when it is stored 15 days in obscurity. concerning water content (wc),peroxide index (pi),acid index (ai) and density (d) parameters,a similar behavior has been observed between the two virgin olive oils (voos). the evolution of oils according to temperature was also evaluated. the samples were slowly heated until the temperatures of 25,40,55,and 70 °c. for,each voo sample,each one of these four temperatures was maintained 10 mn. the same analyses were carried out on voo adulterated by refined olive oil (roo). the sunlight promotes oxidation in dvoo and tvoo so that the pi index increased but has no significant effect on the ai and the density. the wc at 25°c in tvoo is greater than the one in dvoo. in the case of heated oil,water content in dvoo,tvoo and roo decreases progressively with temperature. the olive oil stored in darkness is affected by temperature since it makes the pi increasing from 14.6 to 19.9 o2 meq/kg in tvoo and from 16.9 to 19.9 o2 meq/kg in dvoo. dvoo and tvoo present a considerable decreasing of pi when they are adulterated by roo. ai values of tvoo are higher than those of dvoo and decrease after adding roo,especially below 10% of roo. heating makes ai increasing in oils and the heated oil the greatest ai is tvoo. a consistent result has been recorded in the case of the sunlight effect on the value of ai in tvoo whose acid index was 0.51% in the darkness and 0.73% at sunlight. globally,virgin olive oil density increases according to the temperature and to the adulteration by refined olive oil.