The same sunflower oil used
for the bleaching test was heated at 180 ?C, under vacuum, to simulate the
process of deodorization. There were no significant differences between the
trienes and dienes concentrations before and after deodorization, indicating that
heating at 180 °C for 1 h was a condition not sufficient for the dehydration of
either the hydroxysterols or sterols. Moreover, recoveries of the
hydroxysterols were quantitative with no decomposition reactions, whereas the
recovery of 7-keto-?-sitosterol was ~80%, similar to the recoveries obtained after
bleaching. The authors concluded that dehydration of the hydroxysterols would
occur at higher temperatures (135).
Effect of chemical interesterification
of a blend of refined olive oil and palm stearin on POP content has been
investigated. Generally, chemical interesterification had no effects on the POP
content of the starting oil blend. These results show that processing of
vegetable oils at the temperature used for interesterification (90–120 ?C),
along with catalysis and other steps to produce interesterified fats, does not
generate POP (113).The issue of authenticity is becoming
increasingly important in vegetable oils. Adulteration is generally motivated
by the maximizing benefit by replacing an expensive vegetable oil with a
cheaper one (162).
To detect edible oils and fats adulteration, it is possible to use both major and
minor components as detection tool. Since each oil and fat may have an especial
component at a known level, their presence and amounts should be considered as
a detection tool. The sterol profile can be used as a means of differentiating
between vegetable oils or detecting possible adulteration (18, 163). In addition, it is even possible
to determine the geographical origins of olive oils using minor constituents,
such as cycloartenol and tocopherols (164).
Hazelnut oil is used to adulterate olive
oil due to its similar composition of triacylglycerols, fatty acids and major
sterols (24, 165, 166). However, hazelnut oils have lower
contents of ?5-avenasterol but higher levels of ?7-stigmastenol
than olive oils (167).
Some esterified 4-desmethyl sterols (campesterol, ?7-stigmastenol
and ?7-avenasterol) have been used to detect olive oil adulteration
with hazelnut oil using the Mariani ratio (RMAR1). For
non-adulterated olive oil, RMAR is not more than 1. This method can
be used to detect adulteration at a level of 10% (168, 169).