408
normal value thereby extending the shelf life of foods containing these oils. At the
other extreme, certain oils are virtually completely hydrogenated to iodine values
less than 2. Of greater importance is partial hydrogenation applied to soybean and
other linoleic rich oils to raise the content of solid triacylglycerols. This is achieved
through formation of saturated acids and of transunsaturated acids. Partial hydrogenation of unsaturated oil gives a product of higher melting point (more suitable for
spreads and cooking fats) and of enhanced oxidative stability.
Interesterification Using a Chemical Catalyst
The process of rearranging the fatty acids in oils or in combination of oils thereby
changing the triacylglycerol composition is called interesterification. However this
does not affect the fatty acid composition of the single oil or the blend and it remains
the same. Usually the blend will contain two or more oils differing in chain length
and/or in patterns of unsaturation. The interesterification process could be achieved
with the help of alkaline catalyst such as NaOH wherein the distribution of the fatty
acids is randomly distributed in the product. This is in contrast to the natural vegetable oils that are produced by enzymatically catalysed biological processes and in
the fatty acids are not randomly distributed. It is these changes that are made in triacylglycerol composition that affect thermal behaviour and may also affect bioavailability. This process also results in loss of some oil through conversion to acid
(with NaOH) or ester (with sodium methoxide). Inspite of the loss, this procedure is
also being used to produce fats suitable for use as spreads without hydrogenation.
Interesterification Using an Enzymatic Catalyst
Interesterification can also be carried out with lipases. The enzymatic processes
offers advantages over the chemical process in terms of occurring under milder
conditions, requirement of less costly equipment, and produce less by-product,
thereby reducing wastage and reducing purification process. The major benefit of
using a lipase is the added control over the nature of the product as a consequence
of the specificity shown by many lipases. However, chemical or enzymatic catalysts
interesterified products are generally less stable than the original oils. There is a
perception in some quarters that the enzymatic reaction is superior because it is
‘more natural’ and avoids the use of ‘chemicals’.
Oilseeds Modified by Seed Breeding
Growing wild plants need greater effort and in most cases have a lot number of difficulties. To overcome these modern agricultural practices are being employed to
grow and commercialize them. This method requires reducing the use of chemicals,
apart from which altering the fatty acid composition and levels of other important
S. Asokapandian et al.
normal value thereby extending the shelf life of foods containing these oils. At the
other extreme, certain oils are virtually completely hydrogenated to iodine values
less than 2. Of greater importance is partial hydrogenation applied to soybean and
other linoleic rich oils to raise the content of solid triacylglycerols. This is achieved
through formation of saturated acids and of transunsaturated acids. Partial hydrogenation of unsaturated oil gives a product of higher melting point (more suitable for
spreads and cooking fats) and of enhanced oxidative stability.
Interesterification Using a Chemical Catalyst
The process of rearranging the fatty acids in oils or in combination of oils thereby
changing the triacylglycerol composition is called interesterification. However this
does not affect the fatty acid composition of the single oil or the blend and it remains
the same. Usually the blend will contain two or more oils differing in chain length
and/or in patterns of unsaturation. The interesterification process could be achieved
with the help of alkaline catalyst such as NaOH wherein the distribution of the fatty
acids is randomly distributed in the product. This is in contrast to the natural vegetable oils that are produced by enzymatically catalysed biological processes and in
the fatty acids are not randomly distributed. It is these changes that are made in triacylglycerol composition that affect thermal behaviour and may also affect bioavailability. This process also results in loss of some oil through conversion to acid
(with NaOH) or ester (with sodium methoxide). Inspite of the loss, this procedure is
also being used to produce fats suitable for use as spreads without hydrogenation.
Interesterification Using an Enzymatic Catalyst
Interesterification can also be carried out with lipases. The enzymatic processes
offers advantages over the chemical process in terms of occurring under milder
conditions, requirement of less costly equipment, and produce less by-product,
thereby reducing wastage and reducing purification process. The major benefit of
using a lipase is the added control over the nature of the product as a consequence
of the specificity shown by many lipases. However, chemical or enzymatic catalysts
interesterified products are generally less stable than the original oils. There is a
perception in some quarters that the enzymatic reaction is superior because it is
‘more natural’ and avoids the use of ‘chemicals’.
Oilseeds Modified by Seed Breeding
Growing wild plants need greater effort and in most cases have a lot number of difficulties. To overcome these modern agricultural practices are being employed to
grow and commercialize them. This method requires reducing the use of chemicals,
apart from which altering the fatty acid composition and levels of other important
S. Asokapandian et al.