High-Oleic Sunflower Oils
High value tailor-made raw materials for a widespread industrial utilisation in food and non food sectors - this sounds like future expectations to a more extended use of genetically modified crops. High-oleic sunflowers (HOSF) fullfill these high hopes in many ways, although the cultivated varieties have been developed by conventional hybrid breeding methods. What makes them a modell for future oilseed design?
Oleic acid predominating
The physical-chemical properties and behaviour of an oil or its derivatives, as well as the physiological-medicinical benefits are fixed in the fatty acid composition. Most of the worlds vegetable oils and fats show a mixed fatty acid composition: in triglycerides, the hydroxy groups of a glycerol molecule are chemically bound to different fatty acids (FA), varying in chain length and / or in number and position of chemical functionalities (mainly C-C doublebonds). In high-oleic oils, such as high-oleic sunflower oil (HOSO), all properties are strongly dominated by its high content of oleic acid (C18:1).
Table: Fatty Acid Composition of suitable Oleic Acid Resources
(FA!) Fatty Acid
For human nutritional purposes a fatty acid mixture can be a benefit, in technical applications there is often the need to extinguish or reduce the "wrong" fatty acids (analogously blending of oils is applied to food products). Oleochemistry is the art of cleaning up complex substance mixtures, cutting and turning them into suitable fractions for all kinds of applications with different requirements. But processes like destillation, crystallization or hydrogenation raise costs and sometimes separation of fatty acids gives poor results, like the separation of oleic acid (C18:1) from the C18-PUFA´s linoleic (C18:2) or linolenic acid (C18:3). The latter sometimes is desireable or necessary, due to the bad oxidative behaviour of PUFA´s, shortening products lifetime. Partial hydrogenation of these mixtures is a common industrial process for improvement, e.g. for margarines or frying oils, but due to the lack of selectivity of catalysts, the content of stearic acid and trans fatty acids is rising. No doubt - an oil (or its derivatives!) with an high content of oleic acid and low of PUFA offers many advantages and added value:
for all kinds of applications: high oxidative stability, reduced rancidity, extended shelf life, vegetable resource image ("koscher", "BSE-free");
for nutritional purposes: no trans fatty acids (TFA), "low-cholesterine" fat (low SAFA content; like "best oil" olive oil), GMO-free;
in processing: reduced cleaning costs, liquid - easy transportation / storage
in syntheses: exact defined functionality (double bond), high product yields (less by-products)
Oleic acid is a bulk product in natural oils and in oleochemicals. Up to now, the main source for oleic acid is inexpensive beef tallow. After cleavage into fatty acids, the resulting tallow-oleine is purified by fractionation processes to an oleic acid content of 60-70 % (further enrichement by purification is too expensive). Since the BSE disease and public discussed problems with fat recycling, a growing demand for vegetable oleic sources can be observed. These exist for long times, but they are either limited in amount, like olive oil oleic acid yielded from refining, or low in oleic acid (palm oleine). Since a few years, new high oleic oilseeds are entering the markets.