Proposal for Soybean
Association to Reduce the Sterol
Glucoside Content in Soy-based
Biodiesel
By Haiying Tang
Structures
• Plant Sterols exist as free sterols, steryl esters, steryl
glycosides, and acylated steryl glycosides.
Results:
• Toivo et al (Determination of sterols in foods: Recovery of free, esterified,
and glycosidic sterols. Journal of Food Composition and Analysis 2001;14(6):631643)
– Corn meal and onion contain an appreciable amount of
steryl glycosides
– Rapeseed oil did not contain steryl glycosides.
• Verleyen et al ( Influence of the vegetable oil refining process on free and
esterified sterols. JAOCA, Vol.79, no.10, 2002)
– Water degumming did not affect the sterol content or its
composition.
– A significant reduction in the free sterols during
neutralization; a gradual reduction in the total sterol content
as a function of temperature (220-260 0C) during
deodorization
– A considerable increase in sterol ester fraction during
physical refining; a slight increasing in the free sterols during
acid degumming and bleaching
Continued
• Kochhar (Influence of Processing on Sterols of Edible Vegetable-Oils.
Progress in Lipid Research 1983;22(3):161-188.)
– Sterol occur in free and esterified form in refined
vegetable oil process.
– Conventional refining has minor effects on the sterols;
however, high temperature physical (steam) refining of
oil does affect the sterol composition.
– Reduction in the levels of sterols during degumming,
neutralization, bleaching, hydrogenation,
deodorization,and steam refining.
– The rate of reduction was depended on
•
•
•
•
•
The amount of sodium hydroxide,
Type of bleaching earth,
Conditions of hydrogenation
Time and temperature of steam deodorization
Physical deacidification
– Loss of sterols of between 10-70%
Continued: Sterol Glucosides
– Sterol glycosides are removed during the oil
refining process.
– Degumming vegetable oils effectively
removes sterol glucosides.
– Fully refined oils are invariably free from sterol
glucosides;
– Alkali refines removes a portion of the sterol;
– Both steam deodorization and physical
refining further reduce the sterol glucosides.
Wedel ( Quantitative studies of the pHLip Test Kit for B100, AOCS
presentation, May 2007)
Critical Issue
• No ASTM standard on the analytical
methods to determine sterol glucosides in
biodiesel;
• The effect of refining and processing
strategy on sterol glucoside content in
biodiesel has not been fully elucidated;
• Few studies on reducing the sterol
glucoside content in biodiesel blends.
Objectives
• Evaluate different refining and processing
strategy to reduce the sterol glucoside
content in soy-based biodiesel
– The effect of vacuum distillation on the sterol
glucoside content in biodiesel;
– The effect of cold filtering on the sterol
glucoside content in biodiesel and blends
• Using filter membrane
• Using gravity to settle out, and separate
• Chemical refining
– Water degumming
– Chemical neutralization
– Bleaching
– Deodorization
• Physical refining
– Acid degumming
– Bleaching
– Deordorization
Process
• Water degumming: oil 70 oC at 175 rpm+water(3%) ----at
250 rpm for 30 min----Centrifuging-----supernatant
• Chemical neutralization: water-degummed oil at 55oC +
NaOH (10%) at 175 for 40 min----heated to 75 oC---centrifuge----oil was collected and washed with water.
• Acid degumming:oil 60 oC+0.15% citric acid at 10000rpm
for 1 min__ 60min at 40oC--- cnetrifuging
• Bleachinng: The degummed oil at 95oC under reduce
pressure (50 mbar)+ bleaching earth --- mixed at 85 rpm
for 30 mil--- filter
• Depdorization: at 240oC (2 mbar) with injection of 1.5
and 1% steam, respectively.
Sterol Glycosides
• Crude soy oil: 2300ppm SG
• 19300 ppm SG in gum
• Hydrolysis may be carried out by the
application of steam and alkali or acid:
biodiesel made from acid oil can have high
levels of SG
Analysis method
• Total sterols were analyzed by acid and
alkaline hydrolysis, hydrolysis,
derivatisation to trimethylsilyl(TMS)-esters
and anlysis using GC-FID.
• The steryl glucosides were isolated by
solid phase extraction (SPE), and then
was hydrolysed with acid to release the
free sterols
Extraction and Quantitation of Sterols
Analytical Steps