Abstract
A multi-stage, low temperature solvent fractional crystallization process was developed in this work for the removal of trans fatty acids (TFA) and saturated fatty acids in free fatty acids (FFAs) obtained from hydrolysis of partially hydrogenated soybean oil (PHSO). The effects of host solvents, concentration of FAs, crystallization temperature and time on separation of TFA and SFA were studied. Among all the three solvents examined namely acetone, hexane and ethanol, acetone proved to be promising solvent. By employing acetone as a solvent TFA can be reduced to 11.6% from an initial content of 19.5% and SFA can be drop down to 3% from an initial content of 20%, by applying stepwise crystallization temperatures from 5oC to -20oC. Crystallization temperatures lower than -30oC such as -35oC and -40oC can further lower the TFA content in liquid fraction down to 5-8% by employing acetone as a solvent. TFA content can be reduced down to 12.2% and 14%; and SFA content could be reduced to 3.3% and 3.1% from an initial content of 20% when hexane and ethanol were employed as solvents, respectively. Optimum FAs to solvent ratio was 1:5 (w/v) and with a time period of 12 h for each step of crystallization. The crystallization behavior of TFA strongly depends on the type of solvents employed and crystallization temperature, while SFA crystallization depends mostly upon temperature rather than nature of solvent. Even though total removal of TFA could not be achieved in the present study, a road map has been developed for a fractionation of TFA and SFA from partially hydrogenated oil FFAs.
Highlights
Trans fatty acids (TFAs) have been reported to be risk factors involved in cardiovascular diseases as well as many other negative effects for human (Buckle K, 2010; Valenzuela A & Morgado N, 1999; Semma M, 2002)
Starting from 19.5% in partially hydrogenated soybean oil (PHSO), TFA content could be reduced to 11.6%, 12.2% and 14.0% with acetone, hexane and ethanol as solvent, respectively
Prolonging crystallization time from 12 h to 24 h did not result in significant reduction of TFA content in solution, with ≤0.3% reduction for all the three solvent systems
Summary
Trans fatty acids (TFAs) have been reported to be risk factors involved in cardiovascular diseases as well as many other negative effects for human (Buckle K, 2010; Valenzuela A & Morgado N, 1999; Semma M, 2002). In general TFAs are present in different amounts in a broad range of foods, including most foods made with partially hydrogenated oils, while partial hydrogenation is traditionally a key technology for oil modification in frying oil and plastic fat industries. Even though the main mode now is to rule out the use of partial hydrogenation, the possible removal of TFAs from partially hydrogenated soybean oil (PHSO) is still of interest for part of the industrial sectors as well as for academic documentation since this has not been conducted before. As part of a package strategy including enzymatic selective hydrolysis and following further fractionation, the fractionation of fatty acid mixture is in central concern for this study. The objective of the present study was to separate TFAs from PHSO fatty acids, a mixture was formed during the trans selective hydrolysis of PHSO
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