TGA40 oil (AA content, 40 %; Suntory) was hydrolyzed at 35 8 C for 20 h in a
mixture containing 50 % water and 15 U g–1ofCandidalipase. Although the en-
zyme amount was one-sixth of that in hydrolysis of TGA25 oil, the AA content in
glycerides could be raised to 57 wt% at 35 % hydrolysis, and the loss of AAwas only
9 % of the initial content (Shimada et al., 1999a). This result shows that the oil
containing higher concentration of desired PUFA is useful for the increase in the
PUFA content in glycerides.
8.2.4 Separation of PUFA-rich oil from the reaction mixture
Production of a PUFA-rich oil is completed by the removal of free fatty acids (FFAs)
from the reaction mixture. From the viewpoint of industrial purification, the extrac-
tion of glycerides withn-hexane is not suitable because of the risk of explosion and
high cost. The reaction mixture contained only glycerides and FFAs, and the main
components of the glycerides were triglycerides. The molecular weights of trigly-
cerides and FFAs were completely different; ca. 900 Da and 290 Da, respectively.
Thus, molecular distillation should be effective for removal of FFAs.
An attempt was made to purify GLA-rich oil from borage oil hydrolyzate (Table 2)
(Shimada et al., 1998b). Borage oil (7 kg) was hydrolyzed at 35 8 C for 24 h in a
mixture containing 50 % water and 20 U g–1mixture of lipase using a 30-L reactor
with stirring at 200 rpm. The GLA content in glycerides was raised to 46 wt% at
61 % hydrolysis. The dehydrated oil layer was applied to film distillation appara-
tus, and distillation was performed at 150 8 C and 0.05 mmHg. Most of the FFAs
were recovered in distillate 1-1, but the acid value of the residue was still high
at 40. Hence, the second cycle of distillation was performed after increasing the
temperature to 160 8 C, and 2.3 kg of the residue (acid value, 10) was obtained.
To increase further the GLA content, the glycerides were hydrolyzed again under
the same conditions using a 10-L reactor. As a result, the GLA content was raised
to 55 wt% at 20 % hydrolysis. The distillation of the oil layer at 155 8 C and 0.04
132 8 Production of Functional Lipids Containing Polyunsaturated Fatty Acids with Lipase
Table 1.Main fatty acid content in glycerides obtained by repeated selective hydrolysis of TGA25 oil
withCandida rugosalipase.
Fatty acid content (wt%) AAReaction Hydrolysis
% 16:0 18:0 18:1 18:2 18:3^2 20 : 4
Recovery^1
(%)None^3 – 13.4 6.3 14.8 21.3 3.2 24.9 100
First 52.4 5.7 3.6 6.7 9.6 4.7 49.5 94.6
Second 18.1 3.8 3.2 4.0 5.5 4.9 54.3 87.2
Third 17.2 2.4 2.3 2.5 3.3 5.2 59.7 75.0
(^1) Recovery of the initial arachidonic acid (AA) content of the original TGA25 oil. The recovery was
calculated by assuming that all glycerides were recovered by the extraction withn-hexane.
(^2) c-Linolenic acid.
(^3) Fatty acid composition of the original TGA25 oil.