eluted at 12 min by HPLC analysis contained 95 mol% of AA (Figure 9). This fact
strongly supported the hypothesis.
8.5 Application to regiospecific analysis
Regiospecific analysis of triglycerides in natural oils has been conducted by two
methods. One is the method of analyzing the fatty acid composition of 1,3-diglycer-
ides or 2-monoglycerides obtained by Grignard degradation (Becker et al., 1993),
which was used in this study (Table 4). The other is the method of analyzing the
fatty acid composition of FFA obtained by the hydrolysis of an oil with a free
1,3-positional specific lipase (Luddy et al., 1964; Iwai et al., 1980). When this en-
zymatic method is used, the products in the early stage of the reaction must be ana-
lyzed because the esterification and transesterification occur simultaneously during
the hydrolysis. However, the constituent fatty acids are liberated from the oil accord-
ing to the fatty acid specificity of the lipase. Thus, the erroneous result is obtained
that the fatty acids, on which the lipase acts strongly, exist at the 1(3)-position.
In our reaction system for the production of MLM-type structured lipid at 30 8 C,
the simultaneous hydrolysis and nonenzymatic acyl migration did not occur, and
fatty acids at 1,3-positions of natural oils were efficiently exchanged for CA (see
Tables 3 and 4 and Figure 5). To exchange all fatty acids at 1,3-positions for
CA, the glycerides obtained by the acidolysis were recovered byn-hexane extrac-
tion, and subjected to the reaction three times in total under the same conditions. As a
result, the CA contents in transesterified oils obtained from substrate oils except for
tuna oil reached 66 mol%, although the CA content in transesterified oil derived from
tuna oil was 60 %. Figure 10 shows the results of HPLC analyses of the transester-
8.5 Application to regiospecific analysis 143
Figure 9. Triglyceride components of transesterified oil obtained by acidolysis of tripalmitin with AA
for 24 h. The conditions of analysis were the same as those in Figure 2. A, Arachidonic acid; P, palmitic
acid; S, stearic acid.