Abstract
There are more and more studies on the detection method
of 3-chloro-1,2-propanediol fatty acid esters (3-MCPD esters) at
present. By comparing these methods for the determination of 3-MCPD
esters. Indirect methods, which determine total amount of 3-MCPD after
hydrolysis of the esters, have an advantage over direct methods. The
existing indirect methods, however, may yield unreliable results or
require long hours of alkaline methanolysis. In contrast, the Indirect
enzymatic hydrolysis method has mild conditions and more accurate
results. In this study, we developed a reliable and rapid indirect
method for determinations of 3-MCPD esters. 3-MCPD esters was
enzymatized to 3-MCPD by indirect enzymatic hydrolysis method, and the
conditions of enzymatic hydrolysis were optimized, the content of 3-MCPD
after enzymatic hydrolysis was detected by gas chromatography-mass
spectrometry (GC-MS) and the yield was calculated. Finally, the optimum
conditions for enzymatic hydrolysis of 3-MCPD esters were determined.
According to the optimal enzymatic hydrolysis condition, the contents of
3-MCPD esters in four food oils were determined. The method is simple
and sensitive, and can meet the requirement of 3-MCPD esters detection
in general oils.
Keywords : 3-MCPD esters; 3-MCPD; Indirect enzymatic hydrolysis
method; GC-MS
Introduction
The contamination of 3-MCPD esters is one of the hot issues in the field
of food safety that have been disputed internationally in recent
years[1].The formation of 3-MCPD esters is
directly related to the chemical refining of synthetic oil products, It
has been confirmed that 3-MCPD esters are found in hot processed foods
derived from grains, fish and meat products, coffee, nuts, potatoes and
edible oils[2-4]. 3-MCPD esters are hydrolyzed in
vivo by intestinal pancreatic lipase to produce free 3-MCPD, 3-MCPD has
extremely obvious renal toxicity and high genotoxicity, which has been
strictly classified as 2B carcinogen by the International Cancer
Organization Working Group (IARC) of the United
Nations[5-6].
3-MCPD esters detection mainly has
the direct determination method and the indirect determination method.
By comparing these methods for the determination of
3-MCPD
esters. Direct methods based on LC-MS/MS[7–9]are
available in literature, however, the great complexity of 3-MCPD esters
may lead to the determination of up to several tens of compounds in one
sample for which a respective number of internal standards are
required[10]. This contributes to make the
procedure generally expensive, but the advantages of direct methods are
the lack of derivatization step and the possibility to get direct
information on the content of individual esters and for these reasons
they found wide application in the field[11].
Indirect methods for the determination of 3-MCPD esters in samples
requires a complex pretreatment process with many steps in advance, and
the change of conditions in each experimental step will easily affect
the accuracy of the final detection results, the methods are based on
derivatization, transforming 3-MCPD esters in free 3-MCPD, and
they include several stages such as transesterification, neutralization
and derivatization steps before quantification, using NaOH for
transesterification, sodium bromide for neutralization and phenylboronic
acid for derivatization[12]. But in the alkaline
catalyzed indirect method, if the alkaline hydrolysis reaction time
conditions and salting-out conditions or temperature are not well
controlled, a part of 3-MCPD may be
eliminated or extra produced, thus making the determination result small
or large. Acid catalyzed indirect method is more stable and durable, but
relatively time-consuming. In contrast, the indirect enzymatic
hydrolysis method has mild
conditions and more accurate results.
At present, there are more and more studies on the determination of
3-MCPD esters by indirect enzymatic
hydrolysis method. However, there are no study have reported the optimal
conditions for enzymatic hydrolysis
of 3-MCPD esters. In this work,
3-MCPD esters was enzymolized to 3-MCPD by indirect enzymatic hydrolysis
method, and the conditions of enzymatic hydrolysis were optimized, GC-MS
was used for detection and calculation of yield, then the optimum
enzymatic conditions were determined. Finally, the actual samples were
detected by indirect enzymatic hydrolysis method. The method is simple,
reliable, and rapid, and is suitable for a routine quality control of
fats and oils[13].
Experimental Procedures