Page 277 - Analytical method for food addtives

184 Analytical methods for food additives

was developed for confirming the identity of propylene glycol added to bait fish for
preservation. The identity of propylene glycol in anchovy extracts was success-
fully confirmed using this method.
1
One enzymatic method is based on the oxidation of PG by propylene glycol
dehydrogenase (PGDH) from Microcyclus eburneus, which is accompanied by the
+
reduction of NAD to NADH. The use of the enzymatic reaction resulted in almost
stoichiometric oxidation of PG and the method was found to be relatively free from
interferences and was successfully used to establish the PG content of some
3
commercial Japanese foods. The other enzymatic method uses glycerol dehydro-
genase and glycerol kinase. It is a simple and rapid enzymatic analysis for the
determination of PG in commercial foods. This method can be applied to foods that
contain glycerol because glycerol could be eliminated prior to enzymatic assay of
PG through its conversion to glycerol-3-phosphate by incubation with glycerol
kinase. Glycerol dehydrogenase showed no activity towards this product. Food
ingredients and/or food additives tested (glucose, ethanol, sorbitol, propylene
glycol monostearate and glycerol monostearate) did not interfere with this method.
4
The HPLC method is sensitive for the determination of propylene glycol esters
of fatty acids (PGEs) in foods. PGEs in various foods could be selectively detected
without interference. Peaks of PGE having fatty acids of C16:0 and C18:0 could be
well separated.

15.3 Recommendations

Although various methods have been developed for the analysis of propylene
glycol in foods none of these have been validated by collaborative trial. They
therefore need to be further developed and validated by collaborative trial.

15.4 References

1 ‘Enzymatic determination of propylene glycol in commercial foods’, Hamano T,
Mitsuhashi Y, Tanaka K, Matsuki Y, Nukina M, Oji Y, Okamoto S. Agric. Biol. Chem.
(1984), 48(10), 2517–2521.
2 ‘Confirmation of identities of propylene and ethylene glycols in anchovies by tandem
mass spectrometry’, Matusik J E, Eilers P P, Waldron E M, Conrad S M, Sphon J A.
Journal of AOAC International (1993) 76(6), 1344–1347.
3 ‘Enzymatic analysis of propylene glycol in foods by the use of glycerol dehydrogenase’,
Mitsuhashi Y, Hanano T, Tanaka K, Matsuki Y. Journal of the Food Hygienic Society
of Japan (1985) 26(3), 290–294. [Japanese]
4 ‘Determination of propylene glycol esters of fatty acids in oily foods by HPLC’,
Murakami C, Maruyama T, Niiya I. Journal of the Food Hygienic Society of Japan.
(1997) 38(2), 105–109. [Japanese]