Despite widespread use of citral in foods and beverages, the compound is known to degrade over time under acidic conditions, resulting in a loss of desirable flavours and formation of undesirable off-flavours.
The compound triacetin, also known as glycerol triacetate, is already used by the food industry as a flavour solvent. By incorporating triacetin into oil-in-water emulsions it was possible to alter the stability of citral to chemical degradation, say scientists from the University of Massachusetts and flavour giant International Flavors and Fragrances (IFF) report their findings in the Journal of Agricultural and Food Chemistry.
Formulation of oil-in-water emulsions with citral revealed that triacetin may incorporate the flavour compound in the internal lipid phase. However, the applicability of the development for finished beverage emulsions was questioned since the organic phase used in the study was about 5 per cent, significantly higher than the less than 0.1 per cent found in finished beverage emulsions
“Consequently, this strategy may not work to protect citral in finished beverage products because the majority of the citral may partition into the aqueous phase,” wrote the researchers, led by David Julian McClements from U of M.
“However, it may work to stabilize citral during storage in beverage concentrates, which do have relatively high organic phase concentrations (greater than 20 wt per cent),” they added.
McClements and his co-workers investigated if triacetin and medium-chain triacylglycerols could retard the degradation of citral in oil-in-water emulsions.
Results showed that the triacylglycerols were present as emulsion droplets with an average diameter of 900 nanometres, while triacetin was present as microemulsion droplets with an average diameter of 10 nanometres, said the researchers.
A concentrations of triacylglycerols and triacetin of 5 per cent, an ‘appreciable’ retardation in citral degradation was observed at pH 3, they added.
The triacylglycerols may act as ‘sinks’ for the citral, said the researchers, “thereby protecting it from chemical degradation in the acidic aqueous phase”. On the other hand, triacetin may protect the citral by incorporating it within their fat-loving internal regions.
“These results may have important implications for understanding and improving the chemical stability of citral in beverage emulsions,” wrote the researchers.
Areas for future study
Looking towards potential unanswered questions, the researchers noted that temperature fluctuations during storage, or the presence of other additives may impact citral stability and this needs addition study.
“Consequently, further studies are needed to elucidate the impact of other factors on citral stability in model beverage emulsions,” they added.
Source: Journal of Agricultural and Food Chemistry
Volume 57, Issue 23, Pages 11349-11353, doi: 10.1021/jf902761h
“Stability of Citral in Oil-in-Water Emulsions Prepared with Medium-Chain Triacylglycerols and Triacetin”
Authors: S.J. Choi, E.A. Decker, L. Henson, L.M. Popplewell, D.J. McClements