Long chain omega-3 (n-3) polyunsaturated fatty acids (LC3PUFA) in human diets are mainly obtained from oily fish, fish oil or fish oil based supplements( Reference Lenihan-Geels and Bishop 1 ). Current UK oily fish consumption is significantly short of recommended levels( Reference Bates, Cox and Nicholson 2 ). Non-fish sources of LC3PUFA such as algal oils are particularly important for vegetarians/vegans, non-fish eaters and pregnant mothers( Reference Lenihan-Geels and Bishop 1 ; Reference Ryan and Symington 3 ).
Nanoemulsions are systems with droplet sizes in range of 20 to 500 nm( Reference Solans and Solé 4 ). The incorporation of algal oil into foods using nanoemulsions created with ultrasound has the potential to improve LC3PUFA bioavailability( Reference Lane, Li and Smith 5 ). However, the use of ultrasound in the creation of nanoemulsions may also affect the oxidation stability of LC3PUFA( Reference Pingret, Fabiano-Tixier and Chemet 6 ).
The aim of the present study was to analyse the oxidation stability of a nanoemulsion containing an algal oil rich in docosahexaenoic acid (22:6 n-3; DHA) using gas chromatography headspace analysis (GCHS).
GCHS measurements were conducted to compare bulk oil and nanoemulsions stabilised with soy lecithin (LN) and Tween 40 (TN) solely and in combination (LTN) over a storage period of 5 weeks at temperatures of 4, 20 and 40 °C. A propanal peak was identified and analysed using one -way repeated measures ANOVA tests with Tukey post hoc test.
aSignificantly different at p ⩽ 0·05 compared with week 0 at the same storage temperature; A Significantly different at p ⩽ 0·05 compared with 4 °C at the same storage time.
Increased temperature and storage periods had a significant effect on the development of propanal for all samples stored at 40 °C (p ⩽ 0·05). Nanoemulsions prepared with lecithin alone had significantly higher development of propanal in week 1 at 40 and 20 °C respectively (p ⩽ 0·05). There were no significant differences for emulsion/emulsifier type for samples stored at 4 °C. To further evaluate oxidation status, research should now be conducted over the same storage periods and temperatures to analyse nanoemulsion droplet sizes, fatty acid composition and to identify and measure other recognised volatile compounds.