Product shelf life evaluation of an enriched yogurt drink containing an omega-3 nanoemulsion with enhanced bioavailability

Abstract

Long chain omega-3 polyunsaturated fatty acids (LC3PUFA) have been linked to a range of health benefits, throughout the life cycle (1) . Dietary surveys indicate that LC3PUFA are currently under consumed, particularly amongst vegetarians/vegans, adult men, pregnant/breast feeding women, infants, non-fish eaters and certain ethnic groups (2)(3)(4) . New food vehicles such as micro algae oils have been developed to bridge this gap (5) .Nanoemulsions are systems with droplet sizes in range of 20 to 500 nm (6) . The incorporation of algae oil into foods using nanoemulsion has the potential to improve LC3PUFA bioavailability (7) . However, nanoemulsion may also affect the shelf life of foods as increased droplet surface areas may lead to lipid oxidation (8) .The aim of the present single-blinded sensory evaluation study was to determine whether study participants (n = 62) could detect differences when an algae oil nanoemulsion was integrated with a strawberry yogurt and tasted after storage over 2, 9 and 16 days at 4°C. All samples were prepared using breakfast drinking yogurt, natural sweetener and strawberry flavouring. Products were fortified with nanoemulsified high docosahexaenoic acid (DHA) algae oil to give a dose of 632 mg DHA/100 g yogurt. A full microbial analysis over 23 days established product safety.To determine how shelf life may be affected, seven sensory attributes were chosen to assess consumer acceptability: 1) smell, 2) appearance, 3) flavour, 4) texture, 5) consistency, 6) aftertaste and 7) overall acceptability. Attributes were rated using a 9-point hedonic scale.Results were analysed using one and two-factor repeated measures ANOVA tests with Tukey and Duncan's tests and a Bonferroni correction at 5 per cent. No statistically significant differences were found within the 3 samples when the appearance and consistency was compared. The consistency of the day 16 sample was rated closest to 'just right' (midscale). However, refrigerated storage significantly improved the aroma, flavour, texture, aftertaste and acceptability of the enriched strawberry yogurt drink when compared at 3 intervals over a 16 day period. This may be due to the use of yogurt as a carrier vehicle, the strawberry flavouring and/or changes in nanoemulsion particle sizes over the storage period (9) .

The composition and oxidative stability of vegetarian omega‐3 algal oil nanoemulsions suitable for functional food enrichment

“…However, there were significant detrimental changes in the sensory properties of yogurt when the nanoemulsion systems were used as a fortification vehicle, which may indicate the presence of volatile oxidation compounds . A further 16‐day shelf life sensory evaluation of 50% (w/w) algal oil and lecithin nanoemulsion enriched strawberry yogurt indicated that detrimental sensory changes were detected after 2 days of storage, although significant improvements to several sensory attributes were found after 16 days of refrigerated storage, which warrants further investigation …”

“…20 A further 16-day shelf life sensory evaluation of 50% (w/w) algal oil and lecithin nanoemulsion enriched strawberry yogurt indicated that detrimental sensory changes were detected after 2 days of storage, although significant improvements to several sensory attributes were found after 16 days of refrigerated storage, which warrants further investigation. 21 Lecithin, a zwitterionic natural emulsifier has good emulsifying properties as a result of its molecular structure, which has hydrophilic and lipophilic groups and a hydrophilic-lipophilic balance (HLB) of eight, making it well suited to the successful creation of LC 3PUFA algal oil and marine-based oil nanoemulsions. 22 Lecithin has been used successfully to create physically stable LCn3PUFA nanoemulsion systems in various previous studies 16,19,[23][24][25] and has been found to increase the oxidative stability of emulsions at the same time as maintaining physical stability.…”