Design of complex w/o/w emulsion for salt reduction in food emulsions

Zhang, L (2021) Design of complex w/o/w emulsion for salt reduction in food emulsions. PhD thesis, University of Nottingham.

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The strategy of reducing salt levels in high-moisture foods by using water-in-oil-in-water (w/o/w) double emulsions has generated significant interest in recent years, due to the features of both encapsulation and controlled delivery of double emulsions.

In this research, PGPR was applied as the reference lipophilic emulsifier to stabilise the internal interface of w1/o/w2 emulsions and compared to several food-grade alternative lipophilic emulsifiers, including sorbitan esters, sucrose esters (SE), native soy lecithins, ammonium phosphatide (AMP) and native oat oil. PGPR, SEs and AMP were identified to be able to stabilise w1/o emulsions containing 1.5 %w/w of salt in the water phase. In addition, two high-shear mixers were used to manufacture w1/o emulsions. PGPR stabilised w1/o emulsion processed with Silverson as well as SE O-170 and AMP stabilised w1/o emulsion processed with Ultra-Turrax T25 were stable to droplet coalescence and flocculation for at least 7 days. These w1/o emulsions were then incorporated as droplets into a 0.5 %w/w salt containing external aqueous phase with in-situ gelatinised native waxy rice starch (WRS) to form the double emulsion structure by using a high shear mixer with a high energy input (Method I) or low energy input (Method II).

The effects of different lipophilic emulsifiers and emulsification methods on the microstructure, storage stability and salt encapsulation of w1/o/w2 emulsions were studied, and also both static and dynamic in-vitro oral digestion assays were carried out to investigate the salt release behaviour over w1/o/w2 emulsion. The results indicated that Method II processed w1/o/w2 emulsion containing 0.15 – 0.6 g of PGPR or 0.6 g of SE O-170 were suitable vehicles for long-time salt encapsulation, showing high salt encapsulation efficiency values all above 27%. Although an effective salt release was observed in all these double emulsions during amylase-mediated in-vitro digestion, the maximum salt release efficacy of SE O-170 based w1/o/w2 emulsion reached 13%, 1.5 - 3.5% lower than that of PGPR based w1/o/w2 emulsion.

It was found that both PGPR and SE O-170 molecules can be co-adsorbed at the water-oil interface with WRS molecules, however, the interaction between SE O-170 molecules and WRS molecules at the interface was stronger than that between PGPR molecules and WRS molecules. Investigations lead to the hypothesis that the interaction between WRS molecules and SE O-170 molecules at interfaces inhibit the hydrolysis of WRS molecules during in-vitro oral digestion and thus slow the destabilisation of external interface of w1/o/w2 emulsion, which deserves further research.

Item Type: Thesis (University of Nottingham only) (PhD)
Supervisors: Gould, Joanne
Wolf, Bettina
Keywords: Water-in-oil-in-water, w/o/w, Emulsion, Salt
Subjects: T Technology > TP Chemical technology > TP 368 Food processing and manufacture
Faculties/Schools: UK Campuses > Faculty of Science > School of Biosciences
Item ID: 65984
Depositing User: Zhang, Liling
Date Deposited: 31 Dec 2021 04:40
Last Modified: 31 Dec 2023 04:30

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