Effects of oil-droplet diameter on the stability of squalene oil in spray-dried powder

Factors determining the surface oil concentration of encapsulated lipid particles: impact of the emulsion oil droplet size

Microencapsulation of oxidation sensitive oils aims to separate lipids from the environmental oxygen by embedding oil droplets in a solid matrix, which builds a physical barrier. Some oil droplets are not fully incorporated and are in contact with the powder surface generating surface oil. It is proposed that the probability of oil droplets being in contact with the particle surface increases with the oil droplet size. The aim of the study is to investigate the impact of the oil droplet size on the encapsulation efficiency (EE). Two sets of feed emulsions differing in the applied homogenization pressure and in the protein to oil ratio were spray dried using a pilot plant spray dryer. The oil droplet size of the emulsion was determined by static light scattering (SLS). In addition, nuclear magnetic resonance (NMR) was used to measure the d3,2 of oil droplets in the emulsion and in the powder before and after surface oil removal. Encapsulates were analyzed regarding aw, moisture content, particle size, oil load and EE. The oil droplet size in the emulsion decreased with increasing protein to oil ratio as well as with the homogenization pressure. Large oil droplets and in particular droplet clusters resulted in more non-encapsulated oil. The experimentally determined EE was in accordance with the theoretical one, calculated based on the droplet and particle diameter. For emulsions with a diameter > 1 µm, the d3,2 decreased in the powder and further by removing the surface oil, which was related to the deformation of oil droplets contributing to the non-encapsulated oil.

Effect of different dextrose equivalents of maltodextrin on oxidation stability in encapsulated fish oil by spray drying

Encapsulating fish oil by spray drying with an adequate wall material was investigated to determine if stable powders containing emulsified fish-oil-droplets can be formed. In particular, the dextrose equivalent (DE) of maltodextrin (MD) affects the powder structure, surface-oil ratio, and oxidative stability of fish oil. The carrier solution was prepared using MD with different DEs (DE = 11, 19, and 25) and sodium caseinate as the wall material and the emulsifier, respectively. The percentage of microcapsules having a vacuole was 73, 39, and 38% for MD with DE = 11, 19, and 25, respectively. Peroxide values (PVs) were measured for the microcapsules incubated at 60 °C. The microcapsules prepared with MD of DE = 25 and 19 had lower PVs than those prepared with MD of DE = 11. The difference in PV can be ascribed to the difference in the surface-oil ratio of the spray-dried microcapsules.

Advanced characterisation of encapsulated lipid powders regarding microstructure by time domain-nuclear magnetic resonance

Encapsulation is an established technique to protect sensitive materials from environmental stress. In order to understand the physical protection mechanism against oxidation, knowledge about the powder microstructure is required. Time domain-nuclear magnetic resonance (TD-NMR) has the potential to determine the surface oil (SO) and droplet size distribution by relaxation and restricted self-diffusion, respectively. The amount of SO, the retention and encapsulation efficiency are determined based on a lipid balance. The oil load of the initial powder and after SO removal is measured by TD-NMR. The results correlate with gravimetric and photometric references. The oil droplet size obtained by TD-NMR correlates well with static light scattering. The diameter of droplets in emulsions and dried powder both measured by TD-NMR, correlates (r = 0.998), implying that oil droplets embedded in a solid matrix can be measured. Summarising, TD-NMR allows analysis of the microstructure of encapsulated lipid powders, in a rapid, simple and non-destructive way.

Effect of oil droplet size on the oxidative stability of spray-dried flaxseed oil powders

The effect of the size of oil droplets on the oxidative stability of flaxseed oil in spray-dried powders was investigated. Maltodextrin with a dextrose equivalent of 25 was used as a wall material, and sodium caseinate and transglutaminase-polymerized sodium caseinate were used as emulsifiers. The oxidative stability of flaxseed oil encapsulated in the spray-dried powders was evaluated using lipid oxidation and conductometric determination tests at 105 °C. The powders containing larger oil droplets exhibited higher surface oil content after spray drying, and higher peroxide value and conductivity after storage at 105 °C. Removal of the surface oil from the powders by washing with hexane significantly decreased the conductivity. The results indicated that the surface oil of the spray-dried flaxseed oil powders affected the oxidation stability.