A Fluorescence-based Method for Estimation of Oxygen Barrier Properties of Microspheres

Oxidative stability and oxygen permeability of oil-loaded capsules produced by spray-drying or electrospraying measured by electron spin resonance

The oxidative stability and the oxygen permeability of oil-loaded capsules were investigated by Electron Spin Resonance (ESR). The capsules were produced by spray-drying or electrospraying in the monoaxial or coaxial configuration using glucose syrup as the encapsulating agent. ESR-spin trapping results showed that electrosprayed capsules oxidized faster and during the early stages of incubation, irrespective of the emitter configuration (monoaxial or coaxial), when compared to those produced by spray-drying. Furthermore, ESR oximetry showed that oxygen inside the spray-dried capsules reached equilibrium with the surrounding atmosphere significantly slower than the monoaxially electrosprayed capsules (i.e., ∼2h and ∼10 min, respectively). These findings have been attributed to the larger particle size of the spray-dried capsules influencing the oxygen diffusion area (i.e., lower surface-to-volume ratio) and diffusion path (i.e., thicker encapsulating wall for a fixed oil load). Together, the lower oxygen uptake reported for the spray-dried capsules correlated well with their higher oxidative stability.

Development of chitosan based microencapsulated spray dried powder of tuna fish oil: oil load impact and oxidative stability

The impact of fish oil concentration on the oxidative stability of microcapsules through the spray drying process using chitosan and maltodextrin as wall material was studied. Emulsions were prepared with different Tuna fish oil (TFO) content (TFO-10%, TFO20%, TF030% TF0-40%) while wall material concentration was kept constant. Microencapsulated powder resulting from emulsion prepared with high fish oil load have high moisture content, wettability, total oil and low encapsulation efficiency, hygroscopicity and bulk tapped density. Oxidative stability was evaluated periodically by placing microcapsules at room temperature. Microcapsules prepared with TFO-10% presented high oxidative stability in terms of peroxide value (2.94±0.04) and anisidine value (1.54±0.02) after 30 days of storage. It was concluded that optimal amounts of fish oil for microencapsulation are 10% and 20% using chitosan and maltodextrin that extended its shelf life during study period.

Impact of the oil load on the oxidation of microencapsulated oil powders

The effect of the oil load on the oxidation of microencapsulated fish oil powders was investigated. The oil load was varied between 4.95 and 20.33%(w/w) by spray drying O/W emulsions with different oil to matrix ratios (0.05, 0.1, 0.15 and 0.2(w/w)), whereas solid content (45%(w/w)) and soy protein isolate to oil ratio (0.15(w/w)) were kept constant. A standardized size fraction of particles (50-80 µm) was stored for 82 days and hydroperoxides and anisidine value measured in the total- and encapsulated oil. Oxidation was limited by the oxygen amount rather than by the oil load. The absolute amount of oxidation products (per powder mass) increased with the oil load, which was explained by oxygen diffusion. Calculating oxidation products per oil mass resulted in a faster oxidation of the powder with 5% oil, whereas the oxidation rate for oil loads ≥10%(w/w) was similar, due to a scavenging effect of oil droplets.