Data on the physical characterization of oil in water emulsions

This article contains experimental data and images for the physical characterization of oil in water emulsions. Mentioned data are related to the research article “Effect of stabilizers, oil level and structure on the growth of Zygosaccharomyces bailii and on physical stability of model systems simulating acid sauces” (A.L. Zalazar, M.F. Gliemmo, C.A. Campos, 2016) [1]. Physical characterization of emulsions was performed through the evaluation of Span and Specific Surface Area (SSA) determined by light scattering using a Mastersizer. Furthermore, microscopy images were recorded by confocal scanning laser microscopy (CSLM). The latter are presented to collaborate in the analysis of emulsion microstructure.


Value of the data
Span and SSA data provide further information on the distribution of droplet size of emulsions. Span gives information on the polydispersity of the sample and SSA is associated with emulsion stability. Both parameters are useful to evaluate stabilizers action on emulsion stability.
CSLM provides information about the size, concentration and organization of the droplets in an emulsion.
For studying emulsions, microscopy provides more visual and direct information than other techniques-e.g. light scattering, nuclear magnetic resonance, and conductivity methods. In the case of CSLM, simple sample preparation with minimal alterations of the environmental conditions makes it very suitable to study phase stability.
The data can be useful for other researchers investigating the effects of stabilizers, oil level on physical stability of emulsions.

Data
The data reported include information about the physical stability of oil in water emulsions with different compositions (Table 1) through the estimation of Span and Specific Surface Area (Table 2) and the recorder of confocal scanning laser microscopy images (Fig. 1).

Experimental design, materials and methods
Oil in water emulsions were prepared using a high speed homogenization and their composition is given in Table 1. Emulsion preparation was described in the research article [1].

Span and Specific Surface Area
Span and SSA of emulsions was determined by light scattering using a Mastersizer 2000 with a Hydro 2000 MU as dispersion unit (Malvern Instruments, Worcestershire, United Kingdom). A refractive index of 1.473 for the corn oil phase and its absorption parameter (0.001) was used. Determinations were made after 24 h of emulsification and after 7 days of storage. Span is a measure of polydispersity of oil droplets and is defined as: being d 01 , d 05 and d 09 the fractions of droplets with diameters smaller than 0.1, 0.5 and 0.9, respectively [2,3]. The SSA expresses the ratio between the total area of the droplets and their total weight. It Table 2 Span and Specific Surface Area (m 2 /g) of inoculated and non-inoculated emulsions after one day and seven days of storage at 25°C.

System
Span 7 standard deviations can be estimated as: where ϕ is the volumetric fraction and D 32 is Sauter diameter. Data reported were the mean of ten determinations made on two different emulsions of identical composition. Some emulsions were inoculated with Zygosaccharomyces bailii. Results obtained are shown in Table 2.

Confocal scanning laser microscopy
The microstructure of the emulsions was evaluated by placing aliquots of 10 μL emulsion (without prior dilution) on a slide. The coverslips (22 Â 22 mm) -without sliding-were carefully placed to not induce coalescence of the oil droplets. Then, emulsions were observed with a laser confocal microscope (Model FV 300, Olympus, UK), equipped with a He-Ne laser (543 nm). A PLAN APO 60X objective and 2.5X digital zoom was used. Digital images in TIFF format were purchased in 1024 Â 1024 pixel resolution. The lipid phase was labeled with Nile blue (aqueous solution 0.1% p/v, λ exc ¼ 635 nm) [4,5]. Some of the images obtained are shown in Fig. 1.