PubMed · 4382343
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M J Groves, D C Freshwater. 1967. Polyhedral emulsion particles.. https://doi.org/10.1111/j.2042-7158.1967.tb08066.x
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The functional properties of flours and protein isolates from the legumes Phaseolus lunatus and Canavalia ensiformis were evaluated to determine their potential practical applications. The respective protein isolates were obtained from the flours by using isoelectric precipitation, with a protein content of 71.13% for the P. lunatus isolate (PPI) and 73.75% for the C. ensiformis isolate (CPI). Nitrogen solubility was good in both acid and alkaline pHs for isolates and Canavalia flour (CF), with values as high as 80%, but not for the Phaseolus flour (PF). The flours and protein isolates had good water-holding capacities, with values between 2.65 and 3.80 g/g sample. Oil-holding capacity was highest in PPI (4.59 g/g sample) and CF (3.15 g/g sample). Under alkaline pH, the PPI foaming capacity (147%) was higher than those for CPI and CF, though the flours produced greater foam. Emulsifying activities for the PF, CF, PPI, and CPI were similar (46.78-53.84%) for pH range 6-10. Emulsion stability (ES) was superior in the CF and the CPI, where values reached 100% at pH 7 and 8. Apparent viscosity was pH-dependent.
Emulsification is a complex process, strongly influenced by emulsion composition as well as by preparation procedure, and the characterisation of emulsions with regard to their structure and stability can be carried out with many different methods. To evaluate the influences of emulsion composition and preparation procedure on the structure and properties, oil-in-water emulsions were prepared using the model dispersed phase dodecane and the surfactant Tween on the one hand and the real food components sunflower oil (dispersed phase) and casein (emulsifier) on the other hand. The emulsions were prepared in a small laboratory-scale with a turbo-mixer alone and in combination with ultrasonic treatment. The emulsion activity was measured by photometry, the emulsion stability was evaluated visually and the droplet size was determined by laser particle analysis. The results of the investigations made with the model substances agree only partly with those made with the real food substances. For the model emulsions strong correlation were found between the emulsion activity and the particle sizer data because of the high purity and the defined structure of the model substances. On the contrary, for the emulsions made with the real food components sunflower oil and sodium caseinate the correlation were much weaker. Therefore a proper characterisation of the structure and properties of food emulsions requires examinations with several methods which are independent from each other. Furthermore, for laboratory-scale emulsification the combination of turbo-mixer and ultrasonic treatment is suitable to obtain small droplets and a narrow droplet distribution also for very small emulsion volumes.
Total-intensity light scattering (TILS) and photon correlation spectroscopy (PCS) techniques have been used to determine the droplet size of concentrated, oil-in-water microemulsions formed from soybean oil, polyoxyethylene-10-oleyl ether (C(18:1)E(10)), and water, both in the presence and absence of the lipophilic drug, testosterone enanthate. The TILS data were analyzed using the hard-sphere model of Percus-Yevick to account for interparticulate interactions experienced in the concentrated systems studied and the volume fraction of the hard-sphere droplet obtained from these analyses used to correct the PCS data. Correction of the light-scattering data in this manner yielded a satisfactory agreement between the size of the microemulsion droplets calculated using both techniques. Both the TILS and PCS data showed that, for a constant surfactant concentration, the size of the microemulsion droplets increased with increasing oil content. For example, droplets of radius 52.5 and 65.1 A (as determined by TILS) were obtained at 10.0% w/w C(18:1)E(10) and 0.5 and 2.0% w/w soybean oil, respectively. In contrast, for a constant oil concentration, microemulsion droplet size decreased with increasing surfactant concentration. For example, droplet sizes of 65.1, 59.3, 56.6, 54.5, and 53.3 A were seen with 2.0% w/w soybean oil and 10, 14.0, 18, 22, or 26% w/w C(18:1)E(10), respectively. Furthermore, in the presence of 1.0% w/w of the lipophilic drug, testosterone enanthate, the size of the microemulsion droplet increased by about 6-10 A depending on the concentration of the surfactant; the higher the concentration of the surfactant, the smaller the increase in size. The slight increase in size of the drug-containing microemulsion droplets suggests that some of the drug has penetrated into the core of the droplet.