The Hydrophilic cream reologic features and stability investigation

The paper aims to investigate reologic features and stability of hydrophilic cream. Hydrophilic cream is the object of the paper. Goals of the paper are the following: determine the type of cream emulsion and the pH value; evaluate the size of emulsion droplets and kinematic viscosity of cream produced extemporally and industrially; evaluate stirring speed and time influence on cream viscosity and the size of emulsion droplets; investigate and evaluate cream stability; investigate influence of the pH value on reologic features of cream. Cream emulsion type has been defined by the methods of colour test and electric conductivity. Cream produced extemporally and industrially, the influence of mixing speed and time on the size of emulsion droplets were measured by electronic microscope, while kinematic viscosity was estimated by viscosimeter. Cream stability was measured by differential centrifugation method. Influence of the pH value on reologic features of cream and its stability was measured by viscosimeter and gravimetric method. The results of colour test and electric conductivity have revealed that cream belongs to the group of hydro-creams, a/v type emulsions, which results in the process of product production using two opposite types of emulsifiers (tenzides) - trolamine stearate (a/v) and glycerol monostearate (v/a). The pH value of cream was equal to 8, which shows that cream is basal. The research has revealed that cream production method influences the size of emulsion droplets and viscosity. The size and viscosity of cream particles produced extemporally are significantly different from test parameters of cream produced industrially. It confirms that production method affects cream quality. The measurement of the size of particles has shown that stirring time affects the amount of emulsion droplets in cream: the stirring speed of 7000 rpm, but different stirring time, i.e. 19 min., 21 min., 25 min. and 27 min., has shown that the smallest average size of cream particle is 21 minutes while stirring. The analysis of cream stability, which was carried out by differential centrifugation method, has revealed that the product is the most stable after stirring it for 21 minutes within a speed of 7000 rpm. Interestingly, microscopic test has identified the size of the smallest emulsion droplet in cream produced by this method. It shows that cream stability can be evaluated not only by the measurements of the size of emulsion droplets, but also by differential centrifugation test. The research has revealed that the pH value affects cream stability and viscosity. If the pH value is changed from 8 to 5, cream will change its consistence. Gravimetric stability results, which were obtained within 96 hours, showed that due to reduction of the pH value, the stability of lactic acid decreased by 20% and hydrochloric acid declined 49%. It shows that reduction of the pH value is not advisable