| Abstract [eng] |
Double W/O/W emulsions are considered to have great application potential due to their structural features. One possibility of using these emulsions in food manufactoring is creation of low fat foods by replacing part of the fat with water phase but maintaining the usual properties and texture of the product. Due to the high volume of water phases and the two interfaces, the double emulsion lose its physical and chemical stability more quickly. Therefore, the purpose of this work was to determine the effect of the composition of the double emulsions on their physical and chemical stability. The research objects were W/O /W, where the fat phase was sunflower oil or milk or fish fats. Also we changed the nature and concentrations of interface forming substances. It has been found that the most stable emulsions are produced when primary W/O emulsions are homogenized for 5 minutes, and the double ones for 3 minutes. The best phase ratio has been found to be W/O (40:60) and W/O/W (60:40). What concerns the emulsifier used in the experiments, the best stability was shown by the emulsions which had 0,6 % of polyglycerol polyricinoleate (PGPR) in their oil phase and 0,2 % and 0,3 % of carboxymethyl cellulose (CMC) in their outer phase. The results of the inter-phase rheological study showed that interfacial film with the best rheological properties is formed by polyglycerol polyricinoleate (PGPR), an emulsifier of lipophilic nature, at a concentration of 6 %. After examining the influence of fat on the chemical stability of double emulsions, it has been found that emulsions with oil and fish fats maintained the lowest chemical stability because of their fatty acids, that contain 65-90 % of unsaturated fatty acids composition. The chemical stability of emulsions has also been influenced by the storage temperature and fat emulsification, which causes the early oxidation processes. Having simulated the digestion of double emulsions in vitro conditions, it has been determined that fat hydrolysis is most quickly accomplished in emulsions containing milk fat, i.e. at the end of digestion the greatest amount of free fat acids has been released from the sample. It has been caused by milk fats which are present in the emulsion and which contain ~70 % of short chain fatty acids digested most quickly and most easily. |
