Preparation of cold gel emulsion system using isolated soy protein- Basil seed gum complex as a fat replacement in cream

Fats have a special place in human nutrition and their main role is supplying energy for the body. But scientific findings approve an association between high fat intake and an increment risk of some diseases, such as atherosclerosis, heart disease, and …. Demand for low-fat foods has increased dramatically as people become more aware of fat consumption side effects. However, due to the multiple role of fats in food products, eliminating or decreasing fat lead to poor quality of products. Therefore, it is necessary to use a combination of fat substitutes to maintain the rheological, texture and sensory properties of the low fat food products. The use of emulsion gel structures are new methods for the production of low-fat product that has been studied in this investigation. The Pickering emulsion was used to produce the emulsion. In this method, instead of using surface-active agents, solid particles are used to stabilize the emulsion. The aim of this study was to prepare Pickering Emulsion from Isolated Soybean protein (ISP) and Basil Seed Gum (ISP-BSG) Complex. Finally, emulsion gel systems were applied as fat substitutes in cream.

Basil seeds were purchased from Mashhad market. Isolated soy protein was purchased from Shandong Yuxin Bio-Tech Co. (China). Sodium azide was purchased from Applichem Inc. (Dramstadt, Germany). Sodium dodecyl sulphate (SDS) was obtained from Merck, Germany.  Pickering (solid particles) of soy protein isolate (SPI) and SPI-basil seed gum (ISP-BSG) complex used as emulsifier for stabilization of cold emulsion. ISP-BSG particles were prepared with different mass ratios of ISP: BSG, 1: 0, 1: 1, 2: 1 and 3: 1 and named 1S: 0B, 1S: 1B, 2S: 1B and 3S: 1B, respectively. These solid particles were used as Pickering for emulsion preparation. Cold Emulsion was prepared by adding calcium chloride. The oil leakage, oil leakage after thermal treatments, microscopic structure, textural properties and viscoelastic properties of emulsion gel were studied. Then, the best structures used as a fat substitute in cream (5, 10 and 15%).

Investigation of emulsion gel properties showed that coating the surface of emulsion droplets with solid nanoparticles formed a rigid shell that acted as a barrier against the deformation and transfer of materials from the interfacial surface. The use of ISP-BSG nanoparticles as picking particles caused more homogeneity and stiffness in emulsion gel structure. The rate of water loss in reduced fat cream was in the range of 1-2% by using the emulsion-gel system, which indicates the effectiveness of these systems in reducing dehydration in cream. The increasing replacement percentages led to increase water loss (p <0.05). However, emulsion type had no significant effect on water loss content (p> 0.05). According to the results, ISP-BSG nanoparticles impart high potential to stabilize emulsion with small oil droplets. Based on the results of the sensory test, it was found that the characteristics of the cream samples depended more on the replacement rate than the type of system used as an alternative. The presence of a fat replacement system maintained the desired quality in low-fat cream samples. Most of the samples scored higher than 3, which indicate the high acceptance of low-fat samples.