A comparison of two methods to produce soy protein-lipid films

The formation of soy protein-lipid film was studied with natural soymilk and model systems in attempts to optimize processing and yield by the traditional method and soy protein isolate method. Under optimum conditions, the system gave a film protein incorporation efficiency of over 80 percent based on the total protein in solution. Dispersion included 2 percent dispersible protein and 5 percent fat which emulsify and bind the protein-lipid complex to enhance yield. Associated protein of heavy particle weight, long aliphatic chain lipids, and a mixture of polar lipids favored the protein-lipid association and facilitated the film formation.

The isolate soy protein was prepared by isoelectric precipitation and then centrifuged 20 minutes at 796 G. The sediment was neutralized and was dried for one hour at 100°C. The yield of film was 36 percent compared to a yield of 30 percent by the traditional method, This film contains more protein and less fat than traditional film.

The finished film product by the traditional method and isolate method could be used as a food ingredient directly, or further fabricated into a textured food with enriched protein (52 percent protein in dry-basis in traditional film and 53.6 percent in isolate soy protein film). These two processing methods may be extended to many other protein and oilseed resources, such as cottonseed and peanut.