Conformational changes of polymers in model batter systems

Cake batters are complex systems with their higher content in sugar and fat in compare to other baking products. The interactions between the ingredients affect the structure of the end product. The objective of this work is to understand the protein-lipid-starch interactions and their impact on protein and starch conformational changes. A model system approach was used by mixing flour, pregelatinized wheat starch (PWS), eggs, sugar and fat in the same ratios as in the real cake batter. Protein secondary structure and starch conformational changes were determined by the ATR-FTIR spectroscopy. The FTIR spectra showed that the addition of the fat to flour increased the alpha-helical structures (from 16% to 35% of total) and decreased the beta-sheet structures (from 49% to 22% of total). This could be related to the decrease of the interactions among hydrophilic molecules by fat addition. While the eggs addition increased the beta-sheets (56%) at the expense of unordered structures due to eggs proteins-gluten interaction. When fat and eggs were added together, the fat effect on protein conformation was more pronounced decreasing the beta-sheet structures to 38%. The beta-sheet structures slightly increased when 20% of flour was replaced by the PWS. Whereas the effect of the PWS was more important on starch structures. The intensity ratios of the crystalline starch bands at 1047cm-1 and 1035 cm-1 were 0.91±0.02 and 0.84±0.02 for flour and flour+PWS mixtures respectively. The decrease in crystallinity could be due to the interaction between water and the pregelatinized starch which promoted more amorphous structure. This study revealed the important impact of batter ingredient interactions and the effect of using the PWS on proteins and starch structures which could be the key factor to enhance the cake quality.