Effect of the order of incorporation of cake ingredients on the formation of batter and the final properties: contribution of the addition of pea flour.

The investigation dealt with the effect of the replacement of a part of wheat flour by pea flour on the properties of batters and cakes. As the protein composition of pea flour differs from that of wheat, the effect of its incorporation on batter formation and cake properties was monitored throughout the different steps of cake processing. The incorporation of air, which influences the cell structure and density of the cake, was the subject of particular attention. Four orders of incorporation were first investigated to identify their effects on a standard recipe made with 100% wheat flour. Mixing first egg and sugar together allows introducing air, but most of it is lost after oil and flour introduction. Whatever the order of incorporation, the density of the batter ends around 1.1 ± 0.2 g.cm-1. However, batter consistencies are significantly different and resulting cakes show different crumb structures. These results are discussed in terms of physicochemical mechanisms, and a schematic representation of the phenomena occurring at the different steps of mixing depending on the order of ingredient incorporation is proposed. When 20 and 40% of the wheat flour was replaced by pea flour using the two most energy-efficient orders of incorporation, more air was incorporated into the batter. However, the resulting cakes were denser, but surprisingly softer. Differences in cell structure explain this apparent contradiction.

In vitro digestion of short-dough biscuits enriched in proteins and/or fibres using a multi-compartmental and dynamic system (2): Protein and starch hydrolyses.

The influence of protein and/or fibre enrichment on the nutritional properties of biscuits was studied in terms of proteolysis and amylolysis. Biscuits were digested using a multi-compartmental and dynamic system that simulates the main physiological digestive functions of the upper tract of healthy adult humans: the TIM-1. A control biscuit and three biscuits enriched in proteins and/or fibres were digested under the same conditions. Samples were collected in each compartment of the TIM-1 (stomach, duodenum, jejunum and ileum) at different times of digestion and analysed in terms of proteolysis and amylolysis. Results indicate that both formulation and processing impacted the digestive fate of the biscuits. Incorporating proteins or fibres in biscuits lowered or delayed proteolysis. Moreover a protein-plus-fibre additional or synergic effect was observed. Biscuits enriched in proteins and/or fibres displayed a higher amylolysis degree than the control biscuit, probably due to lower starch amounts and higher gelatinization degrees.

In vitro digestion of short-dough biscuits enriched in proteins and/or fibres, using a multi-compartmental and dynamic system (1): viscosity measurement and prediction.

The effects of biscuit composition on the viscosity generated during digestion were investigated. A control biscuit, one with proteins, one with fibres, and one with both proteins and fibres were digested under the same conditions, using the TNO intestinal model (TIM-1). The TIM-1 is a multi-compartmental and dynamic in vitro system, simulating digestion in the upper tract (stomach and small intestine) of healthy adult humans. Digesta were collected at different times, in the different compartments of the TIM-1 (stomach, duodenum, jejunum and ileum) and viscosity was measured with a dynamic rheometer. Results showed a marked effect of biscuit composition on chyme viscosity. Highest viscosity was obtained with biscuits containing viscous soluble fibres, followed by those enriched in both proteins and fibres, then by protein-enriched and control biscuits. The viscosity was maintained throughout the gut up to the ileal compartment. A prediction of the evolution of the chyme viscosity in each compartment of the TIM-1 was built, based on model curves describing the evolution of the viscosity as a function of biscuit concentration, and on dilution factors measured by spectrophotometry on a blank digestion.