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Comparison of the performance of thermally treated wheat flour during test baking low and high ratio cake formulations
Heat treatment alters the functional properties of wheat flour and hence its performance in baking applications. This work evaluates the effects of heat treatment on the functionality of wheat flour in two cake matrixes termed high- and low- ratio cake formulations.
MATERIALS AND METHODS
• Sample preparation: Commercial wheat flour called T65 [moisture content, 13.5%; protein content, 12.9% (dm)] were subjected to heat at different temperatures, 110, 120 and 130°C for 15 min using a continuous thermal processing unit manufactured by REVTECH process systems (Loriol-sur-Drôme. France). The resulted products were thereafter assessed for their rheological properties and their performances were assessed by test baking low and high ratio cake formulations.
• Moisture and protein content were determined using the Near Infrared System Infraneo®.
• Mixing and pasting behaviors were assessed according to the Chopin+ protocol using the Mixolab® (AACCI Method 54-60.01). Derived parameters such as water absorption capacity, protein weakening (C2), viscosity peak (C3), amylase activity (C4) and starch retrogradation (C5) were determined.
• Solvent retention capacity profiles were assessed using the new SRC-CHOPIN®. Derived parameters such as Water (Wa), Sucrose (Su), Lactic Acid (LA) and Sodium Carbonate (SC) Solvent Retention Capacity (SRC) were determined.
• Baking tests. Low- (sugar to flour ratio of 1.0) and high- (sugar to flour ratio of 1.5) ratio cake tests were carried out at REVTECH process systems, Loriol-sur-Drôme, France. The resulted cakes were characterized based on their specific volume and shape.
RESULTS AND DISCUSSION
1. Mixing and pasting properties
The Mixolab curves of untreated wheat flour and thermally treated samples are shown in Figure 1. Heat treatment induced an increase of the Mixolab C2 parameter, the dough viscosity peak (C3) and the Mixolab C5 parameter. C2, C3 and C5 increased from 0.48, 1.99 and 2.77 Nm for untreated wheat flour to 0.62, 2.15 and 2.75 Nm for thermally treated sample at 130°C, respectively, These results suggested that heat treatment caused a denaturation of the gluten network as well as partial gelatinization of starch granules, in agreement with the findings of Mann et al. (2013) who observed an agglomeration of the gluten network after dry heat of wheat flour (50-90°C) for a duration up to 3h.
2. Solvent Retention Capacity Profiles
The solvent retention capacity profiles of untreated wheat flour and thermally treated samples are shown in Figure 2. As expected, heat treatment induced an increase of all SRC-CHOPIN derived parameters, except for LASRC.
WaSRC, SuSRC and SCSRC increased from 62.7, 98.0 and 76.0 percent for untreated wheat flour to 81.4, 114.9 and 92.9 percent for thermally treated sample at 130°C, respectively, while LASRC decreased from 120.0 percent to 113.2 percent. The decrease observed with the LASRC was in agreement with the rise of the Mixolab C2 reading, suggesting restricted swelling ability of the gluten network.
3. Low- and high- ratio cake test baking
Low- and high- ratio cake tests baking have been conducted on untreated wheat flour and thermally treated samples. The appearance of cakes is shown in Figure 3. Test baking high- ratio cake formulations showed an improvement in baking performance as the resultant cakes gave larger volume than the control flour at optimal heat-treatment (120°C, 15 min). Cakes specific volume increased from 0.63 L for untreated wheat flour to 0.65 L for thermally treated sample at 120°C. On the contrary, the thermal treatment induced a decrease of the cake quality attributes in low-ratio cake recipe. Cakes specific volume decreased from 1.48 to 1.41 L. Similar findings were reported in the literature by Chesterton et al. (2015). According to their study, an increase of cake volume from 526 cm3 for untreated wheat flour to 538.8 and 566 cm3 for lab scale heat treated flour and commercially heat treated flour was noticed during test baking high ratio cake formulation.
Pictures of cakes showed differences in shape and crust colour formation between both formulations. High ratio cakes displayed lower cake height and were darker than those prepared from low ratio formulation. In addition, when looking at the maximum scars opening, all low ratio cakes showed almost centered scars while only heat treated flour at 120°C showed noticeable centered scar in case of high ratio cakes.
Cross-section images of cakes revealed differences in internal crumb texture and structure. Slices of low ratio cakes presented finer crumb texture and homogenous open cells structure whereas those from high ratio cakes showed the presence of uncooked areas and more compacted structure.
Heat treatment affected all flour components. It resulted in the formation of proteins aggregates as well as partial gelatinization of starch. Test baking high- ratio cake formulation performed using thermally treated wheat flours showed slight increase in cake volume at optimal heat treatment, while significant decrease in the volume was noticeable when test baking low- ratio cake formulation. Internal crumb texture and structure were also affected. Cross section pictures showed the presence of finer texture and homogenous open cells structure for low ratio cakes while partially uncooked areas and more compacted structure were observed for high ratio cakes.