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Impact of Sugar Reduction on the rheological properties of wheat doughs
Sugar has always been a commonly used ingredient in the bakery industry for taste enhancement. However, high-sugar diets have been associated with obesity, inflammation, high triglyceride and high blood pressure levels — all risk factors for heart disease. According to the WHO (World Health Organization), limiting intake of free sugars to less than 10% of total energy intake is part of a healthy diet. A further reduction to less than 5% of total energy intake is suggested for additional health benefits.
Cereal products such as pastries or biscuits are one of the main sources of sugar intake. In addition to its effects on health, sugar has recognized impacts on dough rheological properties. Effects that the cereal sector needs to anticipate in order to adapt formulations and/or processes. The objective of this study is to evaluate the impact of sugar reduction on the overall quality of the dough.
MATERIALS AND METHODS
Two wheat flours with different rheological properties (weak and strong flours) were used to evaluate the impact of sugar reduction.
Samples were analyzed using the Mixolab (“Chopin+” protocol AACC 54-60.01) (Figure 1 and Table 1) to simulate the mixing and baking stages. They were also analyzed with the Rheofermentometer F4 (CHOPIN protocol) (Figure 2 and Table 2) to obtain the proofing characteristics.
The flours have been tested alone as references, and with several dosages of classical food sugar : 5%, 2.5%, 1%, and 0% (The percentages of introduction are calculated according to the flour weight). Tests were done at constant dough weight.
RESULTS AND DISCUSSION
The Mixolab results show that sugar reduction has a strong impact on mixing behavior. Reducing sugar content leads to an increase in the amount of water required to reach the same consistency (Table 3) and also impacts the stability of the dough made with the weak flour (Figure 3).
Industrial mixing will need to be adjusted to process doughs with lower sugar content.
The high temperature phase of the Mixolab highlights the fact that sugar reduction causes the gelatinization of starch to appear earlier (Figure 4). In fact, the required temperature to enter the gelatinization phase decreases. This can be explained by the change in colligative properties related to sugar content – more sugar results in a boiling point elevation phenomenon, thus the temperature has to be higher to impart a similar thermal energy to the starch. The weakening of the hot formed starch gel is also more intense without sugar (69,5% increase on the C3-C4 value for the weak flour) (Figure 5).
This indicates that formulation and/or processes must be adapted in the case of the weak flour to compensate for the loss of sugar.
The RheoF4 shows that sugar reduction allows the dough to develop faster (Maximum height is reached 51 min faster in average with 0% sugar instead of 5%) (Figure 6). It can be related to the fact that sugar decreases the activity of the water and increases the osmotic pressure. This results in the release of water from the yeasts. As a consequence, a decrease in yeast activity can be observed. Nevertheless, final development height is lower when reducing sugar content (Figure 7). Industries need to adapt their proofing process when reducing sugar content.
This study shows that all the properties of the tested doughs are impacted by sugar reduction. The intensity of the effects can vary according to the type of flour and the incorporation dose. The Mixolab allows evaluation of the impact of sugar reduction on dough properties through mixing and temperature changes and the RheoF4 on the proofing properties. They are complementary tools which can be used to evaluate the impact of sugar reduction on the overall rheological behavior of doughs.Further studies will be needed to evaluate the impact of sugar reduction on complete formulas (including fat, eggs, …)