Technical Talk: November 2012
October 25, 2012
By Dr. John Michaelides
The debate about the benefits of sodium reduction in our diets rages on.
The debate about the benefits of sodium reduction in our diets rages on. Last year, the Cochrane review of sodium and health concluded that there is not enough evidence to prove that a reduction in sodium consumption lowers our risk of cardiovascular disease. This report was quickly disputed by other scientific reviews and the American Heart Association stated that they are still recommending lowering sodium intake in our diets. The topic is still controversial, but the majority of scientific evidence indicates that reduction of sodium in our diets is a wise choice.
The main source of sodium in our diets comes from salt. Common salt, or sodium chloride (NaCl), contains 39 per cent sodium. Since salt is widely used in food processing, it is a substantial contributor of sodium in our diet, especially in developed countries where a lot of processed foods are consumed. Salt plays several important roles in food processing. It provides flavour and texture. It is a microbial preservative and a processing aid.
Replacing salt’s taste and flavour may be partially achieved with alternatives, but it is hard to find adequate substitutes for its other functional roles. Salt is an inexpensive ingredient, so any replacement adds costs to the product. Furthermore, a reduced-salt product to which consumers add salt at the table would not be beneficial for anyone, so it is imperative that salt-reduced products meet the sensory expectations of consumers.
Salt also plays a very important role in the formulation of baked goods. It is considered one of the major ingredients in bread baking, along with flour, water and yeast. Salt affects the taste in baked goods, not with its taste alone, but by enhancing the other flavours. In fact, at the level that is normally being used in the formulation of baked goods, it does not impart a very salty taste. Baking without salt results in bland bread with no characteristic taste. Salt not only enhances other flavours but also increases sweetness and masks metallic, bitter and other undesirable tastes. For this reason, it is also used in sweet baked goods formulations.
Salt helps control and stabilize yeast fermentation in dough. Salt will prevent over-fermentation, which causes dough to have excessive gas and sourness and will leave finished baked goods with undesirable open grain and poor texture. Salt in yeast lowers gas production rate, and therefore results in longer proof times for a good-quality baked good. The effect of salt on the yeast cells is caused by changes in osmotic pressure and a possible direct impact on cell membranes. This is the effect salt has on other microbes as well, which is why it acts as a preservative. Salt is an effective tool in controlling the action of the yeast and gas formation, especially where temperatures cannot be easily controlled in small bakeries.
Salt affects the proteins in food. The wheat gluten protein, which is the fundamental component of the baking process (especially for the yeast-raised products), is also affected by the presence of salt in the formulation of baked goods. The salt content in the formula dramatically influences the hydration of gluten, as well as its development and strength. The hydration of flour is achieved at a slower rate when there are low levels of salt in the formulation. This is because salt shields the overall positive charges in gluten, reducing repulsion and allowing the proteins to come in closer contact. This causes a slower hydration rate of the flour, and therefore an increase in the mixing time is required to develop the dough. This is of important consequence because longer mixing time will result in slower rate of production in large bakeries, which increases energy consumption and slows outputs. This problem can be corrected by adding salt at a later stage in the process when the dough no longer sticks to the side of the mixer. In addition, salt may reverse the loss of elasticity in dough that has been over-mixed and lost this characteristic. Common salt is known to increase dough strength at its normal level of addition (1.5 to two per cent) in bread formulations. Addition of salt above these levels does not improve the loaf volume of bread. Moreover, salts other than sodium chloride could have a detrimental effect on the loaf volume and other characteristics of the bread.
Salt has a critical effect on both hydrophobic (water repelling) interactions and hydrogen-bonding properties of the gluten proteins, thus affecting the rheology (the study of flow of matter, measured by viscosity, strength and hardness) and the overall development of the dough. Different salts (other than sodium chloride) have different effects on the proteins and some may be suitable as replacements in baked goods. However, the effect they will have on the dough and the yeast is dependent on the type of ions they contain, and this can be a challenge in replacing the common salt.
More research needs to be carried out in understanding what effect alternative salts and their ions (other than sodium) will have on gluten proteins and other important components of the wheat flour. Such efforts will enable us to successfully reduce sodium in baked goods, especially yeast-leavened products.
For more information, or fee-for-service help, please contact Dr. John Michaelides at John Michaelides & Associates at 519-743-8956, or at Bioenterprise at 519-821-2960 at ext. 226, or by e-mail at firstname.lastname@example.org.
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