Salt: Essentially Salt
June 01, 2009
by Donna Berry
Dietary sodium and salt are hot buttons these days, because excessive intake has been shown to raise blood pressure, which in turn increases the risk of heart disease and stroke. The irony is that sodium is a mineral essential to life. The body cannot manufacture it; thus, the only way humans obtain sodium is through dietary sources.
Sodium and salt are different substances. The chemical name for table salt is sodium chloride (NaCl), indicating that sodium, which has the chemical designation of Na, is a component of table salt.
Consumers do not typically realize that sodium is critical for many bodily functions. Further, they don’t understand that sodium is a necessary component of many food formulations, because it makes food more palatable and impacts production and product quality. This is particularly true of baked foods.
“Grains are often quite bland in taste, so the addition of salt provides flavor interest,” said Linda Kragt, technical services manager, Morton Salt, Chicago, IL. “Breads without salt are often described as ‘flat’ or ‘insipid.’ In whole grains, salt can help mask bitter tastes. In sweet baked foods, salt helps to modify an overly sweet taste. Additionally, salt imparts flavor balance to these products.”
Salt is harvested from the sea, salt lakes, natural brines and underground deposits. Salt processors use three basic processes to obtain salt, which, combined with one of many refining methods, results in salt ingredients with varied degrees of solubility and purity.
The three basic processes are: 1 — solar evaporation of saline sea water and natural brines; 2 — direct mining of underground rock salt deposits and 3 — refined openpan and vacuum crystallization of saturated brine.
The vacuum method is the most commonly employed process to manufacture food-grade salt ingredients, because it yields the highest purity and cleanest salt.
“Salt impurities may contribute toward differences in flavor,” said Janice Johnson, PhD, salt applications leader, Cargill Salt, Minneapolis, MN. “The purer the salt, the less impact there is on the anticipated flavor profile.”
In recent years, sea salt harvested using solar evaporation techniques has become quite popular in the food industry. In fact, sea salt has become a specialty food category of its own, with a limitless number of options.
Sea salt is a broad term that generally refers to unrefined salt derived directly from a living ocean or sea. It is typically harvested through the channeling of water into large clay trays, where the sun and wind evaporate the water naturally. Location and harvest conditions impact the salt’s shape, size, color and composition. Some of the most common sources for sea salt include the Mediterranean Sea, the North Sea and the Atlantic Ocean, particularly in France, on the coast of Brittany.
Chefs and food formulators are intrigued by sea salt’s unique properties. Bakers, too, are learning to appreciate and distinguish between the distinctive qualities of the many varieties of sea salt and how these salts enhance the flavor and finish of foods.
Sea salt is highly unrefined — no chemical treatments are employed and no processing aids added. It contains many other minerals in addition to sodium and chloride, including calcium, iron, magnesium, manganese and zinc. These minerals lower the sodium content of the salt, as well as contribute their own unique flavor sensations.
In applications where sea salt’s coarser texture is retained such as a topping on artisan bread, the sea salt provides mouthfeel in terms of crunch as well as changes in flavor because of the different rate of dissolution. Topical sea salt can also provide visual stimulation because it comes in a variety of hues in addition to standard white. For example, Himalayan sea salt is pink in color, while Hawaiian alaea is red. There are even dark sea salts that have been naturally smoked over real wood fires to infuse the salt crystals with natural smoke flavor.
Some suppliers are infusing sea salts with natural flavors. Such salts add another dimension to baked foods. For example, a sea salt infused with aged balsamic flavor can top off a gourmet bagel while vanilla bean-infused sea salt adds zest to shortbread.
A MUST IN BREAD.
Whereas topically applied sea salts are an option for most baked food applications, standard salt in an essential ingredient in some products, particularly yeast-leavened items such as bread.
“Salt impacts a number of factors in the production of yeastraised bakery products,” Dr. Johnson said. “In addition to its beneficial effect on flavor, salt has been shown to help control yeast activity and strengthen gluten. It also affects the water activity of a finished product, which relates to product quality and microbial activity.”
During the fermentation step of breadmaking, salt has a stabilizing effect. When salt is omitted from the dough or not added in sufficient quantity, excessive yeast activity results in gassy, low-pH dough and baked products with open grain and poor texture.
“Salt inhibits the action of the yeast and decreases gas production. This effect appears to be the result of increased osmotic pressure and action of sodium and chloride ions on the yeast cell membrane,” said Brian Strouts, head of research and technical services, AIB International, Manhattan, KS. “Adjusting the salt level in a dough gives the baker a tool to regulate the production rate of carbon dioxide gas and the other byproducts of fermentation. This is especially useful as bakery temperatures fluctuate during seasonal changes.”
Ms. Kragt added, “With higher ambient temperatures in the summer, doughs can over-proof. Salt helps to control the yeast activity, which reduces this condition.”
Dough processing methods, such as the commonly used sponge-anddough or straight-dough methods react differently to adjustments in salt level. “The effect of salt on yeast activity can be observed through increased proofing times as salt addition is increased,” Mr. Strouts said. “There is also some indication that the greatest increase in proofing times occurs when the salt level is 1.5 to 2.1%, on a flour basis. The sponge dough process shows greater sensitivity to this increased salt addition, with its proofing time increasing 33.3% compared with 20.9% for the straight-dough method when salt was increased from 0% to 2.1%.”
The dough-strengthening effect of salt is attributed to its interaction with flour proteins. “Flour gluten protein has a net positive charge in a dough system at normal pH (about 6.0). These positive charges repel each other, preventing the protein chains from interacting. The result is a weaker dough and one that gives lower baked-loaf volume,” Mr. Strouts said. “When low levels of salt are added to the dough system, the salt shields the charges, thereby allowing the protein chains to hydrate more slowly,interact and form bonds. This results in a stronger dough with improved loaf volume and more desirable quality characteristics.
“As the level of salt addition is increased to 1to 1.7%, loaf volume increases slightly. At higher levels of addition, loaf volume remains fairly steady or decreases slightly, depending on the dough process used,” he added. “The best quality bread, as characterized by break-and-shred and crumb-grain scores, is produced when 1% or more salt is used in either the sponge-and-dough or the straight-dough process.”
For non-yeast leavened bakery products, the main use of salt is as a flavoring agent. “Salt may have some limited impact on gluten strength for products such as cracker or pie dough, and salt may also influence moisture retention,” Mr. Strouts said.
All of these effects can be influenced by grade and form selection.
THE RIGHT GRADE AND FORM.
Salt comes direct from Mother Nature. Technology allows ample grades and forms to choose from.
“The salt crystal’s shape and size affects its ability to dissolve, which can dramatically impact its various functionalities in baked foods,” Dr. Johnson said. “In general, crystals that are smaller and/or have more surface area dissolve quicker. In topical applications, this may translate into a quick hit or “pop” in salty taste during the eating experience.”
Vacuum granulated salt, the predominant grade of food-grade salt, exhibits a concentric or cubic crystal form. This cubic crystal structure can be modified by incorporating additives during crystallization or by alterations in the crystallization process. For example, the addition of a trace of sodium ferrocyanide, also called yellow prussiate of soda, to the brine during vacuum crystallization modifies the crystal by creating pores. Referred to as a dendritic crystal, this cubic crystal is marked by highly irregular surfaces. Because of its expanded surface area and lower density, it dissolves faster than standard vacuum granulated salt.
Vacuum granulated salts can undergo a grinding process and be turned into “flour” salt. These jagged fragments of cubes have a very high surface area and rapid rate of dissolution. Vacuum granulated salts can be compacted, which results in “flaked” salt. These rectangular, crystalline aggregates have a flat, smooth surface. They range from coarse to fine flake form.
Grainer grade, and its closely related Alberger grade of salt, is produced by an alteration of the vacuum crystallization process. A corrugated, pyramid-shape aggregate forms, which blends well with other ingredients and has a relatively rapid rate of dissolution. “The Alberger crystals have unique shapes originating from pyramid-shaped salt crystals, which dissolve quickly,” Dr. Johnson said. “This shape allows the salt crystal to stick to the product and absorb more liquids such as oil. Such a salt works very well on top of snack crackers.”
Rock salt varieties are crystalline in structure and extremely hard. They exhibit stress planes that fracture in milling to expose smooth surfaces and a particle that tends to be orthorhombic in shape. Rock salts are among the slowest dissolving salts and tend to be used mostly as a topping. With more than 30 food-grade salts from which to choose, it is important for bakers to understand their options, choosing the appropriate grade for the specific baking process. The time-honored adage“penny wise, pound foolish” often applies to proper grade selection, where subtle improvements in baking quality or processing efficiency could well justify paying an additional one or two cents per pound for salt.
“For a dough salt, common granulated salt is often adequate. Because the addition of salt increases mixing time, some bakers add salt late in the mixing process,” Ms. Kragt said. “If this ‘hold back addition’ method of adding salt is employed, a finer salt such as dendritic salt or fine granulated is recommended because it dissolves faster. If salt is not thoroughly dispersed in the dough, a number of defects can result such as uneven grain or misshapen loaves.
“For most crackers, the salt is applied prior to baking. A flake salt is often used to promote adhesion,” she continued. “Medium and coarse flake grades are preferred to prevent premature dissolution on the surface of the dough, which can result in brown spots or blisters. It is also important the salt exhibit a consistent bulk density since volumetric feeders are often used to dispense the salt onto the dough. Inconsistent bulk density can result in a variable salt level on the surface of the dough.”
When producing baked snack chips, adhesion can be an issue. “For baked chips, a fine salt such as a flour salt is recommended for adequate adherence,” Ms. Kragt said.
Mr. Strouts added, “Salt added to an egg wash amplifies the shine on the final product.”
Salt also perks up the flavor profile of the many varieties of cremes, fillings, icings and spreadable toppings used by bakers. Grade selection depends on method of preparation. For example, if the icing or filling is prepared relatively dilute and concentrated by boiling, there is sufficient moisture and time to dissolve dendritic salt. However, if a low-moisture preparation is mixed directly without the subsequent boiling step, salt should be extremely fine, using at least a flour grade. Fortunately, most bakers purchase such fillings in a ready-to-use format.
Salt is essential to the body and essential to baking. Selecting the best salt for a specific application might help keep usage levels low, which appeals to today’s sodiumdiscerning consumer.