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How humectants aid in increasing the shelf life of foods by lowering microbial activity
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Friday, 16 July, 2021, 12 : 00 PM [IST]
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Norina Fernandes
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A humectant is a substance used primarily in foods and cosmetic products to help retain moisture. These substances are called hygroscopic, which means that they are able to absorb ambient water. Some such additives are beneficial when consumed or used. Others, particularly in some foods, are less helpful, may cause abdominal distress, and should probably be avoided.
Features of Humectant
Food additive - Humectant is excellent in water retention. It can manage pH levels by retaining a subtle amount of moisture in the food item. Cooking and processing of meats, seafood, or poultry items must use this additive. Also, it retains the natural minerals and protein levels of your food. The best part of this agent is it does not shrink in the pan and maintains solubility. This can work wonders for processed and packaged seafood items.
Salt and sugar stand as the oldest natural humectant for most of the food ingredients. Other alternatives used include glycerol, sorbitol, and propylene glycol.
Food additives refer to any mixing agent added in a very small amount. It helps to enhance the flavor, texture, and color of any food item. It helps in improving the safety of any food item by restricting microorganisms' growth in it. The shelf life of most food product increases after controlling oxidation levels
Humectants lower the water activity (aw) of a product because water preferentially binds to them. Each humectant has its own unique ability to lower water activity depending on its chemical makeup. As a general rule, the lower the molecular weight of the humectant, the more powerful its water binding capacity. For example, a simple sugar like sucrose is more effective than a starch, whose interlocked glucose molecules limit available water-binding sites. For this reason, fiber, gums, and waxes are not effective humectants.
When choosing a humectant, it’s important to consider unintended effects. For instance, when protein is present in a cookie dough, if you lower the water activity to 0.7 using a reducing sugar, you enter the ideal range for Maillard browning reactions. The lowered water activity keeps the dough microbially safe, but the product turns brown after only a few hours.
Humectants can also introduce undesirable flavors into a product. Glycerin is an advantageous humectant because it’s flavourless except at high concentrations. It’s also completely miscible in water and won’t precipitate out in solid form when a product’s water activity changes. Salt or sugar can be problematic because, in addition to adding flavor, they form solids if the concentration reaches the saturation point in the product. To address these different challenges, many manufacturers use a combination.
A common humectant in food products is sorbitol. This is a sugar alcohol derived from sugar. It is used in dietetic or sugarless foods and is lower in calories than sugar, so it is a popular choice among those who are dieting. In doses larger than 1.76 ounces, it has a laxative effect and can cause diarrhea. In the 1990s, consumer advocates successfully lobbied to have product warnings placed on foods containing sorbitol, so people could keep their consumption below harmful levels.
Glycerol can be found in foods, but is also sometimes specifically prescribed by doctors for constipation, so again cautious consumption is advised. Perhaps the most beneficial aspect of glycerol is not as a humectant but in the manufacture of biodiesel. With current shortages in oil and rising gasoline prices, many have turned to fuel alternatives like biodiesel, and it is predicted that many more will do so.
Polydextrose is another humectant food additive used to replace sugar. It is not only found in sweet foods, but frequently in other foods like salad dressings. This particular substance not only replaces sugar in some foods, but can also be used as a fat or starch replacement. It has a laxative effect as well, so reading the labels of one’s food can inform selection.
Certain humectant substances can be added to plants at the root level to assist the plant in gathering more ambient moisture. Many gardeners favor this as a way to conserve water. A humectant composed of several oils is also used in embalming fluids. They are said to restore moisture and produce a more life-like appearance for those who will be viewed in open caskets.
Traditional Intermediate Moisture(IMF) Foods are processed by the withdrawal of water, by adsorption or desorption, and/or by the addition of conventional humectants, such as salt (sodium chloride) and sugar (sucrose). Although some traditional IMF, such as dried fruits, are simply dried to the desired water activity, most IMF are prepared by a combination of drying with added humectants. Bakery products are prepared by adding water and other ingredients to low-aw cereals, followed by various processing and heating procedures to yield aw in the range of IMF.
Novel IMF are often processed by using humectants, such as glycerol, propylene glycol, and sorbitol, for aw adjustment. Combinations of several humectants, each at lower concentrations, are often used to reduce off-flavor problems. IMF processed by adsorption normally have slower microbial growth and lipid oxidation due to a lower moisture content than IMF prepared by desorption with identical aw.
Foods that need to be kept moist risk potential bacterial growth. Moisture in food affects microbial activity, physical and sensory properties and possible chemical changes. Moisture in food can be controlled by removing it through dehydration or chemically binding it with humectants. Humectants control moisture changes caused by humidity fluctuations in processing, transit and storage on the shelf.
Dry cereal with raisins, candy with liquid centers, cheese, coconut, marshmallows and baked goods are a few examples of foods that rely on humectants. Humectants also are used in military and space technology to allow foods such as meat to be stored without refrigeration for longer periods of time. Sugar and salt are the oldest and most widely used humectants. Examples of other commonly used humectants include glycerin, honey, sugar alcohols, glucose syrup, egg yolk, egg white, molasses and alpha hydroxy acids such as lactic acid.
Humectants are direct food additives that must be approved before use by US Food and Drug Administration. Assessment of a food substance includes an evaluation of its safety and functionality, including all studies on its stability, purity, potency, performance and usefulness. Humectants continue to be active areas of research and development in an effort to discover safe, natural alternatives and emerging technologies that can offer additional benefits to our food supply and the planet.
Humectants are used in very small amounts to safeguard the food supply and maintain quality during shelf life. Extensive research and testing have deemed these additives safe in approved amounts.
(The author is senior quality assurance executive (F&B) at Cafe Coffee Day Global, Mumbai. She can be contacted at norinafernz1004@gmail.com)
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