Lactylates are organic compounds that are FDA approved for use as food additives and cosmetic ingredients, e.g. as food-grade emulsifiers. These additives are non-toxic, biodegradable, and typically manufactured using biorenewable feedstocks. Owing to their safety and versatile functionality, lactylates are used in a wide variety of food and non-food applications. In the United States, the Food Chemicals Codex specifies the labeling requirements for food ingredients including lactylates. In the European Union, lactylates must be labelled in accordance with the requirements of the applicable EU regulation. Lactylates may be labelled as calcium stearoyl lactylate (CSL), sodium stearoyl lactylate (SSL), or lactylic esters of fatty acids (LEFA).
CSL, SSL, and food-grade LEFAs are used in a variety of products including baked goods and mixes, pancakes, waffles, cereals, pastas, instant rice, liquid shortenings, egg whites, whipped toppings, icings, fillings, puddings, toppings, frozen desserts, creamers, cream liqueurs, sugar confectionaries, dehydrated fruits and vegetables, dehydrated potatoes, snack dips, chewing gum, dietetic foods, minced and diced canned meats, mostarda di frutta, sauces, gravies, and pet food. In addition, these lactylates are FDA approved for use in food packaging, such as paper, paperboard, and cellophane, and pharmaceuticals. Lactylates are also used in a variety of personal care products including shampoos, skin conditioners, lotions, barrier creams, makeup bases, lipsticks, deodorants, and shaving creams. In addition, lactylates are bio-friendly additives for use in polyolefins, flame retardants, pigments, and PVC.
History Lactylates were developed in the 1950s by the C.J. Patterson Company as non-petrochemical alternatives to Sta-Soft, a polyoxyethylene derivative of stearic acid, for delaying the staling of bread. The research into the development of lactylates led to the first lactylate patent application, filed in 1951, and two issued patents in 1956 and 1957. These patents included lab-scale manufacture and applications of several lactylates, including CSL and SSL. In 1954, the inventors published an article showing that CSL improved mix tolerance, bread volume and overall quality. CSL won FDA approval for use as a food additive in April 1961 and was first used as a commercial bakery additive in the United States in 1962. The research was acknowledged as a major achievement in the baking industry, winning the Food Technology Industrial Achievement Award in 1965. SSL use as a bakery additive followed in 1968.
Manufacturing
The original lab-scale preparation of lactylates involved esterification of lactic acid or poly(lactic acid) with an acid chloride derivative of the desired fatty acid. Current manufacturing practices were patented in January 1956 and combine fatty acids (e.g. naturally derived stearic acid) and lactic acid at elevated temperatures. For CSL and SSL, the stearic acid component is typically produced from vegetable oils such as soybean oil or palm oil.
Lactic acid is primarily produced by lactic acid fermentation of sugar with lactic acid bacteria (similar to the bacteria used to produce yogurt). The sugar can be sucrose, fructose, or glucose obtained from corn, sugar beet or sugar cane. Because the lactic acid is derived from plant sources and not from milk or milk products, it does not contain any residual lactose. Therefore, people who are lactose intolerant can consume lactylates without concern.
Lactylates, in the free acid form, are not readily water dispersable. To improve the water dispersibility and emulsification properties, the carboxylic acids comprising lactylates can be neutralized using hydroxides or carbonates of group 1 or group 2 metals such as sodium or calcium.
At room temperature, lactylates can be viscous liquids or solids depending on the starting fatty acid, the total recoverable lactic acid content, and the degree of neutralization. Solid lactylates are often processed into powders. The traditional method is to solidify the liquid into a flake and grind the resulting flake into a powder. Newer methods utilize spray congealing to directly form beads.
The manufacturing process of lactylates is an esterification reaction. The water coproduct is removed by evaporation to drive the reaction towards the desired product composition in accordance with Le Chatelier's principle. Water removal is accomplished either by sparging with a constant stream of dry nitrogen or by vacuum outgassing with the use of a vacuum pump system. Using nitrogen sparging or vacuum outgassing also protects the reaction mixture from undesirable oxidation processes.
The manufacturing process does not produce chemically pure lactylates (e.g. stearoyl-2-lactylate) for two reasons. First, the source fatty acid is not chemically pure since it is typically derived from natural sources. The source fatty acid may contain varying ratios of different fatty acids (e.g. lauric acid (C12:0), myristic acid (C14:0), palmitic acid (C16:0), stearic acid (C18:0), arachidic acid (C20:0), behenic acid (C22:0), etc.). Second, lactic acid readily undergoes self-esterification producing a variety of polylactyls (typically numbering from one to three lactyl groups).
Chemically pure lactylates (e.g. stearoyl-1-lactylate, stearoyl-2-lactylate, etc.) can be produced through an intermediate benzyl ether derivative. This synthetic pathway provides a convenient route to the production of analytical standards of the individual lactylate components.
Functionality
Overview
Due to differences in physical properties, oil does not readily mix with water. Many food and non-food systems require stabilization of mixtures of oil and water in order to prevent phase separation. Therefore, additives are used to provide stability. Lactylates are such additives.
Lactylates are surface active and are therefore surfactants. Lactylates contain hydrophilic polar groups, which interact with water, and non-polar lipophilic groups, which interact with fats and oils. These interactions provide stability to an oil/water system resulting in the formation of an emulsion. Therefore, lactylates are often referred to as emulsifiers. The degree of interaction is dependent on the identity of the fatty acid, the mole ratio of fatty acid to lactic acid, the degree of neutralization and the nature of the neutralizing base (if applicable) used in the manufacture of the lactylate.
As described in the next two sections, applications of lactylates extend beyond their use as surfactants in both food and non-food systems. Such applications include strengthening dough, delaying bread staling, enhancing foam, and preventing microbial growth.
Food applications The largest food application of lactylates is in the manufacture of baked goods such as yeast-leavened bakery products. In these systems, lactylates are added to strengthen dough and delay bread staling (i.e. soften the crumb). Dough in commercial bakeries requires some resistance to mechanical abuse and shock to maintain desirable volume in the finished baked good. Dough strengtheners interact with the protein components (e.g. gluten) in the dough. The interactions reinforce the protein network, preventing collapse of the loaf during baking. These additives ensure each loaf of bread conforms to the visual and textural quality expectations of the manufacturer and consumer. Crumb softeners are added to bread to reduce or delay staling of the finished baked good. Bread staling occurs when the starch components form hard crystals. Crumb softeners complex with the starch components, preventing or delaying the formation of starch crystals. Lactylate enriched bread will remain fresh for up to five days after baking. Bread prepared without lactylates begins to stale within one to three days after production.
In other food applications, lactylates are used as emulsifiers. For example, lactylates are used in non-dairy creamers to help disperse the fat-based creamer throughout the hot beverage. The lactylate stabilizes (i.e. prevents separation of) the oil-in-water emulsion. Another use of lactylates is as whipping agents. In these applications, the lactylate helps aeration of the continuous phase (e.g. egg whites) and stabilization (prevention of collapse) of the resulting foams. In these systems, lactylates are added to decrease the interfacial tension between the mutually insoluble components providing stability to the mixture, referred to as a colloidal suspension.
Non-food applications Lactylates are also widely used in non-food applications such as cosmetics or personal care products. In these applications, lactylates function as emulsifiers, conditioners, foam boosters, or plasticizers. These lactylates are typically manufactured from behenic acid, isostearic acid, or medium-chain fatty acids such as capric acid, lauric acid, and myristic acid. The lactylates may also be partially neutralized. For these applications, calcium salts are not typically used, since the resulting lactylates will not be as readily water dispersible as the sodium analog.
Lactylated esters of fatty acids (LEFAs) manufactured using medium-chain fatty acids (e.g. capric or lauric acids) are microbicides. A recent study indicated that the LEFA sodium lauroyl lactylate might be an effective antimicrobial against the gram-positive bacterium Clostridium perfringens. This bacterium affects the digestive system of poultry, reducing the growth rate of the chickens thereby requiring more time to reach maturity. Antibiotics are often added to poultry feed to help prevent infection and maintain healthy growth. EU legislation banned use of antibiotics for growth promotion on January 1, 2006. Therefore, the industry is looking for viable alternatives.
Some lactylates also have the potential for being biodegradable, biorenewable replacements for certain petroleum-based surfactants, such as ethoxylated alcohols. Preliminary investigations also show that lactylates could be used in oil remediation or recovery applications.
Environmental fate
A 2007 study done by Wildlife International, Ltd. determined a lactylate's ready biodegradability by the carbon dioxide evolution test method. The study was performed on a LEFA sodium salt produced from oleic acid and lactic acid. The test method determines if microbes, in this case activated sludge inoculum, can digest a test material, thereby returning the carbon-based material back into the environment as carbon dioxide to complete the carbon cycle. To meet or exceed the OECD Guideline 301B criteria for "readily biodegradable", a sample must produce 60% of the theoretical amount of carbon dioxide (TCO2) within a 10-day window of reaching 10% TCO2. The LEFA used in the study had a final average cumulative percent biodegradation of 92.0% and the test solution had a pH of 7.1 at the end of the 28-day test. Therefore, the test material met the criteria to be considered readily biodegradable. In the presence of water, lactylates will break down (hydrolyze) into fatty acid and lactic acid. Based on all available information, lactylates do not meet any hazard categories under SARA Title III, Sections 311–313.
Health and safety
Overview