Throughout the shelflife of a food, transformations occur which impact flavor. Over time, organic material changes through a number of processes. In most products, flavor starts to decline, and off-flavors develop due to oxidation. In addition to oxidation, other changes such as crystallization can affect quality. Flavor also can be degraded by exposure to light or be lost during packaging, through heat processing or evaporation. Shifts in pH and ingredient reactions are also contributing factors in flavor decline.
To preserve the flavor of a product, formulators must consider regulations, customer requirements, application, cost, sensory properties, health aspects (i.e., sodium vs. potassium) and potential for ingredient interactions.
“Our approach is to identify consumer insights for their favorite flavors and formats. With each new project, a team of product developers, process and packaging engineers, flavorists, analytical chemists, and sensory and regulatory scientists bring their expertise to the table. We apply known solutions to new challenges or come up with new methods to resolve issues,” offers Barbara Raphael, Ph.D., executive vice president of Cadbury Schweppes Americas Confectionery.
“Cadbury Schweppes surveyed consumers and found that 66% of Americans surveyed wanted a longer lasting chewing gum,” Raphael states. “We have made significant investments in long-lasting flavor technology which was introduced in Stride®, the Ridiculously Long Lasting Gum®.” According to Raphael, Stride was introduced last year and quickly became one of the most successful gum launches in U.S. history.
The company’s strategy starts with using premium materials, such as high-quality flavor oils, specially formulated to remove components that contribute to oxidation of flavors. Antioxidants, encapsulation and packaging also are used to protect flavor where required. Fat, pH, moisture and other product attributes need to be considered and balanced. “For example, fat may affect texture in addition to increasing oxidative stability challenges. Hygroscopic materials can pick up moisture, which can also accelerate deterioration,” adds Raphael.
Physical and Chemical ConsiderationsUnderstanding the chemical reactions that take place during processing and storage is crucial to preventing flavor degradation.
A main consideration in choosing flavor stabilizers is the final target pH, explains Barbara Heidolph, marketing development manager for a popular phosphate supplier. Once the desired pH is determined, ingredients are selected based on their buffering capacity and the amount of pH adjustment needed. (See chart “Titration of Orthophosphoric Acid with Sodium Hydroxide.”)
Fat Content“Food products that contain fat have high risk for off-flavor development during storage,” adds Heidolph. “Fat composition of a food product can affect the flavor preservation approach. For example, the amount and source of fat can affect the stability of a beverage and the performance of the flavor system. When certain fats like fish oil-derived additives or dairy fat are present in a product, oxidative stability of the fat is a serious consideration,” explains Greg Mondro, senior flavor chemist at a supplier of flavor systems. “Flavor of the fat or oil significantly affects flavor stability and perception of the overall product.”
“Fat oxidation can be catalyzed by the presence of metal ions, especially iron. Phosphates can be used to sequester iron and stabilize fat, to reduce off-flavor from rancidity,” contributes Heidolph. “Phosphates and acidulants such as phosphoric acid act as synergists with most antioxidants like butylated hydroxy anisole (BHA),” she adds. Phosphates interact with metal ions such as copper and iron. Acidic salts like sodium or potassium phosphates and acidulants help create a reducing environment of hydrogen ions, which aids in regeneration of antioxidants.
Sausages, for example, are formulated to contain significant levels of fat. Phosphates are used to bind metal ions, especially iron, to slow the rate of rancidity development. Fat is a consideration in other foods as well. Whole-grain baked goods contain higher levels of fat than white bread and, therefore, have shorter shelflives. Fried foods like French fries have off-flavors if the frying fat has deteriorated.
Moisture“Moisture is the bane of stability. Packaging is particularly helpful with keeping moisture out of our products. Moisture is very rigidly controlled, as its presence speeds oxidation and promotes ingredient and product degradation,” mentions Raphael.
Most of the time, low water activity helps keep the product more stable. “Freeze drying is one way to achieve low water activity. This provides an unfavorable environment for microbial and enzymatic degradation, ultimately giving a better shelflife and more wholesome product,” Rayburn adds.
Ingredient InteractionsIngredient interaction is always a consideration. An ingredient used for pH and buffering may also interact with cations like calcium or magnesium. If hydrocolloids are present in a system, interaction with calcium may negatively change the texture of the product.
“When using benzoates and ascorbic acid together in a beverage, benzenes can be formed. Benzene is a non-polar solvent and a powerful carcinogen. However, the FDA has not concluded the studies on this. Even when it does occur, it is found in lower levels than in most drinking waters,” explains Mondro.
Reactions can also be caused by low pH. “The lower the pH, the more challenging to have a stable flavor system,” explains Rayburn. The problem here is that many products rely on a lower pH to optimize the antimicrobial properties of chemical preservatives.
Browning flavor of baked goods is also pH-related. At higher pH levels, greater reaction occurs between sugars and protein. “The more browning, the more flavor associated with the Maillard reaction. The reverse is also true: by maintaining a low pH, the sugar-protein reaction can be inhibited, thereby reducing flavor development,” explains Heidolph.
“High-intensity sweeteners or blends of sweeteners should also be considered. Aspartame, for example, degrades in low-pH systems. Sweetness, cooling and salt are all used to enhance flavors. Additionally, taste potentiators such as nucleotides can generally enhance flavor. These materials are often used in the savory snack industry, but they can be effective in confections as well,” states Raphael.
Common Ingredients that Combat Flavor LossThe food industry has at its disposal an array of ingredients that can be employed to prevent or hinder the chemical reactions leading to flavor loss.
BHA is a popular antioxidant used in citrus and other flavor oils. However, consumer desire for organic or all-natural claims can limit its use.
BHA is prepared from 4-methoxyphenol and isobutylene. Oxygen would preferentially react with it before oxidizing the food product in question, and anti-viral properties are currently being studied. The downside is that there have been carcinogenic effects in animal trials, and it cannot be used in organic or all-natural products.
Citrus-flavored beverages, especially cloudy beverages, have issues with oxidation of the terpenes used in these flavor systems. Also, acid hydrolysis of certain components (citral in lemon and lime flavors is a classic example) degrades these flavors in acidic beverages.
“Of course, consumers have come to accept these off-notes as a normal part of the profile,” contributes Scott Rayburn, beverage applications manager for a popular flavor provider. High levels of sugars, especially reducing sugars such as high-fructose corn syrup, can cause off-color and cooked notes as the sugars age. Use of sucrose increases costs but abates the browning reactions.
Tocopherols and purified rosemary extracts also are used to prevent oxidation and can be more desirable for clean labeling. “Sulfur dioxide is used as an antioxidant and antimicrobial in wines. Sulfur dioxide (usually added in its salt form, sodium metabisulfite) is a preservative for wine and some fruit and fruit juice. It has a powerful flavor in small amounts, but it has become a part of the accepted profile of wine,” contributes Rayburn. There are other less flavorful preservatives to be used in most other food products.
The use of chelating agents such as ethylenediamine tetracetic acid (EDTA) is another method to preserve flavor. This chemical binds metal ions that can be used as building blocks by bacteria or catalyze off-color and flavor changes.
Acidifiers and BuffersAcids generally provide tartness or enhance flavor. Phosphoric acid, for example, is commonly used in cola beverages. Organic acids have their own specific pH/buffering zone as well as their own flavor profile. In some applications, their flavor profile might be ideal for the product. Citric acid may contribute just the citrus note needed for an orange-flavored beverage or dessert. Lactic acid is likewise associated with fermented dairy products such as yogurt.
“All things being equal,” Rayburn states, “an orange-flavored beverage will taste better using citric acid rather than, say, phosphoric acid.” Citric acid enhances citrus-flavored products, just as tartaric acid enhances grape-flavored products. While malic acid tastes great in apple-flavored beverages, its cost is sometimes prohibitive. “Additionally, the varying solubilities of acids can be leveraged to create acid blends that offer both up-front and long-lasting tartness,” includes Raphael.
In general, the pH of a product impacts how it tastes. Acidulants and acid salts are known to affect the rate of evaporation of various volatile ingredients, thus controlling the aroma and flavor of a food.
BuffersPhosphates help maintain flavor via two primary mechanisms: sequestration and pH control/buffering. Buffers and alkalinity adjusters like trisodium phosphate (TSP) and tripotassium phosphate (TKP) raise the pH of fat-containing products. A higher pH helps maintain the emulsion and stabilizes the fat in the system, preventing rancidity or “soapy-type” flavor issues.
“In high-acid products such as Fruit-A-Burst chewing gum and Halls Defense Vitamin C® throat drops, buffer systems help protect flavor and maintain tartness. Otherwise, the acidity can cause chemical changes such as sugar inversion, which can negatively affect texture and appearance. BHT and tocopherols are also used to act as antioxidants that help protect freshness,” Raphael explains.
“The phosphate salts are excellent buffering agents, especially the ortho salts. Depending on the target pH, one or a combination of salts, either sodium or potassium (MSP, MKP, DSP, DKP, TSP and/or TKP) can be used,” states Heidolph. “As phosphate chain length gets longer, the buffering capacity is reduced. Therefore, ortho is better than pyro, which is better than tripoly,” she adds.
LabelingEven after the chemical properties of ingredients are understood and solutions to flavor degradation have been identified, food manufacturers must still consider labeling implications and requirements.
Labeling should be handled on a case-by-case basis, taking into account the ingredient, the end product and its use. FDA regulations are not always specific for changing technologies and uses of generally recognized as safe (GRAS) food ingredients. “There are some very specific uses allowed for some ingredients and broader ranges for others. Regulatory specialists have become a requirement in the food industry to deal with details involved in correct labeling. In short, each ingredient should be checked for permitted use rates in the food item it is used in, as well as any pertinent regulations for the labeling of said item,” advises Rayburn.
A cross-functional team is crucial to determine the best approach for taste preservation over a product’s shelflife. In the end, it is all about coming up with great-tasting products that consumers love, using safe and suitable ingredients, packaging, processing and labeling.
Showcase: Antioxidants, Acidifiers & Buffers for ShelflifeResearch shows a new flavor modifier extends shelflife of fresh, frozen, pre-cooked and further processed meats, plus masks off-notes in meat applications—including those containing soy. Wix-Fresh™ Max from Wixon also preserves the flavor intensity of spice notes and reduces warmed-over flavor in meats. When added directly to breading systems in deep-fried applications, it helps to reduce rancidity associated with frying oils while enhancing overall flavor. Wixon, Ron Ratz, 800-841-5304, Ron Ratz@Wixon.com, www.Wixon.com
An oil-soluble formulation based on rosemary extracts that fight oxidation in fresh and chilled patés has recently been introduced. SyneROX 4, by Vitiva of Slovenia, helps maintain the original flavor, color and taste of the paté and its microbiological stability, extending the product’s shelflife considerably. The easily blendable formulation is allergen and GMO-free and is available from P.L. Thomas in the U.S., Canada and Mexico. P.L. Thomas, Paula Nürnberger, 973-984-0900, firstname.lastname@example.org
Dried plums, powders and juice concentrates provide a natural defense against enemies of food shelflife. Dried plums are naturally rich in fiber and high in sorbitol to bind and maintain moisture in meat and bakery products. Dried plums’ acidic profile, particularly malic acid, and an exceptionally high antioxidant content fend off the ravages of bacteria and oxygen. California Dried Plum Board, Richard Peterson, email@example.com, www.californiadriedplums.org
Microencapsulation technology enables manufacturers to fortify foods and beverages with vitamins, minerals and other nutrients without compromising food flavor and aroma. LycoRed’s microencapsulation process solves the issue of taste, texture and ingredient cross-interactions by microencapsulating the fortification ingredients and then combining them in a ready-to-use premix. Microencapsulation protects ingredients from oxidation, increases stability and shelflife and reduces hygroscopicity. An added cost benefit of LycoRed microencapsulated ingredients is decreased overages, and the ready-to-use premixes cut costs by simplifying the path of manufacture. LycoRed Corp., William Redwood, 201-247-5875, firstname.lastname@example.org, www.lycored.com
A new, innovative ingredient made from 10 different fruits and vegetables helps give food products a distinctive place in the market. Nutrifood® Complex, developed by GNT, is all-natural and antioxidant-rich. Use in beverages, smoothies, bakery inclusions, cereal bars, confections, ice cream, yogurt and other food systems as a means of adding the health benefits and functionality of antioxidants from fresh, high-quality fruits and vegetables. GNT USA Inc., Jeanette Quinn, 914-524-0600, www.gntusa.com