Amino Acids for Flavor Enhancers

Flavor enhancers have a wide range of applications in the food industry, covering processed foods, snacks, beverages, meat products, low-sodium foods, and more. They not only enhance the umami, sweetness, and saltiness of food but also improve texture and depth, meeting consumers' dual demands for both delicious and healthy products. Amino acids are the basic building blocks of proteins and play important physiological roles in the human body. In addition to their basic biological functions, amino acids have extensive applications in the food industry, especially as flavor enhancers. Amino acid-based flavor enhancers are used to modify, enhance, or complement the natural flavors of food and are widely applied in various food processing industries.

What are Flavor Enhancers?

Flavor enhancers, also known as flavor boosters, refer to substances that supplement or enhance the existing flavors of food. Broadly speaking, substances that impart sweet, sour, bitter, spicy, salty, umami, cool, or other tastes can be classified as flavor enhancers. Each type of enhancer has a unique flavor, for example, monosodium glutamate (MSG) provides a strong meat umami taste, DL-alanine enhances the flavor of pickled products, glycine imparts a shrimp and squid flavor, methionine gives a sea urchin flavor, disodium inosinate delivers a fresh fish taste, disodium guanylate gives a shiitake mushroom umami, and succinic acid has a distinct shellfish flavor. Different enhancers have different threshold values for their flavor intensity. For instance, the flavor threshold for L-glutamic acid is 0.03%, monosodium glutamate is 0.012%, monosodium aspartate is 0.10%, disodium inosinate is 0.025%, disodium guanylate is 0.0125%, and succinic acid is 0.055%. There is a significant synergistic enhancement effect between different flavor enhancers. This synergy is not a simple additive effect but rather a multiplicative enhancement. In food processing or home cooking, nucleotide-based flavor enhancers are not used alone but are generally combined with monosodium glutamate to achieve a stronger umami effect. For example, a mixture of 12% disodium guanylate and 88% monosodium glutamate results in a flavor intensity equivalent to 8.1 times that of monosodium glutamate alone.

Fig. 1. Food flavor enhancers.

Types of Flavor Enhancers

Currently, there are over 40 types of commonly used food flavor enhancers, and their development is ongoing. However, there is no unified standard for their classification. They can be classified based on their source into animal, plant, microbial, and chemically synthesized enhancers; or based on their chemical composition, such as amino acid-based, nucleotide-based, organic acid-based, and compound flavor enhancers.

• Nucleotide-Based Flavor Enhancers

Nucleotide-based enhancers, such as disodium 5'-guanylate (5'-GMP) and sodium 5'-inosinate (5'-IMP), are widely used to enhance the umami and flavor complexity of foods. They improve the existing umami in food and act synergistically with amino acid-based enhancers to enhance the overall flavor. Especially, 5'-IMP, when used with monosodium glutamate, makes the umami flavor more pronounced and long-lasting.

• Organic Acid-Based Flavor Enhancers

Organic acid-based enhancers typically enhance food flavors by adjusting the acidity. Common organic acid flavor enhancers include citric acid, acetic acid, and malic acid. Citric acid not only provides a refreshing sour taste but also offers a balanced taste experience in fruit juices, soft drinks, and candies, increasing texture depth. Acetic acid is often used in condiments and pickled foods to effectively enhance the sourness and crispness of food.

• Compound Flavor Enhancers

Compound flavor enhancers are mixtures of various flavor components blended in certain proportions to produce multiple flavor-enhancing effects simultaneously. These enhancers are often used to improve the overall flavor of food and reduce the use of individual enhancers, minimizing any off-flavors or undesirable tastes. Compound enhancers typically contain amino acids, nucleotides, organic acids, and other components and are widely used in sauces, soups, fast foods, and ready-to-eat meals to enhance their overall flavor.

• Amino Acid-Based Flavor Enhancers

Food flavor enhancers made from amino acids and their salts are collectively known as amino acid-based enhancers. These umami enhancers include L-glutamate, L-alanine, glycine, aspartic acid, and methionine. They are aliphatic compounds with taste-active groups such as -COOH, -SO₃H, -SH, -C=O at the molecular ends, and hydrophilic functional groups like alpha-NH, -OH, and C=C within the molecules, such as glutamic acid, histidine, aspartic acid, and peptides. The representative umami substance is L-glutamate, the most widely produced and used food flavor enhancer globally. L-glutamate, commonly known as MSG, is a colorless to white crystalline powder, odorless with a slight sweetness or saltiness, highly soluble in water with a strong umami flavor, and slightly soluble in ethanol but insoluble in organic solvents like ether and acetone. Different amino acids have distinct flavors, for example, DL-alanine enhances the flavor of pickled products, glycine has shrimp and squid flavors, and methionine gives a sea urchin flavor.

Amino Acids in Flavor Enhancers

Amino acids are organic compounds containing amino (-NH₂) and carboxyl (-COOH) functional groups. Amino acids are categorized into essential amino acids, which must be obtained through food, and non-essential amino acids, which can be synthesized by the body. Certain amino acids play an important role in enhancing the umami of food, particularly umami. Umami is considered one of the five basic tastes (along with sweet, sour, bitter, and salty). For example, glutamic acid is considered the primary source of umami, while other amino acids such as aspartic acid and alanine contribute to flavor complexity in some foods. Below are some common amino acid-based flavor enhancers:

• Glutamate

Glutamate is one of the most well-known flavor-enhancing amino acids, particularly in the form of MSG, which is widely used. Glutamate is a naturally occurring amino acid found abundantly in animal products (such as meat, fish, and dairy) as well as some plant-based foods (like tomatoes and mushrooms). It is one of the primary sources of umami, often referred to as the "fifth taste." MSG is the sodium salt of glutamate and is commonly used as a flavor enhancer in food processing. When added to food, MSG enhances the umami flavor, making the taste richer and more satisfying. MSG is particularly effective in processed foods, soups, sauces, snacks, and meat products, where it amplifies the existing savory taste. This effect occurs through glutamate receptors (mGluR1), which recognize and respond to glutamate, activating related signaling pathways to enhance the umami experience. As a result, MSG is highly efficient as a flavor enhancer and significantly reduces the need for salt, aiding in the development of healthier food options.

• Aspartate

There's also aspartate, which adds a level of umami to food, but this is less powerful than glutamate. This is commonly found in animal and plant protein and as a flavor enhancer called monosodium aspartate. Though its umami boost is less than glutamate's, aspartate does still add moderate umami to food. It is usually combined with MSG to make the food more savoury. Additionally, aspartate is linked to sweetness and sourness–making food tangy. It's also very common in fruits and vegetables, especially citrus fruits, berries, tomatoes, and some other fruits. In food processing, aspartate and its sodium salt are used in various food products to enhance their complex flavor profile.

• Alanine

Alanine is another popular amino acid that makes food sweeter by giving it a mild roundness. For flavor, alanine is used to offset and complement sweetness, especially in low-sugar or sugar-free foods. This flavour is mild and mild which makes it an important ingredient in chocolates, drinks, and sweets. Alanine as a flavour enhancer works especially well in sugar reduced or no sugar formulations, because it creates the illusion of sweetness without the use of extra sugar. It also works together with other amino acids and flavors compounds to enhance food's taste.

• Glycine

Glycine is found abundantly in meat, fish, dairy products, and legumes and is used as a flavor-enhancing ingredient in various foods. It can balance bitter or sour notes in certain foods. For instance, in foods with a strong sour taste, glycine effectively mitigates the acidity, providing a smoother texture and taste.

Amino Acids from BOC Sciences

What is the Use of Flavour Enhancers?

Flavor enhancers are widely used in the food industry to improve or enhance the taste of food, elevating its mouthfeel and flavor profile. There are many types of flavor enhancers, among which amino acid-based flavor enhancers are popular due to their distinctive umami characteristics and good safety profile, making them common in food processing.

• Processed Foods

In processed foods, especially canned goods, ready-to-eat meals, seasonings, soups, and sauces, the use of flavor enhancers is essential. These foods often lose their natural flavors due to extended processing and storage, and flavor enhancers can effectively supplement or boost the savory notes of these products. The most commonly used amino acid flavor enhancer is MSG, which is a potent umami enhancer widely applied to meat, fish, soups, sauces, and instant noodles. By adding monosodium glutamate, the food regains its savory taste, enhancing the flavor layers and meeting consumers' demands for deliciousness.

• Snacks and Seasoned Foods

In the snack and seasoned food industry, flavor enhancers are also widely used. Common snacks such as chips, biscuits, puffed foods, nuts, and spicy strips all rely on flavor enhancers to intensify their umami, salty, or aromatic flavors. Amino acid flavor enhancers, particularly monosodium glutamate and monosodium aspartate, are used to improve the umami and taste of these snacks, making them more appealing. In some low-salt or salt-free products, amino acid flavor enhancers can replace part of the salt, helping to reduce sodium intake and cater to modern consumers' demand for healthier diets.

• Beverages and Functional Drinks

Flavour enhancers are widely used in beverages too, and not least in functional beverages such as sports drinks, fruit juices and tea beverages. Amino acids like glycine and alanine can make these drinks more sweet and taste smoother. Amino acid not only adds flavor, but amino acids are also needed for athletes to repair and recoup muscle mass. Additionally, the amino acid can make any sugar-free or low-sugar beverage taste sweeter, thereby reducing the amount of artificial sweeteners in these drinks.

• Meat and Seafood Products

Flavor enhancers are commonly used in meat and seafood products, particularly in sausages, hams, canned fish, and ready-to-eat seafood. Amino acid flavor enhancers can intensify the umami flavor of these products, making their taste richer and more complex. During production, the addition of amino acids compensates for the loss of natural flavors due to high-temperature processing, enhancing the sensory experience of the product. For example, monosodium glutamate and monosodium aspartate are frequently used for seasoning, boosting the savory notes of meat and seafood products.

Prospects of Flavor Enhancers

The overall development trend of food flavor enhancers is moving towards natural, safe, convenient, health-promoting, nutritious, and diversified directions. With the rapid development of modern biotechnology, the development and production of new food flavor enhancers is becoming an important application area for biotechnology. As people's quality of life improves, new food flavor enhancers will increasingly gain popularity in the market.

• Extraction of Natural Flavor Enhancers

In nature, the fresh taste of natural foods has its unique characteristics. For example, the flavor of kelp comes primarily from the glutamic acid sodium it contains; the taste of shiitake mushrooms is mainly due to guanylic acid; and the distinctive taste of shellfish comes from inosine acid salts. However, these flavors are not simple compounds, but are combined with other substances such as peptides, making them difficult to isolate as pure components. Using certain solvents (usually water) to extract flavor compounds from foods can facilitate their combination, followed by concentration and spray-drying to create compound seasonings. This process retains the natural umami flavor and the distinctive aroma of the food.

• Enzymatic New Flavor Enhancers

The formation of food flavors is a biochemical process. Whether formed within a biological system or after being extracted, two prerequisites are necessary: the substrate that forms the flavor compounds and the enzyme system that catalyzes their formation. The so-called flavor enzymes are essentially complex enzyme systems that catalyze the formation of specific flavors from substrates. Enzymes, as biocatalysts in flavor production, can enhance the flavor of food or convert flavor precursors into flavor compounds. They can also activate endogenous enzymes in food to induce the synthesis of flavor compounds or modulate these enzymes to prevent the generation of off-flavors.

• Biotechnology for Flavor Enhancers

By utilizing genetic engineering and cell engineering technologies, new raw materials and superior strains needed for producing umami seasonings can be cultivated. To enhance the umami of seasonings, a widely adopted method is the use of protease hydrolysis to produce animal and plant protein hydrolysates, as well as concentrated extracts from seafood and fish, to produce third and fourth-generation umami seasonings. This not only further enhances the umami but also improves flavor and nutritional value. Additionally, biotechnology, including plant tissue culture, microbial fermentation, and enzyme transformation methods, can be employed to produce new food flavor enhancers.

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