Food acids include citric, acetic, malic, tartaric and lactic acid. They have numerous uses in nature, health and cuisine, each with their own history, properties and behaviors.
1. Citric Acid
Origin: It's first isolated from lemon juice by Carl Wilhelm Scheele in 1784. A self-taught chemist, Scheele makes an astounding number of discoveries but is best known for Scheele's Green, the most toxic pigment in history.
Properties: A weak organic acid with a sour taste, highly soluble in water, it's a natural preservative and potential antioxidant.
Occurrence & Functions: It's abundant in citrus fruits like lemons, limes, and oranges. In plants, it plays a key role in the Krebs cycle, a vital process for energy generation.
Foods: It's predominantly found in citrus fruits, but also added to beverages, candies, jams, and processed foods as a flavoring agent and preservative.
Human Body: Human body produces citric acid during normal metabolism.
Interesting Fact: Citric acid is also used as a cleaning agent and descaler due to its ability to chelate metals.
2. Acetic Acid
Origin: Derived from the Latin word "acetum" meaning vinegar.
Produced through fermentation of ethanol by acetic acid bacteria.
Properties: A colorless liquid with a pungent, vinegary odor. In diluted form, it is vinegar.
Occurrence & Functions: Naturally produced during the fermentation of fruits and grains, it's considered to have antimicrobial properties.
Foods: The main component of vinegar, widely used in salad dressings, pickles, sauces, and as a general food preservative.
Human Body: Acetic acid is a product of the decomposition of ethanol. It is created through the fermentation of ethanol by acetic acid bacteria, common digestive system microbes.
Interesting Fact: The process of making vinegar is one of the oldest biotechnological processes known to humankind, dating back thousands of years.
Vinegar varieties such as apple cider vinegar, balsamic and white vinegar each have distinct flavors and uses. Acetic acid not only gives vinegar its characteristic sour taste but helps preserve food.
However, concentrated acetic acid can cause gastrointestinal problems and throat burning. Store bought vinegar is a moderate 4-6% acetic acid. Artisan, home-made, specialty or distilled vinegars can reach 20% or more.
3. Malic Acid
Origin: Discovered by Carl Wilhelm Scheele in 1785 from unripe apples.
Properties: A dicarboxylic acid with a sour taste, it's often described as tart and slightly lingering.
Occurrence & Functions: It's found in many fruits, especially apples, cherries, and tomatoes. It contributes to the sourness of these fruits and has functions in plant metabolism.
Foods: Malic acid is used as a food additive to enhance flavor in beverages, candies, and baked goods. It can also be found naturally in fruit juices and ciders.
Human Body: Involved in the Krebs cycle, just like citric acid, it can also help increase athletic endurance.
Interesting Fact: Malic acid is often added to hard candies to create a distinct sour taste.
Malic acid is also present in cherries, peaches, and pears. It's active during the ripening process of fruits and helps maintain pH levels in plant cells. 25% of malic acid produced globally is used in the food industry.
Health benefits include potential relief from fatigue during exercise and performance enhancement. Similar to other acids, excess exposure can cause health problems.
4. Tartaric Acid
Origin: Naturally occurring in grapes, tartaric acid is isolated in the 800s AD. It functions in wine flavor and texture.
Properties: A crystalline dicarboxylic acid with a tart taste, it famously forms crystals (cream of tartar) during winemaking. These are sometimes called wine diamonds to increase their appeal.
Occurrence & Functions: It's found in grapes, bananas, and tamarinds. It contributes to stability and flavor of wines.
Foods: Used as an acidulant in baked goods, candies, and beverages. The byproduct cream of tartar is used as a stabilizer in whipped egg whites and frosting. It prevents sugar crystallization.
Human Body: It can have antioxidant properties.
Interesting Fact: Diverse grape varieties yield varying tartaric acid levels, influencing a wine's profile. Tartaric acid contributes to about 80% of acidity in wine.
In the human body, it can have antioxidant effects. Consuming large amounts can lead to digestive discomfort such as vomiting, nausea and diarrhea.
5. Lactic Acid: Microbial Fermentation
Origin: It's produced through fermentation of carbohydrates by lactic acid bacteria.
Properties: A colorless or yellowish syrupy liquid, it has a sour taste.
Occurrence & Functions: It's produced in muscle cells during strenuous use when oxygen supply is limited. It's also integral to fermented foods.
Human Body: Produced during anaerobic metabolism, it can cause muscle fatigue. It occurs during intense exercise. Overaccumulation of lactic acid can cause muscle fatigue and pain, or lactic acidosis.
Food: Lactic acid occurs in fermented foods like yogurt and sourdough bread. It's a natural preservative creating a tangy flavor.
Lactic acid is commonly found as an active ingredient produced by microbes in other fermented food like sauerkraut, beets, pickles and olives. It's also added to bread and desserts to give them longer shelf life.
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