Organic Acids

A partial list of organic acids found in foods follows: ^{Wiki n.p.}

Acetic Acid

Acetic acid, also known as ethanoic acid, is an organic chemical compound best recognized as the sour tast and pungent smell in vinegar.   In the food industry acetic acid is used as an acidity regulator.

Acetic acid is an important chemical reagent and manufacturing chemical that is used in the production of the plastic in soft drink bottles; in cellulose acetate used for photographic film, and polyvinyl acetate for wood glue. It is used in synthetic fibers and fabrics and In household descaling agents.

Ascorbic Acid (Vitamin C)

Ascorbic acid and its sodium, potassium, and calcium salts are commonly used as antioxidant food additives.   These compounds are water soluble and thus cannot protect fats from oxidation. For that purpose, the fat-soluble esters of ascorbic acid with long-chain fatty acids (ascorbyl palmitate or ascorbyl stearate) can be used as food antioxidants.

Benzoic Acid

Benzoic acid is used as food preservative.   In manufacturing, it is a raw material for several chemical substances like benzoyl chloride and plasticizers.

Citric Acid

Citric acid is found in a variety of fruits and vegetables, but it is most concentrated in lemons and limes, where it comprises as much as 8% of the dry weight of the fruit.   It is an effective natural preservative and also is used to add an acidic (sour) taste to foods and soft drinks.   In biochemistry, it is important as an intermediate in the citric acid cycle and therefore occurs in the metabolism of almost all living things.

Citric acid is an environmentally benign cleaning agent and acts as an antioxidant.

Carbonic Acid

Carbonic acid results from the chemical reaction of carbon dioxide and water, such as in carbonated beverages (carbon dioxide added to "soft drinks".   The equilibrium between carbon dioxide and carbonic acid is very important for controlling the acidity of body fluids, and almost all living organisms have an enzyme, carbonic anhydrase, which catalyzes the conversion between carbon dioxide and carbonic acid, increasing the reaction rate by a factor of nearly a million.

Cyclamic Acid (Cyclamate)

Cyclamate is an artificial sweetener used as a food additive.

Erythorbic Acid

Erythorbic acid is a stereoisomer of ascorbic acid.   It is a vegetable derived food additive produced from sucrose. used an antioxidant in processed foods.

Fumaric Acid

Furmaric aic is a common component of food additives and dietary supplements and is sometimes used as a substitute for tartaric acid in beverages or baking powder.   Fumaric acid is used by cells to produce energy from food.   Human skin naturally produces fumaric acid when exposed to sunlight.

Gluconic Acid

Gluconic acid occurs naturally in fruit, honey and wine and is used as a food additive and an acidity regulator.   It is also used in cleaning products to eliminate mineral deposits.   It is a strong chelating agent (water softener to eliminate metalic ions), especially in alkaline solution.

Inosinic Acid

Inosinic acid is a nucleotide present in muscle and other tissues.   Inosinic acid is important in metabolism.   It is the ribonucleotide of hypoxanthine and is the first compound formed during the synthesis of purine.   Compounds derived from inosinic acid include purine nucleotides found in nucleic acids such a as adenosine triphosphate (ADP), which is used to store chemical energy.   Inosinic acid also is used as a flavor enhancer in food.

Lactic Acid

Lactic acic is found in dairy products such as yoghurt and sour milk and is product of cellular fermentation.   Lactate is constantly produced during normal metabolism and exercise, but it does not increase in concentration until the rate of lactate production exceeds the rate of lactate removal.   Lactic acid is used in a variety of foods as an acidity regulator.   Although it can be fermented from lactose (milk sugar), most commercially used lactic acid is derived from bacteria to ferment carbohydrates from sources such as cornstarch, potatoes or molasses.   Thus, although it is commonly known as "milk acid", products claiming to be vegan sometimes use lactic acid as an ingredient.

Lactic acid is used as a milder alternative to glycolic acid in cosmetics.   It is primarily used as an anti-aging chemical claimed to soften lines, reduce photodamage from the sun, improve skin texture and tone and improve overall appearance.   Precautions should be taken when using lactic acid as a cosmetic agent because it can increase UV sensitivity to the sun.

Malic Acid

Malic acid is a tart-tasting organic acid food additive many sour or tart foods.   In its ionized form it is malate used in cell respiration.   Apples contain malic acid, which contributes to the sourness of a green apple.   Malic acid can make a wine taste tart, although the amount decreases with increasing fruit ripeness.   The process of malolactic fermentation converts malic acid to much milder lactic acid.

Methanethiol Acid

Methanethiol is a colorless gas with a smell like rotten cabbage.   It is a natural substance found in the blood, brain, and other tissues of people and animals.   It is released from animal feces.   It occurs naturally in certain foods, such as some nuts and cheese.   It is also one of the main chemicals responsible for bad breath.

Methanethiol is released from decaying organic matter in marshes and is present in the natural gas of certain regions in the United States, in coal tar, and in some crude oils.   Methanethiol is primarily used as an odorant to add warning properties to propane and natural gas used as fuel.   Propane by itself is odorless, as are many sources of natural gas.   Methanethiol is added for safety, so that gas leaks are readily noted by anyone present due to the odor.   Methanethiol vaporizes readily and is odoriferous enough that only small quantities need be used.

Nicotinic Acid (Niacin)

Niacin is a water-soluble vitamin whose derivatives are used in cell respiration.   The designation vitamin B₃also includes the amide form, nicotinamide or niacinamide.   Severe lack of niacin causes the deficiency disease called pellagra, whereas a mild deficiency slows down the metabolism, which in turn decreases cold tolerance and is a potential contributing factor towards obesity.   Nicotinic acid reacts with hemoglobin and myoglobin in meat to form a brightly coloured complex, and thus it has been used as a food additive, typically to improve the colour of minced (ground) meat.   However, sometimes excess niacin is added to the meat during processing.   The liver can synthesize niacin from the essential amino acid tryptophan, but the synthesis is extremely slow and requires vitamin B₆.   Bacteria in the gut may also perform the conversion, but they also are inefficient.   Therefore, eating lots of tryptophan is not an adequate substitute for consuming niacin.   However, this explains why pellagra requires a deficiency of protein as well as niacin.   Large doses of niacin (as nicotinic acid, but not the niacinamide form) are prescribed to combat high blood pressure and to broadly improve blood cholesterol levels.

Oxalic Acid

Oxalic acid and oxalates are abundantly present in many plants, such as rhubarb and sorrel.   Oxalic acid irritates the lining of the gut when consumed, and can be fatal in large doses.   Oxalic acid can also be present in the body due to the consumption of another toxin, ethylene glycol (generally known as automobile antifreeze), because over time, the body metabolizes ethylene glycol into oxalic acid.   Bodily oxalic acid may also be synthesized via the metabolism of either glyoxylic acid or unused ascorbic acid (vitamin C), which may pose a serious health problem for long term megadosers of vitamin C supplements.

Oxalic acid also combines with metals such as calcium in the body to form oxalate crystals which further irritate the gut and kidneys.   The most common kind of kidney stone is made of calcium oxalate.   Because it binds vital nutrients such as calcium, long-term consumption of foods high in oxalic acid can lead to nutrient deficiencies.   Healthy people can safely consume such foods in moderation, but those with kidney disorders, gout, or rheumatoid arthritis are typically advised to avoid foods high in oxalic acid or oxalates.

Foods that contain significant concentrations of oxalic acid include (in decreasing order): buckwheat, star fruit (carambola), black pepper, parsley, poppy seed, rhubarb, spinach, chard, beets, banana, cocoa, chocolate, most nuts, most berries, and beans.   In the case of rhubarb, the only edible portion is the stalk because the root and leaves contain dangerously high concentrations of oxalic acid.   The gritty feel one gets in the mouth when drinking milk with rhubarb desserts is caused by precipitation of calcium oxalate.   Thus, even dilute amounts of oxalic acid can readily "crack" the casein found in various dairy products.   Leaves of the tea plant (Camellia sinensis) are known to contain among the greatest measured concentrations of oxalic acid relative to other plants.   However the infusion beverage typically contains only low to moderate amounts of oxalic acid per serving, due to the small mass of leaves used for brewing.

In addition to its natural occurrence in plants, oxalic acid may also be found in household chemical products, such as bleaches, and rustproofing treatments.   It is also used in wood restorers because the acid dissolves away a layer of dry surface wood to expose fresh material underneath.

Pectic Acid

Pectic acid is a transparent and gelatinous acid existing in ripe fruit and some vegetables.   It is a product of pectin degration in plants.

Phosphoric Acid

Phosphoric acid is used in many soft drinks (primarily so in cola drinks) to create an acid medium that enhances the absorption of carbon dioxide (which is also forms carbonic acid in water), thus reducing the pressure required and allowing the mixture to be bottled with a metal cap.   The carbon dioxide bubbles are released more slowly, particularly if the mixture is chilled.   The sour taste of the phosphoric acid is complemented by adding lots of sugar.   It has become suspect in the increase of the bone deficiency disease osteoporosis in young women.   Traditionally, osteoporosis (literally "porous bones") has been seen mostly in post-menopausal women, particularly those who did not build high bone density in youth, typically due to insufficient calcium intake.   An excess of phosphorus may lead to poor bone density, however.   Nutritionists point out that the body will attempt to maintain a balance between ions of phosphorus and calcium in the blood.   When an excess of phosphorus (through phosphoric acid, for example) is introduced, the body's chemical balance mechanisms will attempt to maintain the proper calcium-phosphorus ionic ratio by extracting calcium from the bones.   The excess phosphorus and calcium are eventually excreted.   Other chemicals such as caffeine (also a significant component of popular common cola drinks) are also suspected as possible contributors to low bone density, which is now seen in increasing prevalence in men of late middle age.

Propionic Acid

Propionic acid inhibits the growth of mold and some bacteria.   Therefore, it is used as a preservative for both animal feed and food for human consumption.   For animal feed, it is used either directly or as its ammonium salt.   In human foods, especially bread and other baked goods, it is used as its sodium or calcium salt.   Propionic acid is also useful as a chemical intermediate.   It can be used to modify synthetic cellulose fibers and to make pesticides and pharmaceuticals.   The esters of propionic acid are sometimes used as solvents and artificial flavorings.

Sorbic Acid

Sorbic acid is a natural organic compound used as a food preservative.   Sorbic acid and its mineral salts, such as sodium sorbate, potassium sorbate and calcium sorbate, are antimicrobial agents often used as preservatives in food and drinks to prevent the growth of mold, yeast and fungi.   In general the salts are preferred over the acid form because they are more soluble in water.

Tartaric Acid

Tartaric acid is a white crystalline organic acid.   It occurs naturally in many plants, particularly grapes and tamarinds, and is one of the main acids found in wine.   It is added to other foods to give a sour taste, and is used as an antioxidant.   Salts of tartaric acid are known as tartrates.