Organic acid

An organic acid is an

–OH, can act as acids but they are usually very weak. The relative stability of the conjugate base of the acid determines its acidity. Other groups can also confer acidity, usually weakly: the thiol group –SH, the enol group, and the phenol

group. In biological systems, organic compounds containing these groups are generally referred to as organic acids.

A few common examples include:

Characteristics

In general, organic acids are weak acids and do not dissociate completely in water, whereas the strong mineral acids do. Lower molecular mass organic acids such as formic and lactic acids are miscible in water, but higher molecular mass organic acids, such as benzoic acid, are insoluble in molecular (neutral) form.

On the other hand, most organic acids are very soluble in organic solvents. p-Toluenesulfonic acid is a comparatively strong acid used in organic chemistry often because it is able to dissolve in the organic reaction solvent.

Exceptions to these solubility characteristics exist in the presence of other substituents that affect the polarity of the compound.

Applications

Simple organic acids like formic or acetic acids are used for oil and gas well stimulation treatments. These organic acids are much less reactive with metals than are strong mineral acids like hydrochloric acid (HCl) or mixtures of HCl and hydrofluoric acid (HF). For this reason, organic acids are used at high temperatures or when long contact times between acid and pipe are needed.^{[citation needed]}

The

conjugate bases of organic acids such as citrate and lactate are often used in biologically compatible buffer solutions

.

Citric and oxalic acids are used as rust removal. As acids, they can dissolve the iron oxides, but without damaging the base metal as do stronger mineral acids. In the dissociated form, they may be able to

chelate

the metal ions, helping to speed removal.

Biological systems create many more complex organic acids such as

epinephrine (adrenaline) by human tissues and catabolism of dietary carbohydrate by intestinal bacteria, respectively. Organic acids (C₁–C₇) are widely distributed in nature as normal constituents of plants or animal tissues. They are also formed through microbial fermentation of carbohydrates mainly in the large intestine. They are sometimes found in their sodium, potassium, or calcium salts

, or even stronger double salts.

alcohol, thiol

. The acidic hydrogen in each molecule is colored red.

In food

Organic acids are used in

C. perfringens, Listeria monocytogenes, and Campylobacter

species.

Upon passive diffusion of organic acids into the bacteria, where the pH is near or above neutrality, the acids will dissociate and raise the bacteria internal pH, leading to situations that will not impair nor stop the growth of bacteria. On the other hand, the anionic part of the organic acids that can escape the bacteria in its dissociated form will accumulate within the bacteria and disrupt few metabolic functions, leading to osmotic pressure increase, incompatible with the survival of the bacteria.

It has been well demonstrated that the state of the organic acids (undissociated or dissociated) is not important to define their capacity to inhibit the growth of bacteria, compared to undissociated acids.

Lactic acid and its salts sodium lactate and potassium lactate are widely used as antimicrobials in food products, in particular, dairy and poultry such as ham and sausages.^[1]

In nutrition and animal feeds

Organic acids have been used successfully in pig production for more than 25 years. Although less research has been done in poultry, organic acids have also been found to be effective in poultry production.

Organic acids added to feeds should be protected to avoid their dissociation in the crop and in the intestine (high pH segments) and reach far into the gastrointestinal tract, where the bulk of the bacteria population is located.

From the use of organic acids in poultry and pigs, one can expect an improvement in performance similar to or better than that of antibiotic growth promoters, without the public health concern, a preventive effect on the intestinal problems like necrotic enteritis in chickens and Escherichia coli infection in young pigs. Also one can expect a reduction of the carrier state for Salmonella species and Campylobacter species.

References

^ Applications for lactic acid.http://www.purac.com/purac_com/67cbf5490d83dc478dafbd96cab841b1.php