A few common examples include:
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 which affect the polarity of the compound.
Citric and oxalic acids are used as rust removal. As acids, they can dissolve the iron oxides, but without damaging the base metal like stronger mineral acids. In the dissociated form, they may be able to chelate the metal ions, helping to speed removal.
Biological systems create many and more complex organic acids such as L-lactic, citric and D-glucuronic acids that contain hydroxyl or carboxyl groups. Human blood and urine contain these plus organic acid degradation products of amino acids, neurotransmitters and intestinal bacterial action on food components. Examples of these categories are alpha-ketoisocaproic, vanilmandelic and D-lactic acids, derived from catabolism of L-leucine and epinephrine (adrenaline) by human tissues and catabolism of dietary carbohydrate by intestinal bacteria, respectively.
Organic acids have been used successfully in pig production for more than 25 years and continue to be the alternative of choice. Even if less work has been done in poultry, the Organic Acids are very efficacious and their use is adapted to the physiology and anatomy of poultry.
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 form.
The key basic principle on the mode of action of organic acids on bacteria is that non-dissociated (non-ionized) organic acids can penetrate the bacteria cell wall and disrupt the normal physiology of certain types of bacteria that we call “pH-sensitive” meaning that they cannot tolerate a wide internal and external pH gradient. Among those bacteria are E.coli, Salmonella spp., C. perfringens, Listeria monocytogenes, Campylobacter spp.
Upon passive diffusion of organic acids into the bacteria, where the pH is near of above neutrality, the acids will dissociate and lower the bacteria internal pH, leading to situations that will impair or stop the growth of bacteria. On the other hand, the anionic part of the organic acids that cannot escape the bacteria in its dissociated form will accumulate within the bacteria and disrupt many metabolic functions and lead 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 extremely important to define their capacity to inhibit the growth of bacteria, compared to undissociated acids.
Logically, 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 GIT, 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 or better than the 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 spp. & Campylobacter spp.
Kansas State University recommends Kemgest, Syneracid, Digest acid, or Tetracid 500 as acidifiers to be fed to pigs weighing less than 12 lb as a complete diet.