Everything about Organic Acid totally explained
An
organic acid is an
organic compound with
acidic properties. The most common organic acids are the
carboxylic acids whose acidity is associated with their
carboxyl group -COOH.
Sulfonic acids, containing the group OSO
3H, are relatively stronger acids. The relative stability of the conjugate base of the acid determines its acidity. Other groups can also confer acidity, usually weakly:
-OH, -SH,
enol group, and the
phenol group. In biological systems organic compounds containing only these groups are not generally referred to as organic acids.
A few common examples include:
Characteristics
Generally, organic acids are weak acids and don't dissociate completely in water, whereas the strong
mineral acids do. Lower molecular weight organic acids such as
formic and
acetic acids are miscible in water, but higher molecular weight 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's 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.
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
HCl or mixtures of HCl and
HF. For this reason, organic acids are used at high temperatures or when long contact times between acid and pipe are needed.
The
conjugate bases of organic acids such as
citrate and
acetate 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 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.
Application in nutrition and animal feeds
Research in the
food preservation field has brought clear explanation on the mode of action of organic acids on bacteria and numerous trials have shown that the concept works in animal nutrition.
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 can't 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 can't 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. & Campilobacter 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.
Sources
Dibner J.J., P. Butin. 2002 - Use of organic acids as a model to study the impact of gut microflora on nutrition and metabolism. J. Appl. Poultry Res. 11:453-463
Patanen K.H., Z. Mroz. 1999 – Organic acids for preservation. Disinfection, sterilization & preservation (S.S. Block editor) Lea Febiger, Philadelphia PA.
Brul S., P. Coote. 1999 – Preservative agents in foods, mode of action and microbial resistance mechnismes. Intl. J. Food Microbiology 50:1-17Further Information
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