Organic Acid Review
By Dr. Mark K. Williams, PhD Biochemist
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. Alcohols, with –OH, can act as acids but they are usually very weak. The relative stability of the conjugate base of the acid determines its acidity. (A conjugate base is what is left over after an acid has donated a proton during a chemical reaction. Hence, a conjugate base is a species formed by the removal of a proton from an acid, as in the reverse reaction it is able to gain a hydrogen ion.) 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. Therefore what we (Mineral Logic) generally refer to as organic acids are also, more specifically, carboxylic acids. These include gallic, caffeic, shikimic, fumaric, cinnamic, phthalic, ferulic, benzoic, protocatechuic, phenylacetic, succinic, malic, acetic and lactic acids; for a total of 14 in AGT-50™
However, strictly speaking, amino acids and fulvic acids are also organic acids. All amino acids contain carboxyl groups and thus can be defined as weak organic acids, and therefore weak antioxidants that do not play a significant antioxidative role in the cell. However, the exceptions to this are tryptophan, tyrosine, cysteine and homocysteine which demonstrate significant antioxidant ability at concentrations which are within the usually reported physiological ranges for antioxidant potency. Therefore scientists only consider the aforementioned amino acids as antioxidants. AGT-50™ contains the antioxidants tryptophan and tyrosine; for a total of 2.
Terpenoids are the largest group of plant-secondary compounds followed by flavonoids, both of which have been identified in AGT-50™ . Terpenoids/Flavonoids can contain phenol, enol, alcohol or thiol groups and thus can be also defined as organic acids. The term “organic acid” is an umbrella term encompassing organic compounds with acidic properties (able to donate or accept a proton). All of the identified terpenoid and flavonoid compounds found in the fulvic powder by Mass Spec analysis have antioxidant properties; for a total of 22.
Therefore, AGT-50™ contains 38 significant antioxidants made up of the organic acids, amino acids, terpenoids and flavonoids.
An interesting side-note that we have discussed before is that organic acids are used in food preservation because of their effects on bacteria. 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 Escherichia coli, Salmonella spp., 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 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, 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 extremely 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, meat and poultry such as ham and sausages.
Application 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 (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.
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.
Function of Organic Acids in Animal Feeds
Approvals for the use of nontherapeutic antibiotics in animal feed are fast disappearing worldwide. The primary effect of antibiotics is antimicrobial; all of the digestibility and performance effects can be explained by their impact on the gastrointestinal microflora. Among the candidate replacements for antibiotics are organic acids, both individual acids and blends of several acids. Like antibiotics, short-chain organic acids also have a specific antimicrobial activity. Unlike antibiotics, the antimicrobial activity of organic acids is pH dependent. Organic acids have a clear and significant benefit in weanling piglets and have been observed to benefit poultry performance. Organic acids have antimicrobial activity; however, there appear to be effects of organic acids beyond those attributed to antimicrobial activity. Reductions in bacteria are associated with feeding organic acids, which are particularly effective against acid-intolerant species such as E. coli, Salmonella and Campylobacter. Both antibiotics and organic acids improve protein and energy digestibilities by reducing microbial competition with the host for nutrients and endogenous nitrogen losses, by lowering the incidence of subclinical infections and secretion of immune mediators, and by reducing production of ammonia and other growth-depressing microbial metabolites. Organic acids have several additional effects that go beyond those of antibiotics. These include reduction in digesta pH, increased pancreatic secretion, and trophic effects on the gastrointestinal mucosa. Much more is known about these effects in swine than in poultry. There appears to be more variability in detecting an organic acid benefit in comparison to that observed with antibiotics. Lack of consistency in demonstrating an organic acid benefit is related to uncontrolled variables such as buffering capacity of dietary ingredients, presence of other antimicrobial compounds, cleanliness of the production environment, and heterogeneity of gut microbiota. Additional research can clarify the role of these factors and how to minimize their impact.