I would like to thank Ing. Pascal Philipsen for this excellent article.
However, I wish to point out that it is not true that essential oils do not mix properly with organic acids. Essential oils, when properly combined with the correct emulsifier, has no problems in diluting or mixing homogeneously in drinking water and the essential oil will not float or appear as an oily layer as the author claims.
With regards to biofilm development in drinking water lines, I feel it is my duty to inform the members of this forum of how water sanitisation with acidifiers can sometimes fail. The failure of drinking water sanitisation to reduce the incidence of natural salmonella in broiler chickens was reported by Al-Chalaby et al. (1985) in the Veterinary Record, Vol. 116, Issue 14, pp 364-365.
Al Chalaby and his team found that the addition of a sanitiser, containing a mixture of organic acids and other approved additives, to the drinking water of broilers, failed to influence salmonella carriage by the chickens, which were still shedding salmonella at market age (7 weeks old).
On the other hand, the antimicrobial action of carvacrol (from oregano essential oil) was examined by Knowles et al (2004) at different stages of dual-species biofilm development by Staphylococcus aureus and Salmonella enterica serovar typhimurium.
It was found that carvacrol pulses (1.0 mmol/h) inhibited S. aureus by 2.5 log CFU/biofilm during the early stages of film formation, ultimately causing a significant reduction (P 0.001) of the staphylococcal population at quasi-steady state.
Initial carvacrol pulsing elicited a 3 log CFU/biofilm reduction in viable S. enterica serovar typhimurium, and additional periodic carvacrol pulses instigated significant inhibition of salmonellae (1 to 2 log CFU/biofilm) during biofilm development.
Comparative studies with a peroxide-based commercial sanitizer (Spor-Klenz RTU) revealed that this commercial sanitizer was more biocidal than carvacrol during early biofilm development. When the biofilm reached quasi-steady state, however, periodic pulses with 1 mmol of carvacrol per h (P [equal] 0.021) elicited a significantly higher inhibition than Spor-Klenz RTU (P [equal] 0.772).
Dual-species microcolonies formed under the influence of continuously fed low carvacrol concentrations (1.0 mmol/h) but failed to develop into a mature quasi-steady-state biofilm and did not reach any stage of film formation in the presence of high concentrations (5.0 mmol/h).
These data show that the addition of a suitable oregano essential oil, such as Orego-Stim Liquid produced by Meriden Animal Health Limited, is an excellent natural intervention to control biofilm formation and may be more effective than using acidifiers in drinking water.
Re- Dr. Tans comments:
Example used in Tans argument about using organic acid based product failed in eliminating Sal. in broiler chickens is rather unfair, as the product used in the Al-Chalabys trial contains about 70[percent] propionic acid When it comes to Salmonella control, one should pay attention to formic acid. Many trials have shown the efficacy of formic acid in Salmonella control.
Once again, the effects of any additive including acidifier and essential oils become rather limited, once chickens have become infected and Salmonella spp have become established in gut-associated lymphoid tissue and mesenteric lymph nodes, where no contact with additives is possible.
Thank you Dr. Tan.
Lily