Antimicrobial Effects of Acids and CitrusDefence®

The market is embracing labels such as 'premium', 'traditional', 'natural' or 'no artificial flavourings', 'preservative free' and 'organic', and products in these segments have shown decent growth in Western markets. This scenario is not any different in Asia where people like their food fresh and are rather particular about quality, wherever they are able to afford the price premium.

But Asian consumers in general do not easily compromise on taste for the sake of convenience and shelf life.

A combination of mild process treatments, either chemical or physical, is often best for fresh and semi-processed food products in order to preserve flavour and texture and give the product a sufficient shelf life and microbial safety.

Meat products, ready-to-eat meals, sauces, dressings, prepared salads and other acidified foods are kept refrigerated (at least after package opening) and are likely to contain preservatives.
If they do receive a heat treatment, it is usually only a mild one.

In these cases, organic acids have proven for decades their ability to perform as natural shelf life extenders and play an important role in a concept known as 'multiple hurdle technology'. Of course, the addition of organic acids or acidification will have an effect on flavour. Sometimes this is desired but at other times it is not.

The major targets for antimicrobials are food spoilage micro-organisms that produce metabolic end products or enzymes which cause :
■ off-odors,
■ off-flavors,
■ texture problems,
■ discolouration,
■ slime or haze,
■ as well as food borne pathogens that cause illness.

Micro-organisms may be inhibited by :
■ chilling,
■ freezing,
■ water activity reduction,
■ nutrient restriction,
■ ermentation or direct acidification,
■ modified atmosphere packaging
■ or through the addition of antimicrobials.

Many antimicrobials are weak acids and therefore pH is the single most important factor. Weak acids are most effective in their undissociated form. This is because iOnce inside the cell, the acid dissociates because the cell interior has a near neutral pH. Protons generated from intracellular dissociation of the organic acid (H+) acidify the cytoplasm and must be removed by the organism. The cytoplasmic membrane is impermeable to protons and they must be actively transported to the exterior creating an electrochemical potential across the membrane called the proton motive force. This process will use energy and the constant influx of these H+ protons will eventually exhaust the micro-organism.

Acids in combination are the most active antimicrobials : acetic, lactic, propionic, ascorbic and sorbic acids.
Citric, malic, fumaric and other organic acids have limited activity but are used as acidulants and for flavourings. Combining acids has the benefit of harnessing synergy between those acids.
This will bring down the pH more effectively as they have different pKa values and since each of the acids act upon a different spectrum of bacteria it will also provide a more powerful preservation effect.n this form they are effectively able to penetrate the cell membrane of a micro organism.

The complex combinations of organic acids create a synergistic reaction present in CitrusDefence® as a powerful biocide at low concentrations. The CitrusDefence® range has broad spectrum activity and is effective against bacteria, (both gram positive and gram negative) and viruses. 

CitrusDefence® formulations do not invoke pathogen mutations. The unique combination of it's active ingredients ensures that the biocide activity (via cell wall intrusion) is not influenced by mutation in the pathogens. This is not the case with most synthetically produced biocides, which have to be periodically substituted to avoid "Pathogen Tolerance" and/or "Pathogen Mutation" to create a powerful and lasting anti-microbial effect. There are no residues after the application of CitrusDefence® .

During the initial anti-microbial contact period, CitrusDefence® combines with the pathogens present on the food and breaks them down into harmless components including CO2 and water. Within a few hours of application the natural components that remain will have either combined with the organic acids and sugars present in the food, or broken down further into harmless components, leaving no detectable residues or toxicity.