What Are Preservatives?
The consumer who purchases a cleaning product expects to receive and use a quality product that remains useable for several months after the initial purchase date. Accordingly, when developing a new cleaning product, a key factor to consider is how long the product will remain stable on the store shelves and in consumer households. Many consumer products designed to be stable for at least two years following manufacture.
In order to meet this time frame, most products contain low levels of materials called preservatives. Preservatives are chemicals added to a product to help prevent decay and spoilage of the product which could render the product un-useable and possibly dangerous..
Preservatives are used in almost all liquid cleaners and some dry products as well. Without preservatives, you may not have confidence in the quality of products you purchase on store shelves and keep in your homes.
Shelf-life Stability is a Key Product Attribute
Preservatives are materials added to formulated products to inhibit bacterial and fungal growth. Bacteria and fungi exist almost everywhere and wherever they find conditions favorable for growth they will grow. Unless formulated cleaning products provide extreme conditions such as very low or very high pH or very low water content, those products that are not protected by preservatives can grow these microbes. As cleaning products become more and more mild to the surfaces that they are used to clean, they provide better conditions for growing microbes that may naturally contaminate the product, increasing the need for preservation.
Secondary Effects of Contamination
Microbial contamination in a cleaning product can lead to a number of problems including the development of “off-odors”, development of “off appearance” including color changes and opacity changes, and loss of performance. Performance impacts are typically caused by the microbes feeding off the surfactants and other active components of the formulation, by the loss of formulation stability due to pH changes associated with microbial metabolism and / or the microbes feeding off the components added to keep the formulation homogeneous. Microbial contamination can also lead to problems with the product packaging including pressurization of the container, corrosion of metal containers such as aerosol cans, and in extreme examples, clogging of the product delivery mechanisms by biofilm.
In addition to these aesthetic and product performance concerns, there is also the risk that the contaminated product can be a reservoir of unknown microbial contamination leading to rapid contamination of a “freshly cleaned” surface.
A Preserved Product is not an Antimicrobial Product
Preservatives should not be confused with biocidal components added to formulations to impart an antimicrobial property to disinfectant and sanitizer products. Preservatives are included only in amounts sufficient to protect the product itself from microbial contamination.
Typically disinfectants and sanitizers are membrane active and work by disrupting / damaging the cellular membranes of microorganisms. Many preservatives however are electrophonic and interact with nucleophilic sites such as thiols, amines and amides of enzymes, amino acids, and protein present in the microbial cell. These interactions disrupt cellular function, respiration, protein synthesis, and energy generation needed for microorganisms to grow. Examples of commonly used electrophilic preservatives are isothiazolones, bronopol and aldehydes which include formaldehyde releasers and glutaraldehyde.