Effects of three acidic preservatives on microbiological quality of cosmetic emulsion from virgin olive oil
The present study aimed to review the challenge test, which is used to evaluate the efficiency of three acidic preservatives in cosmetic emulsion from virgin olive oil. These preservatives were tested during our study: sorbic acid, benzoic acid and salicylic acid.
These conservatives were tested separately and combined between them. The challenge test involved inoculating product with Gram positive bacteria (Micrococcus luteus and Staphylococcus aureus), Gram negative bacteria (Escherichia coli, Salmonella enterica and Pseudomonas aeruginosa) and fungi (Aspergillus niger and Candida albicans). Inhibition growth of these microorganisms at each concentration was followed over a 28 days period.
Interestingly. it was the combination (0.5% sorbic acid and 0.5% salicylic acid) which inhibited most the microbial growth of microorganims while preserving the physicochemical properties of the product. As a result, the challenge test is used in security and stability tests during product development and it is the most suitable to analyse preservative effectiveness.
Chemical preservation has become an increasingly important practice in modern cosmetic technology with the increase in production of processed and convenience cosmetic products. These preservatives are deliberately added to stop or delay nutritional losses due to microbiological, enzymatic or chemical changes and thus increasing its shelf life.
Sorbic acid (trans, trans-2,4-hexadienoic acid) (SA) is an antimycotic agent used as preservative in many pharmaceutical formulations, especially in dermatological and cosmetic preparations. During the last decades (SA) and its potassium salt have been accepted as ‘generally recognized as safe’ substances (1) and have become the leading preservatives for food as well as for pharmaceutical and cosmetic preparations (2). (SA) are generally effective to control mold and inhibit yeast growth, and against a wide range of bacterial attack (3, 4, 5). The pKa of SA is 4.76 and the working pH range is from 3 to 6.5. The extended preservation capacity up to pH 6.5 makes SA superior over other commonly used preservatives such as propionates and benzoates (6).
Benzoic acid (BA) is commonly us ...