Kisa ve uzun ömürlü ayranlarda potasyum sorbat uygulamasinin kaliteye etkisi

The present study was undertaken to investigate the effects of potassium sorbate and various storage conditions on microbiological and chemical quality, sensory attributes and on shelf life of long-life and short-life ayran.Four different types of experimental ayran samples were produced in a local dairy plant in Elazığ as short-life ayran (A), short-life + 0.05% potassium sorbate (B), long-life ayran (C), and long life + 0.05% potassium sorbate (D). The products were stored at 4 ± 1°C or 20 ± 1°C. The samples were taken on days 0., 7., 14., 28., 42., 56., 70., and 84. analyzed for microbiological (total mesophilic aerobes, coliform, yeast and mold, Lactobacillus spp., and lactic Streptococcus spp.and Enterococcus spp counts), chemical (pH, lactic acid, dry-substance without fat, fat, salt, and sorbic acid residues) parameters, and sensory attributes (appearance before and after shaking, texture, odor, flavor, and general acceptance). The study was composed of three replicates.The numbers of total mesophilic aerobe bacteria increased until days 28-56 depending on the treatment groups in products stored at 4 ± 1°C followed by a decrease during the remaining period of storage. In those stored at 20 ± 1°C, however, the numbers of these bacteria progressively increased during the entire storage period. Nevertheless, the effect of potassium sorbate on mesophilic aerobic bacteria was not significant (p>0.05).No mold was found in any of the treatment groups during the storage. However, numbers of yeasts showed a progressive increase regardless of the storage temperature, although the growth was slower in groups containing potassium sorbate. The effect of potassium sorbate on the numbers of yeasts were found significant (p<0.05).The numbers of coliforms continuously decreased during storage and dropped below detection limit (<-0.52 log10MPN/ml) on day 42. Potassium sorbate was not significantly effective on coliforms when used at 0.05% concentration (p>0.05).Lactobacillus spp., in general, showed an increase during storage. Lactic Streptococcus spp. increased in products stored at 4 ± 1°C until days 28-56 depending on the treatment group. However, the numbers of these bacteria decreased during the remaining period of the storage. The effect of potassium sorbate at the level of 0.05% on either Lactobacillus spp., or lactic Streptococcus spp. was not found significant (p>0.05)pH and lactic acid level did not change significantly in products stored at 4 ± 1°C during storage (p>0.05). In contrast, the changes were at 20 ± 1°C (p<0.05). In all treatment groups, dry substance without fat, fat and salt levels were not different from each other (p>0.05). Level of sorbic acid decreased on days 70 and 84 at 4 ± 1°C in samples of group B (p<0.05).Results of sensorial evaluation of ayran samples indicated that storage at 4 ± 1°C, group A samples on day 56 and group C samples on day 70 were determined to be spoiled. On the other hand, products B and D containing 0.05% potassium sorbate remained acceptable even on day 84. For those products stored 20 ± 1°C, group A samples on day 7, group B samples on day 28, group C and D samples on day 14 were found unacceptable. As the general acceptance scores were evaluated, short-life ayran with potassium sorbate (group B) received a higher score.In conclusion, the results of the current study revealed that addition of 0.05% potassium sorbate to long life or short-life ayran, in general, improved the microbiological and sensorial quality of the products and increased the shelf life of the products to at least 70 days. In addition, those long-life ayran samples containing 0,05% potassium sorbate were determined to be acceptable by sensory evaluation on day 84 of the storage at 4°C but these samples were not in compliance with the microbiological criteria established in standard for long-life ayran by Turkish Standards Institute.Key words: Ayran, potassium sorbate, shelf life, microbiological quality, chemical composition, sensory attributes