Evaluation of the antimicrobial and antioxidant activity of rosemary and thyme extracts and their use as natural preservatives to improve meat quality and safety during refrigerated storage

Abstract:

This research was conducted with the purpose of assessing the antimicrobial and antioxidant effects of rosemary and thyme extract, as well as their potential for being used as natural preservatives to enhance the quality of meat products and safety during refrigerated storage. There was a total of 3 treatment groups: 0.1% rosemary extract group, 0.1% thyme extract group, a mixture of both extracts (0.5% rosemary + 0.5% thyme), and a control group with no additives. These groups were compared by looking at how well they produced antimicrobial or antioxidant properties while stored at 4°C for 1, 6, and 12 days.

The evaluation of changes to the meat involved using various physical, chemical, and microbial methods of testing. Physical methods used to evaluate the samples included the cooking loss from the product as it was cooked, water-holding capacity of the meat sample, and the oxidation index using the Thio barbituric acid reactive substances (TBARS) test. Various chemical tests included the measurement of the pH and the peroxide value of the meat samples. Microbial analyses conducted during this study were to measure total bacterial counts, cold-loving bacterial counts, and yeast and mold counts present on the meat samples. Additionally, sensory analyses were performed on the samples based on odor, taste, and overall acceptability.

All treatments researched in this study affected the physical properties of meat positively by significantly decreasing cooking loss and increasing water-holding capacity, compared with control samples; the greatest effect was with the mixture treatment. Additionally, TBARS and peroxide values were significantly lower, showing that all treatments are effective at inhibiting lipid oxidation processes, with relative pH stability.

Microbial analysis of the samples showed that plant extract-based treatments significantly decreased total, psychrophilic, and yeast and mold counts compared to untreated controls, confirming that these extracts were effective in reducing microbial growth at refrigerated temperatures. Sensory evaluation results indicated that all treatments exhibited improved aroma, flavor, and overall acceptability when compared with untreated controls, with the mixture treatment receiving the highest overall preference score of all treatments.

The results show a synergy between oregano and rosemary extracts (both antioxidants and antimicrobials), leading, together, to improved shelf stability and enhanced quality and safety of refrigerated meats; therefore, they are both innovative natural alternatives to synthetic preservatives.