Comparison of antimicrobial activities of microencapsule and fresh royal jelly, and determination of efficacy of storage periods on antimicrobial activity

Royal jelly (RJ) is a secretion of the hypopharyngeal and mandibular glands of young worker bees for the nutrition of larvae and the queen bee. Besides being a nutritional product for bees and also humans, it is rich in bioactive components. Due to these components, RJ exhibits different biological properties including antimicrobial, antioxidant, antitumor, immunomodulatory effect as well as antidiabetic, antihypercolesterolemic, hypotensive and antiinflammatory properties. RJ, which contains valuable ingredients for human nutrition and health, is very sensitive and affected by the improper production and storage conditions. As a result of being a seasonal product and its perishable structure, it should be taken to cold chain as soon as it is harvested, and stored at +4°C for short-term or at -18°C to preserve more. Lyophilization is the most common method because of elimination of cold chain necessity at the storage period. The microencapsulation method, which has not been tried in royal jelly until today, is thought to be an alternative to lyophilization by being a simple and low cost production method. For this purpose, the antimicrobial activities of fresh and microencapsulated royal jelly were compared and antimicrobial effects of these two products were investigated at 1, 3 and 6 months in the storage period. The microorganisms used in the study were four pathogen bacteria; Escherichia coli ATCC 25922, Salmonella Enteritidis, Micrococcus luteus ATCC 9341, Staphylococcus epidermidis ATCC 12228 and, four species of fungi Candida albicans ATCC 10351, Candida parapsilosis ATCC 22019, Penicillium digitatum, Aspergillus flavus. Antimicrobial activity was determined by broth microdilution and agar well diffusion method. Antimicrobial activity of fresh and microencapsulated royal jelly was increased depends on the concentration increase. The MIC against test bacteria was about 15,6 - 31,25 mg/mL for fresh RJ, while 15,6- 125 mg/mL for microencapsulate royal jelly. According to zone diameters; S. epidermidis was most sensitive and M. luteus was moderately sensitive, E. coli and S. Enteritidis were found to be resistant to fresh and microencapsulated royal jelly. Fresh royal jelly had a MIC of 15.6 mg/mL on yeasts and microencaspulated royal jelly inhibited the growth at 62.5 mg/mL. When the MIC and MFC values were compared, C. parapsilosis was found to be resistant than C. albicans. Although fresh RJ had similar efficacy on A. flavus and P. digitatum, microencapsulated royal jelly had a higher MIC value on P. digitatum. During storage, no change observed in the MICs of fresh and microencapsulated RJ for 6 months on M. luteus, E. coli, S. Enteritidis and yeasts. For the tested molds, the MIC values of samples were increased in the third month. There was no statistically significant difference between the inhibition zones of fresh and microencapsule RJ on bacteria and molds (p <0.05). In the following months, it was determined that the change in inhibition zones differed according to microorganism and applied concentrations. The results indicated that the antimicrobial activity is maintained after the encapsulation process and while stored at room temperature. In conclusion, it is thought that the data obtained in this study will contribute to the other studies and researches about biological activity of royal jelly and changes on it in the storage period. With improving microencapsulated formulations, it will be possible to maintain biological properties of RJ for longer periods and be considered as functional food. Keywords: Royal Jelly, Microencapsulation, Antibacterial, Antifungal, Storage