Design of probiotic yoghurt with the addition of royal jelly

Abstract

This study aimed to develop a probiotic yoghurt enriched with royal jelly to enhance its nutritional and functional qualities. The effects of incorporating Lacticaseibacillus casei RC-1 and royal jelly on the physicochemical, antioxidant, microbiological, and rheological properties of yoghurt were evaluated over 21 days of refrigerated storage. Three yoghurt formulations were designed and tested: control yoghurt with classic starter culture (Yc), yoghurt with classic starter culture and probiotic strain (Ypro), and yoghurt with classic starter culture, probiotic strain and royal jelly (Ypro+RJ). Parameters such as pH, titratable acidity, water content, water holding capacity (WHC), fat content, colour (L*, a*, b*), total polyphenols, antioxidant activity (DPPH, FRAP), and microbial counts were analyzed. Ypro+RJ maintained the highest pH and lowest acidity, indicating reduced acidification. WHC improved in all samples, with Ypro+RJ reaching the highest value. Colour shifts were minimal, suggesting little perceptible difference. Ypro+RJ had the highest polyphenolic content and strongest antioxidant activity, reflecting a synergistic effect between the probiotic and royal jelly. Microbial analysis showed increased lactic acid bacteria (LAB) counts in Ypro and Ypro+RJ, while the total plate count and yeast/fungi counts remained within safe limits. Rheological testing revealed shear-thinning behavior in all samples. Overall, royal jelly addition enhanced the yoghurt’s functional properties, boosting antioxidant activity, microbial viability, and storage stability. These results suggest that royal jelly-enriched probiotic yoghurt could serve as a next-generation functional food with potential health and consumer benefits.