Functional fresh cheese and the impact of enrichment with royal jelly

¹ Department of Milk and Dairy Products, University of Food Technologies, 26, Maritsa Blvd., 4002, Plovdiv, Bulgaria.
² Department of Organic Chemistry and Inorganic Chemistry, University of Food Technologies, 26, Maritsa Blvd., 4002, Plovdiv, Bulgaria
³ Department of Physics and biophysics “Prof. Dr. Paraskev Stoyanov”, 55, “Professor Marin Drinov” street, 9002 Medical University,Varna, Bulgaria
⁴ Department of Microbiology and Biotechnology, University of Food Technologies, 26, Maritsa Blvd., 4002, Plovdiv, Bulgaria

^* Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Abstract

Fresh cheeses are an important segment of dairy products valued for their nutritional richness and sensory properties. This study aimed to develop probiotic cheese enriched with royal jelly (RJ) and to evaluate the impact of Lacticaseibacillus casei RC-1 and royal jelly enrichment on the physicochemical composition, fatty acid, metabolite profiles and microbiological quality of fresh cheese during refrigerated storage. Three fresh cheese formulations were tested: Control cheese (C), probiotic cheese (Pro), and probiotic cheese enriched with royal jelly (Pro+RJ). Physicochemical analysis showed that Pro+RJ had higher titratable acidity on the first day (1.30% lactic acid) compared to control (1.19%) and Pro (1.21%), and remained stable over 14 days of storage. Moisture content decreased in Pro+RJ from 31.30% to 19.09%, while protein content remained stable (8.82-8.95%). Ash content was higher in Pro+RJ (0.65%) than in other samples (0.52–0.55%). Microbiological analysis revealed that Pro+RJ limited total microbial counts and yeast growth compared with control. The fatty acid profile demonstrated differences in medium- and long- chain fatty acids: Pro+RJ contained lower palmitic acid (29.10%) and higher oleic (19.78%) and linoleic acids (2.82%) at the end of storage. Notably, 10-hydroxy-2-decenoic acid (10-HDA), a characteristic compound of royal jelly, was detected only in Pro+RJ cheese. Metabolite profiling indicated higher levels of essential amino acids (e.g., leucine, isoleucine, lysine) and reduced lactic acid accumulation in Pro+RJ compared with control sample. In conclusion, probiotic fresh cheese enriched with royal jelly exhibited improved microbial stability, distinct lipid and metabolite profiles, and retention of nutritional quality, supporting its potential as a functional dairy product.