Effect of Rosemary (Rosmarinus officinalis L.) Supplementation on Probiotic Yoghurt: Physicochemical Properties, Microbial Content, and Sensory Attributes

Rosemary (Rosmarinus officinalis L.) is a natural aromatic plant that belongs to the family of Lamiaceae. The rosemary plant has been utilized to preserve food due to its ability to prevent oxidation and microbial contamination. This study aimed to investigate the effect of fortifying yoghurt with rosemary extracts and probiotic bacteria (LAB) (Bifidobacterium longum ATCC15707 and two lactic acid bacteria, Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus) on its chemical composition, total phenolic compounds, antioxidant capacity, and sensory properties. The study results revealed significant differences in the total solids, protein, and ash content when rosemary concentration increased beyond 2%. However, there were no significant differences among the treatments in acidity and pH value. The sensory evaluation results indicated that the addition of aqueous extract of rosemary affected the sensory properties of yoghurt (flavour, body and texture, appearance, and overall grade), wherein an increasing concentration of rosemary extract increased score of flavour, body and texture, appearance, and overall grade. On the other hand, rosemary extract did not affect the sensory properties and chemical composition. To sum up, it can be stated that rosemary was used in the preparation of yoghurt with increased health benefits, acceptable sensory attributes, and the production of synbiotic yogurt.