Gracilaria gracilis Aqueous Extract and White Chlorella as Functional Ingredients in Yogurt: Effects on Quality, Nutritional and Physicochemical Properties

The growing demand for functional foods has increased interest in natural ingredients with nutritional and bioactive properties for dairy applications. This study evaluated Gracilaria gracilis (G. gracilis) aqueous extract and White Chlorella as functional ingredients in yogurt. Three formulations were prepared: control yogurt (CY), yogurt containing G. gracilis extract (GY), and yogurt containing both G. gracilis extract and White Chlorella (GWY). Proximate composition, total phenolic content (TPC), antioxidant activity, color, pH, texture, and water-holding capacity (WHC) were assessed after fermentation and over 21 days of refrigerated storage. GY exhibited a pink coloration that was clearly perceptible relative to the control (ΔE* > 3) and remained stable throughout storage (ΔE* < 0.6 relative to Day 1). GY also showed lower firmness, consistency, cohesiveness, and WHC than CY, differences that may be attributable, at least in part, to the dilution introduced with the aqueous extract. Compared with GY, GWY contained 32% more protein (3.66 vs. 2.78 g/100 g) and showed higher firmness, consistency, and WHC, in some cases reaching values comparable to those of the control. TPC did not differ significantly among formulations (p > 0.05), while the antioxidant activity of both supplemented yogurts was lower than that of the control. Instrumental color changes during storage were small in magnitude, while texture remained generally stable across the 21-day storage period.