Rheological, texture, structural, and functional properties of Greek-style yogurt fortified with cheese whey-spent coffee ground powder

Document Type


Publication Date



American Dairy Science Association


Journal of Dairy Science




Suppl. 1






rheological properties, texture, fortification


The present study evaluated the feasibility of the fortification of Greekstyle yogurt with a newly developed ingredient consisting of cheese whey-spend coffee ground (CW-SCG) powder. The yogurts were analyzed using a battery of tests, including whey production, water holding capacity, firmness, rheological properties, protein content, available lysine, and antioxidant activity. The milk base was fortified to 15% dry matter with different skim milk powder to CW-SCG ratios (100/0, 75/25, 25/75, and 0/100 wt./wt.). The addition of CW-SCG up to 75% did not significantly change the acidification curve when comparing with the control sample (P > 0.05), reaching the target pH 4.7 after 270–300 min. The available lysine decreased with the addition of CW-SCG, yielding values of 78.55 ± 1.56, 28.89 ± 2.45, 23.61 ± 4.42, 20.03 ± 2.71 mg per 100 g for 0-, 25-, 75-, and 100-CW-SCG, respectively. The highest value of whey production was obtained in those samples fortified with 100-CW-SCG (6.33 ± 0.35%), followed by 75- and 25-CW-SCG (5.17 ± 0.99 and 3.01 ± 0.81%, respectively). The antioxidant capacity increased proportionally to the added CW-SCG powder, yielding values of 68.41 ± 2.78, 80.71 ± 2.54, 100.51 ± 3.44, and 120.21 ± 3.18 μmol TEs per 100 g for 0-, 25-, 75-, and 100-CW-SCG, respectively. Fortification of the yogurt with CWSCG decreased the water holding capacity by 13 to 25%, depending on the level of fortification. Similarly, the addition of CW-SCG significantly decreased the hardness of the yogurts from 76.57 ± 1.18 to 30.27 ± 1.73 N s (P < 0.05). Additionally, fortified yogurts with CW-SCG yielded a product with less shear-thinning behavior as compared with control. The scanning electron images of the fortified yogurts revealed the incorporation of spent coffee ground particles within the protein network. Polyphenol-Protein associations may explain the texture and rheological behavior of the yogurts. The fortification of the yogurt up to 25% of CW-SCG yielded comparable properties than the control. The industrial development of fortification of yogurt with small amounts of CW-SCG will require further studies to evaluate consumer acceptance and storage stability