Physicochemical and rheological characteristics of commercial Greek-style yogurt enriched with Polygonum cuspidatum roots or the P. cuspidatum beta-cyclodextrin inclusion complex

Abstract

In this work, the effects of enriching commercial Greek-style yogurt with β-cyclodextrin-encapsulated Polygonum cuspidatum hydroalcoholic extract powder (YE) or P. cuspidatum root powder (YR) on the physicochemical properties of yogurt were compared. Greek-style yogurt was used as a control (YC). The yogurt samples were characterized by their pH, color, water content, water activity, droplet size, small amplitude oscillation shear (SAOS), and large amplitude oscillation shear (LAOS) viscoelastic properties, thixotropy, and syneresis. The pH, water content and water activity did not significantly differ among the yogurt samples. The YR and YE had yellowish-green colors, displaying values of 79.8, -5.39 and 23.42 and 68.29, -3.45 and 25.45 for L*, a* and b*, respectively. The average particle size of YE (30.3 µm) was larger than those of YR (26.8 µm) or YC (25.2 µm), displaying bimodal distributions. The yogurts predominantly exhibited elastic behavior, with slight frequency dependence, characteristic of weak gel structures. The SAOS and LAOS results showed that YE presented the highest viscoelastic properties, probably due to the greater degree of structuration provided by the free hydroxyl groups of the encapsulated polyphenols and the yogurt proteins. The thixotropy results revealed that YE (-501 ±29 Pa) and YR (-468 ± 31 Pa) exhibited greater restructuring after deformation than did YC (-1022 ± 68 Pa). However, compared with YC, YE resulted in gels with a greater degree of syneresis (∼7% more). These results suggest that Greek-style yogurt could be an effective route for incorporating beneficial antioxidant compounds. However, more studies are needed to demonstrate its efficacy and acceptance by consumers.