Glycemic Index of Traditional Tarhana Varieties from Türkiye: An In Vitro Study

Tarhana is a traditional fermented cereal–yogurt food widely consumed in Türkiye. It is often described as a low-glycemic index (GI) food, but this belief is based mostly on secondary sources, and direct evidence is limited. This study aimed to evaluate the in vitro GI of different tarhana varieties produced in Türkiye. Seven types—Konya flour, Beyşehir crisp, Maraş, Elbistan, grape, cornelian cherry, and Muğla Göce tarhana—were analyzed using the Englyst hydrolysis method with white bread as the reference. Hydrolysis index (HI) values were calculated and converted to GI using established equations. GI values ranged from 57.25 ± 2.22 to 95.09 ± 0.70, showing clear variation among samples. Konya flour tarhana was classified as low GI, cornelian cherry tarhana as medium GI, and the other five varieties, including grape, Elbistan, and Maraş tarhana, as high GI. These findings challenge the common belief that tarhana is always a low-GI food. They also show that its glycemic response depends strongly on ingredients and processing methods. Although tarhana is nutritionally valuable, some types may impose a high glycemic load. This is especially important for individuals who need to control blood glucose, such as those with diabetes or metabolic syndrome. Because this study was conducted in vitro, further in vivo research is required to confirm the results and guide dietary recommendations.