A comparison of the quality of plain yogurt and icelandic yogurt (skyr)

The consumption of high-protein products has increased in recent years owing to their high nutritional value and attractive flavor and texture. Icelandic yogurt (skyr) is an example of such products. The available scientific literature lacks the results of a direct comparison of the quality parameters of skyr and traditional yogurt. Therefore, the aim of this study was to compare the quality of plain yogurt and skyr produced from cow’s milk. Regular and drinkable yogurt and skyr produced with the use of Lactobacillus bulgaricus and Streptococcus thermophilus bacteria were analyzed. The physicochemical properties (color, pH, titratable and volatile acidity, water-holding capacity) of both products, and the fatty acid profile and nutritional value of yogurt fat (drinkable yogurts) were compared. The color analysis revealed that skyr was darker (P≤0.05) than plain yogurt, and that the value of a* (redness) was higher (P≤0.05) in drinkable skyr, whereas the value of b* (yellowness) was lower (P≤0.05) in regular skyr. Skyr was also characterized by higher (P≤0.05) titratable acidity and water-holding capacity, and pH was lower (P≤0.05) in regular skyr. No significant differences (P>0.05) in volatile acidity or the nutritional value of fat were observed between the compared products, excluding the n-6/n-3 PUFA ratio which was higher (P≤0.05) in plain yogurt. Further research is needed to identify the factors that are responsible for the observed differences in the quality of plain yogurt and skyr. They can be resulted from natural differences in the milk matrix, but also from production technology, including the quantity and quality of added protein.