Syneresis provides an indication of the non-homogeneities in the gel system of the yogurt; thus, higher whey separation is related to gel instability which is also related to the pH of the yogurt system (Lucey et al., 1998). Fig. 4 shows the syneresis of lentil flour and skim milk supplemented yogurt and control samples immediately after production and after 14 and 28 days of storage. On day 1, the 3% lentil flour showed the lowest syneresis, which was significantly lower (p b 0.05) than for the 1–3% skim milk supplemented samples, whereas the 1–2% lentil flour supplemented samples had the highest amount of whey separation, which was significantly higher (p b 0.05) than all the other samples. After 14 days storage, the 3% lentil flour supplemented yogurt still showed little syneresis. After 28 days, the 1–3% skim milk
supplemented yogurt samples had the maximum homogeneity (lowest syneresis), followed by the 3% lentil flour, control sample, 2% and 1% lentil flour supplemented samples. Yogurt supplementation with an increase in the total solid content, especially protein content, results in stronger texture and less whey separation (Peng et al., 2009; Lucey, 2001 ). This can explain the lowest syneresis in 3% lentil flour and 3% skim milk supplemented yogurt at day 7 (results not shown) and day 14.