Investigation on the rheological properties of fortified yogurt containing pumpkin powder
2021
Simindokht Johari | Seyyed Hossein Hosseini Ghaboos | Taher Shahi
Yogurt is popular because of its high levels of calcium, vitamins, minerals and low levels of fat, as well as its health-promoting effects and inhibiting harmful bacteria and helping to prolong life. Pumpkin is a good source of β-carotene, water-soluble vitamins and amino acids. In this study, syneresis, pH, acidity and rheological properties of yogurt (1.5% fat) containing 0, 2.5, 5 and 7.5% pumpkin powder were investigated. The results showed that the highest amount of acidity (74° Dornic) was related to the control sample. The results showed that by adding 2.5% pumpkin powder to the control sample, the strength of the formed gel decreased and with increasing concentration up to 7.5%, this property was increased. In the study of the viscoelastic behavior of the samples, it was found that by adding a concentration of 2.5% powder to the control sample, the ratio of viscous to elastic component increases, but with further increase in concentration, this ratio remains almost the same and therefore the viscoelastic behavior remains balanced. The values of loss tangent in the viscoelastic region for the control sample, 2.5%, 5% and 7.5%, were 0.173, 0.308, 0.317 and 0.319, respectively. Therefore, with greater structural cohesion, the consumer feels the same flexibility of the gel regardless of the gel concentration. Also, in all samples, in the whole frequency range, the elastic behavior prevailed over the viscous behavior, which increased by adding 2.5% powder to the control sample, the type of gel structure (b) increased, and the strength of the structure (a) decreased. This means that the yogurt gel becomes weaker and with increasing concentration of the powder, b decreases and a increases; Therefore, the strength of our structure increases.
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