Physicochemical, rheological and stability characterization of a caramel flavored yogurt

The effects of formulation and storage time on the physicochemical and rheological properties of a stirred yogurt, with the inclusion of a Mexican caramel jam (“cajeta”) as a flavor source, were studied. The systems were prepared by following a factorial design, analyzed after formulation and during four weeks of storage by studying three factors: fat, caramel, and κ-carrageenan with different levels. Formulation as well as the storage time influenced in a different degree both properties: physicochemical and flow. Soluble solids and moisture were stable, pH decreased while acidity augmented; the luminosity remained constant but redness and yellowness showed an inverse relationship as a function of storage. The non Newtonian behavior of the flavored yogurt was fitted by the Herschel and Bulkley model, in which fat increased the yield stress and consistency coefficient; both parameters increased with storage in contrary to the flow behavior index. Dynamic tests and microscopy observations completed the characterization, a weak gel was identified.