Simultaneous Effects of Total Solids Content, Milk Base, Heat Treatment Temperature and Sample Temperature on the Rheological Properties of Plain Stirred Yogurt

Ana Lúcia Barretto Penna¹*, Attilio Converti² and Maricê Nogueira de Oliveira³

¹UNESP-Universidade Estadual Paulista, Dept. Food Technology and Engineering, Rua Cristóvão Colombo 2265, 15054 000 São José do Rio Preto, Brazil
²Università degli Studi di Genova, Dipartimento di Ingegneria Chimica e di Processo, Via Balbi 5, I-16126 Genova, Italy
³USP–Universidade de São Paulo, Dept. Pharm. Biochem. Technology, Av. Lineu Prestes 580, 05508 900 São Paulo, Brazil

Article history:
Received July 6, 2005
Accepted January 30, 2006

Key words:
yogurt, rheology, apparent viscosity, consistency, flow behaviour

Summary:
Response surface methodology was used to establish a relationship between total solids content, milk base, heat treatment temperature, and sample temperature, and consistency index, flow behaviour index, and apparent viscosity of plain stirred yogurts. Statistical treatments resulted in developments of mathematical models. All samples presented shear thinning fluid behaviour. The increase of the content of total solids (9.3–22.7 %) and milk base heat treatment temperature (81.6–98.4 °C) resulted in a significant increase in consistency index and a decrease in flow behaviour index. Increase in the sample temperature (1.6–18.4 °C) caused a decrease in consistency index and increase in flow behaviour index. Apparent viscosity was directly related to the content of total solids. Rheological properties of yogurt were highly dependent on the content of total solids in milk.

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