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European Project RHEOLACT'

jun 01 2020

RHEOLACT’ (MP0007019) is an innovative regional project, co-funded by the European Union. The Engineering School INP Purpan, the cheese producing company Marzac, and Formulaction are part of the project consortium. The focus of the work is to use new measurement techniques for the characterization of dairy products. In two main working groups, methods are developed for the use of RheolaserMASTER as a powerful tool for characterization of the textural properties of yogurt and for determination of the optimal cutting time of soft cheese preparations.

THE PROJECT IN DETAILS

Working Package 1: A new approach for yogurt characterization using Rheolaser Master

In a first step, different yogurt recipes with varying starter cultures and proteins were prepared (4 different starters and 3 different proteins). A total of 8 recipes using whole and skimmed milk were prepared and analyzed with Rheolaser MASTER. The instrument then allowed the determination of the viscoelastic properties, such as viscosity, elasticity, and solid-liquid behavior. In a third step, a trained panel of testers was involved to describe several recipes after 10 days from fabrication to select key parameters, such as whey amount, stiffness, heterogeneity in the mouth, or after stirring. Finally, the sensorial panel tests were correlated to the microrheological data using a multiparametric linear regression. Model equations were used to describe yogurts with the results of the microrheological data right after preparation to give sensorial descriptors.

These predicted sensorial properties (obtained with the model the day of fabrication) compared to the panel test results on day 10 after preparation. As a result, the models allow a faster screening of starters and proteins in the development of yogurt preparation.

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Working Package 2: Characterization of cheese preparation 

One of the important steps in cheese preparation is the gelation of milk using rennet. Depending on the recipe, milk preparation, and composition, the coagulation time is different. Usually, it is the cheese maker who decides at what time the cheese is to be cut (cutting time) after ripening. Cheese yield and cheese quality depend on the cutting time. The study aimed to develop a model allowing to determine the cutting time based on rheological data obtained in the early stage of cheese preparation.

Yield Cheese maker Rheolaser
Cow 1 18% 19%
Cow 2 13% 13%
Goat 1 16% 18%
Goat 2 17% 16%
Sheep 1 30% 29%
Sheep 2 27% 28%

In the first step, 20 different recipes of soft cheese were analyzed with RHEOLASERMaster and the results were compared to standard cheese-making methods (spoon test, visual observation). In a second step, the microrheological data (Elasticity Index as a function of time) was fit to establish statistical models. Then, the cheese manufacturer Marzac (Revel, France), prepared soft cheeses using cow, goat, and sheep milk in industrial quantities (200L). These were later studied with Rheolaser technology to analyze gelation and determine the cutting time using the preliminary model. After the ripening of the cheese, it was observed that the yield of cheese is in the same order of magnitude than the yield obtained with the cheese maker’s method. 

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