Application Note | CoaguSens™ Flex

Yogurt quality control: Measuring key factors

A case study measuring different brands of Greek yogurt

Common challenges in yogurt manufacturing

Producing yogurt with consistent quality is a technical challenge, even for experienced dairy processors. Variations in milk composition, starter culture activity, and processing conditions can significantly influence the product’s final texture, flavor, and stability. Seasonal changes in milk protein and fat levels, for example, may alter gel structure and syneresis behavior.

Another common challenge is balancing shelf life with sensory quality. While heat treatment and culture selection help ensure microbial stability, they can also impact texture and flavor development. Overacidification during fermentation can lead to excessive sourness and a brittle gel, while underacidification may cause poor firmness and weak structure. Controlling post-fermentation handling, storage temperature, and packaging is equally critical to avoid defects like whey separation or graininess.

Quality parameters in yogurt evaluation

Assessing yogurt quality involves evaluating key rheological and sensory attributes. Parameters like firmness, texture, consistency, and viscosity are not only indicators of consumer acceptance but also essential for process control. Each of these attributes reflects complex interactions between milk proteins, fat, culture selection, fermentation parameters, and processing steps, and each responds differently to formulation and environmental changes.

Yogurt firmness and texture

Firmness describes the gel’s resistance to deformation, closely linked to casein micelle interactions and total solids content. Greek yogurt, with its higher protein concentration, typically exhibits greater firmness and a denser texture compared to set or stirred yogurts. Textural uniformity is a sign of proper gel formation, while brittleness or lumpiness may indicate overacidification, insufficient total solids, or poor mixing practices.

Yogurt consistency

Consistency relates to the cohesiveness and flow behavior of yogurt during spooning or pouring. In Greek yogurt, ideal consistency is thick and uniform without visible whey pockets. It is influenced by protein network density, fat content, and homogenization efficiency. Low consistency can result from excessive whey separation, whereas overly dense consistency may reduce consumer appeal for certain applications.

Yogurt viscosity

Viscosity measures yogurt’s resistance to flow under applied force and is a critical attribute for consumer perception. In strained products like Greek yogurt, viscosity is generally high due to concentrated protein and reduced moisture content. Processing conditions such as incubation temperature, fermentation time, and shear during mixing can either enhance or weaken viscosity. Maintaining target viscosity ensures both mouthfeel quality and stability during transportation and distribution.

Understanding these parameters allows manufacturers to detect early deviations in the production line and implement corrective actions. In the next section, we will explore a practical evaluation of these attributes through testing Greek yogurt texture, consistency and viscoelasticity, comparing multiple commercial brands.

Case Study: Testing Greek yogurt texture, consistency and viscosity

Instrument: CoaguSens™ Flex - Precision sensor for milk coagulation

CoaguSens™ Flex is a specialized and easy-to-use instrument for monitoring milk gel firmness during coagulation and the final yogurt viscoelasticity . Because the coagulation stage defines much of a yogurt’s texture, stability, and sensory profile, CoaguSens™ Flex provides dairy processors with a powerful way to measure and adjust these properties from the lab. Its precise data help manufacturers adapt formulations, improve product uniformity, and optimize process parameters—ensuring that the final yogurt meets both quality specifications and consumer expectations. The instrument typically tests:

the shear elastic modulus (G′): measuring the firmness of the gel;
the shear loss modulus (G’’): measuring the viscous behavior of the gel;
the loss tangent [tan(δ)]: defined as the ratio G’’/G’ indicating the proportion of viscous behavior compared to the elastic behavior of the sample.

Results

Figure 1: CoaguSens™ Flex macro holders with Greek yogurt.

Figure 2: Comparison of the elastic modulus (firmness) of three commercial brands of Greek Yogurts (Oikos, Liberté, Olympic and Skotidakis) at 4 °C.

Figure 3: Comparison of the loss tangent [tan(δ)] and viscous behavior of three commercial brands of Greek Yogurts (Oikos, Liberté, Olympic and Skotidakis) at 4 °C.

The CoaguSens™ Flex was employed to characterize the viscoelastic properties of commercially available Greek yogurts marketed in Canada. The shear elastic modulus (G′), reflecting gel firmness, and the loss tangent [tan(δ)], indicative of viscous dissipation, were quantified for four yogurt samples from different brands. Rheological data were compared with macroscopic observations (visual inspection) and sensory perception (mouthfeel). Results indicated that yogurts perceived as smooth and creamy were associated with lower G′ values and higher tan(δ), suggesting a softer gel structure with enhanced viscous behavior. Conversely, yogurts characterized as thick and firm exhibited higher G′ values, while maintaining comparable tan(δ) values, indicating a more elastic and structured network.

Using precise viscoelastic data to enhance yogurt production

Conclusion

This study highlights the importance of precise rheological measurement in understanding and controlling yogurt quality. Yogurt production presents inherent challenges, as variations in milk composition, starter culture activity, fermentation parameters, and processing conditions can significantly alter the final product’s firmness, consistency, viscosity, and sensory appeal. Traditional reliance on visual inspection and consumer feedback, while valuable, does not provide the level of accuracy needed for consistent industrial quality control.

By employing the CoaguSens™ Flex, we were able to quantify key viscoelastic parameters—namely the shear elastic modulus (G′), associated with gel firmness, and the loss tangent (tan(δ)), indicative of viscous behavior. These measurements were carried out on four commercial Greek yogurt brands available in Canada and correlated with macroscopic observations and mouthfeel. The data revealed a clear relationship between rheological signatures and sensory attributes: yogurts perceived as smooth and creamy showed lower G′ values and higher tan(δ) reflecting a softer, more viscous gel network, whereas thicker and firmer yogurts displayed higher G′ values and similar tan(δ), consistent with a more elastic and structured protein matrix.

These findings demonstrate that objective rheological testing can directly predict consumer-relevant qualities, bridging the gap between process parameters and market expectations. Moreover, they underscore the potential for tools such as CoaguSens™ Flex to serve not only in product development but also in routine quality assurance, where early detection of deviations enables corrective action before products reach the market.

In conclusion, integrating precise viscoelastic measurements into yogurt production workflows provides manufacturers with actionable insights to reduce batch-to-batch variability, optimize formulation strategies, and enhance consumer satisfaction. As dairy processors continue to innovate in response to evolving consumer preferences, such tools will be critical in ensuring both product differentiation and long-term brand reliability.

Testing Sour Cream & Crème Fraîche

Sour cream and crème fraîche are fermented dairy products valued for their smooth texture, delicate acidity, and richness. Despite their apparent simplicity, manufacturing them at scale involves controlling multiple variables. Variations in cream composition, starter culture performance, type and dose of hydrocolloids (or none) and processing conditions can lead to differences in texture, viscosity, and flavor directly impacting product quality and consumer perception.

Real Time Monitoring of Viscoelasticity of Animal and Plant-Based Milk Gels during Fermentation in Industrial Yogurt Production

How to measure yogurt formation in real time – animal and plant-based

The viscoelastic properties of yogurt significantly influences the overall sensory experience of the consumer. A smooth, creamy consistency enhances mouthfeel and consumer satisfaction, serving as a key differentiator among brands. Viscoelasticity affects flavor perception, with variations in thickness and creaminess potentially altering the taste experience, making texture crucial for yogurt appeal and enjoyment.

Yield optimization journey – Phase 3 : Optimizing cheese yield for maximum ROI

Cheese is obtained from coagulating milk by separating the milk gel into solid curds and liquid whey. The milk gel is cut into small cubes to increase curds surface/volume ratio and allow whey expelling from curds, a phenomenon called syneresis. The objective of any cheesemaker is to optimize the retention of fat and proteins in cheese while the level of moisture is maintained at a controlled level.

Yield optimization journey – Phase 2: How to stabilize cheese yield

Cheese is obtained by coagulation of milk and subsequent separation of the milk gel into liquid (whey) and solid (curd) phases. An essential step of the cheesemaking process involves cutting the formed milk gel into small cubes to allow whey separation by increasing curd surface/volume ratio. Cutting time selection greatly affects the yield, moisture and quality of cheese. Cutting the gel too soon when the curd is not firm enough leads to lower cheese yield through increased curd fines and fat loss, whereas delayed cutting results in higher cheese moisture content due to reduced collapse of the gel.