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Measuring the pH of yogurt presents significant challenges due to its semi-solid consistency that hinders effective interaction between the reference electrolyte and the sample. Traditional pH sensors struggle to penetrate the yogurt without risking damage to their delicate, spherical sensing membranes. The high fat and protein content of yogurt further complicates the process by reducing miscibility, leading to unstable readings and longer response times. These factors along with others outlined below, contribute to the overall difficulty in obtaining accurate pH measurements of yogurt.
METTLER TOLEDO’s InLab Solids Pro-ISM is a cutting-edge sensor designed specifically for accurate and precise pH measurement in yogurt. Featuring a spear-shaped tip made of toughened glass, this sensor can be directly inserted into yogurt samples without risk of damage. Its low-maintenance solid XEROLYT®EXTRA polymer reference system offers two key advantages: a clog-free open junction that prevents protein fouling, and an interaction mechanism that uses diffusing ions, overcoming the immiscibility issues of aqueous reference electrolyte with the sample. The specialized design and advanced technology of the InLab Solids Pro-ISM ensure reliable and consistent pH measurements, which are crucial for maintaining high standards in yogurt manufacturing and quality control.
Download our application note on pH measurement in yogurt for detailed insights and learn about the advantages of using the right sensor and best measuring practices.
In this section, we delve into yogurt manufacturing and the crucial role of pH in ensuring consistent quality.
What is yogurt?
Yogurt is a nutritious food created through the bacterial fermentation of milk. It serves as a probiotic carrier thanks to its live bacterial strains.
What happens during the fermentation process?
In yogurt production, bacterial cultures convert milk sugars (lactose) into lactic acid, imparting the product's characteristic tartness and texture. This process lowers milk's pH from 6.7 to 4.6 pH units or below, a crucial step in creating high-quality yogurt.
What are the different stages in yogurt manufacturing?
- The process starts with homogenizing, pasteurizing, and cooling the milk to the incubation temperature before adding the starter culture.
- Fermentation begins with the introduction of live bacterial strains at an optimal temperature.
- The decrease in pH due to lactic acid formation is carefully monitored and controlled until it reaches the manufacturer's target, typically below 4.6 pH units.
- The yogurt is partially cooled to below 20°C, and any desired fruit or flavoring ingredients are added.
- Finally, the yogurt is transferred to cold storage to halt further acid development and preserve quality.
Why is monitoring the pH of yogurt important?
A correlation between the pH of post-storage yogurt and the survival of probiotic bacterial strains serves as an indicator of the shelf life of the yogurt products. Accurate pH measurements are essential throughout the manufacturing and quality control processes, as they influence the probiotic benefits, taste, and shelf stability of yogurt. Therefore, monitoring pH during manufacturing is a key parameter in ensuring the quality and consistency of the final product.
