Moisture and Total Solid Determination of Milk-Based Products Comparing Automated Thermogravimetric and Air Oven Loss-on-Drying Techniques

Significance of the Topic

Accurate moisture and total solid analysis in milk-based products is essential for quality assurance, safety, and regulatory compliance. Moisture content influences texture, taste, microbial stability and is a key factor in calculating product purity and yield on a dry basis.

Objectives and Study Overview

This study compares an automated thermogravimetric analyzer with a manual air oven loss-on-drying method following official AOAC protocols for milk and cheese analysis. Four commercial milk and four cheese samples were evaluated to assess performance, precision and throughput.

Methodology

Manual methods were conducted according to AOAC 925.23 for total solids in milk and AOAC 948.12 for moisture in cheese, involving sample drying in air ovens at specified temperatures, followed by desiccation and weighing.

Instrument Used

The automated analyzer is a thermogravimetric instrument capable of processing up to 16 samples simultaneously, controlling temperature ramp, hold time and gas flow, and detecting endpoints based on mass constancy. Multiple sample crucible sizes and atmospheres are supported.

Key Findings and Discussion

Results from the automated analyzer were consistent with manual oven methods. The automated system demonstrated improved precision, with standard deviations reduced by up to an order of magnitude in some samples. Analysis times were shortened by 30 to 40 minutes under fixed time protocols and up to 150 minutes using mass constancy endpoint detection.

Benefits and Practical Applications

• Compliance with official AOAC methods and flexibility for method modifications
• Reduced operator involvement and minimized sample handling
• Higher throughput and faster results
• Enhanced precision and reproducibility

Future Trends and Potential Uses

Automated loss-on-drying systems are likely to see broader adoption in dairy and food laboratories, integration with laboratory information systems, and application to a wider range of matrices. Advances in real-time data analysis and endpoint detection algorithms may further reduce analysis time and improve reliability.

Conclusion

The automated thermogravimetric approach offers significant advantages over traditional air oven methods, delivering accurate, precise and efficient moisture and total solid determinations for milk-based products.

References

• AOAC Official Method 925.23 Solids Total in Milk
• AOAC Official Method 948.12 Moisture in Cheese