Analysis of dairy products

Importance of the topic

Analytical profiling of dairy products ensures food safety, quality control, and compliance with regulatory standards. Monitoring acidity, ionic content, oxidative stability, and lactose levels is critical for product consistency and consumer health.

Objectives and Study Overview

This bulletin presents validated methods for:

• Titrimetric determination of titratable acidity in milk, dried milk, and yogurt
• Argentometric analysis of chloride in milk, butter, and cheese
• Thermometric titration of sodium in milk
• Oxidation stability assessment of fats and oils by the Rancimat method
• Ion chromatographic quantification of sugars including lactose and lactulose in lactose-free milk

All procedures align with current ISO, IDF, DIN, and AOCS standards to support routine laboratory practice.

Methodology and Instrumentation

A range of instruments and consumables were employed:

• Potentiometric titrator (SET and DET modes) with Porotrode and Ag Titrode electrodes, burettes and stirrers
• Thermometric titrator configured with Thermoprobe HF sensor for Al/K thermometric titrations
• Rancimat oxidative stability tester for accelerated aging studies
• Ion chromatograph equipped with Metrosep Carb 2 column, inline dialysis, and pulsed amperometric detection

Main Results and Discussion

• Titratable acidity in fresh milk ranged from 160–190 mL of 0.1 M NaOH per liter, with elevated values indicating spoilage or udder disease.
• Chloride levels of 90–110 mg/100 mL in milk; salted butter contains 0.5–2 % salt while unsalted remains below 0.1 %.
• Thermometric titration enabled rapid sodium determination (~40–50 mg/100 mL) with high precision.
• Rancimat induction times for clarified butter typically doubled with each 10 °C decrease, illustrating temperature-dependent stability.
• Ion chromatographic separation achieved clear resolution of lactose and lactulose in lactose-free milk, with lactose detected below regulatory limits.

Benefits and Practical Application

These automated, standardized assays offer:

• High throughput and reproducibility for QA/QC laboratories
• Compliance with international food regulations
• Capability to distinguish product quality attributes (e.g., spoilage, adulteration)
• Minimal sample preparation and reduced reagent consumption

Future Trends and Potential Applications

Emerging directions include:

• Integration of online sensors for real-time process monitoring
• Miniaturization and lab-on-a-chip platforms for field testing
• Advanced data analytics and AI-driven quality control
• Green chemistry approaches to reduce hazardous reagents

Conclusion

The suite of titrimetric, thermometric, Rancimat, and chromatographic methods constitutes a comprehensive toolkit for dairy analysis, balancing speed, accuracy, and regulatory compliance.

References

• ISO/TS 11869 / IDF/RM 150
• ISO 6091 / IDF 86
• DIN 10316
• EN ISO 5943 / IDF 88
• ISO 15648 / IDF 179
• ISO 21422 / IDF 242
• AOCS Cd 12b-92
• ISO 6886 / GB/T 21121