ISO 7238:2004

Overview

ISO 7238:2004, published by the International Organization for Standardization (ISO) in collaboration with the International Dairy Federation (IDF), specifies a potentiometric method for determining the pH of the serum phase in all types of butter. This standardized test method is essential for assessing the acidity and quality of butter by measuring the pH of its aqueous serum phase using precise electrochemical means. The method ensures reliable, reproducible results necessary for quality control and regulatory compliance in dairy production and research.

Key Topics

• Scope: Applicable to all varieties of butter, this standard defines the procedure to measure the pH of the aqueous serum separated from butter.
• Principle: The pH is determined potentiometrically by measuring voltage differences between a glass electrode and a reference electrode immersed in the serum, expressing results as pH units.
• Sample Preparation: Butter is melted and centrifuged to separate the aqueous phase, which contains dissolved proteins and other soluble components.
• Apparatus: Requires a calibrated pH meter with combined electrodes, centrifuge, water baths (hot and ice), and standard laboratory glassware.
• Calibration: Utilizes buffer solutions at known pH levels (commonly pH 4 and 7) adjusted to measurement temperature to ensure meter accuracy.
• Measurement Procedure:
  • Heat and centrifuge butter to isolate serum.
  • Equilibrate serum to test temperature.
  • Calibrate pH meter.
  • Immerse electrodes and record pH value at stability within 0.01 pH units.
  • Clean electrodes properly to maintain accuracy.
• Results Expression: pH values are reported with 0.01 unit precision along with the temperature at measurement.
• Accuracy and Reproducibility:
  • Repeatability limit: 0.03 pH units under same conditions.
  • Reproducibility limit: 0.10 pH units across different labs and operators.

Applications

ISO 7238:2004 is widely adopted in the dairy industry and laboratories for:

• Quality Control: Monitoring pH ensures product quality, freshness, and consistency of butter.
• Shelf-life Assessment: pH changes can indicate spoilage or microbial activity.
• Product Development: Evaluating effects of production variables on butter acidity.
• Regulatory Compliance: Assists manufacturers in meeting food safety and labeling regulations.
• Research: Provides standardized data for scientific studies on dairy chemistry and microbiology.

This method benefits manufacturers, quality assurance personnel, and food scientists requiring precise characterization of butter acidity to maintain high standards and optimize production processes.

Related Standards

• ISO 707: Guidelines for sampling milk and dairy products, essential for obtaining representative butter samples for testing.
• ISO 3696: Specifies the quality requirements for laboratory water used in analytical testing, ensuring reagent purity.
• ISO 2446:1976: Method for determining fat content in milk, complementing pH testing by providing compositional data.
• Additional standards by ISO and IDF on dairy product testing reinforce consistent, accurate analyses across the dairy sector.

Keywords: ISO 7238:2004, butter pH determination, potentiometric method, butter serum phase, dairy quality control, pH measurement butter, butter acidity testing, dairy standardization, butter quality analysis, ISO butter testing method.