ISO 935:1988

Overview

ISO 935:1988 is an internationally recognized standard established by the International Organization for Standardization (ISO) that specifies a precise method for the determination of the titre (solidification temperature) of animal and vegetable fats and oils. The titre is an essential physical characteristic indicating the temperature at which water-insoluble fatty acids derived from fats and oils solidify upon cooling. This standardized test method focuses on saponifying the fats or oils, isolating the insoluble fatty acids, and measuring their solidification temperature through controlled cooling and stirring. Note that this method applies only to fats and oils with titres above 30°C.

Key Topics

• Scope and Applicability

  • Designed for animal and vegetable fats and oils
  • Methods tailored to water-insoluble fatty acids
  • Not applicable for titres below 30°C

• Test Principle

  • Saponification of test samples with potassium hydroxide solution in glycerol
  • Separation and washing of insoluble fatty acids using hot sodium chloride solution
  • Drying and filtering to obtain purified fatty acids
  • Melting followed by controlled cooling with continuous stirring to observe solidification temperature

• Reagents and Materials

  • Potassium hydroxide solution in glycerol
  • Sulfuric acid solution for neutralization
  • Sodium chloride and sodium sulfate for washing and drying
  • Methyl orange indicator to determine neutralization
  • Distilled or equivalent purity water

• Apparatus Requirements

  • Glassware including flat-bottom flask or beaker, Büchner flask
  • Electric hot plate with temperature regulation
  • Cooling apparatus with continuous agitation mechanism
  • Precise thermometer with 0.1°C graduations

• Test Procedure Highlights

  • Sample saponification by heating with potassium hydroxide-glycerol mixture
  • Acidification and phase separation
  • Washing and drying of fatty acids at elevated temperatures
  • Melting and cooling while observing temperature changes to identify the titre
  • Performing duplicate tests to ensure repeatability within 0.2°C

• Result Expression

  • Report titre as the mean of two consistent determinations
  • Include all operational details and deviations in the test report

Applications

The ISO 935:1988 method is essential in quality control, research, and regulatory compliance within the fats and oils industry. Accurate determination of the titre helps in:

• Assessing the physical properties and consistency of animal and vegetable fats and oils
• Controlling processing parameters in food manufacturing and cosmetics
• Ensuring conformity with trade specifications and international standards
• Characterizing raw materials and finished products for proper classification
• Supporting product development through detailed thermal property analysis

The method’s reliable assessment of solidification temperature assists industries in handling, storage, and formulation decisions, impacting product texture, stability, and performance.

Related Standards

• ISO 661 - Preparation of animal and vegetable fats and oils samples for testing
• ISO 5555 - Sampling techniques for animal and vegetable fats and oils
• Additional ISO standards related to fat and oil composition, quality, and testing methods

For comprehensive understanding, ISO 935 is often employed alongside these standards to ensure consistency, accuracy, and full compliance in analytical workflows.

Keywords: ISO 935, titre determination, solidification temperature, animal fats, vegetable oils, fatty acids, saponification, standardized method, fats and oils testing, potassium hydroxide solution, quality control in fats and oils.