ISO 1955:1982

Overview

ISO 1955:1982 is the reference method published by the International Organization for Standardization for the determination of total essential oils content in citrus fruits and derived products. The method uses boiling and steam entrainment to collect volatile oils into a graduated trap for direct volumetric measurement. It is intended as a laboratory reference method to support quality control, product specification and regulatory testing.

Key Topics

• Principle: Boil a test portion (diluted or undiluted) and entrain essential oils by steam; collect oils in a graduated tube and read the separated oil volume after cooling.
• Scope: Applicable to whole fruits, pieces, peels, juices, concentrates, beverage bases and sweetened products. Thick or pulpy products are diluted 1:1 with water before testing.
• Apparatus: Modified Clevenger‑type entrainment and recovery apparatus comprising a condenser and trap terminating in a graduated tube (capacity ~4 ml, 0.05 ml divisions). A 3 litre flask, 2 litre graduated cylinders and a boiling aid are specified.
• Test portion: Typical test portion is 2 litres of sample (measured before dilution). For products very rich in essential oils the test portion may be reduced (e.g., 1 litre) with corresponding apparatus adjustments.
• Procedure: Heat until boiling and maintain a slow distillate rate (about one drop per second). Allow 1–3 hours of boiling so oils accumulate in the trap. Stop heating when oil volume stabilizes for 15–30 minutes; cool and adjust the lower oil boundary to the zero mark before reading the upper meniscus.
• Results & repeatability: Perform two determinations on the same sample and report the arithmetic mean, expressed in mL per 100 mL or per 100 g of product. Repeatability requires the two values to differ by no more than 5% (relative) of the mean.

Applications

• Quality control and specification testing of citrus juices, concentrates and flavor bases
• Verification of raw material and finished product oil content for sensory and stability assessments
• Support for regulatory compliance and trade agreements where essential oil content is a defined attribute
• Development and calibration of routine laboratory methods where a reference procedure is required

Related Standards

• Developed by ISO Technical Committee ISO/TC 34 (Agricultural food products); consult this committee for related fruit and juice standards.
• For laboratories adopting ISO 1955:1982 as a reference, cross‑check with relevant national standards and internal SOPs for sample preparation and equipment validation.

ISO 1955:1982 remains a practical, repeatable reference method for accurate measurement of essential oil content in citrus products, providing a standardized basis for laboratory QC and regulatory reporting.