ISO 2169:1981

Overview

ISO 2169:1981 - "Fruits and vegetables - Physical conditions in cold stores - Definitions and measurement" standardizes the physical factors and measurement practices used in industrial cold storage for fruits and vegetables. It defines key storage parameters (temperature, relative humidity, air-circulation ratio, air-change rate), describes measurement methods, and lists suitable instruments and calibration/placement guidance for reliable monitoring in refrigerated rooms.

Key Topics

• Temperature definitions
  • Lethal temperature (causes freezing and tissue death), critical temperature (below which physiological disorders or inhibited ripening occur), and optimal conservation temperature for long-term storage.
  • Distinction between product temperature and air/ambient temperature; cold and hot points within a store.
• Measurement approaches
  • Permanent (continuous reading or recording) vs intermittent monitoring (periodic checks or additional spot measurements).
  • Sensor placement guidance: at characteristic points (cold/hot spots), protected from condensation, radiation and mechanical shock.
• Instruments & calibration
  • Common thermometers: liquid-in-glass, bimetal, vapor-tension, resistance thermometers, thermistors and thermocouples.
  • Hygrometers: hair hygrometers (low accuracy, recommended frequent calibration), electrical probes (suitable up to ~95% RH), and psychrometers (recommended for high RH and accurate calibration).
  • Calibration recommendations: annual calibration for thermometers; regular calibration for hygrometers (document cites monthly calibration example for hair hygrometers); perform calibration under representative airflow/temperature conditions.
• Humidity and equilibration
  • Relative humidity in refrigerated stores depends on product load, packaging, evaporator design, air distribution and the time to reach equilibrium - measure after stabilization.
  • Use aspiration/rotating psychrometers for high RH accuracy.
• Air movement
  • Distinguishes brassage (internal air circulation to homogenize temperature/humidity) and air renewal (ventilation bringing fresh air in).
  • Defines brassage coefficient as air volume moved per hour relative to chamber volume and discusses the need for air renewal to prevent buildup of CO2, ethylene and volatile compounds during cooling and ripening.

Applications

• Cold-storage operators, refrigeration engineers, food technologists, packhouse managers and quality-control teams will use ISO 2169 to:
  • Specify measurement points and instrumentation for monitoring cold rooms.
  • Set monitoring and calibration schedules to ensure food safety and reduce physiological damage (chilling, internal browning, abnormal ripening).
  • Design ventilation and air-circulation systems to control humidity and remove respiratory gases and volatiles.
  • Implement documented, repeatable measurement procedures for audits and compliance.

Related standards

ISO 2169 was prepared by ISO/TC 34 (agri-food products). For best practice, users typically apply ISO 2169 together with other ISO and industry standards on refrigeration systems, storage conditions and packaging - consult relevant ISO technical committees and national guidelines for complementary requirements.