ISO 10399:2017

Overview

ISO 10399:2017 - Sensory analysis - Methodology - Duo‑trio test specifies a standardized, forced‑choice discrimination procedure (the duo‑trio test) for determining whether a perceptible sensory difference or similarity exists between two product samples. The method is applicable when differences may be in one or several sensory attributes and is effective even when the nature, size or direction of the difference is unknown. It is statistically less efficient than the triangle test (ISO 4120) but is easier for assessors to perform and is suitable when products are fairly homogeneous.

Key technical topics and requirements

• Test principle: Assessors receive a triad (one reference plus two coded samples); they must identify which coded sample is the same as (or different from) the reference. Correct responses are counted and assessed against statistical criteria.
• Two techniques:
  • Constant‑reference: use when one product is familiar to assessors (e.g., control from production).
  • Balanced‑reference: use when neither product is more familiar.
• Assessors:
  • All assessors should have equivalent qualification and be familiar with the duo‑trio format.
  • Typical panel sizes: ~32–36 assessors for difference testing; roughly double (≈72) for similarity testing to achieve comparable sensitivity.
  • Guidelines for replication and monitoring assessor performance are provided.
• Test conditions:
  • Follow general sensory test-room guidance (ISO 8589) and vocabulary (ISO 5492).
  • Samples must be prepared identically, coded randomly, presented under controlled lighting/temperature and served in equal portions.
  • Prevent assessor communication and bias; collect completed scoresheets between triads.
• Analysis and reporting:
  • Use the standard’s statistical tables and procedures to evaluate significance (α and β risks).
  • Test report must document objective, procedure, panel details, results and interpretation.
• Annexes: normative tables and informative examples (precision and bias considerations).

Practical applications

• Quality control and product QA: detect changes after formulation, processing, packaging, handling or storage.
• Product development and reformulation: confirm whether a change produces a perceptible difference.
• Sensory panel management: selecting, training and monitoring assessors.
• Regulatory or supplier verification where demonstrable sensory equivalence is required.

Who should use ISO 10399:2017

• Sensory scientists and laboratory managers
• R&D and product developers in food, beverage and other consumer goods
• Quality assurance and QC teams
• Consumer insights and regulatory professionals

Related standards

• ISO 4120 - Triangle test (more statistically efficient discrimination test)
• ISO 8589 - Test room design
• ISO 5492 - Sensory analysis vocabulary

Keywords: ISO 10399, duo‑trio test, sensory analysis, discrimination test, similarity testing, constant‑reference, balanced‑reference, assessors, quality control.