ISO 4833-2:2013

Overview

ISO 4833-2:2013 - "Microbiology of the food chain - Horizontal method for the enumeration of microorganisms - Part 2: Colony count at 30 °C by the surface plating technique" defines a standardized surface-plating method to enumerate aerobic bacteria, yeasts and moulds that form colonies on solid media after incubation at 30 °C. The method is intended for food and feed products and for environmental samples from food/feed production and handling areas. An annex also describes a rapid surface-count option using a spiral plater.

Key topics and technical requirements

• Scope & applicability: Designed for products with heat-sensitive or obligately aerobic organisms (e.g., psychrotrophs, Pseudomonas spp.), foods with small particles or intense colour, and situations where colony morphology discrimination is needed. Applicability to some fermented foods and feeds is limited; alternative media/incubation may be more appropriate.
• Principle: Surface plate specified sample volumes on Plate Count Agar (PCA); incubate aerobically at 30 ± 1 °C for 72 ± 3 h, then count colonies on plates with fewer than 300 colonies.
• Culture media: Plate Count Agar (PCA) is specified (enzymatic digest of animal tissues, yeast extract, glucose, agar; skimmed milk powder may be added for dairy). Preparation, pH control and sterilization follow ISO 11133.
• Sample handling: Test portion, initial suspension and decimal dilutions in accordance with ISO 6887; follow ISO 7218 for general microbiological requirements.
• Inoculation volumes: Typical inoculum is 0.1 ml per plate; for lower detection limits, 1.0 ml may be used on larger or multiple plates. Pour 15–20 ml agar into plates (90–100 mm or 140 mm diameter).
• Counting rules: Include pinpoint colonies, treat spreading colonies as single colonies with guidance for partially overgrown plates; select plates with fewer than 300 colonies for calculation.
• Quality & performance: Media productivity and performance testing per ISO 11133; reference strains and productivity ratio criteria are provided.

Applications and users

• Who uses it: Food and feed microbiology laboratories, QA/QC teams, regulatory agencies, contract testing labs, and equipment suppliers (e.g., plate spreaders, spiral platers).
• Practical uses: Routine total viable counts for raw materials, finished products, environmental monitoring of production areas, product release testing, shelf-life studies and troubleshooting suspected aerobic spoilage.
• Benefits: Standardized enumeration, improved colony discrimination on coloured or particulate matrices, and an option for higher throughput using a spiral plater.

Related standards

• ISO 4833-1 (pour plate technique) - complementary method
• ISO 6887 - sample preparation and dilutions
• ISO 7218 - general microbiology requirements
• ISO 11133 - culture media preparation and performance testing

Keywords: ISO 4833-2, surface plating technique, colony count at 30 °C, Plate Count Agar, spiral plater, microbiology of the food chain, enumeration of microorganisms, aerobic incubation.