ISO 10718:2015

Overview

ISO 10718:2015 - "Cork stoppers - Characterization of a low‑in‑germs stopper…" specifies a microbiological method to characterize low‑in‑germs cork stoppers. The standard defines how to enumerate colony‑forming units (cfu) of yeasts, moulds and bacteria that can be extracted from ready‑to‑use cork stoppers into an alcoholic medium and are capable of growth within three months after delivery. It also sets the limit values that define a stopper as low‑in‑germs.

Key topics and technical requirements

• Scope and applicability: Applies to all types of ready‑to‑use cork stoppers that have undergone a sanitation process and are aseptically, hermetically packaged.
• Extraction medium: Corks are extracted in an alcoholic solution with added tartaric acid and wetting agents; extraction conditions (shaking, temperature) are specified to simulate release into alcoholic beverages.
• Membrane filtration: Extracts are filtered through a 0.45 μm membrane prior to culture. Two filtration approaches are described:
  • Ready‑to‑use sterile filtration systems and ready‑to‑use media.
  • Traditional sterilizable filtration systems with dehydrated media prepared in the laboratory.
• Culture media:
  • WLD for counting bacteria (with added diphenyl to specified concentration).
  • M‑Green for counting yeasts and moulds.
• Incubation and counting: Plates are incubated at 30 °C ± 2 °C for 3 days with daily observations. Results are expressed as cfu per cork stopper (N/4 for four stoppers per flask) and reported as the arithmetic mean rounded upwards.
• Acceptance criteria (low‑in‑germs):
  • < 10 cfu bacteria per stopper
  • < 10 cfu yeasts and moulds per stopper
• Quality controls: Includes blank tests, aseptic sampling (ISO 17727 referenced), and general microbiological practice (ISO 7218 referenced).

Applications and users

ISO 10718:2015 is used by:

• Cork manufacturers and suppliers for product qualification and certification of sanitation processes.
• Microbiological testing laboratories performing quality control on cork batches.
• Wineries, bottlers and beverage producers who require assurance that stoppers will not introduce spoilage organisms into alcoholic products.
• Regulatory and certification bodies overseeing packaging hygiene and food safety.

Practical value: Implementing ISO 10718 helps reduce microbiological spoilage risk in bottled alcoholic beverages, supports traceable QC, and provides objective acceptance limits for low‑in‑germs cork stoppers.

Related standards

• ISO 7218 - Microbiology of food and animal feeding stuffs: general requirements and guidance for microbiological examinations.
• ISO 17727 - Cork stoppers for still wine: sampling plan for quality control of cork stoppers.

Keywords: ISO 10718:2015, cork stoppers, low‑in‑germs, colony‑forming units, yeasts, moulds, bacteria, alcoholic medium, membrane filtration, WLD, M‑Green, microbiological testing.