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ISO 21527

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This standard test method deals with the procedures for the enumeration of viable yeasts and molds in foods and animal feeds. Since such microorganisms naturally occur in many environments, food spoilage and health hazards are associated with large populations. Testing products for conformity to this standard means assurance of the quality of the microbe population in such products. Since water activity impacts microbial growth, it is divided into two parts:

  • ISO 21527-1: Applied to products with water activity greater than 0.95 (such as fresh produce, meats, and soft cheeses). These products are perishable and highly susceptible to fungal contamination.
  • ISO 21527-2: Targets products with water activity of less than or equal to 0.95. Examples include grains, spices, and dried fruits, and these are less prone to spoilage and more likely to harbor osmophilic yeasts and xerophilic molds.

ISO 21527 Test Conditions

The test conditions are:-

  • Temperature: The plates are incubated at 25°C ± 1°C. This incubation temperature is optimal for mesophilic yeast and mold species, which are common pathogens affecting food and feed products. This critical temperature is necessary for ideal colony growth and to avoid false negative results.
  • Incubation Period: Incubation typically lasts 5 to 7 days, depending on the water activity of the product under test.
  • For ISO 21527-1: Products with high water activity (aw > 0.95) incubate for five days.
  • For ISO 21527-2: Products with lower water activity might take up to 7 days for the full development of slow-growing osmophilic yeasts and xerophilic molds.
  • Medium: Two selective culture media are specified:

Dichloran-rose Bengal chloramphenicol agar (DRBC) is used for products with higher water activity, and dichloran 18% glycerol agar (DG18) is used for drier products.

  • Oxygen Conditions: Plates are aerobically incubated.

ISO 21527 Test Requirements

  • Sample Preparation: Test portions are homogenized to ensure even microbial distribution.
  • Serial Dilutions: Decimal dilutions are used to allow the enumeration of viable microorganisms.
  • Sterile Equipment: Pipettes, Petri dishes, and incubators must be sterile to avoid contamination.
  • Contamination Prevention: Proper aseptic handling is essential to ensure reliable results.
  • Identification: If necessary, microscopic examination is used to confirm doubtful colonies​

ISO 21527 Test Methodology

The process involves the following steps:

1. Sample Preparation

Samples are homogenized to achieve an even microbial distribution. Peptone water broth is used to make dilutions with a concentration of 0.1% to obtain sustainable microbial counts for enumeration. 

2. Inoculation of Agar Plates

A known amount of the diluted sample is plated to each of the sterilized petri dishes. The sample is then spread evenly all over the agar plate by using the sterile spreader. The inoculated plates are dried out in a sterile environment that has to minimize the chances of contamination and maximizes the clear colony growth.

3. Incubation

Plates are incubated at 25°C ± 1°C for 5 to 7 days. Some plates may need exposure to diffuse daylight for one or two days for better fungal growth and more visible colonies.

4. Colony Enumeration and Identification

  • After incubation, the plates are examined visually or with the help of a binocular magnifier.
  • For example, if the colonies appear ambiguous-contaminated by bacteria or mixed colonies-microscopic observation of a wet mount confirms the identity of yeast or mold colonies.
  • The total microbial load is measured in terms of colony-forming units per gram or milliliter (CFU/g or CFU/mL) of the product tested.

Importance of ISO 21527 Test

This standardized test method evaluates contamination by yeasts and molds on food and feed products which would, therefore, compromise on safety and quality. Its application will help businesses avoid spoilage while offering a more extended shelf life. Following this standard helps businesses meet the regulatory requirements and assure customers about their products. This test also supports international trade since it maintains standards as per the market, which reduces the risk of product recall and subsequently maintains the high quality of the product.

Compliance and Industry Standards for ISO 21527

This standard ensures that food and feed products meet the global requirements of safety and quality control. Alignment of frameworks such as HACCP and ISO 9001 will ensure uniform control of microbes, reduce the risks of contamination, and ensure compliance with regulations from different markets. Further compliance in quality standards ensures international trade since it meets the expected quality standards from global regulatory bodies.

Pros of ISO 21527 Test Standard

  • Accurate detection of microorganisms: This product can precisely enumerate yeasts and molds, providing proper contamination control.
  • Broad Applicability: Through this test standard, it is possible to test a wide range of food and feed products, including those with varying water activity levels.
  • Supports Compliance with Regulatory Standards: This standardization ensures food safety compliance with international standards such as  HACCP .
  •  Facilitates Global Trade: Eases access to international markets by ensuring compliance with global standards ISO 9001.

Conclusion

This test standard is crucial in providing a reliable method that will allow the detection of yeasts and molds to ensure the safety, quality, and regulatory compliance of food and feed products. It provides the standard approach that helps prevent spoilage and manage contamination risks, so it may prove helpful to manufacturers to maintain their product integrity along the supply chain. It also supports the smooth execution of international trade because it avails global standards, such as HACCP and ISO 9001, thus promoting consumer trust.

MIS offers comprehensive validation services that meet the highest industry standards, ensuring your products are safe, effective, and ready for market success. Contact us today to learn more about our testing services.

FAQs

It is a standard test that is recognized for the enumeration of yeasts and molds in food and animal feed products.

The standard test method applies to food and feed products, which include fresh produce, dairy, meats, grains, dried fruits, spices, and baked goods, based on their water activity levels.

The turnaround time typically ranges from 5-7 days , depending on the product’s water activity and microbial growth rate.

Commonly used organisms include Candida albicans and Saccharomyces cerevisiae for yeasts, and various Aspergillus species for molds

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