ISO 11816-2:2024— Fluorimetric Method For Cheese

Expert hands inspecting cheese with a magnifying glass in phytocontrol laboratory performing fluorimetric food testing methods that adhere to ISO 11816-2:2024.

There are a few food safety tests that can be performed on cheese to assure its food safety. One method is fluorescence techniques. ISO 11816-2:2024— Milk And Milk Products – Determination Of Alkaline Phosphatase Activity – Part 2: Fluorimetric Method For Cheese covers a fluorimetric food testing method for cheese.

What Is Fluorimetry?

Fluorimetry is an analytical method that uses ultraviolet light stimulating the compounds, causing them to emit visible light. The energy/light emitted by the substance has a linger wavelength than absorbed. Fluorimetry is used for detecting and measuring fluorescence in compounds or targets such as cells, proteins, or nucleotides. Fluorescence is a type of luminescence caused by photons exciting a molecule, raising it to an electronic excited state.

Fluorometric Techniques in Food Testing

Fluorescence techniques are used for authentication of different food products. In particular, fluorimetry is used for detection of quality changes in food products as well as for determination of the level of lipid oxidation (which is a leading cause of food spoilage) in foods such as fish, meat, and cheese. Lipid oxidation is caused by different factors such as temperature or the presence of light and oxygen. Besides confirmation of food authenticity, fluorescence analysis is used for monitoring various types of bioprocesses, such as yeast or bacterial cultivations.

What Is ISO 11816-2?

ISO 11816-2:2024 specifies a fluorimetric method for the determination of alkaline phosphatase (ALP) (EC activity in cheese. This method is applicable to soft cheeses, semi-hard, and hard cheeses provided that the mould is only on the surface of the cheese and not also in the inner part (e.g., blue veined cheeses). For large hard cheeses, ISO 11816-2:2024  notes that specific conditions of sampling apply.

What To Look For When Testing Cheese

When cheese and cheese products are tested, several characteristics like taste, appearance, texture, and smell are examined. Some cheeses such as blue cheese have a white mouldy appearance and a pungent smell, but they are meant to be that way. As such, cross-matching test results is important; for example, if certain characteristics were present in a block of cheddar, it would not pass the lab test.

How Is Cheese made?

Once milk is brought to the cheese plant, the cheesemakers take samples to assure it passes quality and purity tests. Once it passes, the milk goes through a filter and is standardized (fat, cream, or protein is added). Standardization is important because cheesemakers need to start with the same base milk in order to make a consistent cheese.

Next, the cheese is pasteurized. Pasteurization is necessary because raw milk can harbor dangerous bacteria, and pasteurization kills those bacteria. At this point, good bacteria or “starter cultures” like yeast are added to the milk, fermenting the lactose (milk’s natural sugar) into lactic acid. This process helps determine the cheese’s flavor and texture. Different types of starter cultures are used to create different types of cheese. After the starter culture, a few other ingredients are added, including rennet, which causes the milk to gel.

The amount of rennet and time needed for the cheese to separate into curds can vary from cheese to cheese. Once the cheese starts to gel, the cheesemakers cut it, allowing the whey to come out. Once the curds are cut, they are stirred and heated to release even more whey. At this point, the curd is separated from the whey. Depending on the type of cheese, the curd is either salted and then pressed in a form (e.g., cheddar and colby cheeses), or the curd is pressed into a hoop that is brined (e.g., mozzarella and Swiss cheeses). While the cheese is pressed, more whey comes out, so it eventually becomes the shape and consistency of cheeses we see at the grocery store.

ISO 11816-2:2024— Milk And Milk Products – Determination Of Alkaline Phosphatase Activity – Part 2: Fluorimetric Method For Cheese is available on the ANSI Webstore.

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