3M helps keep lactic acid bacteria under control

The 3M Petrifilm Lactic Acid Bacteria Count Plate

3M Food Safety has launched a plate to monitor lactic acid bacteria levels in food products and manufacturing environments.

The 3M Petrifilm Lactic Acid Bacteria Count Plate eliminates the need for anaerobic equipment used with traditional methods, said the firm.

It combines oxygen-scavenging technology and oxygen-barrier films to create a self-contained anaerobic environment.

3M said it is for manufacturers of meat, juices and milk, fish and poultry products, processed foods, produce, dairy products, and dressings and sauces.

Food processors and testing laboratories can get anaerobic results using aerobic incubation conditions, providing enhanced recovery of lactic acid bacteria within 48 hours.

All in one method

John David, 3M Food Safety global marketing manager, said the method for lactic acid bacteria testing can depend on the type of food or the type of lactic acid bacteria.

“Lactic acid bacteria are a large, diverse group of organisms. There isn’t one single method; it can depend on the type of food or the specific lactic acid bacteria. Traditional agar-based culture methods can take up to five days and require incubation under anaerobic conditions, which adds complexity and cost. 

“We wanted to create an all-in-one method for lactic acid bacteria testing that can be used across a wide variety foods and also environmental samples, capturing the range of these bacteria – as universal a method as we could develop.”

There is no single agar for lactic acid bacteria testing but there are two main types based on selectivity - MRS (deMan, Rogosa and Sharpe) and APT.

The test involves three steps - after preparing dilution of the sample, typically 1 to 10, add 1mL of sample to the plate, incubate for 48 hours and then count colonies.

A red indicator dye in the plate reacts with growing bacteria allowing colony visualization.

Heterofermentative (gas producing) lactic acid bacteria produce gas bubbles near the colony, allowing for differentiation from homofermentative (non-gas producing) lactic acid bacteria without extra steps.

David said if high levels of lactic acid bacteria are found a solution could be to look at raw material quality or implement enhanced cleaning for equipment to control environment.

“Enumeration of lactic acid bacteria is not highly regulated, as lactic acid bacteria are a quality indicator and are not pathogenic. Lactic acid bacteria can cause spoilage, leading to food waste and recalls, for example, if a product is seen to be bloating. It could be a part of an environmental monitoring program used in some plants.

“With hot-filled or shelf stable products such as condiments or pasta sauces, levels of lactic acid bacteria as low as 1 cfu/g could be a problem.

“We conduct verification testing at 3M, and also pursue external validations with organizations such as AOAC International and NF Validation by AFNOR Certification.

“We recommend that customers test the plate alongside their current method, determine the criteria, and we work with them to analyse results and start implementation.” 

Used as a hurdle

David said lactic acid bacteria could be used as a hurdle for other microorganisms as it outcompetes them, but it was important to get the balance between protection and spoilage right.

“There is also the bio-protective aspect of lactic acid bacteria. They are used to protect from pathogens such as Clostridium botulinum. Lactic acid bacteria are used as a hurdle to prevent growth, the level lowers pH of the food product and outcompetes Clostridium botulinum from growing.”

Lactic acid bacteria can help produce fermented foods from smooth yogurts to crunchy pickles or for probiotic purposes.

But under low oxygen or temperature and acidic conditions, the bacteria can cause spoilage, discoloration, bloated packages and textures and odours and flavors that displease customers.

The firm is pursuing scientific validations such as AOAC and ISO for the technology.

Lactic acid bacteria commonly found

Cari Lingle, global technical service at 3M, said lactic acid bacteria are ubiquitous and found commonly and naturally in food products.

“They are typically found in meat, poultry, dressings and sauces. Lactic acid bacteria grow faster in anaerobic conditions. They typically come in through raw materials or environment and can affect quality of the finished product.

“There are no regulations for lactic acid bacteria level, with the exception of some countries which require a level for yoghurt but it is not highly regulated. It depends if it is a supplier providing raw materials to a producer or the producer producing the product, some low levels are tolerated on meat, for example, if it does not affect quality."

“Spoilage organisms may not cause illness but if a product spoils before end of the stated shelf life and a customer notices, they may choose to go with another brand.” 

She said the food producer must determine the level and its impact on the shelf life of the product.

“For cleaning and sanitation, an environmental monitoring program that incorporates lactic acid bacteria can be beneficial. They are susceptible to heat and common cleaning methods.

“Foods that use lactic acid bacteria as a starter culture will be monitored to ensure the culture is viable to get the quality of product desired.”

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