It's that time of year again.. things are hotting up, people are spending more time outside and ice cream sales will begin to rocket. The ice cream sector is a $5 billion+ a year* industry in the United States alone and with every batch produced, manufacturers are responsible for making sure that they create a quality product.

Aside from a few tragic high profile incidents, outbreaks caused by contaminated ice cream are relatively rare (most likely due to the freezing temperatures involved). However, continued microbiological monitoring is an important component of effective health and safety / hygiene protocols.

Pathogens / bacteria that can contaminate ice cream:

• Listeria
• Streptococcus
• Staphylocuccus
• Pseudomonas
• E Coli
• Salmonella
• Coliforms

Much like all dairy products, regular bacteria testing is recommended. The factors that can cause bacteria in frozen desserts may depend on whether the ice cream is homemade or produced by a small or large company as different techniques, equipment and ingredients are used. Ingredients in ice cream such as raw eggs or milk could contain bacteria such as salmonella or E Coli that has not been eliminated through freezing temperatures. Unsanitary equipment / working environment and personal hygiene can all contribute to contamination.

Pasteurisation is used in most commercial ice creams as a way to help eliminate bacterial growth. This process may not be used by home made producers and this may be an issue when using ingredients such as raw eggs. Even after pasteurisation, bacteria can contaminate the product and precautions need to be taken to try to avoid this from occurring.

Regular equipment sanitisation and swabbing / testing throughout the production process is recommended. Large commercial producers may use ingredients from external suppliers. These ingredients may be added post pasteurisation so companies need to ensure that their suppliers are also performing stringest testing and cleaning protocols.1

There are many small, family run producers who have revolutionised their dairy farm businesses by making ice cream for extra revenue. These producers already have numerous health and safety policies to adhere to and can't afford their own microbiologists like large creameries.

Small producers may benefit from periodically sending samples to labs or by using microbiological testing equipment (dipslides etc) on site. It is important to follow food safety guidelines that are set by the governing body in the country where the production facility resides.

Self serve dispensing machines (not unlike drinks dispensers) can harbour high levels of bacteria as they need to be kept extremely clean and hundreds of consumers a day will come into contact with the equipment (carrying their own microbiological contaminants). This as well as other factors such as condensation within the machine can cause bacterial growth. Even if the machine is not self serve and only staff members use the dispenser, the equipment still needs to be sanitised daily.

Retailers of packaged ice cream products also need to be aware that melted and re-frozen ice cream should be discarded as temperature changes can cause opportunity for bacteria to grow.

Contaminated ice cream (like all food products) can cause a wide variety of symptoms / infections (depending on the bacteria present). These can include gastroenteritis, urinary tract infections, sore throats, nausea and more serious symptoms. Those with compromised immune systems are much more likely to be affected by ingesting contaminated food.

Many producers state on documentation or on their websites that they conduct microbiological testing and follow other food safety programs. This is encouraging as it enables consumers to make informed decisions and shows that the producer is serious about their health and safety responsibilities.

However, it's not all bad news when it comes to ice cream and bacteria. Last year, researchers in Scotland announced that they were studying a bacterial protein called BslA that produces a bacterial film that protects the environment from water and competing 'bad' bacteria. When used in ice cream, the protein will assist the perfect combination of fats, water and sugar in the ice cream (no separation), will help prevent excessive ice crystalisation and improve the 'creaminess' of the dessert. The process can also aid in ice cream being produced with less saturated fat.2

Also last year, another study was carried out by Indian researchers to test the effectiveness of probiotic ice creams on oral health. The research was specifically looking at whether the consumption of probiotic ice cream could affect the levels of Streptococcus mutans, Lactobacillus and Candida albicans in saliva.3

A control group of young adults and another group who consumed the probiotic version of the ice cream did so for 10 days. Before and after which colony forming units were counted. Findings revealed that there was a reduction of salivary Streptococcus mutans and Candida albicans in the probiotic group with an increase in Lactobacillus. The increase in Lactobacillus is explained by the presence of lactobacillus acidophilus as an ingredient of probiotic ice cream and samples been taken directly after consumption.3

It is important to remember that this was a one off study carried out with a small number of participants and further research would need to be undertaken to prove the benefits of probiotic ice cream in terms of oral health.

So that concludes this article regarding the bacteria present in some ice cream products - the good, the bad and the ugly. 
For information on all of our food testing dipslides including Listeria dipslides, see the 'Our Dipslides' section.

References

*data from IRI
1. http://www.idfa.org/docs/default-source/d-news/idfa-iica-listeria-control-resource-guide-051316.pdf
2. https://www.researchgate.net/publication/287483778_Connecting_the_dots_between_bacterial_biofilms_and_ice_cream
http://www.cbc.ca/news/technology/bacteria-ice-cream-1.3227854
3. http://iosrjournals.org/iosr-jdms/papers/Vol14-issue1/Version-3/N014136468.pdf