How long do your home made muffins remain fresh? When does the home made sausage start to spoil? Or how long can you store that cheese? When you make products at home you tend to use common sense and experience for determining whether you can still eat something. However, once you start to scale up your production and sell it to others, you’ll have to tell your consumers for how long it can be stored!
Determining shelf life is often an important step in scaling up your food production. For some products it’s easy, for others it’s more complex. But it’s a step that always has to be considered in some shape or form.
So, as part of the scaling up food production series, it’s time for a deep dive into shelf life determination.
Please note, this article is not meant as official (legal) advice. If having to look into the topic always consult local regulations or experts.
Why shelf life determination
Anyone buying food will want to know until when they can consume the product. Both to know whether the food is safe as well as to know whether it will still taste good. A freshly baked caked might not taste as nice one week later, but it might not have spoiled yet either. So it’s safe, but not necessarily nice to eat.
As a producer it’s your responsibility to determine a proper shelf life for your product. The best way to do this might be hard to find, as it tends to be different for each product group!
Not all foods need to have a shelf life written down on them. Which exactly depends on local regulations, but common examples are freshly baked bread from a bakery, or fruits and vegetables which haven’t been cut or peeled. Generally it’s foods that haven’t been pre-packaged (thus made/sold) fresh at location) or its foods that have indefinite shelf life (an example in the EU is chewing gum).
But for most packaged foods some sort of shelf life has to be indicated. For some it’s all about food safety (think fresh meat or dairy), for others it’s mostly about product quality (think chips or a spice mix).
In Europe the legislation that describes labelling of food and the shelf life notice is the so-called 1169/2011 regulation. It’s a pretty expansive piece of regulation mentioning a lot of different aspects of food labelling. For this, we’ll focus on the shelf life bit.
The regulation states which foods do and which do not require shelf life labelling. It also defines two different types of dates.
Two types of dates
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In the 1169/2011 EU regulation two types of dates of minimum durability are mentioned: a ‘best before’ and a ‘use by’ date. The two different dates apply to two different groups op products:
- Best before: this describes a date after which the quality of the product cannot be guaranteed anymore, but it’s not necessarily unsafe.
- Use by: this describes a date after which the safety of the product cannot be guaranteed anymore. This applies to foods such as fresh meats or dairy, they are more perishable from a microbiological perspective.
If you’re producing a product which requires a ‘use by’ date you can be sure you’ll need to do some sort of microbiological validation of the product to determine the shelf life. However, if you make a product that requires a ‘best before’ date the approach can be different.
If your product requires a ‘use by’ date you will most likely need to prove the product is microbiologically safe until the date you’re stating. That means you will have to investigate which micro organisms will cause spoilage of the product. This often involves sending product to a microbiology lab.
A ‘best before’ date on the other hand does not always require an extensive microbiological research. This could also be only a sensory validation. Let’s zoom in a little further on how this could work.
How to determine a product’s shelf life
When determining the shelf life of a product there are several steps and considerations that you should take into account. Start by defining the following:
- At which temperature will the product by stored by the store/consumer? Keep in mind that you should use a reasonable ‘worst case scenario’ approach. So if your product should be stored in the fridge you should probably assume a temperature of 7°C, since most fridges are at that temperature. Even though you know storing it at 4°C will keep it good for longer.
- Under which conditions will it be stored, in other words, how will it be packed? Is there a specific atmosphere, a vacuum?
When determining shelf life either way, you should take these two answers and use them during your trials. Any shelf life testing will have to use this information. (A quick note here, sometimes a shelf life is very long, in that case you might want to speed up testing by storing the product at a higher temperature than you normally do.)
How will your product spoil?
Now that we know how the product is stored and thus where it should be tested. The next important question will therefore be: how will your product spoil?
Ask at least the following questions:
- Based on what you know about you product. How long do you expect your product to stay good? What will be the reason it cannot be kept any longer (this is again related to the first two questions)?
- Is growth of micro organisms at all possible in your product? Micro organisms cannot grow at all under certain conditions (e.g. a low pH-value, a very high sugar content, a very low water content). This is one of the most relevant questions to ask as it can save you a lot of work. If no growth at all is possible, the shelf life determination becomes a lot easier. Read more here.
- If there is growth of micro organisms possible, will the product spoil microbiologically? In other words, is the first thing that ‘goes wrong’ related to growth of micro organisms? Will there be yeasts, growth of bacteria?
- Or are the sensory properties limiting during the expected shelf life (this is just about always the case if you answered ‘no’ to the first question)? For example, will your cookie become soft instead of crispy before actually spoiling?
These questions might be hard to answer in some cases. So do some literature searching. Your national government or inspection might well have guidelines for various product groups stating how to evaluate these. It is well worth to look these through. In some cases they might have done the validation work for you, so you can use their data.
The most important bit you should get out of these questions is that you should know whether your product becomes unsafe at the end of shelf life, or whether it merely becomes less appetizing.
If it’s microbiology that will spoil your product you will most likely need to do testing for micro-growth in a laboratory. If, on the other hand, it’s sensory that limits you, you should focus on testing sensory properties.
When testing for the food safety of your product during shelf, thus microbiological growth, there will be various tests you should do. Which exactly again depend on the product.
Let’s give an example. For meat common spoilage micro organisms are (not limited to) E. coli and overall aerobic count. If you have a product that you expect will keep for 5 days at 7°C you should package the product and at least analyze it after 5 days of storage at 7°C to show it does indeed meet the required criteria for the specific micro organisms.
Again, do some literature searching and investigation with your national authorities for guidelines regarding your products.
And that brings us to another piece of European regulation: 2073/2005. This regulation describes microbiological testing that is required for certain groups of food. You will find a lot of meat products, dairy, seafood and ready-to-eat foods in there. If your product falls under one of these categories you will have to comply with the tests described in there.
Take care, some of these tests describe tests that are not linked to shelf life. They are there to safe guard the foods at any point of the process. Nevertheless, some of them are linked to shelf life since they describe maximum values during the entire shelf life. In other words you have to prove your product will stay below those.
When you’ve found out that it’s the sensory aspects of your product that are the limiting factor. It’s best to set out tests to determine their effect. So if you’ve made cookies and have determined that it’s not the micro organisms that spoil it but their sensory characteristics, you’ll do a sensory test.
Pack and store the product the way you would and evaluate the sensory perception at regular intervals. Determine when the quality of the product isn’t acceptable anymore. That will be your shelf life.
That’s been a lot of information. I hope you’re still with us. A quick re-cap, by now you’ve:
- Written down the storage conditions for your product (temperature and packaging type).
- Determined whether your product’s shelf life will be limited by growth of micro organisms or sensory aspects.
- Had a quick look into two pieces of regulation (if you’re located in Europe that is).
- Learned the basics of doing these tests and determining which type of tests to do.
Get started! Determine your shelf life
Now it’s time to get to work. Let me know how you’re coping.