Which inspection technologies can be used in ready meals?

Ready meals are a quickly growing category. But they’re not straightforward to inspect.

What is a ‘ready meal’? Principally, they are pre-cooked full meals, either frozen or chilled, that people simply reheat at home. It’s a meal on the table in minutes that’s all done for you. And in the words of CSIRO Professor Martin Cole: “Ready meals are not 1970s TV dinners, but highly nutritious packages designed by chefs.”

Cole, director of CSIRO Flagship of Food, Nutrition and Bioproducts, told last September’s Future of Food conference that ready meals as a business are taking off globally. “Everyone is time poor and yet everyone wants really good quality food.”

Recently, the category has widened to include more online options. As well, we’re seeing the convergence of home delivery of set ingredients for people to cook set recipes at home — a ‘ready meal that you cook’. Lots of new companies have entered this space. However, for the purposes of this article, I’ll look at the ‘done it for you’ version.

Growth upon growth

The past few years in particular have seen the rise of ready meals in Australian households, with the category’s value growing 8% in 2015 on top of 10% the year before. According to IBISWorld, the category’s revenue now sits at $900 million per annum.

Several factors are driving this growth: as Cole said, time-poor consumers like the convenience (particularly those living alone or younger adults without cooking skills), while health-conscious consumers favour low-fat meal options available for them.

Historically, less affluent consumers have been the main consumers of ready meals, but Euromonitor research has highlighted increasing numbers of more-affluent consumers taking the ready-meal option over their former preference of eating out or getting takeaway when cooking is not on the menu. This has been directly attributable to improved quality and attractiveness, as well as improvement in the perceived quality. IBISWorld data also attributes “premiumisation” as boosting the popularity of high-value, pre-cooked and pre-marinated meat varieties especially.

But the category’s growth isn’t just in a wider audience choosing this for their evening meal — ‘occasion’ is also a growth factor. Euromonitor market research shows chilled ready meals are also being promoted as the ideal lunch option — especially for those whose workplaces aren’t near a cafe or milk bar (I’m speaking from experience here; see below). This can be seen by the growing range of ready meals available: salads, meat and rice based dishes, and sandwiches — now available at the local supermarket.

Complexities in casserole

So now we come to an obvious question: how do ready-meal processors keep their customers safe and satisfied with fit-for-purpose products? What inspection equipment is suitable?

Manufacturers typically want to check each ready meal has all its components; however, one of the complexities is that ready meals have multiple elements. So while a manufacturer might think each is the same — for example, in that it has potatoes, carrots, peas, meat and gravy — to a machine, every meal is different. That’s because the amount of meat varies slightly, the shape of the potato varies, the position of the peas might vary. So it is actually quite difficult for a machine to look at ready meals and make a distinction that something is wrong or missing.

In order to check the presence of each component, the components need to be distinctly separated. Some ready meals come in this format, with trays of segmented elements; say the top left is meat, bottom left is peas, bottom right is potato and so on. The segmentation means it’s possible to check each element is there with a vision system or potentially an X-ray inspection solution. But there are still a few challenges; as I began with, it’s not simple.

Peas anyone?

A common inspection method is checking weight. However, while a checkweigher will make sure the total weight is correct, it won’t tell you if the individual components are correctly there. For instance, the entire tray could be filled with peas, and still be the correct weight, yet you wouldn’t be aware — at that point — that the meat and potatoes were missing.

So there are some challenges with inspecting ready meals. Now it’s time to look at the plus side: what is possible to inspect?

As just mentioned, a checkweigher will tell you if the total pack weight is right; any over- or under-weight packs will be immediately pushed off the line for rework.

Checking for contaminants

Ready-meal manufacturers can inspect with a metal detector or X-ray to make sure a knifepoint, bolt or other piece of metal hasn’t fallen in. Magnets can be used to make sure there are no fine metal pieces in a pack, but their uses are limited and they’re not very good for a ready-meal application. That’s because magnets aren’t effective on stainless steel (which is what most food processing machinery is made from); they only pick up ferrous metal — plain steel — but on top of that, if there’s a little crumb of steel in a piece of meat, that piece of meat will be too dense for the little piece of metal to move through (to get to the magnet) and too heavy for the whole piece of meat to stick to the magnet.

Inspecting ready meals can be complicated. It’s important to have a tailored system that allows you to keep your products fit for purpose and your consumers — and brand — safe.

However, metal detectors and X-rays can be used to check that metal is there, rather than isn’t.

For instance, I often buy a prepared salad at the supermarket for my lunch the next day. Manufacturers in this case can use a metal detector to check for the inclusion of the oxygen absorption sachet or an X-ray to check for the presence of a knife and fork, or the tartare sauce, or other components with metal attributes. For example: if a knife and fork are detected then the pack is passed as ‘okay’. If either is missing then the pack is rejected.

Vision systems can also perform this function, but need to be used to inspect the pack before it is sealed; whereas the metal detector or X-ray can do it after the pack has been sealed.

Right pack, right product

Vision systems can be used to inspect the product, as well as the packaging, to make sure the right front and back label are being used for the product being run and/or that the packaging is sealed. Anyone in the packaging industry will know that these are real issues, and there are plenty of examples of recalls where the label on a pack does not match what’s inside the pack!

A common vision inspection application is where the manufacturer wants to check, say, that potato salad is running through the processing line in potato salad tubs. There are two common ways that such a system operates:

1. A sample product is made and checked by quality control. If it passes, then it is used as a reference sample to ‘teach’ the system what to expect. After the system is taught that ‘this is potato salad’ from the first one, everything else running through which matches the reference sample is passed, and therefore anything that does not match is rejected. The only risk with this system is that if there is a defect on the reference sample, then the system will pass any products with that defect as good! This just means the operator needs to be certain the ‘teaching’ product is perfect.
2. Many manufacturers go an extra step and create a library of items they can choose from when they run the line. This is superior to the first method as it has the advantage of being less reliant on the operator because there is a reduced requirement to ‘learn’ the product at the start of production. In this case, the vision system refers to the library for the reference sample and makes the pass or reject decision based on a comparison of the product with the sample from the library. This gives a higher level of control and reliability.

For packaging inspection, a common method is to for the system to verify there is a label on the top and a barcode on the bottom of the pack, and whether that label and barcode match ‘potato salad’. If everything matches, then the product is ready for sale. Conversely, anything that does not match is rejected.

A vision system can also check for proper seals. Tubs or trays not sealed correctly can let in air, which, of course, can allow bacteria to grow. But again, this is not necessarily simple; with clear film and a clear tray, this can usually be done; but if the tray or film is a strong colour, such as black, it gets more difficult.

One at a time

A golden rule for inspection is that products must be checked one at a time.

Ready meals are predominantly packed in trays, and I’ve been in ready-meal factories where the tray machines feed out several at a time. Often these then go in rows of multiples across a conveyor belt and feed through a metal detector or X-ray. It’s fine to do this on an X-ray, as most units have the capability to inspect each item individually — even when presented in a random fashion or in multiples at a time. However, it’s a definite no-no if using a metal detector. There are multiple problems here; for example: the metal detector won’t be able to tell which product is the one with the stray pocket knife, so, if there are five products all coming across the conveyor at once then all five would be rejected.

That is clearly wasteful of all resources, so, unless you are using an X-ray, products should always be run through inspection in single file. Of course this potentially takes a bit more line length, which can be a problem in some factories. If that’s the case, then talk to your supplier about how you can do it.

Customise

The ready-meals market is booming, everywhere. Indeed, at that Future of Food conference last year, CSIRO’s Prof Cole said there was a renewed charge in fresh produce value adding, by making nutritious ready meals to export to Asia. (This is good news for Australian manufacturing and comes on the back of decades of declining food manufacturing, struggling exports and a strong Australian dollar.)

But as we’ve seen, it’s actually quite complicated to inspect ready meals. As a matter of necessity though, this is changing.

The other point to make is that while it seems there are lots of things that inspection can’t do, there are countless things it can do. The key is to talk to a reputable supplier, to create a tailored system for your business while working within the capability of the equipment being used. That will allow you to keep your products fit for purpose and keep your consumers — and your brand — safe.

*Andrew Key has over 25 years’ experience with packaging machinery, inspection technologies and identification technologies. His career spans across organisations like Alfa Laval, TNA and others; helping manufacturers to effect process improvement using the latest technology from around the globe. He has designed and implemented systems that have saved companies hundreds of thousands of dollars. In his current role as the Business Development Manager for Inspection Technologies at Matthews Australasia, he is constantly looking at cutting-edge technologies for customers to improve quality control. Andrew grew up in the country and loves the outdoors. In his spare time he enjoys sailing, snow skiing, water skiing, bushwalking and camping.