Batch vs Continuous – Scaling up a food production process

When scaling up your production process you’ve got to cover a lot different topics: how to transform your kitchen recipe into one suitable for a small factory/food business, what to consider when scaling up the process itself, how to determine the shelf life of your product, and what to think off when choosing your packaging. For some of you that will probably be more than enough to get a start with your scaling up.

But, for those looking towards significantly larger scale production, or for those already having a small production facility: you might be looking into batch vs. continuous production for your current or new production line. It’s a decision you’ll get to when scale really starts to add up for you.

These terms are a lot further away from kitchen science and relate more to engineering and processing principles. For those educated in chemical engineering, they form the basis for a lot of the work they do. However, for chefs and cooks, this might be a totally new world they’re entering into.

What are batch, semi-batch and continuous processes in food?

Before discussing why to choose for a certain process type, let’s first discuss the definitions of the three different process systems: batch, semi-batch and continuous. These terms relate to how a production process in run in the production facility. We will use a bakery as an example to explain these three processes.

A batch process is a process in which one batch is made and finished before the other is started. In a small scale bakery most processes will be batch. Kneading the dough will be done in a bowl with a mixer blade. Only when all the dough is finished, the bowl will be emptied and the next batch is started. The same for the oven: a rack of dough is put in the oven, only when this batch is finished will a new batch be put in.

A continuous process on the other hand goes on continuously. In other words, you don’t wait until a batch is finished before starting the new process, instead, you keep on doing the one process. Again, when looking at a bakery, in a large scale bakery, the oven is run continuously. Bread is continuously going in and out. This is done by using a belt which runs through the oven, this keeps on running all the time.

Last but not least, semi-batch. A semi-batch process is a combination of a batch and a continuous process. This type of process tends to have elements which are batch and elements which are continuous. This can again be seen in a large scale bakery. Even in large scale facilities dough often tends to be kneaded in a batch wise manner, in a mixing bowl. However, the process after (shaping & rising the dough) will be continuous. Since it will take a while for a whole batch to be portioned out onto the belt for the next steps, the next mixer will have enough time to knead the next portion of dough. That way, dough kneading is batch-wise, but the steps after can still be continuous.

Want every bread to look different? Batch processing will probably do so. Want a more homogeneous look? Continuous processing is the way to go.

Advantages & disadvantages of batch processing

The great advantage of batch processing is that it is a flexible process. You can make small batches of products and it is easy to make slight variations in your products from batch to batch. Let’s say you’re making cupcakes, lemon, raspberry and chocolate. After every mixing bowl, you’ll start a new one thus you can make a new flavour, no problem.

Another advantage is that you have some flexibility in how you perform your process. If your ingredients behave slightly different, it is relatively easy to change some aspects of the batch slightly and still make it work.

Also, equipment for batch processing tends to be cheaper. It probably requires less stringent control. That said though, you often need more labour to make your product. Someone will have to put those breads in the oven and take them out, whereas an automatic belt oven will not require anyone to do that.

For smaller manufacturers batch processing generally makes most sense. A batch process can be started and stopped relatively easily. Although, a disadvantage is that you have to keep on cleaning/starting up between every batch. That said, overall risk with a batch process can be lower as well. If with a continuous process something goes wrong (e.g. you have a microbiological contamination), the effect can be huge. However, if you produce in a food safe manner, the impact will be smaller with a batch process, most likely, only one batch will be affected.

Advantages & disadvantages of continuous processing

The big advantage of continuous processing is the consistent continuous quality of the product. It will be pretty much identical no matter when it’s made on the line. That said, it is less flexible than a batch process, it is often harder to change between those different muffin flavours.

Another big avantage is that once the process is running, there’s not a lot that has to be done anymore. No cleaning of bowls in between, the process will keep running. This requires less labour for production. However, investment costs are often a lot higher than for a batch process. Whether or not this will make sense mostly depends on the volumes you need.

Dutch pancake mix label
A product made in large volumes, with a standard composition, this has probably been made in some sort of a continuous process.

Continuous vs batch processing in food production

When choosing for batch vs continuous processing there are several aspects that will play a role, the most important probably being scale. A continuous process really only makes sense if you need enough product to run a continuous line for longer stretches of times. A continuous process might take a while to start and stop, but once it’s running, it just keeps on going. So, if you only need 1 hour of production at a time, a continuous process doesn’t make sense. In that case a batch process will probably suit you better.

Whether or not your scale is large enough greatly depends on your production volume, the process, the flexibility you need within the process. Do you only make 10.000 vanilla cupcakes, or do you make 2.000 cupcakes of 5 different varieties? Chances are that the 10.000 vanille cupcakes are more likely to be suitable for a continuous process than the 2.000 cupcakes of 5 varieties.

Besides scale a lot of other reasons will influence your choice, we’ll list a few:

  • Flexibility: have you set your recipe, or are you still tweaking and changing things all the time? Continuous processes, once designed, are often less flexible
  • Variation in ingredients: how stable are your ingredients? Do they vary a lot, depending on the season, supplier? If so, you might want to control that some more before looking into continuous processing.
  • Investment: starting up and still have to find prove in the market? Batch is most likely the way to go, the lower investments will make it easier to start. That said, if you work with another company as your external manufacturer, things might be different.

Get started

As with most articles in this scaling up series, the theory is not all. You have to start collecting data, get digging and start learning. Hopefully, this article has given you to first direction for your decision on batch vs. continuous processing (or has finally made clear what the differences are). Do leave a comment or send a message if the article has been helpful or if you have further questions!

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