Updated September 2024 to include new information.
Love them or hate them, mushrooms are one of the world’s most cherished and nutritious food crops. And they are big business; mushrooms boast a £40 billion market globally. Not too bad for fungus.
But mushroom packaging has always been a tough nut to crack. The garden varieties of common consumer mushrooms are soft, vulnerable and highly prone to rapid decay after being harvested. For the most part, we’ve addressed the soft and vulnerable aspect of our favourite fungi, by packaging them in HDPE or cardboard cartons for strength. But the rapid spoiling has only recently been solved by food packaging science – saving millions of mushrooms from being wasted.
The answer? Microperforated film; a breathable membrane that keeps dirt out and freshness in. But what is this stuff, how does it work – and why would anyone want holes in their packaging?
What is microperforated film?
Microperforated film is a type of machine film with tiny holes running all the way through it. This might seem odd, given that we like to have perfectly sealed packaging in most industries, but these tiny holes are very useful for packaging things – like mushrooms.
That’s because, as soon as mushrooms are harvested, they begin giving off water vapour. This can condense, allowing water to collect in sealed packaging. And this causes big problems for freshness. Wet mushrooms decay rapidly, becoming slimy and smelly within a matter of days, even in the fridge.
Microperforated films are a clever solution. The tiny holes allow vapour to escape from the packaging and improve air circulation – but they are so small that dirt and even water droplets can’t pass through. This provides an effective seal under normal supermarket and transportation circumstances, holds the produce safely in the packaging, and maximises shelf life.
Read more: Polythene in the food industry
Of course, mushrooms aren’t the only products to benefit from microperforated film packaging – freshly baked goods (typically crusty loaves, baguettes, pasties and sausage rolls) are often wrapped in microperf film, to enhance visibility without steaming them into a mushy mess. These films offer better protection and sealing than paper bags, without making the product invisible.
How is microperforated film made?
There are three main methods to perforate plastic films;
- Cold needle process
- Hot needle process
- Laser perforation
Both the hot and cold needle process use rollers covered with very narrow needles. As the film passes over the rollers, the needles puncture it at precise intervals to achieve the perforation, before it gets wound back into a roll of film.
Laser perforation uses hot laser beams to cut a highly accurate, tight pattern of holes. This method is commonly reserved for smaller sections, or patterns that can’t be achieved with rollers and needles. Running them over an entire width isn’t cost effective for simple patterns – but in some scenarios, lasers are the only solution. This method can also achieve custom perforation patterns and have higher levels of automation applied.
Microperforated polythene film is most commonly made using the cold needle process – where very narrow needles on a roller puncture through the polythene to create tiny holes. Because polythene is flexible, this doesn’t cause any deformation or damage the integrity of the film. Hot needles can also be used, but this uses more energy. It’s typically reserved for use on rigid and brittle films without much elasticity, as they are more likely to tear instead of puncture. Heated needles glide effortlessly through more brittle material, leaving a ring of reinforced material, similar to the laser perforation process.
Other uses for microperforated film
Vapour barriers in construction
In construction projects, polythene is the preferred material for vapour barriers. It’s moisture proof, highly cost-effective, lightweight and workable. Microperforated film is often used in high humidity areas, allowing interior moisture to be drawn out.
Using Polythene Sheet in Construction: Understanding Vapour Barriers
Optical filters
Although not something we come across often in our line of packaging work, microperforated film is used as an optical filter for glass and plastics. It can be used as a “frosting” effect for privacy, to control ambient lighting, or for use in optical experiments. PVC is commonly used for its adhesion to glass, but polythene is a viable alternative for covering other optical materials.
Perforated films
So now we’ve got microperforated film covered, let’s talk about perforated film.
The holes in perforated film are bigger and easier to spot, and are usually spaced farther apart. Perforated films are often used in agriculture and horticulture, where perforated films shield plants while controlling the temperature and humidity. The perforations can allow moisture into grow bags while keeping the soil and nutrients inside. In irrigation systems, these holes allow water to percolate into the soil slowly, so it can still be distributed through the whole system.
Learn more: Polythene For Farming And Agriculture
The benefits of using polythene microperforated film
Polythene microperforated films are highly customisable, durable, flexible and versatile over many applications. With additives, UV resistance can be achieved, as well as sub-zero temperature compliance. It’s highly transparent, and the microperforations stop fogging and condensation from appearing inside the packaging.
Polythene is food safe, and odourless, too – unlike rival materials, which can have a certain smell to them. It’s 100% recyclable, oil-safe and professional looking, all while remaining competitively priced.
Microperforated polythene film – for professional packaging
Microperforated films bring controlled ventilation to your packaging. The minuscule holes allow for airflow and moisture escape, while mitigating the effects of dirt, debris and even spills during transport and storage. These films are vital in the food industry, preserving the freshness of some types of produce – but their use extends outside of the supermarket.
Order microperforated film for filtering, vapour barriers, fresh produce and food production, made to your exact specifications. Get a quote now or call us on 01773 820415 to start your order.
