If the 21st Century has told us anything, it is that there is far more to light than meets the eye.

To demonstrate this, imagine a piano with all of the colours humans can see, from deep purple, to simply red, spanning across the keys of a single octave (eight white notes). If we extend the piano to include all the light waves we know exist, then there would be a whopping twenty-five octaves (two-hundred white notes) in both directions.

From our piano, you can see that the visible spectrum of light only comprises a tiny amount of all the light that exists. Although we can’t see these mysterious wavelengths with our eyes, we can definitely use them, and hyperspectral imaging in the food industry is one of their most amazing applications.

A different way of seeing

How exactly can shining light at an item of food and taking a photo of it, tell us what is happening inside it? The answer lies within the science of spectroscopy.

Spectroscopy is the study of light emission, absorption and the matter it interacts with. This often focuses on splitting light up into its many constituent wavelengths - such as the infrared spectrum, which our eyes cannot see naturally. Essentially, by looking at specific light waves, we can view the world in a way that would not be naturally possible.

Let’s take a look at an example of spectroscopic evolution in nature.

As humans, we are unable to detect ultraviolet wavelengths - if someone shines an ultraviolet light at us, it won’t look like a light is on at all. However, a honeybee’s eyes have evolved to make use of these short, ultraviolet wavelengths. Why? Well, a flower’s petals reflect ultraviolet light, meaning that when a bee hovers, scanning a dense grassy field for flowers, these petals appear to “light up”. The bee is drawn to this signal.

The most important part of this spectroscopic evolution of the honeybee’s eyes is how it allows the insect to conserve energy. The quicker a bee finds a flower, the quicker it can take nectar back to its hive, the quicker honey is produced, and so on. This idea of “energy conservation” is also key to understanding why scientists are so interested in spectroscopy. Rather than “conserving energy”, we can minimise wastage by improving food processing.

The many secrets uncovered by light

The honeybee example shows us how these insects draw a signal from the petals of flowers. This signal is produced by specific wavelengths reflecting more clearly than others, according to the unique chemical properties of petals. Similarly, by using imaging technology and sensors, we can look for signals like these as well.

When scientists want to analyse a fruit or a vegetable, they take a photo, while only looking at a specific “band” of wavelengths. This means they restrict the range of light waves analysed. An example of this is the Near-Infrared band, which only analyses light with wavelengths between 700-1100nm. Within this range, a computer can scan for specific reflections, which show that different chemicals are present, and compare those to other similar fruits. After thousands of images have been analysed, scientists develop “spectroscopic signatures”, which demonstrate a standard pattern of chemicals and show us properties of the fruit. Crucially, we can then compare this to what fruit looks like when something is wrong with it. In some foods, these signatures may indicate bruising beneath the surface, a fungal infection, grade-quality in the meat industry, or even sugar and fat content of an item of food.

Consequently, scientists make food inspection far more efficient, by taking human error out of the equation entirely. A computer “inspects” a thousand pieces of fruit in a minute and will tell you exactly which ones will deteriorate first. Or rather than waiting until the harvest arrives, you could scan an orchard as the apples are growing, predicting a poor harvest ahead of time, or quarantining infected trees before they spread disease.

What does this mean for the future?

You may have heard that the world is currently suffering from a food shortage, and this is due to a variety of complex reasons. One problem we struggle with in the UK is wastage of food during the inspection-stage. It has been suggested that 20% of our food is removed for purely cosmetic reasons, and the UK actually allows for a further 5% wastage during processing. That is a staggeringly huge amount of wasted food, and that’s before it hits supermarket shelves, where those wastage figures continue to rise.

It’s clear that investment in these lighting technologies serves interests across the globe, as the world-food-crisis shows no sign of letting up soon. If we can reliably put more food on shelves during processing, then cost of food will improve for everybody, and we will take another step toward solving food-poverty.

Sources:

1. Clarity VG.
2. Wikipedia.
3. Science Demonstrations.
4. Food Waste Feast.
5. Lords Library.