Researchers at UNSW Computer Science and Engineering have developed a smartphone sensor that can detect if milk is fresh or spoiled without opening the package, to help in cutting down the amount of wasted milk.
The UN's Food and Agriculture Organisation has estimated that 20 per cent of dairy products are wasted globally each year – and a huge part of that is made up of wasted milk. Additionally, a lot of food-borne illnesses have been linked to the intake of spoiled dairy products.
VibMilk uses a smartphone's vibration motor and inertial measurement unit (IMU) to assess milk freshness without needing to open the package, allowing for real-time detection of whether milk is safe to consume.
UNSW Computer Science and Engineering professor, Wen Hu, led the team behind the technology.
“You can smell or taste if milk is off, but that requires opening the package. Doing so exposes it to bacteria, and that accelerates spoilage,” said Hu.
“VibMilk is non-invasive, which means you can test the freshness of the milk without breaking the seal.”
Milk goes off due to the growth of bacteria, which increases lactate levels and decreases glucose levels. Milk changes from a colloid to a mixture of curds, whey, and water, affecting its density, viscosity, and surface tension. These different physical properties lead to different responses to vibration signals.
VibMilk captures vibration signals produced by the smartphone motor using the IMU sensor in smartphones. It then leverages machine learning algorithms to analyse the signals and classify the spoiling milk at 23 pH levels.
Source: UNSW Sydney
Testing on four common smartphones showed that VibMilk can predict the pH values of milk with an average accuracy of 98.35 per cent and achieved a 100 per cent accuracy for indicating fresh milk.
VibMilk isn’t the first non-invasive way to test the freshness of milk. However, previous methods required either specialised and costly equipment, a custom cup, or only work with semi-transparent or transparent containers; all factors that limit widespread adoption.
Use-by dates printed on packaging can’t accurately predict when milk will actually go off, representing an indication rather than a definitive expiration.
“When manufacturers set these dates, they make assumptions about factors like temperature and storage duration based on worst-case scenarios,” said Hu.
“If milk is kept at the correct conditions (e.g. temperature), it could still be safe to consume a couple days past the labelled date. But if it’s not, it might not even be good until that date. That’s why we believe consumers should be able to test food items right around that date or even just past it before making a decision about consumption.
“This can help prevent unnecessary discards, which is crucial in areas facing food shortages. In the future, we aim to collaborate with charities to promote this technology in areas where people don’t have enough food and it’s most beneficial,” he said.
To further develop the technology, the team plans to investigate how different packaging materials affect vibration signals, as the signals pass through the packaging. The team is also working with a manufacturer of milk in NSW who is trying to find an efficient and reliable way to quality-check thousands of bottles of milk during production in their factory.
“While we have good results with our current methods, we can't guarantee the same with products from other manufacturers using different materials. So, before consumers can widely adopt this technology, we need to work with more manufacturers,” said Hu.
“While we’re looking for something similar, since it’s a factory environment, we don’t need to use a smartphone; we can use more sophisticated, yet non-invasive, sensors. We’re developing a system with them to measure the pH values of their milk before it is sent to stores.”
