Researchers Find Way to Detect Sour Milk Using Smartphone

The modern smartphone has long been a universal device, but this ubiquitous gadget gets new features and capabilities almost every day. One of the most ingenious ways you will probably be able to use your pocket device in the near future is to check milk for spoilage, both in your own kitchen and at the store, without even opening the container.

Researchers at UNSW Computer Science and Engineering have recently developed a new smartphone sensor called VibMilk, which uses the gadget’s vibration motor and inertial measurement unit (IMU) to test the freshness of milk without having to open the container. The high-tech method could one day reduce the current 20% of dairy waste.

"You can smell or taste if milk has gone bad, but you need to open the packaging to do this," said Professor Wen Hu from UNSW. "This exposes it to bacteria, which speeds up spoilage. VibMilk is non-invasive, meaning you can check the freshness of milk without breaking the seal."

Interestingly, VibMilk is not the world’s first non-invasive method for testing milk freshness. However, previous methods either required expensive equipment, were too inconvenient, or only worked with transparent and translucent milk containers. VibMilk, on the other hand, facilitates mass adoption because it relies on the built-in vibration motor of the average smartphone.

The researchers came up with VibMilk after analyzing how milk spoils. This happens because bacteria increases, which in turn leads to increased lactate levels and decreased glucose levels. When milk spoils, it changes physical properties such as density, viscosity, and surface tension, each of which responds differently to vibration signals.

VibMilk records the response to vibrations created by a smartphone motor as it passes through milk, then uses machine learning algorithms to analyze the signals and classify spoiled milk into 23 different pH levels.

Contrary to popular belief, best before and use by dates cannot accurately predict when milk will go bad as it depends on a number of factors such as storage and transportation conditions, container insulation, etc. Milk stored at the right temperature can remain good for a couple of days before the expiration date, whereas improper conditions can cause it to spoil before the expiration date, so it is wiser for consumers to check the freshness just before consumption to avoid unnecessary waste or food poisoning.

"Testing on four common smartphones showed that VibMilk could predict milk pH values ​​with an average accuracy of 98.35% and achieved 100% accuracy in detecting milk freshness," the University of New South Wales said on its website.