Pakistani scientists develop low-cost java plum sensor to detect spoiled milk

This summer, when you eat delicious Java Plum or Agejust remember the shiny pulpy fruit could save billions of litres of milk worldwide from spoilage. Thanks to a low-cost sensor made from its extracts and regular filter paper by Pakistani scientists. This piece was first published in DW URDU.

Without any electronics, the biologically driven probe was devised by researchers from the Department of Chemistry at the University of Education Lahore, in collaboration with the Interdisciplinary Research Centre for Biomaterials (IRCBM) at COMSATS University, Lahore.

They have developed an eco-friendly milk freshness sensor based on the natural compounds that give Java Plum (Syzygium cumini) its vibrant purple color. This sensor, which changes color, can effectively indicate whether milk is fresh or spoiled.

According to a research paper published in the prestigious journal Food Chemistrythe team isolated a natural compound called anthocyanin (ACN) from fully ripe Java Plum pulp. They then combined it with specific chemicals and passed it through filter paper to isolate it in its pure form.

To stabilise the compound, the fruit-infused liquid was dipped in a solution of chitosan—a sugar derived from the exoskeletons of crabs and shrimp—ensuring the ACN did not degrade or evaporate.

The colourful world of ACN

ACN is responsible for the rich colours in fruits, flowers, and vegetables. It is water-soluble and serves as a natural dye, also used in food colouring. ACN is particularly sensitive to acids and alkalis, causing its colour to change when exposed to such environments. This unique property made era a prime candidate for extracting ACN to create a sensor that would change colour to indicate spoiled milk.

Milk’s freshness is closely linked to its pH level, which is a key indicator of its quality. Fresh milk, whether from cows or buffaloes, typically has a pH level between 6.5 and 6.9. As harmful bacteria increase, the milk becomes more acidic, with its pH dropping to between 4.4 and 4.5, rendering it unfit for consumption.

A close view of Jaman fruit sensor, which changes color according to pH of milk. Photo: Muhammad Naeem Shabbir

To test the sensor, the researchers obtained three samples of milk from a market in Lahore. The era-infused filter paper was cut into strips and immersed in the milk for three days. The filter, reinforced by the chitosan coating, preserved the ACN compound, ensuring the sensor remained effective.

Over time, the milk began to spoil, and the filter paper changed colour, fading from purple to white, a clear indication that the milk had gone bad. Colour changes were also tracked using computer software, which analysed shifts in red, green, and blue (RGB) values.

Although milk cartons typically have expiry dates, they are often considered vague, particularly when it comes to milk’s real-time freshness. In contrast, this innovative paper sensor can provide an immediate and accurate indication of milk quality.

This low-cost, biodegradable, and reliable sensor has several advantages over traditional methods. “The purple paper sensor not only determines milk’s freshness and quality but is also more effective than many conventional sensors.

Instead of using chemical dyes or synthetic polymers, we used fruit pulp, which makes it an environmentally friendly invention that decomposes naturally,” explained Dr Naeem Shabbir, a researcher at the University of Education Lahore.

The eureka moment!

The journey to this discovery was not without its challenges. Initially, the team faced difficulty in stabilising the ACN on a suitable material. Numerous attempts with different bio-polymers failed, with the compound quickly losing its effectiveness.

However, during one of the trials, they made an unexpected discovery: the fruit-infused filter paper, previously discarded in dustbin, still retained its vibrant purple colour days later.

This surprising finding led to the realisation that the simple paper could be used to retain the ACN’s effectiveness, sparking the breakthrough.

Funding for commercial product

The initial results of the fruit sensor are very promising; however, much support and funding is needed to make a reliable commercial product. The whole team is optimistic for any startup-based or spinoff investment at the moment.

The research was conducted under the supervision of Dr Muhammad Akram at IRCBM and Dr Muhammad Aslam at University of Education Lahore. PHOTO: Muhammad Naeem Shabbir

While boxed milk consumption in Pakistan is relatively low—given that most milk is sold fresh—this invention could play a significant role in the global market, saving millions of litres of milk each year from going to waste. The fruit sensor could be game changer for the dairy milk industries.

It is important to note that all stages of sensor development, research, and testing were carried out at the IRCBM, located within COMSATS University. As a result, all rights related to this project are exclusively held by IRCBM.

This crucial research would not have been possible without the institution’s support and facilities, as the financial resources for the project were also provided by the same institution.

The lead researcher of this study is Muhammad Naeem Shabbir, who conducted this significant research under the supervision of Dr Muhammad Akram at IRCBM and Dr Muhammad Aslam at the University of Education Lahore.