Guwahati: A chemical derived from the combination of water and formaldehyde, formalin is commonly used on freshly caught produce to extend its shelf life and enhance sensory attributes such as color.
However, it’s important to note that according to the Food Safety and Standards of India (FSSAI) regulations of 2011, the use of formalin in food products is strictly prohibited.
The use of formaldehyde in food is illegal in many countries, as it is a known carcinogen.
The presence of formalin in fish in Assam has created quite a scare. A team of researchers from Nagaon College conducted research for about three months and detected the presence of 15 per cent formalin as well as toxic cadmium, arsenic in the consignment fish imported from outside the state.
The good news is that scientists from Gauhati University have developed a cost-effective formalin sensor using tin oxide-reduced graphene oxide composite that can effectively detect the presence of formalin in adulterated fishes.
The low-cost sensor has been tested for adulterated fish at lab scale as well as on fish available in the fish markets of the Guwahati region. The research for this was supported by DST-PURSE (Promotion of University Research and Scientific Excellence) and was published in the journal ACS Appl. Nano Mater. It was observed that the sensor could detect the presence of formalin in many fish sample units that are imported from regions outside the state of Assam. The crucial importance of this work is the non-invasive detection of formalin.
Commercial formalin sensors for fish are primarily electrochemical-based or colorimetric-based. Electrochemical sensors are extensively used but are expensive. On the other hand, calorimetric sensors are less expensive. “But both methods are invasive in nature. Moreover, low-level detection and selective detection are two major issues with these sensors,” said scientists associated with the study.
The development of 2D materials-based gas sensors has created a new avenue of effective detection of toxic vapors at room temperature. These sensors have the potential to detect the formalin evaporated from adulterated food products.
Graphene oxide (GO), the oxidized form of graphene, exhibits high solution processability and ease of chemical modification with other materials such as metals, metal oxides, or polymers. However, the low electrical conductivity of GO posed a challenge and the scientists overcame this by developing a tin oxide-reduced graphene oxide composite (rGO- SnO2).
While reduced graphene oxide (rGO) has been used to detect various toxic gases and VOCs, tin oxide (SnO2) has been extensively investigated for formaldehyde detection in pristine form and by incorporating it with various compounds, including graphene, due to its high stability and high sensitivity toward low concentrations of formaldehyde.
The researchers synthesized graphene oxide (GO) through a process called wet chemical approach and tin oxide-reduced graphene oxide composite (rGO- SnO2) was synthesized by hydrothermal route followed by calcination of the obtained product. They found that the sensor made of tin oxide decorated reduced graphene oxide effectively sensed formaldehyde vapor at room temperature.
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“The designing of the prototype is in process in the lab which may be regarded as a breakthrough in the field of food adulteration. The prototype of this sensor will open new avenues for the development of affordable formalin sensor devices” a statement from the Department of Science and Technology stated.
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