New biosensor monitors sulfite levels in foods An EU-funded project has developed new technology enabling a fast, accurate and simple approach to monitoring sulfite levels along the entire food supply chain. Climate Change and Environment Food and Natural Resources Health © nirapai boonpheng, Shutterstock Sulfites are food additives with antioxidant and preservative properties. However, they are recorded as allergens by the main international bodies for food safety because of possible adverse health effects. Therefore, the maximum concentration of sulfite levels are carefully regulated by the agricultural and food processing industries. The EU-funded SO2SAFE project developed and tested a miniature, ready-to-use enzymatic sulfur dioxide (SO2) biosensor for rapid food safety monitoring. The biosensor consists of a disposable screen-printed electrode (SPE) modified with a specific enzyme, sulfite oxidase (SOx), for sulfite recognition and quantification. The amount of each component was optimised to achieve the greatest sensitivity. Sulfite detection in crustaceans The result is a highly sensitive and user-friendly handheld device, which rapidly and reliably determines sulfite levels in crustaceans and water. Project coordinator Asier Albizu explains: ‘The crustacean market has been identified as being the most affected by potential sulfite problems, but this additive is also used extensively in other foods as well as beverages.’ Large-scale producers used the developed biosensor to analyse sulfite levels in the water of bins where shrimps are collected. The crustaceans are then mixed with water, ice and sulfite to prevent discolouration (melanosis). This form of monitoring early in the supply chain will help to avoid failures in the control of melanosis, thereby preventing excessive amounts of sulfite in the final product. These analyses are performed in the field, in close proximity to the pools where the shrimps are collected. Examination of water from the pools where the shrimps are cultured was not done previously because a suitable methodology was not available. ‘The handheld device developed by SO2SAFE has allowed shrimp production companies to implement a new control point, because the device is suitable for sulfite analysis in the field,’ Albizu confirms. Wider applications of biosensor technology Miniaturised sensor technology developed by the SO2SAFE project has also been applied to the analysis of malic acid in grapes, musts and wines. In addition, assays for analysing sulfite in meat and beer are being conducted, while promising results have been obtained for the development of a miniaturised biosensor for sulfite analysis in beer. This innovative approach is also suitable for designing point-of-care solutions for the health sector for diagnostic, drug monitoring and therapy monitoring applications. SO2SAFE outcomes will not only benefit the food industry but also the wider population due to the direct impact that sulfite has on health. ‘Most cases of high concentration of sulfites in crustaceans have been due to contaminated shrimps imported from countries outside the EU. This demonstrates the importance of monitoring sulfites in raw and processed food material originating from both Europe and from outside it,’ concludes Albizu. The project’s advances will dramatically reduce cases of high concentration of sulfites, thereby helping to provide consumers with safe and healthy food. The SO2SAFE device will also make it easier and cheaper for the food industry to control the food supply chain by monitoring and maintaining food safety, according to the required regulations of food safety bodies. Keywords SO2SAFE, sulfite, biosensor, shrimp, crustaceans, food safety, health, melanosis, additive, screen-printed electrode
