Introduction: New smart packaging using algae as accurate and adjustable sensors, preserves food quality and reduces waste. Sensors and smart packaging are very effective in controlling and monitoring food quality and spoilage. Sensors detect changes in food spoilage by changing color, enzymes and living cells, and temperature and time sensors. These technologies are used in food packaging such as meat, fish, dairy and fruits. Electrochemical biosensors as smart packaging generate electrical signals based on analyte concentration. The use of natural pigments in sensors has low toxicity and few environmental effects. In this way, it measures the chemical and biological changes of the product (such as the pH change) and always controls the quality of the product. Among the natural pigments are anthocyanins, which are soluble in water and have antioxidant, anti-inflammatory and anti-cancer properties. Also, with changes in pH, the chemical structure of anthocyanin is changed and it produces different colors.
Methods: In this article, related articles published in 2020-2023 in Springer, Science direct, Scopus and John Wiley databases were reviewed to obtain the latest findings in the field of biosensors in smart food packaging. In this review article, appropriate keywords were selected by searching the MeSH website and based on them, fifty one new review and research articles were collected
Results: In a research, anthocyanin was used to control spoilage of carp. In this way, a two-layer hydrogel film sensitive to pH, the first layer of gelatin and ZnO and the second layer of gellan gum with anthocyanin extract was made. The fish was inserted into the film, then the color of the film changed from pink to light green and finally to yellow as TVB-N increased. Due to the production of NH3, it changed the color of the film and the hydroxyl group (OH-) was hydrolyzed in the hydrogel film, and as a result, alkaline conditions were created. Betalains are another group of water-soluble nitrogenous colored compounds derived from betalamic acid. These pigments include red to purple betacyanins and yellow to orange betaxanthins. Betalins have high antioxidant capacity and ability to inhibit lipid peroxidation at low concentration. In addition, these pigments are stable at pH between 3 and 8. Curcumins are another group of pigments that are polyphenolic and are extracted from turmeric root. Curcumins as a sensor material with tara gum and polyvinyl alcohol create films that keep the quality of shrimp fresh. Although fresh shrimp in the films causes a yellow to orange-red color change, pectin films with curcumin and sulfur nanoparticles showed that the color change from yellow to orange indicates shrimp degradation. Naphtoquinones are sensitive to acidic and basic environments and also increase the resistance of films against moisture. Researchers used naphthoquinone and cellulose pigment to make a pH sensor in shrimp packaging, the results showed that with the change of pH and ammonia production, the color change from rose-red to purple and then to blue-violet, different stages of food spoilage. it shows.
Conclusion: In general, the use of smart packaging in the food industry with bio-pigments, such as anthocyanin and curcumin pigments, can help to detect the freshness and degradation of products. In addition to antimicrobial and antioxidant properties, these pigments improve product shelf life with integrated packaging. Also, the use of biopolymers and ZnO nanoparticles helps to stabilize pigments. It will be interesting to combine these pigments with other active compounds and essential oils. However, for the commercialization of smart packaging, sensitive and environmentally friendly sensors and message transmission and warning systems are necessary.