Plant betalains: Recent applications in food freshness monitoring films

Betacyanins are pH−sensitive pigments of red/violet in buffers of pH 2–8 but brown/light yellow above pH 8. Foods have characteristic pH, biochemical, physical, sensorial, microbial, and other profiles that are associated with their freshness. Changes in these profiles, especially pH and volatile amines, can be used for monitoring food freshness. This review covers recent advances on the use of betacyanins−incorporated packaging films for food freshness monitoring. Incorporation of betacyanins imparts pH−sensitivity, antioxidant and antimicrobial activities, and water vapor and UV−vis light barriers to the films. Type and concentration of polymers, pH of filmogenic solution, film preparation conditions, food items to be stored, food biochemistry, and storage conditions have been reviewed to account for their effect on the performance of betacyanins as freshness indicator in active/intelligent films. Betacyanins incorporation does not cause any unfavorable changes in physicochemical and mechanical properties of the films, suggesting their suitability in active/intelligent packaging applications.