Janus principle applied to food safety: An active two-faced indicator label for tracking meat freshness

Abstract The lack of monitoring of food freshness during the cold chain has been reported in the literature as either a problem faced by meat industries enforcing stricter controls and public health security needs. This paper presents an innovative solution for real-time food freshness discrimination: a printable, easy-to-use, and non-toxic two-faced Janus color-indicator label. This sensor is based on the pink to purple variation of a multilayer pH-sensitive composite (cellulose acetate and black carrot anthocyanin) film in the turnover process of fresh to spoilage chicken. The microstructure and permeability of the composite, and also the impact of the psychrotrophic aerobic bacteria on the optical properties of the indicator label, were investigated. This sensor demonstrating a short response time (∼ 2 min), great color stability, and provides interactive information of food freshness, being capable of communicating directly with consumers via two simple images: “happy face” for fresh meat and “sad face” for spoilage. As far as we know, this is the first time that the Janus (or Emoji) principle is designed for tracking food quality to allow consumers to have easy information on food freshness.