Application of pH Indicator Label Based on Beetroot Color for Determination of Milk Freshness

Introduction: Applying of a new indicator in food packaging can be effective to inform consumers about the freshness and quality of the products. Materials and Methods: In the current study, a new milk freshness label was investigated containing beetroot color and multi layers of polystyrene. The label characteristics were investigated by estimating color number, release test, and scanning electron microscopy (SEM). The total bacterial count, pH, lactic acid concentration in milk, and label color number were measured using standard plate count, pH meter, titration of acidity, color analysis software, and UV spectrophotometry on days 0, 3, 4, 5, 6, and 7 at refrigerator temperature (4 ± 0.2°C). Results: The label reacted to total bacterial count and pH changes with a visible color during milk spoilage. A positive correlation was found between the label color changes, total bacterial count, and pH. The color of label turned from dark red to light brown, which was related to the chemical changes and bacterial count of milk. Conclusion: According to this simple, visible, and affordable label, the shelf life of pasteurized milk was estimated as five days.