Proof-of-concept study of a whey protein isolate based carbon dioxide indicator to measure the shelf-life of packaged foods

A whey protein isolate (WPI) based carbon dioxide (CO2) indicator was studied under different CO2 conditions. WPI based CO2 indicators were prepared and incubated in a CO2 filled chamber in order to investigate the CO2 dependent transition behavior in visual appearance. Transparency of the WPI based CO2 indicator with 0.1% WPI changed from 91.8% to 24.6%. An indicator with 0.3% WPI changed from 73.7% to 7.7%. The change in visual appearance at the transition point was definite. The indicator showed an irreversible visual change due to the hysteresis behavior of the indicator. Desorption of CO2 did not restore the transparency. The CO2 dependent visual transition point was controlled by adding different concentrations of NaCl to the indicators. A WPI based CO2 indicator has potential for application as a CO2 dependent spoilage and over-ripeness indicator for a variety of foods.