Development of Whey Protein-based Carbon Dioxide Indicator to Monitor Food Freshness

Introduction: Partial pressure of carbon dioxide (CO₂) can be used as an indicator of food quality in a food package as microbial spoilage or respiration of agricultural products typically results in CO₂ accumulation. Therefore, a visual CO₂ indicator provides to easily check the food quality, simply by changing transparency depending on the CO₂ concentration in headspace of food package.

Purpose: The aim of this study is to develop whey protein isolate (WPI) based carbon dioxide indicator, and determination of its physicochemical properties.

Methods: WPI powder was added at the level of 0.1, 0.3, 0.5, 1, 2 and 4 g in 100 ml of distilled water, and the solution was stirred for 1 h after adjusting pH to 7.0 by 1 M HCl and NaOH. Then, the solutions were stored under 100 % CO₂ atmosphere. Thereafter, the solutions were measured in terms of pH and transparency.

Results: Changes in transparency of 0.1, 0.3, 0.5, 1, 2 and 4% WPI indicator solutions were 67.2, 66.0, 21.3, 31.7, 13.5 and 3.1%, respectively. A 0.1% WPI indicator solution exhibited the highest transparency change, but a 0.3% WPI indicator solution was selected because it exhibited optimal visual change in turbidity.

Significance: From these results, we can conclude that the change of transparency and pH decreases as concentration of WPI increases. WPI-based indicators can be used for various food packages containing agricultural products and processed foods which can accumulate different levels of CO₂ by respiration and fermentation during storage.