Table 5.

Characteristics of indicators used in the food industry

Indicator name	Characteristics	Target to be detected	Application in foods	References
Gas indicators	To determine the scavenging activities in the food commodity. They offer an alternative approach for identifying any leakages or sealing issues in the pack. The chip detects the leak and converts the signals into visual colorimetric change	Gases like CO2, O2	Oxygen inhibitor films using an alginate polymer coating	Vu and Won (2013)
Freshness indicators	Provide immediate product quality data regarding microbial growth or any chemical changes or modifications in the packaged food. Generally used for maintaining shelf life	Monitoring of nitrogen, amines, ammonia, CO2 pH sensing in food packages	Meat and fish	Kuswandi (2017)
Time–temperature indicators	Used for measuring food deterioration. Lab-on-a-chip device provides visual information concerning food quality, distribution, spoilage issues, and storage	Bacterial adulteration	Milk and other perishable foods	Zhang et al. (2013), Vanderroost et al. (2014)