Table 3.

Classification of various biosensors, along with their key features.

Classification System	Biosensor	Key Features	Reference
Bioreceptors Based	Enzyme biosensors	Enzyme based microreactors are developed that interact with the food environment and detect changes.	[159]
	Antibody biosensors	Antibody layer in the sensor is used to recognize the target, often a pathogenic or spoilage microbe and convert it into a signal.	[160]
	Aptamer biosensors	Aptamers can be defined as a type of oligonucleotides that have high specificity and affinity for the target organisms in food that cause spoilage. Biosensors based on aptamers have great potential as a tool for pathogen detection in food.	[161]
	Whole cell biosensors	Living cells as biosensors offer features such as a easy fabrication process and flexibility of detection stratagems.	[162]
	Nano biosensors	Magnetic nano-sensors can be useful in detecting various residues (such as pesticide, antibiotics), additives (antioxidants) or analytes (bisphenol A, aflatoxins) in food in extremely low quantities.	[163]
Transducer Based	Electrochemical biosensors	They can be further categorized into amperometric, potentiometric, voltammetric, conductometric, and impedimetric. Low cost, ease of operation, portability, simplicity, and easy miniaturization are some of the advantages of electrochemical biosensors. Recent works showed that they work best with two-dimensional nanomaterials, as these enhance the sensitivity, repeatability, and specificity of the electrochemical biosensors.	[164]
	Optical biosensors	This works on the principle of a signal generation proportionate to the concentration of analyte in a sample. They enable screening of a plethora of analytes or compounds and the use nanostructured materials for assessment of optically active materials. They enable smart colorimetric detection, making the food package active and smart. The low cost of fabrication is one of the striking features of optical biosensors.	[165]
	Electronic biosensors	Biosensors that act as electronic tongues or noses have been developed based on pattern recognition principles, and act as freshness indicators for various fruits and vegetables. Observation by the naked eye is a huge advantage.	[166]
	Gravimetric biosensors	They are also known as mass-based biosensors. These produce measurable signals upon detecting a change in mass on the sensor surface.	[167]
	Acoustic biosensors	Acoustic biosensors are based on the ability of the target molecule to bind and vibrate at the frequency of the piezoelectric crystals used in the sensors. The physical attributes of the acoustic waves thus generated are analyzed, and inferences about the analyte and its concentration are drawn.	[168]
Technology-Based	Nano biosensors	Nanomaterials offer great electrochemical, optical, mechanical, magnetic, and conductive properties. Examples include nanowires, quantum dots, and nanotubes that amplify the initial signal and lower detection limits.	[169]
	SRP biosensors	Stimuli-responsive polymers (SRPs) respond to the changes in the food environment or external stimuli such as pH, enzymes, etc., and aid in detecting spoilage in food packaging systems.	[170]
	Chip based biosensors	These act as promising point of care (POC) devices, enabling target detection. Liquid crystal technology is used for the development of chip-based biosensors in food.	[171]
	Electrometers	These come in handy when monitoring the real-time quality or estimating the perishability of food material. The dielectric properties of biopolymers aid in analysis based upon electrical conductivity and electrets state, and the peaks thus obtained are studied.	[172]
Detection system based	Optical biosensors	They ensure food safety owing to their application in POC devices. These sensors are quick, competent, and dependable.	[173]
	Electrical biosensors
	Electronic biosensors
	Thermal biosensors
	Magnetic biosensors
	Mechanical biosensors