Food safety and quality have received increasing attention in recent years, and they greatly impact people's health. Food adulteration is a problem with food quality and safety that affects people worldwide and is challenging to identify. Pesticides are chemicals used for the control of pests in different doses eventually leading to damage of foods produced from plants and crops due to their toxic nature. Their detection is always important in hazard analysis. Different techniques are involved in detecting chemicals and adulterants present in food. The types and concentrations of adulterants in various food types can be precisely determined using modern detection techniques such as high-performance liquid chromatography, and gas chromatography-mass spectrometer. However, the use of these techniques is limited due to their cost, complex sample preparation, and operating characteristics. The use of nanostructures in biosensors is known as nano biosensors which bring the food freshness or contamination monitoring. This chapter thus discusses the nature of nano biosensors and their applications in identifying infections, toxins, and chemical contamination, adulteration which is present in commodities, thus increasing their shelf life and assuring the end user's safety.