# Electronic Sensing Technologies in Food Quality Assessment: A Comprehensive Literature Review
## 2 Methodology
The use of intelligent sensors to detect fresh food can provide hierarchical selection and determine the parameters of quality, maturity and freshness, and shelf life. In addition, it can also monitor the product quality in real time and respond to the product quality at any time. At the same time, food traceability can be ensured. Consumers can obtain relevant information on prices, production site, harvest date, variety, authenticity, etc. In this way, the quality of fresh food is guaranteed throughout the supply chain [58]. As these instrumental sensory technologies become the subject of engineering research, we can expect future e-tongues and e-noses that will be portable and much cheaper than today. The continuous development of e-sensor technologies may enable the next generation to rapidly ensure food safety and detection in the coming era when food will not be as abundant as it is today [57]. Although significant progress has been made in more precise and accurate applications of electronic noses, eyes, and tongues, individual applications of electronic systems are not complete enough to simulate humans for the purpose of evaluating meat and meat products. It should be remembered that humans perceive the quality of meat and meat products by combining and simultaneously processing stimuli from the eyes, nose, and tongue. In this sense, the integration/fusion of e-nose and e-tongue data sets is a natural progression towards automation in production and the evaluation of meat and meat products. The benefits of data fusion are proper classification and quality prediction, but new problems pose additional challenges in terms of data, computational time, and applicability to real food processing [59]. Unwanted changes in the data sets that affect data quality can make it difficult to obtain useful data from e-eye and e-tongue measurements, resulting in missing data, noise, baseline shifts, and peak shifts [60; 61]. Electronic sensors are based on different principles. The principle of operation of electrochemical sensors is to detect changes or current caused by chemical reactions between a sensing electrode and a reference electrode. Optical sensors detect an analyte using its absorption, fluorescence, or reflective properties. Piezoelectric sensors, on the other hand, use the vibrations of a crystal exposed to the analyte and the generated electric current that can be measured [23; 62]. Examples of specific sensors used in electronic sensors are pH sensors, ion electrodes, and gas sensors. Sensors detect chemical properties of the analyte, such as acidity, ionic strength, or gas concentration. In general, the selection of the type of sensor used in e-tongues and e-noses depends on the specific application and the properties of the analyte being studied. Many sensors operating on different principles can be used to provide comprehensive analysis of the odor or composition of a sample. Much information about the achievements in the literature on electronic sensors can be found separately for e-tongue and e-nose applications in specific processes. However, there are increasingly examples of using both systems to increase their efficiency [23]. Of note, e-noses and e-tongues are effective, safe, and economical methods of food identification and are now competing with traditional laboratory tests [63]. E-tongues and e-noses are often used in research to assess the quality, taste, and condition of food. For example, e-tongues have been used to determine the umami taste of Hanwoo meat [64]; compare the tastes of Koji mold and Camembert cheese using different strains of Koji [65]; identify the botanical origin of honey using a potentiometric e-tongue to distinguish among single-flower, multiflower, and honeydew honey [66]; and differentiate between types of lager based on their electrochemically active compounds using screen-printed electrodes [67]. Precision farming is now important for increasing food production and optimally utilizing the cultivation space. To achieve this, regular soil health checks are important.