Biosensors: Applications for Dairy Food Industry ABSTRACT Biosensors are defined as indicators of biological compounds that can be as simple as temperature-sensitive paint or as complex as DNA-RNA probes. Food microbiologists are constantly seeking rapid and reliable automated systems for the detection of biological activity. Bio- sensors provide sensitive, miniaturized systems that can be used to detect un- wanted microb ial activity or the presence of a biologically active compound, such as glucose or a pesticide. Immunodiag- nostics and enzyme biosensors are two of the leadin g technologies that have had the greatest impact on the food industry. The use of these two systems has reduced the time for detection of patho- gens such as Salmonella to 24 h and has provided detection of biological com- pounds such as cholesterol or chymo- trypsin. The continued development of biosensor technology will soon make available “on-line quality control” of food production, which will not only re- duce cost of food production but will also provide greater safety and increased food quality. (Key words: biosensor, methods, microbiology, industrial application) Abbreviation key: E IA = enzyme imunoas- say. INTRODUCTION The science of biosensors is a multidiscipli- nary area for which sharp delineation does not exist (3, 5 ) . A biosensor may be defined in Received August 19, 1992. Accepted May 19, 1993. EDWARD R . RICHTER Silliker Laboratories Columbus. OH 43212 many ways. Two of the most commonly used definitions of biosensor are given: 1. A biosensor may be a device or instru- ment comprising a biological sensing element coupled to a transdu cer (15). Us - in g this definition, examples of biologi- cal sensing elements might include en- zymes, organelles, antibodies, whole cells, DNA, and tissue. Transducers might includ e those that are electrochem- ical, calorimetric, optical, acoustical, or mechanical. 2. A biosensor may be a self-contained ana- lytical system that responds directly and selectively to biologically important spe- cies (5 , 10); that is, a device or system that detects a biological event. Clearly, the term biosensor is used in di- verse ways, but, generally, a biosensor should respond selectively, continuo usly, rapidly, spe- cifically, and ideally without added reagent to biological events. The biosensor does not need to be an integral part of the transducer. En- zyme biosensors may respond as quickly as 30 s, but 15 min is acceptable for immunosensors. In order to define biosensors for use in the food industry, the types o f biological events that might be acceptable for biosensor meas- urement need to be known (5). Food microbiology has changed little in the past 30 yr. The standard plate count, using agar-based media in a Petri dish, remains one of the principle tests used to determine microb iological quality of food. Recent contri- butions to science have brought about unique microbiological and chemical food testing methodologies. These include advances in genetic engineering (probe production, assay development, and amplification polymerase chain reaction), advances in immunology (monoclonal antibodies, antibody purification, immunoassays), electrochemical methods (con- ductance and impedance), and chemilumines- cence. All of these methods have the same 1993 J Dairy Sci 76:3114-3117 3114
