Biosensing Techniques for Detecting Abnormal and Contaminated Milk

Abstract

The development of biosensors to detect milk unsuitable for human consumption is a major objective of our groups. Since zoonotic infections such as TB and paratuberculosis are generally dealt with by pasteurisation, one of the main remaining causes of milk unsuitable for human consumption is deterioration in milk quality as a consequence of infections such as mastitis. We propose a sensor to identify milk from animals with a mastitis infection and to allow robotic milking to meet the European directives. The use of conductivity sensors is misleading in this context since they have low sensitivity to some inflammatory responses and do not detect systemic infections unless these also lead to mastitis. We propose a mastitis sensor based on the detection of elevated levels of the enzyme N-acetyl glucosaminidase (NAGase), released into milk as a result of tissue damage when the cow is resisting a clinical intra-mammary infection. The sensor is an adaptation of a screen-printed carbon electrode and utilises the ability of NAGase to convert 1-naphthyl N-acetyl-β-D-glucosaminidine to 1-naphthol. The resulting 1-naphthol is detected electrochemically by oxidation at an appropriate applied potential. The operational principle of the system is described and some preliminary results are presented. The mastitis detection system can be designed to utilise the sample presentation and signal transduction systems currently under development in the automatic ovulation prediction system described elsewhere.