A portable biosensor system for bacterial concentration measurements in cow's raw milk

Marco Grossi,Diego Matteuzzi,Roberto Lazzarini,Anna Pompei,Massimo Lanzoni,Bruno Ricco

doi:10.1109/iwasi.2011.6004703

Abstract

Bacterial detection is of primary importance in many fields, such as food and environmental monitoring. Measurements of bacterial concentration are traditionally carried out by means of the Standard Plate Count technique, a reliable method for microbial screening that, however, features long response time and is carried out by qualified personnel in microbiology laboratories. The impedance technique for bacterial concentration detection represents a method very competitive with Standard Plate Count in terms of response time (3-12 hours vs. 24-72 hours) as well as for the possibility to be realized in automatic form. This paper presents an embedded portable biosensor system for the measurement of bacterial concentration in cow's raw milk. The possibility to perform measurements “on the field”, hence without the need to ship samples to distant laboratories, and to transmit the data on wireless communication systems or on the Internet represents a substantial advantage in terms of time and cost, thus making the presented system an important tool for in-situ bacterial screening.

Highlights

Microbial detection is essential in important applications, such as, for instance, quality control in the food industry and environmental control
Since the bacterial concentration is inferred by the time needed for the bacterial population to reach the critical threshold of 107 cfu/ml, in order to obtain a good correlation between Detect Time (DT) and microbial concentration it is necessary to choose the incubation temperature so as to minimize the dispersion in TG for all the bacterial strains potentially present in the sample
Data from the literature are very controversial about the best choice of incubation temperature: some of the pioneering works on impedance microbiology [18] reported good correlation between DT and bacterial concentration from Standard Plate Count technique (SPC) at 18°C (i.e at a temperature representing a trade-off between the optimal temperature for mesophilic and psycrotrophic strains), while bad results were obtained at 30°C

Summary

Introduction

Microbial detection is essential in important applications, such as, for instance, quality control in the food industry and environmental control. The time needed for the electrical parameters to deviate from the baseline values, hereafter denoted as Detect Time (DT), presents a linear relationship with the logarithm of the sample bacterial concentration: this latter can be worked out from the measured value of DT.

Results

Conclusion