A piezoelectric transducer for bacteria counts monitoring the application of piezoelectric transducer on food detection

In this paper, a piezoelectric transducer (PT) was developed for determination of bacteria counts in fresh milk in real time. The system consists of detection cell, oscillator, frequency counter and computer. The determination was based on the sensitive response of the transducer to the change of culture media during bacteria growth. The frequency shift versus time response curves were recorded by self-developed software. Bacteria detection time (BDT) corresponding to the significant change of frequency shift value was used as a parameter to quantitatively determine bacteria. The calibration curve of detection time against the logarithm of bacteria initial concentration showed a linear correlation coefficient (R²= 0.96) over the range of 12~1.1×10⁶ cfu·ml^-1. The transducer could acquire sufficient data rapidly (within 6.2 h) and enabled real-time monitoring of bacteria growth. Comparing tests were also carried out using pour plate counts. The results showed that the transducer has potential application in the detection of bacteria concentration in food at management of quality sampling.