Ultrasonic internal defect detection in cheese

Abstract

Different ultrasonic signals and detection techniques were used and compared to detect internal foreign bodies present in semi-soft cheeses. The signals were a pulse or a chirp and the detection was carried out by using either correlation with a reference signal or a wavelet decomposition. The principle of the detection consisted in measuring the time of flight of the transmitted signals and of the echoes, the latter in the absence of foreign body should be the double of the former. The presence of a foreign object affected this pattern in several ways. In order to assess the method, a small plastic cylindrical object of 3 mm in diameter was introduced in one half of the cheese and was tested for detection, the second half being used as reference for the control cheese. The results showed that the two signals and the two detection methods were able to localise the transmitted signals and the echo from the opposite face of the cheese under all circumstances. For the foreign body detection, the correlation method gave superior results, in term of signal to noise ratio as well as in term of error rate, while the two signals gave similar results. The analysis of the mean and standard deviation of the signal to noise ratio of the object echo showed that some samples presented peak values close to those due to the noise. Nevertheless, the object was detected in 90% of the tests. There was no significant effect of temperature on the detection technique.

Noninvasive techniques for detection of foreign bodies in food: A review

“…Leemans and Destain () evaluated foreign bodies contained in a semi‐soft cheese based on the time of flight of the transmitted signals and the echo signals. A plastic cylinder with a diameter of 3 mm was inserted into the cheese.…”

Emerging Technologies for Targeted Food Processing

“…At lower treatment intensities US can be applied to the detection of foreign bodies in packaged and nonpackaged food (Knorr et al 2004;Leemans and Destain 2009) and for nondestructive testing. Low-intensity US has been used to monitor the gelation process in milk and tofu (Dwyer et al 2005;Ting et al 2009) and to measure the mechanical properties of cheese products (Benedito et al 2000).…”

Applying non-destructive techniques to inspect preserved egg products by decay rates

“…The decay curve A 0 e Ànxnt is termed the envelope curve.In the case of ultrasonic defect detection in cheese (Leemans and Destain, 2009), the envelope curve was assessed using the Hilbert transform, and the correlation with the mode yielded better results than detection based on the wavelet decomposition. In this study the superior peaks in the time domain, which eliminates noise, are used to create an envelope line with the index of regression analysis (shown in Fig.…”