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CRANFIELD UNIVERSITY Eleni Anthippi Chatzimichali ...

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5.2.2.2 Fourier Transform Infrared Spectroscopy (FTIR)<br />

Similar to case study 1, the FTIR dataset was generated from measurements based on<br />

a thin slice of the aerobic upper surface of the beef fillets that was excised and placed<br />

in intimate contact with the crystal (Argyri, 2010; Panagou et al., 2010; Argyri et al.,<br />

2013). The spectrometer was programmed to collect spectra in the mid-IR range<br />

between 4000 and 400cm -1 . Out of the initial 1,739 variables, only the spectra that<br />

reveal the metabolic fingerprint of spoilage, between the ranges of 1500 and<br />

1000cm -1 , were extracted and used for classification purposes. Thus, the final FTIR<br />

dataset consists of 150 samples of minced beef with their replicates and 259 variables.<br />

Based on the provided sensory scores, the 150 samples of FTIR consist of 28 fresh<br />

(F), 52 semi-fresh (SF) and 70 spoiled (S) samples. Figure 5-2 shows the mean FTIR<br />

spectra of the samples of minced beef per each distinct class in the fingerprint region<br />

between 1500 and 1000 cm -1 .<br />

Figure 5-2 Mean FTIR spectra for case study 3 in the fingerprint region (1500-1000 cm -1 )<br />

The plot depicts the mean FTIR spectra of minced beef samples (stored aerobically and under MAP at<br />

5°C) per each distinct class. The spectral region between 1500 and 1000cm -1 reveals the metabolic<br />

fingerprint of spoilage. Colour representation is used to identify the three classes as determined by the<br />

relevant sensory scores: fresh (red colour), semi-fresh (orange colour) and spoiled (green colour).<br />

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