## 3 Results and Discussion  
### Development of the Calibration Model  
Table 1 presents the chemical composition (mean, standard deviation, and range of values) of the traditional sausages, as determined by application of the reference methods and by application of NIR spectroscopy for the calibration set of samples. The basic composition was similar to the one reported in the market surveys of [PERSON] et al. [3], [PERSON] et al. [4] and [PERSON] et al. [5]. Moisture content varied to almost 30% between samples even though sausages were purchased one to two days after their production in an attempt to standardize their moisture content. The differences are related to the fact that some producers use drying chambers whereas others prefer to air dry the sausages. Variations in ash content are related to differences in spices, conditions, and seasonings used by the producers in their attempt to create product differentiation. The average protein content was higher than 12% and in accordance with the requirements of the Greek Code of Foodstuffs, Beverages, and Objects of Common Use [2]. There was one sample that the protein content was lower than 12%. Finally, the average fat content did not exceed the highest permitted value of 35%, by the Greek Code of Foodstuffs, Beverages, and Objects of Common Use [2]. However, in 23% of the examined samples, this value was exceeded. The findings in relation to protein and fat content enhance the need for in situ monitoring of the chemical composition of the sausage batter to enable compliance with the legislation. The contents of all components were very variable, but according to [PERSON] et al. [14], this is expectable due to the limited degree of mechanization and control of the final product, causing a higher degree of heterogeneity. This finding is corroborated by the findings of the study of [PERSON] et al. [6] that reported batch variability in the range of 2.40-18.05%, 7.55-17.66%, 2.34-11.11%, and 9.52-26.71% for moisture, ash, protein and fat contents respectively, in sausages produced by the same butcher shop. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Parameter** & **Mean Values** & **Standard Deviation** & **Range** \\ \hline \hline \multicolumn{4}{c}{Reference Methods} \\ \hline Moisture (\%) & 47.73 & 5.215 & 31.87–59.24 \\ Ash (\%) & 2.49 & 0.369 & 1.85–3.28 \\ Protein (\%) & 17.61 & 2.222 & 11.08–22.41 \\ Fat (\%) & 31.41 & 6.888 & 20.72–53.76 \\ \hline \multicolumn{4}{c}{NIR Spectroscopy} \\ \hline Moisture (\%) & 47.21 & 4.865 & 34.65–59.94 \\ Ash (\%) & 2.41 & 0.305 & 1.62–3.09 \\ Protein (\%) & 17.82 & 2.412 & 10.65–21.88 \\ Fat (\%) & 31.33 & 6.320 & 19.48–49.32 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Chemical composition according to the reference measurements and NIR spectroscopy for the calibration set of samples (n = 39). Typical spectra of traditional sausages with NIR spectroscopy, are presented in Figure 1. The ability of NIR spectroscopy to estimate the chemical composition of traditional sausages is presented in Table 2.  
The calibration correlation coefficients (RMSEC) in all components were greater than 0.80, indicating that NIR spectroscopy can reliably estimate the chemical composition of meat and meat products [24]. The highest correlation coefficient for the calibration (RMSEC) was observed for the prediction of the fat content and the lowest to the protein content. [PERSON] et al. [11] and [PERSON] et al. [12] observed comparable results for pork sausages. As reported in the review studies of [PERSON] et al. [10,25] and [PERSON] et al. [24], ash content is not frequently determined in trials examining the applicability of NIR spectroscopy for the prediction of the chemical composition of meat and meat products. The ash and protein cross-validation correlation coefficients (RMSECV) were less than 0.80, suggesting uncertainty in estimating the contents of the above components. Figure 2 presents the prediction plots for moisture, ash, protein, and fat contents for the calibration set of sausages.