Assessment of Nitrite Content in Vienna Chicken Sausages Using Near-Infrared Hyperspectral Imaging

Abstract

Sodium nitrite is a food additive commonly used in sausages, but legally, the unsafe levels of nitrite in sausage should be less than 80 mg/kg, since higher levels can be harmful to consumers. Consumers must rely on processors to conform to these levels. Therefore, the determination of nitrite content in chicken sausages using near infrared hyperspectral imaging (NIR-HSI) was investigated. A total of 140 chicken sausage samples were produced by adding sodium nitrite in various levels. The samples were divided into a calibration set (n = 94) and a prediction set (n = 46). Quantitative analysis, to detect nitrate in the sausages, and qualitative analysis, to classify nitrite levels, were undertaken in order to evaluate whether individual sausages had safe levels or non-safe levels of nitrite. NIR-HSI was preprocessed to obtain the optimum conditions for establishing the models. The results showed that the model from the partial least squares regression (PLSR) gave the most reliable performance, with a coefficient of determination of prediction (R_p) of 0.92 and a root mean square error of prediction (RMSEP) of 15.603 mg/kg. The results of the classification using the partial least square-discriminant analysis (PLS-DA) showed a satisfied accuracy for prediction of 91.30%. It was therefore concluded that they were sufficiently accurate for screening and that NIR-HSI has the potential to be used for the fast, accurate and reliable assessment of nitrite content in chicken sausages.

Keywords: calibration; classification; models; prediction; quality control.

Figure 1

Sample presentation and schematic drawing of the NIR-HSI unit.

Figure 2

The average spectra of the background and the average spectra of the Vienna sausages from the NIR-HSI scan.

Figure 3

Spectrum of nitrite standard solution from a UV-VIS spectrophotometer.

Figure 4

The absorbance spectrum of all chicken Vienna sausages (a) and the average absorbance spectrum of chicken Vienna sausages (b).

Figure 5

The scatter plot of predicted values and actual values of residual nitrite content in samples using the partial least squares regression model in both the calibration set (a) and the prediction set (b).

Figure 6

Predictive images of Vienna chicken sausage based on residual nitrite concentration.

Figure 7

PCA of spectral data of safe nitrite level samples (<80 mg/kg) and unsafe nitrite level samples (≥80 mg/kg).

Figure 8

The scatter plot of predicted values and actual values for the group classification of 0 (<80 mg/kg) and 1 (≥80 mg/kg) in the calibration set (a) and the prediction set (b).