NIR Technology Australia

Application Note 64: Calibration of Fat in Polish Cream using the Series 3000 Food Analyser.

September 2005.

Introduction:

It is possible to measure fat in cream using near infrared instruments. The petrii dish sampling system of the Series 3000 Food Analyser does not lend itself to the sampling of liquids. However, cream is usually a relatively firm substance despite it’s liquid state. It was therefore possible to measure the fat in cream using the Series 3000 Food Analyser. A new cream calibration was created using Polish produced creams.

The sample preparation for use with the Series 3000 Food Analyser required 100mls of cream to be placed in a petrii dish levelled to a consistent thickness of 6mm. This method proved to be the best and most consistent means of sampling.

This study was undertaken to demonstrate the feasibility of measuring fat in Polish made creams. The Series 3000 Food Analyser was used for the purpose of this study.

Procedure:

19 samples of Polish cream were prepared by placing 100mls into a glass petrii dish, levelling the cream by use of a vibrating plate for 10 seconds to produce an even pathlength. The samples were then scanned over the wavelength range of 720nm to 1100nm collecting 10 scans per sample. The samples were then redone and the scanning process repeated. The spectra were uploaded into NTAS (NIR Technology Australia Software) and Partial Least Squares Regression (PLS) was used to develop a calibration for Fat and Moisture.

Results:

Figure 1, below, shows the NIT spectra, over the wavelength range of 720nm to 1100nm, for the 19 samples of Cream.

Figure 1: Plot of NIR Spectra for Cream.

Figure 2 shows the calibration statistics for the NIR Fat values versus the reference Fat value. The Standard Error of Calibration is 0.63% with a correlation (R²) of 0.99.

Figure 2: Plot NIR Predicted Protein value vs. Reference Protein value.

Conclusion:

It can be seen in figure 2 that the Series 3000 Food Analyser can be calibrated to measure the Fat values of Polish produced creams. The laboratory reference data for the Fat values in these creams was reported to only 1%. Therefore, an inherent error of ±0.5% from the reference method does affect the overall reliability of the calibration. Despite this potential error the calibration shows excellent linearity and good predictability. Therefore, any improvement in the reference testing methodology will only help to enhance the existing calibration further reducing any error in prediction.