October 27/Cesana, Italy/Food Business Week -- "The control of gelato powder mixture production usually is carried out by evaluating the gelato liquid phase. The rheological measurements from the present study were conduced on gelato unfrozen liquid phase in order to indirectly evaluate its rheological properties by FT-NIR spectroscopy applied on gelato powders," scientists in Italy report.

"The calibration set was composed by samples obtained from different recipes having increasing percentage of thickeners, maintaining the proportions of the others' compounds constant. After the NIR acquisitions, the powders were mixed with warm milk, blended and than settled in order to obtain the unfrozen liquid phase needed for the rheological measurements. For each of the 60 tested recipes, three batches with the same thickeners concentration were prepared. The flow curves were obtained with a rotational viscosimeter and were evaluated by using the Ostwald de Waele's equation, and the goodness of fit was evaluated by the R-2, which was above 0.95. Predictive models of rheological parameters were set up by means of PLS regressions in order to predict the apparent viscosity (eta), the consistency coefficient (K) and the flow behavior index (n) from spectral acquisitions. A high correlation of calibration was found between NIR spectra and apparent viscosity with R-2 of 0.943. A good correlation was also found between the NIR spectra and the consistency coefficient (K) and flow behavior index (n), with a determination coefficient (R-2) of 0.895 and 0.874, respectively," wrote F.A. Silaghi and colleagues, University of Bologna.

The researchers concluded, "The good prediction of the models encourages applying them to reduce significantly the time of the powder mixing control during production."

Silaghi and colleagues published their study in Food Research International ("Estimation of Rheological Properties of Gelato by FT-NIR Spectroscopy." Food Research International, 2010;43(6):1624-1628).

For additional information, contact F.A. Silaghi, University of Bologna, Food Science Campus, Pzza G Goidanich 60, I-47512 Cesana Fc, Italy.

From the November 15, 2010, Prepared Foods E-dition