Effect of Different Pre-Treatments and Drying Techniques on Physical and Chemical Properties of Potato Flour

The present study evaluated the effect of different pretreatment (blanching, immersion in ethanol, and their combination) and drying techniques (convective drying and microwave drying) on the physical and chemical properties of potato flour. The color, moisture content, water activity, hygroscopicity, densities (bulk, tapped and particle), total phenolic content, DPPH radical scavenging activity, and flow characteristics of samples were analyzed. Pretreatments showed an increase in the L* value of samples, while those did not cause a statistical change in b* and chroma values. Microwave drying resulted in higher a*, b*, and chroma values in the samples compared to convective drying. The mix of blanching and immersion in ethanol, pre-treatment increased the brightness of the potato flour in comparison to other pretreatments. While microwave drying did not provide any change in the total phenolic content of the samples, it provided higher antioxidant activity (۲۴۳۰.۷۸ mg TEAA/kg) concerning convective drying. Pretreatments caused a decrease in the total phenolic content and antioxidant activities of the samples. The lowest bulk (۰.۵۰ g/cm۳) and tapped (۰.۶۲ g/cm۳) densities in flour samples were determined in immersion in ethanol+blanching pretreatments. The results showed that the flowability and stickiness of all samples were poor and moderate, respectively. The gelatinization temperatures examined using differential scanning calorimetry of samples dried by microwave drying were higher than convective dried samples, while the enthalpy value was lower. Additionally, samples produced after immersion in ethanol showed similar gelatinization temperatures (۶۴.۰۳°C) to the control samples. These results could be associated with distinctions in the crystallinity degree of starch granules, which was affected by drying processes. Consequently, the best pre-treatments and drying techniques for potato flour production could be microwave drying incorporating immersion in ethanol, and blanching. Overall, this study showed that the pretreatments and drying processes used can affect the functional properties of potato flour and samples with different characteristics can be produced by these treatments.

کلیدواژه ها:

Potato flour ، Ethanol ، Blanching ، Microwave drying ، Convective drying