Comprehension of drying kinetics and stone milling process of chestnuts: a focus on moisture content, milling speed,...

Chestnut flour plays an important role in the production of bread, bakery products, and gluten-free foods. Most of the references in the literature focus on the drying process itself and not on the effects of the drying and milling processes. Moreover, the literature is lacking recommendations regarding optimal moisture content and milling speed, thus motivating the present study. The first aim is to understand the chestnut drying process through an in-depth evaluation of drying kinetics; the second aim is to assess the effects of three different moisture content (2%, 4% and 6%) and three different stone rotational speeds (120, 220 and 320 rpm) on operative milling parameters (flour yield, milling time, energy consumption, temperature increase, average power, specific milling energy), flour particle size distribution, and chestnut flours characteristics.

The results show that moisture content and stone rotational speed have statistically-significant effects on milling operative parameters, flour particle size and chestnut flour composition. In particular, stone rotational speed affected almost all the tested variables (mill operative parameters, flour particle size distribution, and flour characteristics). Therefore, as the stone rotational speed increases, energy consumption, average power, specific energy, and damaged starch content significantly increase.

These findings clearly show that moisture content and stone rotational speed are powerful tools that allow the exploiation of the milling process to modulate the characteristics of the obtained flours. In conclusion, two different approaches for chestnut milling were suggested depending on the type of flour to be produced. © 2024 Society of Chemical Industry.