This study aimed to examine the effects of porous structure and water plasticization on the mechanical glass transition temperature (T-g) of freeze-dried trehalose solid and cookie. The thermal T-g and mechanical T-g were evaluated by differential scanning calorimetry (DSC) and thermal rheological analysis (TRA), respectively. The mechanical T-g of the porous trehalose sample was slightly higher than that of the pellet sample. The mechanical T(g)s for pellet and porous trehalose samples were higher than thermal T-g. Although pellet, crust, and crumb cookie samples showed indistinct glass transition behavior in the DSC thermosgrams, TRA revealed a clear glass transition. There were little differences in the mechanical Tg of the cookie samples. The mechanical T-g decreased with an increase in water content, and mechanically and thermally critical water contents (water content at Tg = 25 degrees C) were evaluated. Fracture properties of the cookie sample changed discontinuously at the thermally critical water content. (C) 2017 Elsevier Ltd. All rights reserved.