Effect of pumpkin powder as a fat replacer on rheological properties, specific volume and moisture content of cake

Reducing fat and calorie is an important priority in optimization of bakery products including high–fat cakes. The aim of this research was to evaluate the effects of shortening replacement with pumpkin powder at 0 %, 20 % and 40 % with or without water level increment on rheological properties of cake batter and two properties of produced cake. Pumpkin powder was obtained from pumpkin flesh through drying, grinding and sieving processes. The rheological attributes of the batter and the specific volume and moisture content of cakes were examined using a rheometer, rapeseed displacement method and air–oven method, respectively. Increasing shortening replacement, enhanced viscosity (87.00 Pa.s), while increasing water in shortening–replaced treatments reduced it (11.30 Pa.s). Samples showed shear thinning behavior. In linear viscoelastic range, samples indicated solid viscoelastic behavior. Loss tangent, storage and loss moduli obtained from frequency sweep test, were investigated in three frequencies. In each frequency, with increasing shortening replacement, their viscoelastic properties enhanced. Contrary, increasing water amount in shortening reduced–batter samples, weakened system structuring. With increasing frequency, both moduli of treatments increased and the loss tangent of 20 % reduced–shortening cake without water level increment showed a more similar trend to the control (0 % replacement without increasing water amount). The moisture content of cakes containing pumpkin was greater than control. The specific volume of cake with 20 % replacement without additional water (2.68 cm/g) was similar to the control and higher than other shortening– replaced treatments. Therefore, this treatment was chosen as the best reduced–fat cake. Keyword: Cake batter, Pumpkin, Rheological properties, Shortening replacement, Specific volume.