Characterization of gluten free cake batter with walnut flour: water mobility and textural behavior

BURBANO MOREANO, J.J.; CABEZAS, D.M.; REPO-CARRASCO-VALENCIA, R.; CORREA, M.J.

Congreso; ICBC 2021 - 16th ICC Cereal and Bread Congress; 2021

International Association for Cereal Science and Technology

Walnut flour (WF) is a by-product of the oil industry, obtained from the press cake milling. The compositional characteristics (high lipid, protein, and fiber contents) made WF attractive for improving the nutritional and technological quality of gluten-free products. This work aimed to characterize WF and evaluate the effect of WF addition on the water mobility and textural behavior of gluten-free batters. The proximate composition, water activity (aw), organic molecule absorption (OMAC), and water (WHC) and oil (OHC) holding capacities of WF were obtained. Besides, particle size distribution and microstructure by low vacuum scanning electron microscopy (LVSEM) of WF were evaluated. The control batter formulation contained rice flour and corn and cassava starches, and two levels of WF were used: 15% (WF15) and 20% (WF20). The water mobility and texture of batters were determined by low-resolution 1H-NMR and back-extrusion, respectively. WF presented a aw value (0.565 ± 0.02), high lipid (55.7%), protein (24.6%), and dietary fiber content (9.4%). Regarding interaction with other ingredients, the value of WHC for WF was 2.58 ± 0.1 mL/g WF. Also, the OHC and OMAC were 0.72 ± 0.05 and 0.77 ± 0.09 g oil/g WF, respectively. With respect to WF particle size, WF exhibited only one peak centered at 264.8 µm (D(0.5)) but when WF was submitted to sonication particles deagglomerated, and a shift to smaller particle sizes were observed (D(0.5)= 13.4 µm) Besides, in this case, one defined peak was observed together with two overlapped and broad peaks. The micrographs showed that WF has not intact cells and is composed primarily of thin layers of cell walls and agglomerated protein bodies. The small particle size and the absence of intact cells could contribute to the bioaccessibility of WF lipids. Otherwise, relaxation times describe the mobility of water protons in the batter matrix. The relaxation spectra were fitted with an exponential decay equation and the spin-spin relaxation times (T2) and proton fraction (Ii) were obtained. The fraction of protons (Ii) affected by magnetic field increased with the addition of WF. Also, the amount of free water decreased with WF level as the decrease of T2 showed. The relaxation time decreased from 18.73 ms for the control to 14.33 ms for WF20. This effect could be related to the protein and fiber content of WF that bound the water in the batter. Concerning the textural properties, the increase of WF concentration in the batters increased their firmness, consistency index, viscosity index, and cohesiveness. Particularly, the addition of 20% WF almost doubled the batter firmness and cohesiveness. Likewise, the higher consistency and viscosity indexes of WF20 batter were probably the reason that pouring that batter into the beaker was easier. These results showed that besides improving the nutrition value of batters. WF addition makes the batters easier to handle during its manufacture.