Structural and physical changes of a sponge-cake during frozen storage and its relation with its absorption capacity

Sponge-cakes are an ideal product to be added with syrups. However consumer's demand has promoted their commercialization as a frozen product, which can change their crumb structure, resulting in a lesser absorption capacity. The aim of this work was to study the change in the syrup absorption capacity of a sponge cake and its relation with the change in the crumb structure during frozen storage. Samples were stored at sub-zero temperature (-20 ± 2°C) for 3 months. The absorption capacity was evaluated by determining the quantity of commercial syrup the sample after immersion can retain. Crumb structural changes were quantified by image analysis on samples obtained from the whole cake at different heights (up, middle and bottom). SEM images were acquired at these same points. Results showed that the specific volume did not change during the first two months of storage (2.51±0.02 cm ³/g), but a decrement in volume afterwards was noticed (2.39±0.04 cm ³/g). Moisture content, as well as weight followed a similar path (200.3±0.59g to 198.87±0.41g,) while the crumb absorption capacity increased (108±11-234±12%) as result of storage time, being the values related to the sampling position (bottom, centre and top). X-ray diffraction analysis showed changes as a result of freezing, but only at the upper position which could be related to a drying process. These results indicate a possible relationship among a drying process, the kind of pores and the syrup absorption capacity.