Effect of structure in the sensory characterization of the crispness of toasted rusk roll

Crispness is a salient textural attribute of toasted foods strongly related to their preference. Crispness is affected by water content, mechanical properties and morphology of the food. Sound emission and force characteristics during food crushing play a key role in crispness. The aim was to assess the effect of product morphology on sensory crispness grading of toasted rusk roll, a cellular solid food. Products with coarse and fine structures were studied. Additionally, the effect of water on crispness was studied by using samples with water activities from 0.30 to 0.8. The sensory test showed that upon absorption of water the product became tough and soft and lost its crispness. The morphology of the product had a significant effect on crispness intensity. Coarse products were rated crispier than those with a fine crumb grain. Deterioration of crispness (Aw10%) started at 0.46 and 0.50 water activity (6.2% and 7.1% H2O) for the fine and coarse structure product, respectively. The critical water activity (Awc) at which the products lost 50% of the crispness was 0.57 and 0.59 (9.1% and 9.7% H2O), respectively for the fine and coarse structure produc