Expansion of fried foods has been explained using the concept of rapid increase in molecular volume of water during evaporation (Rossell, 2001). During the frying process, crackers expand into porous products and the degree of expansion, called linear expansion, is one of the important quality parameters of crackers (Yu, 1991). The observations for linear expansion with different combinations of the process parameters are presented in (Fig. 1(c). It can be observed that mainly temperature and time as well are significantly increasing the linear expansion (p ⩽ 0.05) and temperature is more effective at short frying times. Nurul et al. (2009) found that the oil absorption of the fried crackers is higher in samples with higher linear expansion and lower in samples with lower linear expansion.