Three-dimensional visualization of oil permeation in rice crackers and evaluation of changes in texture

We established a method for visualizing the three-dimensional oil distribution in rice crackers, and analyzed the correlation with sensory evaluations of texture to clarify the effect of oil permeation on the texture. The internal structure of the model rice crackers permeated by oil was investigated at 5 levels (oil content ranging from 10 % to 50 %), and the permeation distribution was recorded by X-ray micro-computed tomography (CT). To clarify the relationship between the degree of permeation and the texture, texture evaluation terms related to oil were classified into 8 groups, e.g., crispness (as "kari-kari" in Japanese), tenderness ("shittori"), and hardness ("zaku-zaku"), by cluster analysis, and the model rice crackers were evaluated using these terms. The oil content tended to be higher near the surface than in the deep interior proportion to the total amount of permeated oil. The crispness increased up to 30 % oil content but dropped sharply at 40, 50 %, showing that the oil content and texture were not well correlated. On the other hand, the oil distribution analysis showed that permeation into the deep interior influenced the crispness and tenderness, and permeation into the middle layer enhanced the hardness. The model enabled quantification of the optimum oil distribution to create the desired texture.