Development of quantitative analysis for relationships between viscoelasticity and air-bubble structure of bread

Abstract

Viscoelasticity and air-bubble parameters were measured to estimate the texture of bread from Sudachi (air-bubble structure) and the relationship was quantified. A sampling size in cross-sectional surfaces of the slices of bread was optimized to quantify relationships between viscoelasticity and air-bubble parameters of bread. As a result, a cubic sample (20 X 20 X 20 mm) cut from the slices of bread was determined to be used to measure the viscoelasticity, and its central square area (10.2 X 10.2 mm) was determined to be tested to measure the air-bubble image. Four viscoelastic moduli (instant elasticity, retardation elasticity, retardation viscosity, and permanent viscosity) of the bread samples were calculated by applying four-element Voigt model to the data acquired by creep test. Additionally, four bubble parameters (average air-bubble size, average air-bubble perimeter, the number of air-bubbles in a unit area, and the ratio of bubble area to the whole area of the bread samples) were also calculated by applying a bubble detection method using image processing on the data taken by an image scanner. Finally, significant correlations (r > 0.59, p< 0.05) were found between instant elasticity, retardation elasticity, permanent viscosity and the ratio of bubble area (the ratio of bubble area to the whole area). This indicates that crumb hardness increases as the ratio of air-bubble area increases.