Detection of Textural Difference between Cultivars of Bunching Onion using the Device for Acoustic Measurement of Food Texture

Abstract

The acoustic vibration signals of 9 cultivars in 3 groups (Kaga, Senju and Kujo) of bunching onion were acquired using a device for acoustic measurement of food texture. To imitate biting bunching onion with an incisor, a stainless steel wedge-type head was introduced to fresh tissue perpendicularly and parallel to the longitudinal axis. A half-octave multifilter was developed to analyze the obtained signals in the frequency domain, and then the root-mean-square amplitude in each frequency band was computed and defined as a texture index. The results showed that the signals obtained with the perpendicular insertion were larger than those obtained with the parallel insertion. The total texture index, which is the summation of texture indices in 18 frequency bands, of each cultivar was grouped together as the same cultivar group, except for ‘Shimonita’ cultivar of the Kaga-group. Principal components analysis (PCA) also clustered successfully each cultivar group in the space of the first two principal components (PCs), also excluding ‘Shimonita’. Furthermore, the ratios of the texture index of perpendicular to parallel penetration clearly distinguished each group. These results suggested that the device could detect textural differences among cultivar groups of bunching onion.