Summary The purpose of this study was to investigate the relationships of carrot sensory crispness with acoustic signal characteristics and microstructure after storage under common shelf conditions. The results showed that carrot sensory crispness declined significantly after the 14th day of storage, and the sensory score reduction was nearly up to 42% after the 28th day of storage. The carrot sensory crispness was positively related to both the waveform index (r = 0.785, P < 0.01) and sound intensity (r = 0.732, P < 0.01) of the acoustic signals in the time domain. Hilbert–Huang transform is a useful method for the observation of frequency changes in the time domain. The overall frequency bands were distributed around 200–2000 Hz through the Hilbert spectra. Rupture did not occur until the 14th day (crispness declined significantly) of storage through the scanning electron microscopy images of microstructure, and the crispness declined gradually with the increase of rupture.

The purpose of this study is to investigate the relationships between carrot firmness with acoustic signal characteristics. The results showed that carrot firmness was positively related with the wave form index (r 5 0.72, P < 0.01) and sound intensity (r 5 0.81, P < 0.01) of the acoustic signals in the time domain. The overall frequency bands were distributed around 0-10,000 Hz by Hilbert-Huang transform. The carrot firmness was negatively related with the relative energy in high-frequency domain (r 5 20.73, P < 0.01). PRACTICAL APPLICATIONSTextural properties, defined by "firmness," "crispness" and so on, are key quality attributes in assessing the quality and acceptability of fresh and processed food products. Texture study is one of the most important aspects of food sciences and engineering. Acoustic technology is new and convenient method and can be applicable to evaluate crisp food or crisp processed food, such as watermelon, apple, chips and so on. In this study, the relationships between carrot firmness with acoustic signal characteristics were investigated. The firmness was positively related with the wave form index, and sound intensity in the time domain was negatively related with the relative energy in high-frequency domain. These conclusions could be useful for evaluating the carrot or other process food texture by acoustic technology.