Evaluation of crisp texture of persimmon flesh by an acoustic vibration method

N. Sakurai, T. Suzuki, T. Niikawa
'Taishu' persimmon (Diospyros kaki) fruit was introduced to the Japanese market 20 years ago to increase consumption, especially among the younger generation, who prefer fruit with a crisp texture. Fruit firmness, however, did not correspond to crispness scores by a sensory test. Therefore, accurate evaluation of the perceived crisp texture is a prerequisite for research on maintaining high crispness during shipping and storage. Persimmon flesh texture was evaluated using an acoustic measurement of crispness (AMC) method. A wedge-type probe (5 mm diameter) was inserted at 22 mm s-1 in to a two cm thick disc of flesh excised from the equatorial plane of the fruit. Vibration of the probe on insertion was detected by a piezoelectric sensor directly attached to the bottom of the probe. Voltage signals from the sensor were amplified for computer analysis. The voltage signals were passed through a half-octave band-pass filter and allotted to 19 bands by a custom-made program. Texture index (TI) was defined as: TIi = (fi2/n) × Σ(V2), where fi is a frequency of ith of 19 bands, V is an output voltage from the sensor and n is the data number. TI is physically equivalent to kinetic energy density of probe vibration. Sensory tests showed that the crispness score of the flesh decreased when the fruit was stored at room temperature. TI of 2240 to 25600 Hz decreased during storage. Combined use of 0.06 mm thick polyethylene (PE) film and 1-methylcyclopropane (1-MCP) maintained high crispness scores by sensory test and high TI values above 6400 Hz for 12 days. Changes in sensory score and TI values were very similar under different storage conditions (r=0.736 to 0.861). These results suggest that the AMC method objectively evaluates the crispness texture of 'Taishu' persimmon fruit and a combined use of PE film and 1-MCP extends the storage life by maintaining the crisp texture.
Sakurai, N., Suzuki, T. and Niikawa, T. (2018). Evaluation of crisp texture of persimmon flesh by an acoustic vibration method. Acta Hortic. 1195, 189-196
DOI: 10.17660/ActaHortic.2018.1195.30
crispness, texture, persimmon, piezoelectric sensor, sensory test, polyethylene

Acta Horticulturae