Crisp Texture Evaluation of Persimmon Fruit by a Swing-arm Device

Abstract

Crispness of persimmon flesh was evaluated by a swing-arm texture device. A conical probe was inserted into the flesh, and horizontal and vertical vibrations of the probe were separately monitored from 0 to 51,200 Hz. The vibrations were used to calculate the energy texture index. Out of the seven persimmon varieties tested, sensory tests showed that three varieties: ‘Taishuu‘, ‘Neo sweet’, and ‘Reigyoku’, were more crisp than the other varieties: ‘Maekawa-Jiro’, ‘Matsumotowase-Fuyu’, ‘Shinsyuu’, and ‘Kanshu’. There was a significant positive correlation between the energy texture index of horizontal vibrations and the sensory score. However, the sensory score was found to be influenced by the flesh firmness. Vibration ratios were obtained by dividing the horizontal by vertical vibrations, which were correlated with the elasticity index and sensory score. The vibration ratios calculated in 3,200–4,480 or 4,480–6,400–Hz frequency bands were especially useful for evaluating the crisp texture of each variety. In addition, the food friction index obtained by the swing-arm device had a highly significant positive correlation with the sensory score for flesh firmness and also with the elasticity index. The food friction index may be used for evaluating the flesh firmness of persimmon. These results show that the swing-arm device for texture evaluation can simultaneously measure both crisp texture and flesh firmness with single probe penetration. Furthermore, a scatter plot of the food friction index on the horizontal axis and vibration ratio on the vertical axis makes it possible to classify the flesh texture characteristics of persimmon varieties.