Effects of different vibration spectrum shapes on mechanical damage of postharvest Huangguan pear during transportation

Abstract

Mechanical damage of the horticultural produce during postharvest transportation is an important criteria for fruit sorting and grading. The vibration during transportation has a significant effect on the mechanical damage of the fruit. In this study, the effect of different vibration spectrum shapes on mechanical damage of Huangguan pear (Pyrus bretschneideri Rehd, cv. Huangguan) was investigated. Four acceleration spectrums (spectrum Ⅰ, spectrum Ⅱ, spectrum Ⅲ, and spectrum Ⅳ) with same vibration level and different shapes were evaluated. The power spectral density (PSD) amplitude in the resonant region was in the order of spectrum Ⅰ > spectrum Ⅱ> spectrum Ⅲ > spectrum Ⅳ. The change in appearance, physiological properties (respiratory rate and weight loss), and mechanical properties (firmness and elastic modulus) of the pears were evaluated after vibration. Results showed that vibration resulted in quality deterioration of pear. Compared to the control group, respiratory rate and weight loss of the pears increased while the flesh firmness and elastic modulus of the pears decreased after vibration. The mechanical damage became more serious as stacked position increased. The effect of spectrum shape on the mechanical damage of pear was also obvious. Different degree of mechanical damage was observed under spectrum Ⅰ, spectrum Ⅱ, spectrum Ⅲ, and spectrum Ⅳ vibration. The higher the acceleration PSD in resonant region, the more serious the mechanical damage of pear. In comparison with the control group, pear under spectrum Ⅰ effect showed the most mechanical damage and the pear under spectrum Ⅳ effect had the minimum mechanical damage. Furthermore, S−Grms curves (damage area - vibration level) showed a clockwise rotation from spectrum Ⅰ to Ⅲ vibration. This study reveals the mechanical damage mechanism of pears based on acceleration spectrum shape and provides guidance for postharvest loss reduction using simulated test.