Effects of simulated transport vibration on respiratory pathways and qualities of Xinjiang apricot fruit

Abstract: Effects of simulated transport vibration on respiratory pathways and qualities in Xinjiang apricot were studied based on the similarity simulation. About 1.50 t fresh apricots (Xiao baixing) in physiological maturity stage were packaged in plastic crates and transported in a refrigerated truck at the average velocity of 60 km/h. X-axial (lateral), Y-axial (longitudinal) and Z-axial (vertical) vibration accelerations of apricot crates in refrigerated truck were measured using digital 3-dimensional (3D) acceleration recorders with a sampling rate of once every 2.0 seconds during the 10-hour highway transportation. A vibration simulation platform (self-triturating equipment) loaded 120 kg apricots packaged in plastic crates where the vibration of horizontal direction and vertical direction both initiated from 0 to 8.0 Hz with 1.0 Hz rise every 5 minutes. During the simulation, vibration was measured with 3D acceleration recorders sampling once every 50 ms to select the proper vibration frequency close to the real transportation. According to the repeatable measurements, the simulated vibration was 57.60%-67.75% similar to real transportation at 0.5 Hz. Frequencies of low acceleration vibrations on lateral, longitudinal and vertical directions were higher than real transport. Apricots were divided into 2 groups: one group was stored in static state for 20 d at 3℃; the other group was stored for 17 days 3 days after the simulated transport under the selected vibration condition at 3℃. The differences between simulated transport and static storage in respiratory pathways, firmness, SSC (soluble solid content) and pericarp color of apricots were analyzed. The total respiration rate of apricot reached peak in the first 2-day simulated transport vibration, which was earlier 8 days than the apricot in static storage, and the peak value raised by 3.26 times. Apricot TCAC (tricarboxyficacid cycle) respiration rate reached peak in first 2-day simulated transport vibration, which was earlier 3 days than the apricot in static storage, and the peak value raised by 1.22 times. Apricot EMP (Embden - Meyerhof - Parnas) and CP (cytochrome pathway) respiration rates also reached peaks in first 2-day simulated transport vibration; the peak values were respectively 4.62 times and 9.64 times higher than that of the apricot in static storage. Apricot PPP (phosphopentose pathway) respiration rate reached peak in the first day of simulated transport vibration, which was earlier 9 days than the apricot in static storage, but peak values were similar. The apricot's major respiratory pathway of simulated transportation was switched from TCAC pathway to EMP pathway, and the major electron transport chain was switched from AP (alternative pathway) to CP. The shift of major respiratory pathway resulted in further maturity and quality deterioration in the apricots at late storage. 13.18%-19.34% loss of firmness was significantly correlated with the increases of TCAC respiratory rate and CP respiratory rate during the simulation transport. 12.26%-27.15% rise of SSC was the consequence of the increases of EMP, TCAC and CP respiratory rate during the simulation transport. The pericarp chroma was increased by 7.09-11.49 times, which was significantly correlated with the increases of EMP respiratory rate and CP respiratory rate during the simulation transport. The pericarp color turned yellow by 3.82, which was significantly correlated with the increase of EMP respiratory rate during the simulation transport. Results provide a reference for developing quality-control techniques of the cold-chain transport of the apricot.