Tantamacharik Thirawat, Leong Sze Ying, Leus Michelle J, Eyres Graham T, Burritt David J, Oey Indrawati
Department of Food Science, University of Otago, PO Box 56, Dunedin 9054, New Zealand.
Riddet Institute, Private Bag 11 222, Palmerston North 4442, New Zealand.
Foods. 2019 Aug 26;8(9):368. doi: 10.3390/foods8090368.
This study investigated whether pulsed electric field (PEF) treatment can induce structural changes of whole, intact red onion bulb ( L. var. Red Pearl). Onion bulbs were treated at electric field strengths of 0.6 and 1.2 kV/cm combined with energy inputs of 6 and 60 kJ/kg at different onion orientations with respect to the high voltage electrode. Results showed that onion cells across all fleshy scales experienced uniform cell damage with a higher proportion (>80%) of non-metabolically viable cells after PEF treatment at 1.2 kV/cm when the root end was positioned facing toward the PEF electrode. The findings were supported by cryogenic-scanning electron micrographs (cryo-SEM), where the underlying storage circular cells were completely damaged owing to the PEF treatment. In this study, it was found that the treatment intensity of PEF to induce structural damage across all the scale layers of an onion bulb coincided with an increase in dipropyl disulfide (DPDS) released from the onion bulbs. Therefore, DPDS was used as a volatile marker indicating cellular disruption within whole, intact onion bulbs. A considerable increase of DPDS, up to 52-fold, was detected from PEF-treated onion bulbs compared to untreated bulbs.
本研究调查了脉冲电场（PEF）处理是否会引起完整红洋葱鳞茎（红珍珠品种）的结构变化。将洋葱鳞茎在电场强度为0.6和1.2 kV/cm的条件下进行处理，并结合6和60 kJ/kg的能量输入，处理时洋葱相对于高压电极有不同的朝向。结果表明，当根部朝向PEF电极时，在1.2 kV/cm的PEF处理后，所有肉质鳞片中的洋葱细胞都经历了均匀的细胞损伤，其中非代谢活性细胞的比例较高（>80%）。低温扫描电子显微镜（cryo-SEM）图像支持了这一发现，图像显示由于PEF处理，下层的贮藏圆形细胞完全受损。在本研究中，发现PEF诱导洋葱鳞茎所有鳞片层结构损伤的处理强度与洋葱鳞茎释放的二丙基二硫化物（DPDS）增加相吻合。因此，DPDS被用作指示完整洋葱鳞茎内细胞破坏的挥发性标志物。与未处理的洋葱鳞茎相比，经PEF处理的洋葱鳞茎中检测到DPDS显著增加，高达52倍。
