The potential of energy-divergent ultrasound, slightly acidic electrolyzed water and peracetic acid in sweet potato preservation to control Rhizopus stolonifer

Abstract

Soft rot of sweet potato caused by Rhizopus stolonifer is a destructive post-harvest disease that leads to significant losses of sweet potatoes during storage. The inhibitory effects of energy-divergent ultrasound (EDU) combined with slightly acidic electrolyzed water (SAEW) and peracetic acid (PA) on R. stolonifer were investigated, to explore new methods suitable for sweet potato storage. Compared with EDU, SAEW or PA individually or combined, EDU + SAEW&PA, first treating with 70 mg/L SAEW for 2.5 min at 500 W, following by 70 mg/L PA for another 2.5 min at 500 W, completely inhibited mycelial development and spore outgrowth of R. stolonifer, resulting in severe cytoplasmic leakage. EDU + SAEW&PA also caused significant damage to the ultrastructure of R. stolonifer, increased cytomembrane permeability, collapsed mitochondrial membrane potential, and induced substantial cellular reactive oxygen species (ROS) accumulation. This effect was more pronounced compared to SAEW or PA alone. Furthermore, EDU + SAEW&PA effectively controlled R. stolonifer infection, prevented soft rot symptoms during 20 days of storage, significantly increased disease-resistance-related enzyme activities, reduced lipid peroxidation products, and preserved starch, sugar components and sweetness. Therefore, EDU + SAEW&PA could serve as an effective, environmentally friendly method to improve the storage quality of sweet potatoes.