Control Of Blue Mould In Kiwifruits By Postharvest Oxalic Acid And Potassium Oxalate Treatment And Its Partial Mechanism

The effects of oxalic acid (OA) and potassium oxalate in controlling Penicillium expansum growth and patulin accumulation were evaluated by both in vitro and in vivo studies. In vivo test, the kiwifruits (Actinidia deliciosa.cv. Bruno) were dipped in50mM oxalic acid and50mM potassium oxalate (pure water as control) for15min, respectively, and then stored at20±1℃. The kiwifruits were inoculumed15μL2×106cfu·mL-1Penicillium expansum conidial suspension respectively after treated with oxalic acid or potassium oxalate for48h, and then stored at20±1℃for indicators measuring. The main results were as follows:1. In vitro, spore germination, growth of Penicillium expansum and patulin accumulation were significantly reduced by5mM and10mM oxalic acid with and without neutralization, which seemed that oxalic acid could directly inhibit the growth of Penicillium expansum and patulin accumulation besides by lower the pH of medium. Potassium oxalate could also inhibit the growth of Penicillium expansum when concentration was1mM, but the growth of Penicillium expansum and patulin accumulation were promoted by treatment with10mM potassium oxalate.2. In vivo, as compared to control, the both postharvest oxalic acid and potassium oxalate treatment significantly delayed the disease incidence, reduced the lesion diameter and patulin accumulation during the earlier periods of the inoculation on kiwifruits. In addition, oxalic acid and potassium oxalate treatment also enhanced the activities of peroxidase (POD) and the levels of total phenolic compounds. None of the treatments did impair quality parameters (firmness、SSC、Vc、TSS、 TA、pH) of kiwifruits.