Abstract: An antagonistic yeast for controlling Rhizopus rot of postharvest peaches was selected by in vivo tests. Then its biocontrol efficacy against natural decay of peaches and its effects on the quality of peaches were investigated. The conditions for producing a solid preparation of this antagonistic yeast by spray drying method were optimized by single-factor experiments and after being stored for 90 d, the obtained preparation was used to control Rhizopus rot of peaches. The results showed that the decay incidence of 72 h-stored peaches caused by Rhizopus rot was decreased by Pichia membranaefaciens (26.23%) compared with that of the control (95.70%). The antagonistic yeast also evidently reduced the natural decay incidence without adverse effect on the quality of peaches. The optimized conditions for producing the solid preparation were as follows: gum Arabic-to-trehalose ratio 1:1 (m/m); protectant concentration 100 g/L, atomizer pressure 200 kPa, inlet air temperature 100 ℃, and feeding speed 15 mL/min. The survival rates of this yeast strain in the obtained solid preparation were 66.97% and 82.91%, respectively after being stored at 25 and 4 ℃ for 90 d. The biocontrol efficacy of the solid preparation stored for 90 d at 4 ℃ was very obvious, although the decay incidence (37.04%) was significantly higher than that obtained with the freshly prepared yeast suspension (31.48%).

Key words: peaches; postharvest disease; antagonistic yeast; spray drying; solid preparation