Isolation, Identification and Biological Characterization of Spoilage Mold in Seedless White Raisins

Raisins were highly susceptible to microbial contamination during their processing, storage, and transportation. To understand the mold contamination of Xinjiang's specialty dried fruit, seedless white raisins, in this study, seedless white raisins were selected as the experimental subject. The mold contaminating the surface of the seedless white raisins was isolated and purified after being stored for three months in a high temperature and high humidity environment. The spoilage molds were screened according to the time and degree of molding by performing return infection experiments, they were identified and biologically characterized using rDNA-ITS sequence analysis combined with morphological and microstructural analyses. Results showed that, among the four strains of molds contaminating the surface of the raisins, strains A1, A2 and A4 caused rot. Aspergillus tubingensis, Aspergillus niger, and Penicillium steckii were also detected. Aspergillus tubingensis had an optimum growth temperature of 28 ℃, an ambient humidity of 90%, a pH of 7, and a lethal temperature of 60 ℃. Aspergillus niger had an optimal growth temperature of 28 ℃, an ambient humidity of 90%, a pH of 7, and a lethal temperature of 65 ℃. Penicillium steckii had an optimum growth temperature of 30 ℃, an ambient humidity of 90%, a pH of 7, and a lethal temperature of 55 ℃. This study provides a theoretical basis for mold growth, control, and optimization of storage conditions during raisin storage.