Abstract: In order to establish a complete detection system for spoilage yeasts and to monitor the quality of orange juice in market, the colony dynamic development and cell characteristics of yeast strains Y25 and Y32 isolated from orange juice were examined. The domain sequences 26S rDNA D1/D2 from Y25 and Y32 were amplified with NL1 and NL4 primers, respectively. The results showed that the morphological features of colonies for the same strain changed with culture time and were clear and concise and could therefore be used to identify the yeast strains isolated. Through comparison with the homologous gene sequences published in GeneBank, Y25 was identified as Debaryomyces hansenii, and Y32 as Candida parapsilosis. Their similarity degrees to the homologous gene sequences were both higher than 99%. The combination of morphology and molecular technology can allow to more accurately and reliably identify yeast strains and will provide valuable references for the identification and monitoring of other spoilage microorganisms in orange juice.

Key words: orange juice, yeast colony, cell characters, molecular identification, opportunistic pathogens