Microflora of two varieties of sweet cherries: Burlat and Sweetheart

The epiphytic microflora of two widely cultivated sweet cherries 'Burlat' and Sweetheart' from Aragon (Spain), were characterized immediately after harvesting. Microbial analyses of total mesophilic aerobic, Enterobacteriaceae family and mould and yeast counts were carried out. Total mesophilic aerobic counts averaged 4.00 and 2.00 log cfu g(-1) for Burlat and Sweetheart cherries, respectively. The Enterobacteriaceae family was the microbial group with the lowest counts averaging 1.56 and 0.07 log cfu g(-1). Yeasts were the most prevalent micro-organisms in both varieties, with a mean of 4.10 and 2.30 log cfu g(-1) for Burlat and Sweetheart cherries, However average mould counts slightly exceeded 2.00 log cfu g(-1). Statistical differences in microbial counts between the two varieties were detected These results confirmed the lower susceptibility of Sweetheart cherries to microbial colonization and spoilage. Six hundred and seventy-nine strains, 103 belonging to the Enterobacteriaceae family, 100 mold strains and 442 yeast strains were isolated for the identification. Identification of Enterobacteriaceae species revealed that Pantoea agglomerans was the prevalent species in both varieties. Enterobacter cloacae and Serratia liquefaciens were also present on the Burlat cherry. Investigation of the external mycota led to three genera: Cladosporium, Alternaria and Penicillium. Yeasts were identified using the Deak and Beuchat simplified scheme (SIM) as belonging to five species included in three genera. Trichosporon pullulans was the dominant species, while Rhodotorula glutinis, Rhodotorula rubra, Cryptococcus albidus and Cryptococcus neoformans were present at low numbers. Results of the yeast identification were compared with two commercially available kits, Api 20C AUX and PROLEAL. The PROLEAL values agreed with the SIM results; whereas the Api 20C AUX kit led to misidentifications in all strains tested. (C) 2002 Elsevier Science Ltd.