Heat resistance of fungi isolated from frozen blueberries

This study dealt with the isolation, characterization, and identification of the fungal microflora of frozen blueberries imported from Canada. The thermal inactivation rates of the rarely studied isolated heat-resistant molds, Devriesia spp. and Hamigera striata, in naturally and artificially contaminated blueberry slurries were also determined. The D-values of naturally contaminating Devriesia spp. at 70, 80, 85, and 90 degrees C were 714, 114, 44.4, and 14.1 min, respectively. The D-values of H. striata at 70, 80, 85, and 90 degrees C were 909, 286, 42.6, and 10.3 min, respectively. The z-values calculated from the thermal death time curves were 11.0 and 6.9 degrees C for Devriesia spp. and H. striata, respectively. Results also showed that in both test mold species, the naturally occurring molds had significantly higher thermal resistance than did the artificially contaminated counterparts. The results established by this study may be used by blueberry processors to prevent losses due to spoilage caused by the heat-resistant microorganisms.