CHARACTERIZATION OF MOLD GROWTH IN ORANGE JUICE

Mould growth rates at 0, 3, 7, 10 and 15 degrees C were measured by dr y weight analysis of the mycelium and as a function of mycelial growth across the surface of an orange juice-based agar medium. Penicillium italicum produced significantly greater (P less than or equal to 0.05) mass and was capable of significantly (P less than or equal to 0.05) faster growth than the other test fungi at most temperatures. Only P. italicum and Cladosporium cladosporioides grew at 0 degrees C. P, citr inum was most sensitive to refrigerated temperatures and did not grow at 7 degrees C or below: After growth of fungi in orange juice at 10 d egrees C for 12 days, there was a slight reduction in degrees Brix alt hough pH and total titratable acidity did not change. Invertase produc tion by P. digitatum caused a reduction in sucrose levels accompanied by concomitant increases in glucose and fructose. Results suggest pref erential utilization of glucose by Geotrichum and fructose by P. digit atum. Destruction of cloud was observed in orange juices inoculated wi th penicillia but not Geotrichum. (C) 1995 Academic Press Limited