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Studies have been conducted to determine growth requirements for fungi belonging to the genus Byssochlumys. Incubation temperature significantly affected growth, with visual detection in 2 days at 30°C and 4 days at 20°C. Sugar concentration was important in liquid culture techniques, with no growth observed in 30" Brix apple drink base after 2,640 hr vs growth in 15" Brix apple drink base after 48 hr. Thermal death studies of three Byssochlumys isolates (G-5, G-52, and M-78) demonstrated wide variation in heat resistance with z-values of 7", 9.5", and 14°F respectively. Excellent electron micrographs were obtained of conidia, aleuriospores, and ascospores using a JEOL JSM 35 scanning electron microscope. The micrographs also revealed asci with thicker walls in older (90 days vs 30 days) M-78 cultures. A modification of the Shaeffer-Fulton Spore Stain Technique was used to stain the ascospores within an intact ascus.

Automated impedance measurements were used to classify samples of frozen concentrated orange juice as acceptable (< IO4 CFU/ml) or unacceptable (72 IO4 CFUlml). Calibration curves relating initial microbial concentration to impedance detection time were generated for several orange juice isolates. Cut-off times of 10.2 hr for bacteria and 15.8 hr for yeasts were adopted. More than 96% of 468 retail samples were correctly classified using automated impedance measurements. This technique has several advantages over other automated systems, including lower cost and reduced demand for technician time, and it provides reliable results much quicker than does the agar plate count. Cultures MATERIALS & METHODSTwo bacterial species (Lactobacillus fructivorans, Leuconostoc mesenteroides) and two yeasts (Candida tropicalis, SaccharomJaces chevalieri) were used for preparation of calibration curves. Each was isolated from orange juice (OJ) and propagated by transfer every 3-5 days into sterile single strength OJ (I2"Brix) at 30°C. Impedance Measurements