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level: Microscopic and Sampling Methods

Questions and Answers List

level questions: Microscopic and Sampling Methods

QuestionAnswer
Direct Microscopic count- breed count developed by R.S. Breed - widely used in dairy industry - 0.01ml food sample smeared on 1cm2 of glass slide - heat fixed, defatting, stained with dye, air drying - observed under microscope - somatic and bacterial cell count
Calculate direct microscopic count- count somatic cells in 5 random MFs on slide and avg the counts - calculate number of MFs in 1cm2 area of slide (1 cm2/area MF) - multiply by avg cell count/MF - result = count in 0.01 mL milk, express count per mL milk
How to calc direct count when area MF not available?Use stage micrometer, given diameter find area (pi * r2)
Direct microscopic count: advantages and disadvantagesAdvantages: rapid, simple, observe cell morphology, can use fluorescent probes Disadvantages: technician fatigue, viable & nonviable cells counted, food particles/clumps of cells counted, some cells don't stain well
Howard Mold Count- slide with standardized chamber - designed to count mold mycelia - count mold fragments in canned beverages, fruit, pizza sauce, juices - indicate that raw materials poorly sorted/trimmed of fungal rot - no info on mold type