| 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 disadvantages | Advantages: 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 |
