As the concentration of cells increases, the turbidity of the culture increases.

A standard curve is produced by plotting the absorbance versus known cell concentrations (determined from a direct count using a haemocytometer)


  • Concentrated yeast culture
  • Turbidity meter
  • Cuvettes
  • Pasteur pipettesimage 1

Instructions – preparation of standard curve

Make serial dilutions of the yeast culture.

For each cell suspension obtained, measure the absorbance and calculate the cell concentration using a haemocytometer to directly count the cells. Where the cells are too numerous to count (TNTC), serially dilute the suspension till a countable number is achieved.

zero colorimeter with sterile medium

measure the absorbance of the cell suspension