Rapid determination of yeast numbers by impedance measurement using a Bactometer 32

Abstract

Yeasts can be detected by the Bactometer 32 both in broth and in broth containing 10% yogurt culture. Several broths gave results which agreed well with the colony count. and Malt Extract broth incorporating 2% glucose was selected as satisfactory. With yogurt it was necessary to include antibiotic (20 ppm chloramphenico[) in the broth to suppress the bacterial signals and allow good detection of the yeasts. Results were available three days earlier than for a colony count, even with a yeast of slow multiplication rate.Impedance measurements have been used to determine bacterial numbers in a variety of foods during the last few years.

Estimation of yeast numbers in fruit mix for yogurt

“…Although work by Shapton & Cooper (1984) had shown that Malt Extract broth (MEB) with 2% glucose was satisfactory in the Bactometer B32, yeast glucose peptone broth (YGPB) gave equivalent results, and preliminary experiments using the M120B showed that MEB gave longer detection times than did YGPB. YGPB was therefore compared with carbon base ammonium sulphate broth (CBAS), which is recommended for yeast work in the M120B.…”