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A modified direct epifluorescent filter technique for the detection and enumeration of yeast in yoghurt
Author(s) -
Rowe M.T.,
McCann G.J.
Publication year - 1990
Publication title -
letters in applied microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.698
H-Index - 110
eISSN - 1472-765X
pISSN - 0266-8254
DOI - 10.1111/j.1472-765x.1990.tb00182.x
Subject(s) - rowe , queen (butterfly) , northern ireland , library science , enumeration , operations research , history , biology , computer science , management , ethnology , economics , mathematics , ecology , combinatorics , hymenoptera
A modified direct epifluorescent filter technique (DEFT) for the detection and enumeration of visible yeast in fruit‐flavoured yoghurt is described. The method involves an initial enrichment in oxytetracycline glucose yeast peptone broth (OGYP, 30d̀C/24, 48 h), prefiltration prior to DEFT and use of the vital stain Viablue 1. Additional yoghurt samples were subjected to prolonged incubation at 12d̀C or spiked with Kluyveromyces fragilis . When DEFT was compared with the plate count, regression and correlation coefficients of 1.12 and 0.85 respectively were obtained for values above the sensitivity threshold of DEFT (10 3 cells/ml). The use of an enrichment stage (OGYP, 30D̀C/24 h) enabled, by calculation, a theoretical minimum yeast contamination level of 7 yeast cells/g in the original yoghurt to be detected assuming the cells exhibit no lag phase of growth.