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Research article - Peer-reviewed, 2021

Use of natural plant extracts as a novel microbiological quality indicator in raw milk: An alternative for resazurin dye reduction method

Madushan, Ranga; Vidanarachchi, Janak K.; Prasanna, P. H. P.; Werellagama, Shanika; Priyashantha, Hasitha


In the present study, we propose a novel field-scale analytical tool for rapid screening of microbiological quality in raw milk using aqueous extracts of plant materials, i.e. flowers (e.g. Hibiscus rosa-sinensis L. and Clitoria ternatea), taproots (e.g. Beta vulgaris) and pricklypears (e.g. Opuntia dillenii). For each plant extract, the colour changes in raw milk were evaluated between 4.5 and 6.5 pH against the resazurin dye as a control. The plant anthocyanin content in each extract was analyzed by the differential pH method using a spectrophotometer. The Hibiscus rosa-sinensis flower extract was opted to further test since it had a pH-sensitive colour change (6.5; maroon to 6.2; light-pink) compared to other plant extracts, which did not indicate a noticeable colour variation with pH. Anthocyanin content of the Hibiscus extract was 0.59 g/mL. The novel method showed high linearity (R-2 = 0.95), 100% accuracy and greater repeatability with an intermediate level of precision. The limit of quantification and detection was 0.46 and 0.15 g/mL, respectively. In conclusion, we demonstrated the potential in using water extract of Hibiscus rosa-sinensis L. flowers as an alternative to the resazurin dye reduction method for rapid and accurate microbiological quality control for raw milk procurement in remote areas.


Anthocyanin; Plant aqueous extracts; Microbiological safety; Milk keeping quality; Platform test

Published in

Food Science and Technology
2021, volume: 144, article number: 111221
Publisher: ELSEVIER

Authors' information

Madushan, Ranga
University of Peradeniya
Vidanarachchi, Janak K.
University of Peradeniya
Prasanna, P. H. P.
University of Peradeniya
Werellagama, Shanika
University of Peradeniya
Swedish University of Agricultural Sciences, Department of Molecular Sciences

UKÄ Subject classification

Animal and Dairy Science
Food Science

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