Food Sensing: Detection of Bacillus cereus Spores in Dairy Products

Abstract

Milk is a source of essential nutrients for infants and adults, and its production has increased worldwide over the past years. Despite developments in the dairy industry, premature spoilage of milk due to the contamination by Bacillus cereus continues to be a problem and causes considerable economic losses. B. cereus is ubiquitously present in nature and can contaminate milk through a variety of means from the farm to the processing plant, during transport or distribution. There is a need to detect and quantify spores directly in food samples, because B. cereus might be present in food only in the sporulated form. Traditional microbiological detection methods used in dairy industries to detect spores show limits of time (they are time consuming), efficiency and sensitivity. The low level of B. cereus spores in milk implies that highly sensitive detection methods should be applied for dairy products screening for spore contamination. This review describes the advantages and disadvantages of classical microbiological methods used to detect B. cereus spores in milk and milk products, related to novel methods based on molecular biology, biosensors and nanotechnology.

Keywords: Bacillus cereus; biosensors; detection; milk; spores.

Figure 1

(a) Formation of spores by endospore-forming B. cereus. Upon unfavorable environmental conditions, the vegetative cell differentiates and enables spore morphogenesis. Mature spores are released and will germinated to give rise to a vegetative cell under favorable conditions. (b) Schematic diagram of bacterial spore structure.

Figure 2

Envisioned spore diagnostic workflow by a classical method (a) and biosensors (b).

Figure 3

Illustration of the immunomagnetic lateral flow sensing principle.

Figure 4

Illustration of principle for B. cereus spore detection and electrochemical set-up for signal measurement using a miniaturized aptasensor (from Reference [97]).