Staff PhD

Integrated characterisation of food products quality and microbiological safety

Sandie Mejer Møller

Background

Food safety is one of the most important issues for the consumers, food manufacturers and retailers, and factors such as pH, temperature, oxygen concentration and water activity are today used as preservation techniques. Another factor affecting the microbial survival is foods microstructure, where the water availability and the distribution of water are of importance. Even though a food product has a high global water activity, the local activity can be otherwise and can either be favourable or unfavourable for the growth and survival of microorganisms. The microstructure is different for each food product, and varies among others with protein concentration, salt concentration and pH of the product. It is therefore of interest to develop a method which by looking at water availability and distribution of water can predict food safety.

Aim

The aim of the ph.d. project, is to develop methods for simultaneous characterisation and determination of both food products quality and microbiological safety. Further the aim is to obtain a better understanding of the connection between the food products components, their structure, molecular interactions and food products microbiological safety.

Research Outline

In order to understand the connection between the NMR pattern and the microstructure, several studies on well characterised systems are performed, these are among others growth media containing glass beads and protein gels, where the microstructure and the pore size can be controlled and thus varies under controlled conditions. The systems are studied with and without inoculation with relevant pathogen bacteria’s, i.e. Salmonella Dublin, Salmonella Typhimurium, Listeria monocytogenes, verotoxin producing Escherichia coli (VTEC) or Stahylococcus aureus, following experiments are performed.

• Low-field 1H NMR relaxation measurements
• Water activity, using the traditional pressure measurements
• Quantitative microbiological examinations using plate spread on appropriate selective media for the inoculated bacteria’s
• Possible supplementary physical measurements, such as differential scanning calorimetry (DSC) and electric conductivity

All measurements are compared, and multivariate models are set up to test the connection between water availability, microstructure and the microbiological viability.

The following activities are planned

1. Studies on model systems

2. Studies on cheese (Danish feta and cream cheese)

3. Studies on meat with variation in water activity

4. Studies on meat products (Fermented Sausages)