Description du projet :
A central domain of activity of the research group Food & Natural Products is non-thermal processing. To valorise and supplement the existing PEF equipment and to gain knowledge on the application of PEF, we propose the following project.
Occasionally, liquid tea extracts from industrial extraction process show microbial instability. The commercial extraction process is done at 85° C for 1 h (twice 30 min). Under these conditions, vegetative germs are killed and only spores can survive.
It is believed that the combination of hot extraction and PEF will lead to a sufficient reduction in the spore numbers. The aim of the present study is to use the hot extract from the thermal extraction process (60 and 80 °C) and to apply PEF to reduce spore-forming bacteria at least 105 times in the tea extracts.
Therefore, the spore forming bacteria from the tea are isolated, quantified, identified and cultivated. To quantify the effect of thermal process and PEF treatment, the cultivated spores are added in appropriate amount to the tea.
With the Innovation Partnership Grant (Bilateral research collaboration with Asia 2017-2020), we obtained money for consumables and equipment, but no budget for hours to do experiments.
From this money, 2000,- CHF are used to construct a smaller batch chamber, to supplement the PEF system. Smaller electrode distance enables higher electric fields, which are a prerequisite for microbial decontamination (> 30 kV/cm).
About 1000,- CHF are used to analyse the spore forming bacteria and to buy material for the microbiology lab. The work in the pilot plant will be done by scientific collaborator (80 h). The microbial analysis will be done by Bruno Lehner/ Martine Baudin (80 h).
Supplementary work from ISI to complement the work on the batch chamber, as follows:
The high electric fields mentioned above require a modification of the sample chamber containing the electrodes between which the electric field is excited. In addition, the modification of the sample chamber will have an influence on the charging behaviour of the capacitance linked to the chamber. Therefore, accompanying the experiments in the laboratory will require the presence of a expert of high voltage electronics from ISI, to assure quality, correct application and functioning of the PEF machine.
The redesign of the sample chamber will be done by Christian Cachelin (60 h), the power electronic measurements and modifications of the electronics will be done by Aurelien Carrupt (80 h).
Equipe de recherche au sein de la HES-SO:
, Brück Wolfram Manuel
, Beyrer Michael
, Udrisard Isabelle
, Axelrod Robert
, Lehner Bruno
, Baudin Martine
Durée du projet:
01.02.2019 - 24.12.2019