Thesis-1989-Ferreira.pdf (5.84 MB)
Rapid methods to assess fungal contamination in tomato products
thesis
posted on 2018-04-10, 14:03 authored by Maria F.H. Pacheco FerreiraSome new, rapid methods were used in this study for tomato products as
alternatives to the traditional Howard mould count. This method proved to be
a fastidious but subjective method and therefore inaccurate for use in tomato
quality control and/or for legislative purposes.
The Apizym system was used to assess fungal presence in tomatoes, tomato
juice and crushed tomato, where different patterns of extracellular enzymes
were obtained for the different mould species. Growth medium was also found
to have an effect. This suggested the possibility of using this method to
assess fungal presence in tomato products and tentatively identify them using
their enzymic profile. Use of this method may not only apply to assessing raw
material quality, but also as a possible monitoring test for assessing heat
treatment adequacy or post process contamination.
ATP photometry was found to be suitable for assessing mould contamination
in tomato juice, but erroneous results were obtained with crushed tomato. This
may be related to various difficulties associated with the separation of
microbial ATP from the food material, or with its extraction from the fungal
hyphae, in some mould species.
The Direct Epifluorescent Filter Technique (DEFT) despite slightly
overestimating the total viable count, possibly due to the effect of heat
treatment on acridine orange staining characteristics, proved useful because
of its rapidity in detecting fungal presence in tomato juice. Therefore, it could
be used to assess quality during tomato juice production or to predict the
shelf-life of the product.
Impedance microbiology was used to detect mould presence in tomato
juice. In this study it proved very useful in assessing tomato juice sterility
using the relationship between impedance detection time and contamination
levels. lt also had the advantage of enabling rapid rejection of tomato juice
contaminated with mould. This involved the use of a calibration curve based on
the above relationship for which a cut-off point corresponding to the minimum
detection time was determined.
Funding
British Council. Portugal, Junta Nacional de Investigação Científica e Tecnológica (JNICT).
History
School
- Aeronautical, Automotive, Chemical and Materials Engineering
Department
- Chemical Engineering
Publisher
© Maria Fernanda H. Pacheco FerreiraPublisher statement
This work is made available according to the conditions of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) licence. Full details of this licence are available at: https://creativecommons.org/licenses/by-nc-nd/4.0/Publication date
1989Notes
A Master's Thesis. Submitted in partial fulfilment of the requirements for the award of Master of Philosophy at Loughborough University.Language
- en