Microbial Spoilage of Grated Cheese : Growth Patterns of Yeast and Lactic Acid Bacteria in Relation to Intrinsic Factors
(2026) KMBM05 20261Applied Microbiology
- Abstract
- Grated cheese is a convenient and ready-to-use food product. However, due to its increased surface area, grated cheese is susceptible to spoilage. This master’s thesis aimed to improve the understanding of growth patterns of spoilage microorganisms in relation to intrinsic factors in both grated mozzarella and grated hard cheese. Cultivation of yeast and lactic acid bacteria, using pour plating- and surface plating techniques, was conducted every fifth day during a 40-day period, along with measurements of pH, water activity, and salt concentration. Sugar and metabolite concentrations were further monitored using High Performance Liquid Chromatography (HPLC). Macroscopic and microscopic observations combined with Matrix-Assisted Laser... (More)
- Grated cheese is a convenient and ready-to-use food product. However, due to its increased surface area, grated cheese is susceptible to spoilage. This master’s thesis aimed to improve the understanding of growth patterns of spoilage microorganisms in relation to intrinsic factors in both grated mozzarella and grated hard cheese. Cultivation of yeast and lactic acid bacteria, using pour plating- and surface plating techniques, was conducted every fifth day during a 40-day period, along with measurements of pH, water activity, and salt concentration. Sugar and metabolite concentrations were further monitored using High Performance Liquid Chromatography (HPLC). Macroscopic and microscopic observations combined with Matrix-Assisted Laser Desorption-Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF MS) identification were used to investigate the spoilage microorganisms present in the samples. Mozzarella was found to be more prone to microbial spoilage than hard cheese, showing higher total colony counts of both yeast and lactic acid bacteria. This may be explained by the more favourable composition of mozzarella for microbial growth. Furthermore, differences in sugar and metabolite concentrations between mozzarella and hard cheese indicated variations in cheese composition related to the production process and metabolic activity during fermentation. Multivariate analysis using Principal Component Analysis (PCA) revealed possible correlations between intrinsic factors and microbial growth patterns. In addition, Analysis of Variance (ANOVA) identified statistically significant differences within the system, further demonstrating the complexity of cheese as a biological matrix. Consequently, these findings contributed to an improved understanding of spoilage dynamics in grated cheese and may support future strategies for predicting and prolonging shelf-life. (Less)
- Popular Abstract
- Have you ever opened a package of grated cheese, only to find out that it has gone bad before you finished it?
Grated cheese is a practical product, but its large surface area makes it highly sensitive to spoilage. Cheese provides a nutrient-rich environment with favourable conditions for spoilage microorganisms, such as yeast and lactic acid bacteria, to easily thrive.
The industrial processing of grated cheese contains several steps, from raw milk to finished product, which give the spoilage microorganisms several opportunities to contaminate the product.
Understanding how cheese behaves and changes over time is therefore important, both to reduce waste and make food production more sustainable. A win-win for both the planet and... (More) - Have you ever opened a package of grated cheese, only to find out that it has gone bad before you finished it?
Grated cheese is a practical product, but its large surface area makes it highly sensitive to spoilage. Cheese provides a nutrient-rich environment with favourable conditions for spoilage microorganisms, such as yeast and lactic acid bacteria, to easily thrive.
The industrial processing of grated cheese contains several steps, from raw milk to finished product, which give the spoilage microorganisms several opportunities to contaminate the product.
Understanding how cheese behaves and changes over time is therefore important, both to reduce waste and make food production more sustainable. A win-win for both the planet and the producer.
To investigate this, two different types of cheese, grated mozzarella and grated hard cheese, were studied over a 40-day period. The goal was to see how different internal parameters affect the growth of spoilage microorganisms. The parameters included pH, water activity, salt- and sugar concentration, all important for the composition of cheese.
So, what did the results say?
The biggest difference was that mozzarella experienced higher growth of both yeast and lactic acid bacteria compared to the hard cheese. This means that mozzarella is a much more sensitive product that requires extra care. The study also showed that all internal parameters have a purpose, demonstrating the complexity of cheese. Because of this complexity it is difficult to pinpoint just one single parameter to change to prevent microbial spoilage. However, the results give a good understanding of the different relationships between the parameters and may help the industry to predict and prolong the shelf-life of cheese in the future. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/student-papers/record/9234004
- author
- Christensson, Sandra LU and Hammarlund, Klara LU
- supervisor
- organization
- alternative title
- Mikrobiologisk förskämning av riven ost : Tillväxtmönster hos jäst och mjölksyrabakterier i förhållande till intrinsiska faktorer
- course
- KMBM05 20261
- year
- 2026
- type
- H2 - Master's Degree (Two Years)
- subject
- keywords
- Microbial spoilage, Growth patterns, Yeast, Lactic acid bacteria, Cheese, Intrinsic factors, Applied Microbiology
- language
- English
- id
- 9234004
- date added to LUP
- 2026-06-10 08:52:35
- date last changed
- 2026-06-10 08:52:35
@misc{9234004,
abstract = {{Grated cheese is a convenient and ready-to-use food product. However, due to its increased surface area, grated cheese is susceptible to spoilage. This master’s thesis aimed to improve the understanding of growth patterns of spoilage microorganisms in relation to intrinsic factors in both grated mozzarella and grated hard cheese. Cultivation of yeast and lactic acid bacteria, using pour plating- and surface plating techniques, was conducted every fifth day during a 40-day period, along with measurements of pH, water activity, and salt concentration. Sugar and metabolite concentrations were further monitored using High Performance Liquid Chromatography (HPLC). Macroscopic and microscopic observations combined with Matrix-Assisted Laser Desorption-Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF MS) identification were used to investigate the spoilage microorganisms present in the samples. Mozzarella was found to be more prone to microbial spoilage than hard cheese, showing higher total colony counts of both yeast and lactic acid bacteria. This may be explained by the more favourable composition of mozzarella for microbial growth. Furthermore, differences in sugar and metabolite concentrations between mozzarella and hard cheese indicated variations in cheese composition related to the production process and metabolic activity during fermentation. Multivariate analysis using Principal Component Analysis (PCA) revealed possible correlations between intrinsic factors and microbial growth patterns. In addition, Analysis of Variance (ANOVA) identified statistically significant differences within the system, further demonstrating the complexity of cheese as a biological matrix. Consequently, these findings contributed to an improved understanding of spoilage dynamics in grated cheese and may support future strategies for predicting and prolonging shelf-life.}},
author = {{Christensson, Sandra and Hammarlund, Klara}},
language = {{eng}},
note = {{Student Paper}},
title = {{Microbial Spoilage of Grated Cheese : Growth Patterns of Yeast and Lactic Acid Bacteria in Relation to Intrinsic Factors}},
year = {{2026}},
}