Effectiveness of potassium sorbate and sodium benzoate against microbial growth in pear syrup under variable pH and Brix conditions
(2025) KMBM01 20251Applied Microbiology
Biotechnology
Biotechnology (MSc)
- Abstract
- This thesis investigates the antimicrobial effectiveness of potassium sorbate and sodium benzoate in a pear syrup product under varying conditions of pH and Brix. Eight microorganisms were selected for inoculation, representing common spoilage yeasts and bacteria found in fruit-based beverages. The study evaluated eight preservative treatments: potassium sorbate (100, 200, 300 mg/L), sodium benzoate (50, 100, 150 mg/L) and selected combination of the preservatives. These were tested across two pH levels (3.2 and 4.2) and two Brix values (40 and 60). Microbial growth was assessed using colony-forming unit (CFU) counts, MALDI-TOF identification, and visual inspection after 5 days of incubation.
Results showed that both preservatives... (More) - This thesis investigates the antimicrobial effectiveness of potassium sorbate and sodium benzoate in a pear syrup product under varying conditions of pH and Brix. Eight microorganisms were selected for inoculation, representing common spoilage yeasts and bacteria found in fruit-based beverages. The study evaluated eight preservative treatments: potassium sorbate (100, 200, 300 mg/L), sodium benzoate (50, 100, 150 mg/L) and selected combination of the preservatives. These were tested across two pH levels (3.2 and 4.2) and two Brix values (40 and 60). Microbial growth was assessed using colony-forming unit (CFU) counts, MALDI-TOF identification, and visual inspection after 5 days of incubation.
Results showed that both preservatives inhibited microbial growth, with greater effectiveness observed at lower pH and when using the preservatives in combination. The most consistent microbial suppression was achieved using 100 mg/L of potassium sorbate and 50 mg/L of sodium benzoate at pH 3.2 and 40 Brix. While most bacteria were fully inhibited, some yeasts, including Saccharomyces cerevisiae, exhibited partial resistance, particularly under higher sugar and pH conditions.
These findings support the combined use of potassium sorbate and sodium benzoate at moderate concentrations as an effective strategy for microbial control in high-sugar, low-pH beverages. The study highlights the importance of condition-specific preservative planning and recommends further testing and research into long-term shelf-life of syrup products. (Less) - Popular Abstract
- This thesis investigated how well potassium sorbate and sodium benzoate protect pear syrup from microbial spoilage. These preservatives are widely used in juices and syrups to inhibt the growth of bacteria and yeasts, but there is a growing interest in reducing their use.
The study explored how effective these preservatives are under different conditions, focusing on acidity (pH) and sugar content (Brix). Laboratory-prepared syrups were combined with eight microorganisms commonly found in food production. Microbial growth was monitored over five days to reflect realistic industrial conditions.
Results showed that preservatives were most effective in acidic and lower-sugar environments. Using both preservatives together at moderate... (More) - This thesis investigated how well potassium sorbate and sodium benzoate protect pear syrup from microbial spoilage. These preservatives are widely used in juices and syrups to inhibt the growth of bacteria and yeasts, but there is a growing interest in reducing their use.
The study explored how effective these preservatives are under different conditions, focusing on acidity (pH) and sugar content (Brix). Laboratory-prepared syrups were combined with eight microorganisms commonly found in food production. Microbial growth was monitored over five days to reflect realistic industrial conditions.
Results showed that preservatives were most effective in acidic and lower-sugar environments. Using both preservatives together at moderate concentrations was more effective than using them individually. However, some microorganisms, especially the yeast Saccharomyces cerevisiae, were able to survive even under these treatments. This suggests that some organisms may require non-chemical control strategies.
Overall, this thesis offers producers a way to optimise preservative use while staying within legal limits and meeting consumer demand for fewer additives. It helps identify when preservatives are most effective and suggest that, under well controlled conditions, the amount of preservatives can pottentially be reduced. (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/9206731
- author
- Furberg, Solveig Alvilde Drøpping LU
- supervisor
- organization
- alternative title
- Effektiviteten av kaliumsorbat och natriumbensoat mot mikrobiell tillväxt i päronkoncentrat under varierande pH- och Brix-förhållanden
- course
- KMBM01 20251
- year
- 2025
- type
- H2 - Master's Degree (Two Years)
- subject
- keywords
- potassium sorbate, sodium benzoate, antimicrobial, preservatives, syrup, applied microbiology
- language
- English
- id
- 9206731
- date added to LUP
- 2025-09-22 10:10:14
- date last changed
- 2025-09-22 10:10:14
@misc{9206731,
abstract = {{This thesis investigates the antimicrobial effectiveness of potassium sorbate and sodium benzoate in a pear syrup product under varying conditions of pH and Brix. Eight microorganisms were selected for inoculation, representing common spoilage yeasts and bacteria found in fruit-based beverages. The study evaluated eight preservative treatments: potassium sorbate (100, 200, 300 mg/L), sodium benzoate (50, 100, 150 mg/L) and selected combination of the preservatives. These were tested across two pH levels (3.2 and 4.2) and two Brix values (40 and 60). Microbial growth was assessed using colony-forming unit (CFU) counts, MALDI-TOF identification, and visual inspection after 5 days of incubation.
Results showed that both preservatives inhibited microbial growth, with greater effectiveness observed at lower pH and when using the preservatives in combination. The most consistent microbial suppression was achieved using 100 mg/L of potassium sorbate and 50 mg/L of sodium benzoate at pH 3.2 and 40 Brix. While most bacteria were fully inhibited, some yeasts, including Saccharomyces cerevisiae, exhibited partial resistance, particularly under higher sugar and pH conditions.
These findings support the combined use of potassium sorbate and sodium benzoate at moderate concentrations as an effective strategy for microbial control in high-sugar, low-pH beverages. The study highlights the importance of condition-specific preservative planning and recommends further testing and research into long-term shelf-life of syrup products.}},
author = {{Furberg, Solveig Alvilde Drøpping}},
language = {{eng}},
note = {{Student Paper}},
title = {{Effectiveness of potassium sorbate and sodium benzoate against microbial growth in pear syrup under variable pH and Brix conditions}},
year = {{2025}},
}