Frederic Melton
Mozzarella cheese is a popular dairy product with a short shelf life due to its susceptibility to microbial growth. The production of mozzarella involves the use of specific bacteria, such as Lactobacillus, which contribute to its unique characteristics like meltability and stretchability. The microbiological aspects of mozzarella cheese are crucial, as they influence its safety, quality, and functionality. The selection of starter cultures, including Streptococcus and Lactobacillus species, plays a significant role in determining the physical and sensory attributes of the final product. Additionally, the microbial diversity in mozzarella cheese is positively correlated with its lactic acid content, impacting its taste and texture. The study of mozzarella cheese microbiology also involves evaluating the impact of different acidification methods and the presence of undesirable bacteria.
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What You'll Learn
- The role of Lactobacillus acidophilus in Mozzarella
- Microbiological safety and quality of Mozzarella
- The effect of salt on microbial growth in Mozzarella
- The use of molecular techniques to study the Lactobacillus community in Mozzarella
- The impact of different acidification methods on the microbiota of high-moisture Mozzarella
The role of Lactobacillus acidophilus in Mozzarella
Dairy products, including mozzarella cheese, have a reduced shelf life because they are an excellent growth medium for a wide range of microorganisms. Lactobacillus acidophilus is a probiotic strain that has been incorporated into mozzarella cheese to improve its microbiological safety and quality.
Lactobacillus acidophilus is a heat-tolerant and acid-tolerant probiotic strain that has been shown to survive in the conditions of commercial cheese production. It also exhibits antimicrobial activity against pathogens such as Salmonella typhimurium, Escherichia coli, and Staphylococcus aureus. This makes it an ideal strain for incorporation into mozzarella cheese to inhibit the growth of spoilage bacteria and improve the hygienic state of the product.
A study by Astashkina et al. (2014) collected ten separate samples of fresh traditional yogurts from local markets in Lahore, Pakistan, and stored them at 4 °C to avoid contamination during transportation. The samples were processed for microbiological analysis, and Lactobacillus acidophilus was isolated and identified. Three types of cheese were then made: cheese A with free cells of Lactobacillus acidophilus, cheese B with encapsulated cells of the probiotic, and control cheese with no added probiotic. The microbiological analysis of the prepared cheese revealed a lesser loss of Lactobacillus acidophilus from the encapsulated form compared to the free cells.
Another study by Patil and Vishwanath (2012) reported that Lactobacillus acidophilus is potentially safe to use as a probiotic in mozzarella cheese. They also found that the count of Lactobacillus acidophilus increased during the storage of mozzarella cheese, indicating its ability to survive and potentially improve the shelf life of the product.
The incorporation of Lactobacillus acidophilus into mozzarella cheese has been shown to have positive effects on the quality and sensory attributes of the cheese. It has been found to increase the acidity, dry matter content, amount of protein, and ripening index of the cheese during storage. Additionally, the addition of probiotic bacteria has been associated with higher sensory scores and improved textural properties, such as decreased chewiness values, in mozzarella cheese.
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Microbiological safety and quality of Mozzarella
Dairy products, including mozzarella cheese, have a reduced shelf life because they are an excellent growth medium for a wide range of microorganisms. This makes it imperative to monitor the microbiological quality of dairy products, especially the total viable count and concentration of Escherichia coli, as they are indicators of the hygienic state of these products.
To ensure the quality and safety of mozzarella cheese, cheese makers should frequently monitor the concentration of lactic acid bacteria (LAB) and spoilage bacteria during fresh cheese production. LAB are the major components of starter cultures used in cheese production, contributing to the taste and texture of fermented products and inhibiting food spoilage bacteria by producing growth-inhibiting substances.
The microbiological survey (MBS) method developed by Roma Tre University (Rome, Italy) allows for faster and less expensive microbiological analyses compared to traditional methods. This method can be used to monitor LAB concentration, total viable count, and E. coli concentration in the production line of mozzarella cheese, as well as during the shelf life of the product. The MBS method is particularly useful for small- to medium-sized dairy factories that do not have internal microbiological laboratories, as it does not require any specialized instrumentation other than MBS vials and a thermostat.
In addition to the MBS method, other studies have explored the incorporation of locally isolated Lactobacillus acidophilus into mozzarella cheese to improve its microbiological safety and quality. Lactobacillus acidophilus has been shown to exhibit antimicrobial activity against undesirable bacteria such as Salmonella typhimurium, Escherichia coli, and Staphylococcus aureus. By incorporating this probiotic strain into mozzarella cheese, it may be possible to extend the shelf life and improve the overall safety and quality of the product.
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The effect of salt on microbial growth in Mozzarella
Dairy products, including mozzarella cheese, have a reduced shelf life because they are an excellent growth medium for a wide range of microorganisms. Therefore, the microbiological quality of dairy products, especially the total viable count and concentration of Escherichia coli, must be monitored as they are indicators of the hygienic state of these products.
To understand how microbial incidence affects mozzarella cheese quality, fresh mozzarella cheese with high (2%) and low (0.5%) salt concentrations was produced and packaged. The high-salt cheese was stored dry, while the low-salt cheese was stored dry or in 0.5% salt brine. The cheeses were then evaluated for surviving microbes by aerobic plate counts, coliform counts, and psychrophilic bacterial counts. It was found that coliforms and psychrophiles were not detected over 9 weeks. However, aerobic plate counts remained at 100 to 300 cfu/g for the first 2 weeks but increased by 1,000 to 10,000 times between 4 and 6 weeks, regardless of salt levels and storage conditions.
Furthermore, portions of the cheeses were inoculated with Escherichia coli or Enterococcus faecalis, which increased by 100 times over 90 days of storage. Interestingly, E. coli added to the cheese brine grew in the brine before attaching to the cheese, while Enterococcus faecalis attached to the cheese within 24 hours and only grew on the cheese. These findings suggest that incident bacteria may attach to cheese curd and survive differently in fresh mozzarella cheese than in brine.
Overall, the study concluded that 2% salt was insufficient to control bacterial growth, and slow-growing, cold- and salt-tolerant bacteria may still survive and spoil fresh mozzarella cheese. Therefore, the effect of salt on microbial growth in mozzarella cheese is complex and dependent on various factors, including storage conditions, type of bacteria, and salt concentration.
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The use of molecular techniques to study the Lactobacillus community in Mozzarella
Dairy products, including mozzarella cheese, have a reduced shelf life because they are an excellent growth medium for a wide range of microorganisms. Therefore, it is important to monitor the microbiological quality of dairy products, especially the total viable count and concentration of Escherichia coli, as they are indicators of the hygienic state of these products.
The natural Lactobacillus community involved in traditional mozzarella cheese production has been investigated using molecular techniques. The bacterial associations of whey, curd before stretching, and mozzarella were analyzed using randomly amplified polymorphic DNA (RAPD) to follow growth kinetics and 16S rDNA sequencing to identify the taxonomical position of isolated strains. Analysis of RAPD fingerprints revealed that the Lactobacillus community was composed of 13 different biotypes, including L. plantarum, L. fermentum, L. helveticus, and L. casei subsp. casei.
The use of molecular techniques, such as polymerase chain reaction (PCR) protocols, has allowed for the development of randomly amplified polymorphic DNA (RAPD) fingerprints from lactic acid bacteria and enterococci isolated from dairy products. These techniques have been instrumental in studying the Lactobacillus community involved in traditional mozzarella cheese processing and have provided valuable insights into the complex bacterial community of mozzarella cheese.
The initial identification of Lactobacillus strains in mozzarella cheese is typically based on conventional morphological and biochemical analysis, while the final confirmation is done using advanced molecular tools such as 16S rRNA gene amplifications. The application of molecular techniques has also helped to study the growth kinetics and taxonomical identification of the Lactobacillus community involved in traditional mozzarella cheese processing, contributing to our understanding of the important role of this microbial group in mozzarella production.
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The impact of different acidification methods on the microbiota of high-moisture Mozzarella
The microbiological quality of dairy products is essential to monitor, as indicated by the total viable count and concentration of Escherichia coli. This is especially true for mozzarella cheese, which has a short shelf life and is susceptible to a wide range of microorganisms.
Mozzarella cheese is a hot-stretched cheese involving a kneading treatment. The microbiota of high-moisture mozzarella cheese produced with different acidification methods has been evaluated using various techniques, including pyrosequencing of the 16S rRNA gene and Next-Generation Sequencing. The acidification method used in production clearly influences the resulting microbiota.
Cheeses produced with the addition of starters were dominated by Streptococcus thermophilus, with some lactic acid bacteria and spoilage microorganisms present at low levels (0.01-1%). The direct addition of citric acid resulted in a more diverse microbiota, including lactic acid bacteria and psychrotrophic γ-proteobacteria. For brands that did not specify their acidification method, the cheese was dominated by thermophilic lactic acid bacteria, with a variety of other subdominant bacteria present.
The type of milk used also impacts the microbiota of high-moisture mozzarella cheese. Cow mozzarella cheese generally exhibits higher bacterial diversity than buffalo mozzarella, with a higher prevalence of psychrophilic taxa. In contrast, buffalo mozzarella has higher levels of Lactobacillus and Streptococcus.
Salt levels during storage also play a role in the growth of bacteria in mozzarella cheese. While 2% salt was insufficient to control bacterial growth, higher salt concentrations in the storage brine can help limit the growth of undesirable bacteria.
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Frequently asked questions
The microorganisms used to make mozzarella cheese include Streptococcus salivarius ssp. thermophilus, Streptococcus thermophilus, Lactobacillus helveticus, and L. delbrueckii subsp. bulgaricus.
Microorganisms are responsible for inducing the fermentation process, which involves the conversion of lactose to lactic acid, acidifying the milk. This process is essential for the unique functional properties of mozzarella cheese, such as meltability, stretchability, and browning.
Different factories may use varying acidification methods, such as direct acidification with citric acid or the use of thermophilic defined or undefined starters, which can result in different microbial diversities in the final product.
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