Patrick Oconnell
Measuring the pH of cheese is an essential step in the cheese-making process. The pH of cheese can have a dramatic effect on how well it melts and stretches. It is also important for determining the right time for cutting the curd and controlling the growth of bacteria. The pH of cheese is a crucial factor in determining the growth and survival of pathogens. Cheese with a pH below 5.2 is considered acidic, and this favours the growth of lactic acid bacteria, which are used to make hard, acidic cheeses like cheddar. The pH of cheddar cheese is typically around 5.3.
| Characteristics | Values |
|---|---|
| pH level | Cheddar cheese has a pH level of around 5.3 at the end of the cheddaring process when salt is added. |
| Effect on melt | Lower pH levels result in cheese that melts better. |
| Bacteria growth | A pH level below 5.2 is considered acidic and favors the growth of lactic acid bacteria, which are necessary for the creation of hard, acidic cheeses like cheddar. |
| Bacteria type | Lactic acid bacteria are used in the creation of most cheeses, including cheddar. |
| Bacteria impact | Bacteria consume lactose, a sugar present in milk, and produce lactic acid, which lowers the pH level. |
| Bacteria control | The amount of bacteria can be controlled by adjusting the amount of salt and whey present during the cheddaring process. |
| Optimal temperature | During the cheese-making process, the optimal temperature is between 5.1 and 5.9. |
| Protein interactions | Lowering the pH of cheddar cheese affects protein interactions, which in turn impacts cheese functionality. |
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What You'll Learn
The pH of cheddar cheese is around 5.3
The pH of cheese is a measure of its acidity, which is very important in cheese-making. The pH level is determined by the number of free protons (H+ atoms) floating around in the cheese. The more protons there are, the more acidic the cheese is. In other words, a lower pH indicates higher acidity, and a higher pH indicates lower acidity.
Cheddar cheese is considered a hard, acidic cheese, with a pH of around 5.3. This is lower than the pH of milk, which usually starts around 6.7. During the cheese-making process, bacteria are added to the milk, which consume lactose (a sugar present in milk) and produce lactic acid, lowering the pH. The optimal temperature for this process is between 5.1 and 5.9.
The pH of cheddar cheese can be controlled by adjusting factors such as the amount of initial starter culture, stir time, scald temperature, curd size, pressing time, and salt ratio. For example, adding salt earlier in the process can help increase the pH of cheddar cheese. Additionally, the more whey the curds hold, the more lactose is available for bacteria to produce acid, resulting in a lower pH. Therefore, removing whey by washing the curd can also help increase the pH.
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Measuring pH is crucial in the cheese-making process
The pH level also impacts the melting and stretching characteristics of cheese. A lower pH, indicating higher acidity, is associated with better melting properties. Additionally, the pH influences the rate and extent of acid development, which in turn affects the flavour, microbiological content, and structure of the cheese. Therefore, measuring pH during the cheese-making process is vital for quality control and ensuring consistent fermentation. It helps cheesemakers track the progress of their cheese and refine their production methods to consistently create the desired end product.
Measuring pH is essential for determining the optimal time for cutting the curd and controlling the growth of bacteria. The process of cheesemaking involves acidifying the milk by adding a starter culture of bacteria, which lowers the pH by producing lactic acid. The pH of the initial milk is important as it indicates the quality of the milk, with a high pH potentially signalling mastitis. During the cheesemaking process, the pH continues to change, and measuring these changes is crucial for controlling the rate and extent of acid development and moisture loss.
To measure pH, cheesemakers can use a pH meter, such as the Portable Cheese pH Meter - HI99165, which is specifically designed for cheese analysis and offers automatic calibration and temperature compensation. While some home cheesemaking books may not reference pH levels to avoid complexity, measuring pH provides valuable insights into the cheesemaking process and helps ensure the safety and consistency of the final product.
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pH affects the growth of bacteria
The pH level is a crucial factor in determining the growth and survival of pathogens in cheese. The pH scale is a 14-point scale that measures the acidity of a substance, with lower pH values indicating higher acidity. In the context of cheese, pH levels can vary depending on the type of cheese and the cheese-making process. For example, blue cheese initially has a very low pH due to the high acidity of the blue mold, but its pH increases as the mold metabolizes.
The pH level significantly impacts the growth of bacteria in cheese. Cheese with a pH below 5.2 is considered acidic, promoting the growth of lactic acid-producing bacteria. These bacteria further lower the pH, creating an environment that inhibits the growth of other bacteria. This process results in the production of hard, acidic cheeses like cheddar and Parmesan. On the other hand, cheese with a pH above 6.5 is considered basic, favoring the growth of bacteria such as Pseudomonas and Enterobacteriaceae. These bacteria produce ammonia, which raises the pH and contributes to the creation of softer, more pungent cheeses like Brie or Camembert.
The pH level also plays a critical role in food preservation and microorganism survival in the stomach. For instance, Salmonella spp. has an optimum growth pH range of 7.0–7.5, but its minimum growth pH is around 4.2. Most bacteria, including Escherichia coli, are neutrophiles, thriving in near-neutral pH environments. However, pathogenic strains of E. coli and other intestinal pathogens exhibit higher resistance to stomach acid.
Additionally, the pH level affects the structure of macromolecules. At high pH levels, hydrogen bonds between DNA strands can break, and lipids can be hydrolyzed by extremely basic conditions. The proton motive force responsible for ATP production in cellular respiration is influenced by the concentration gradient of H+ ions across the plasma membrane. Changes in pH can disrupt this gradient, impairing energy production. Proteins are particularly sensitive to pH modifications, which can alter their ionization and disrupt hydrogen bonding, leading to changes in molecule folding and potential denaturation.
Furthermore, the interaction between microbes and their environment is influenced by their metabolic processes, which can modify the pH. This, in turn, affects the growth and interactions of different bacterial species. Microbes can change their environment by consuming resources and producing metabolites, impacting the growth of both themselves and other microbes. These pH changes can create feedback loops that facilitate or hinder bacterial growth and, in extreme cases, lead to the extinction of bacterial populations.
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pH impacts the texture of cheese
The pH level of cheese is a crucial factor in determining its texture, flavour, and safety. The pH of cheese is influenced by various factors throughout the cheesemaking and ageing processes. Measuring the pH of cheese is an essential step in the cheese-making process, as it helps determine the right time for cutting the curd and controls the growth of bacteria.
Cheese with a pH below 5.2 is considered acidic, and this acidity favours the growth of lactic acid-producing bacteria. These bacteria further lower the pH level, creating an environment hostile to other bacteria. This leads to the production of hard, acidic cheeses like cheddar and Parmesan, which have a drier and more crumbly texture. The lower pH results in increased whey expulsion and lower moisture content in the cheese.
On the other hand, cheese with a pH above 6.5 is considered basic, and this pH level favours the growth of bacterial strains such as Pseudomonas and Enterobacteriaceae. These bacteria produce ammonia, which raises the pH level of the cheese, resulting in a softer, more pungent cheese like Brie or Camembert. Higher pH levels contribute to softer and moister cheeses due to reduced whey expulsion.
The interaction between pH and enzymes during the cheesemaking process is crucial for curd formation and moisture retention, ultimately shaping the final texture of the cheese. Enzymes like rennet break down proteins in milk and facilitate curd formation. The pH level directly impacts the activity of these enzymes and cultures, influencing the firmness, elasticity, and structure of the curd. When the pH of the milk is too low, it accelerates the rennet coagulation process, leading to a firm and rubbery texture in the final product. Conversely, if the pH is too high, it hinders coagulation, resulting in a soft and slimy texture or even preventing coagulation altogether.
Additionally, the breakdown of proteins (proteolysis) in cheese is another critical factor influencing texture development. As the pH changes during the ageing process, the enzymes responsible for protein breakdown become more or less active, leading to variations in protein breakdown. This breakdown of proteins impacts the texture by influencing the size and distribution of protein aggregates, contributing to the cheese's overall structure.
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pH changes while cheese is being made and ripened
The pH level of cheese is a crucial factor in determining the growth and survival of pathogens. It is a measure of acidity, which is very important in cheese-making. The pH level can have a dramatic effect on how well a cheese will melt, and it also serves as a safety measure—as more acid is developed (i.e. lower pH), pathogens don't grow as quickly. Cheese with a pH below 5.2 is considered acidic, and this environment is hostile to most bacteria but favors the growth of lactic acid bacteria. These bacteria produce more lactic acid, which lowers the pH level even further. This leads to the production of hard, acidic cheeses like cheddar and Parmesan.
On the other hand, cheese with a pH above 6.5 is considered basic, and this environment favors the growth of other bacterial strains, such as Pseudomonas and Enterobacteriaceae. These bacteria produce ammonia, which raises the pH level of the cheese, creating a softer, more pungent cheese like Brie or Camembert. Measuring the pH of cheese is an essential step in the cheese-making process, as it helps determine the right time for cutting the curd and controlling the growth of bacteria.
The process of making cheese involves several steps, and the pH level changes throughout. It starts with milk, which usually has a pH of around 6.7. The first step in making cheese is to acidify the milk by adding a starter culture of bacteria, which lowers the pH. The bacteria consume lactose, the sugar present in milk, and produce lactic acid, which further lowers the pH. During the cheese-making process, the optimal temperature is between 5.1 and 5.9. Once the pH has been lowered, an enzyme called rennet is added to the milk, causing it to coagulate and form a curd. The curd is then cut into small pieces and heated.
The pH of cheese can continue to change during the ripening process. For example, Blue cheese starts with a very low pH (~4.6) and high acidity, but then the growth of blue mold increases the pH (~6.5) and lowers the acidity. The use of a freeze-dried Tibetan kefir co-culture as a starter for the production of Camembert-type cheese has also been shown to affect the pH during ripening, with an initial decrease in pH followed by an increase in alkalinity in the later stages of ripening.
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Frequently asked questions
Cheddar cheese typically has a pH of 5.3 at the end of the cheddaring process when salt is added. The pH of cheddar can be as low as 4.7, but this is usually achieved through acidulant injections.
The pH of cheddar cheese is important because it determines the growth and survival of pathogens. Cheddar cheese with a pH below 4.5 is considered relatively safe from pathogen growth. The pH also affects the texture of the cheese, with lower pH resulting in a harder, more crumbly cheese.
The pH of cheddar cheese can be controlled by adjusting factors such as the amount of starter culture, stir time, scald temperature, curd size, pressing time, and salt ratio. For example, increasing the stir time releases more whey, which provides more food for the bacteria to produce acid, resulting in a lower pH.
