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What is spongy coliform?

Spongy coliform is a defect in cheese caused by coliform bacteria such as Escherichia coli and Enterobacter. These bacteria ferment lactose, producing gas and acids that disrupt the cheese structure.

The defect is classified as a type of early blowing, occurring during or shortly after fermentation. It is characterised by small, irregular holes and an unpleasant flavour or odour. Spongy coliform can affect both soft and hard cheeses, making it a concern for a wide range of cheesemakers.

Another type of early blowing can be due to yeast contamination. And the most common type of late blowing is due to Clostridia bacteria. We’ll dive into the differences a bit further down.

What are coliform bacteria?

Coliform bacteria are Gram-negative, rod-shaped microorganisms that can contaminate cheese during production. They are naturally present in soil, water and the intestines of warm-blooded animals. While many coliforms are harmless, their presence in cheese often indicates poor hygiene or contamination during processing.

Coliforms in cheese are generally categorised into two groups:

1. Total coliforms

• These are all coliform bacteria commonly found in the environment.
• Examples include Enterobacter, Klebsiella and non-pathogenic strains of Escherichia coli (E. coli).
• While not all are harmful, their presence in cheese signals lapses in sanitation.

2. Faecal coliforms

• A subset of coliforms originating from the intestines of animals.
• Includes strains like E. coli, often used to detect faecal contamination.
• Some strains, particularly pathogenic ones like E. coli O157:H7, pose serious health risks if present in cheese.

Understanding these bacteria helps cheesemakers address contamination risks and maintain the highest standards of safety and quality.

Causes of spongy coliform

Spongy coliform typically arises from contamination during cheesemaking. Common causes include poor milk quality, insufficient pasteurisation and unsanitary equipment.

1. Poor milk hygiene: Raw milk often contains coliform bacteria, especially if it comes from animals kept in unsanitary conditions. Contaminated milking equipment can worsen the problem. Even small amounts of coliform bacteria in milk can multiply during cheesemaking.
2. Improper pasteurisation: Pasteurisation kills most bacteria, but it must be done correctly. If the milk is not heated to the right temperature, coliforms may survive. These surviving bacteria can thrive during the cheesemaking process.
3. Dirty cheesemaking equipment: Cheesemaking tools and surfaces must be thoroughly cleaned and sanitised. Contaminated equipment can introduce coliforms to the milk or curd. Bacteria on utensils or vats can spread quickly, affecting entire batches of cheese.

How to identify spongy coliform defects

Cheesemakers should look for certain signs to identify spongy coliform. These include:

• Irregular, sponge-like holes in the cheese body.
• Sour and acidic notes
• Faecal or barnyard smells
• Rancid or soapy flavours
• Bitter aftertaste

Testing milk and curds can also help detect coliform bacteria early. Laboratory tests can measure coliform counts to assess milk quality.

Spongy coliform vs yeast contamination vs late blowing

Cheese defects like spongy coliform, early blowing caused by yeast and late blowing are common challenges for cheesemakers. Each defect results from different microbial activity, impacting texture, flavour and overall cheese quality. Understanding the causes, timing, and prevention strategies is crucial to maintaining high production standards.

This guide compares these three defects, highlighting their key differences to help cheesemakers identify and address them effectively.

Swipe across if on a mobile device to see the complete table.

How spongy coliform creates a sponge-like texture

The sponge-like texture in cheese caused by coliform bacteria is primarily the result of gas production during fermentation. This process is driven by the bacteria’s metabolism and their interaction with the cheese’s components. Here’s how it works:

Coliform bacteria metabolism

• Coliform bacteria, such as Escherichia coli or Enterobacter, thrive in nutrient-rich environments like cheese curds.
• These bacteria ferment lactose (milk sugar) and other available carbohydrates.
• The by-products of this fermentation include:
  • Carbon dioxide (CO₂): A gas that forms bubbles within the cheese matrix.
  • Organic acids (e.g., acetic and lactic acids): These can further alter cheese texture and flavour.

Formation of gas pockets

• As CO₂ is produced, it becomes trapped in the dense protein structure of the curd.
• The gas cannot escape easily, leading to the formation of irregular holes or bubbles.
• Unlike the controlled eye formation in Swiss cheese, these gas pockets are uneven and chaotic, resulting in the “spongy” appearance.

Impact on protein structure

• The activity of coliform bacteria can also weaken the protein network in cheese.
• Enzymes secreted by the bacteria may break down casein, the primary milk protein.
• This degradation contributes to a softer, less cohesive texture, making the cheese feel sponge-like.

Environmental factors that exacerbate the issue

Several conditions in the cheesemaking process can amplify the effects of coliform bacteria:

• Temperature: Warm temperatures during early stages encourage rapid bacterial growth and gas production.
• pH Levels: Coliform bacteria thrive in slightly alkaline environments, which can occur if proper acidification doesn’t take place.
• Moisture Content: High moisture levels provide an ideal medium for bacterial activity, increasing the risk of spongy defects.

Chemical reactions in cheese

• Over time, the texture becomes more irregular as the curd stretches and collapses around the gas pockets.
• The acids produced by coliform bacteria can disrupt the delicate balance of calcium and phosphate in cheese.
• This imbalance weakens the curd structure, allowing gas to accumulate more freely.

How unpleasant smells and flavours arise from coliform contamination

When coliform bacteria contaminate cheese, they produce a range of metabolic by-products during fermentation. These compounds are responsible for the unpleasant smells and flavours associated with spongy coliform defects. Here’s a breakdown of how this occurs:

1. Fermentation of lactose

Coliform bacteria ferment lactose, the primary sugar in milk, producing:

• Acetic acid: Contributes sour, vinegary flavours.
• Lactic acid: Adds an overly tangy or sour taste if produced in excess.
• Carbon dioxide (CO₂) and hydrogen gas: While these gases affect texture, they can also carry volatile compounds that intensify odours.

2. Production of volatile compounds

During fermentation, coliform bacteria generate volatile organic compounds (VOCs), which contribute to odour and flavour. Examples include:

• Diacetyl: Often associated with buttery flavours, but in excess can taste rancid or harsh.
• Ammonia: Produced during protein breakdown, giving a sharp, unpleasant smell.
• Sulfur compounds: Result in rotten egg or sulphurous odours.

3. Protein breakdown (proteolysis)

Coliform bacteria release enzymes that degrade milk proteins like casein. This process creates:

• Amines (e.g., putrescine and cadaverine): Responsible for strong, faecal or rotting odours.
• Peptides and amino acids: While these are normal in cheese ripening, their breakdown by coliforms produces bitter or astringent flavours.

4. Fat breakdown (lipolysis)

Coliform bacteria can also break down fats in the cheese, producing:

• Free fatty acids: These contribute to rancid or soapy flavours.
• Ketones: Compounds like methyl ketones can add strong, unpleasant aromas.

5. Environmental influence

• Moisture and Temperature: Warm, humid conditions accelerate bacterial metabolism, intensifying the production of odorous and flavour-altering compounds.
• pH Levels: High pH environments, often resulting from coliform contamination, enhance the activity of enzymes that produce these unpleasant by-products.

Preventing spongy coliform in cheese

Preventing spongy coliform requires strict attention to hygiene and cheesemaking techniques. Cheesemakers should follow these steps to minimise risk:

• Source high-quality milk: Start with milk from trusted suppliers. Farmers should ensure animals are kept in clean environments. Milking equipment must also be regularly cleaned and sanitised.
• Use proper pasteurisation techniques: Milk must be pasteurised at the correct temperature and time. This process eliminates most bacteria, including coliforms. Ultra-pasteurisation can be an option for some cheese types.
• Maintain rigorous sanitation: Cheesemaking equipment, tools, and surfaces must be cleaned and sanitised after each use. Steam or chemical sanitisers can effectively kill bacteria. Regular testing of equipment can identify contamination risks.
• Use reliable starter cultures: Starter cultures play a key role in cheese fermentation. They help outcompete undesirable bacteria like coliforms. Choose cultures that are well-suited to the specific cheese being made.
• Monitor pH levels carefully: Maintaining the correct pH during cheesemaking is critical. Coliform bacteria thrive in higher pH conditions. Acidification of the milk and curd can help prevent their growth.

What to do if spongy coliform occurs

Spongy coliform can be devastating for a cheesemaker, but taking prompt and effective action can mitigate the damage. Here’s how to handle an outbreak of spongy coliform:

1. Identify the affected cheese: Examine your cheese for signs of spongy coliform. Look for small, irregular holes and check for sour or rancid smells.
2. Dispose of the affected cheese: Unfortunately, cheese with spongy coliform cannot be salvaged. Discard the affected batches responsibly to prevent cross-contamination. Consider composting the cheese for an eco-friendly disposal.
3. Trace the contamination source: Investigate where the contamination might have occurred. Test raw and pasteurised milk for coliform bacteria levels. Review cleaning and sanitisation procedures for equipment and facilities. And verify the integrity and effectiveness of the starter cultures used.
4. Clean and sanitise thoroughly: Coliform bacteria can persist in cheesemaking environments, so deep cleaning is essential.
5. Test subsequent batches: Before resuming production, test the next few batches for signs of coliform bacteria. Conduct microbial testing on milk, curds, and early-stage cheese. And monitor for abnormal gas formation or pH changes during fermentation.
6. Implement stricter controls: Take this opportunity to improve practices to reduce the risk of recurrence: use higher-grade milk from trusted sources, adjust pasteurisation parameters to ensure coliforms are eradicated and increase the frequency of hygiene checks and microbial testing.
7. Document the incident: Maintain detailed records of the incident, including test results, affected batches, and corrective actions taken. This documentation can help track patterns, demonstrate compliance, and avoid regulatory issues.

By acting decisively and addressing the root cause, cheesemakers can recover from spongy coliform outbreaks. More importantly, these steps help ensure the problem doesn’t happen again.

Conclusion

Spongy coliform is a challenging defect that can harm both cheese quality and a cheesemaker’s resolve. However, it can be prevented with proper milk handling, sanitation and pasteurisation. By understanding the causes and implementing strict hygiene standards, cheesemakers can produce high-quality, defect-free cheeses.

Cheesemaking is both an art and a science. With knowledge and care, you can ensure that every wheel of cheese meets the highest standards.

Jonah Kincaid

Cheese lover. Scientist. Created a website and a Youtube channel about cheese science because he could not find answers to his questions online. 

cheesescientist.com

The post Spongy Coliform Defect In Cheese (Causes & Prevention) appeared first on Cheese Scientist.

SEE ALSO: The most important pieces of equipment you need to start making your own cheese →

What is late blowing?

Late blowing occurs when gas-producing bacteria multiply in cheese during ageing. This gas causes the cheese to swell, crack or develop an irregular texture. The problem often arises weeks or months after the cheese has been made, hence the term “late blowing.”

Causes of late blowing

Late blowing is primarily caused by Clostridium tyrobutyricum, a spore-forming bacterium found in soil, silage or contaminated milk. These bacteria thrive in anaerobic environments, converting lactate into butyric acid and gas, which creates the characteristic defects.

Key causes of this contamination include:

1. Poor milk hygiene: Contaminated raw milk or milk from cows exposed to silage can introduce Clostridium spores.
2. Improper sanitation: Unclean equipment can harbour bacteria that contribute to late blowing.
3. Inadequate starter culture: Weak or insufficient starter cultures may fail to outcompete unwanted bacteria.
4. High moisture content: Excess moisture in cheese creates an ideal environment for Clostridium growth.
5. Improper salt levels: Salt inhibits bacterial growth. Insufficient salting can allow harmful bacteria to thrive.

Other clostridium species causing late blowing

While Clostridium tyrobutyricum is the most common culprit of late blowing, other Clostridium species can also contaminate cheese and cause similar issues. These include:

1. Clostridium butyricum: Similar to C. tyrobutyricum, this species ferments lactate to produce butyric acid, carbon dioxide and hydrogen gas. It thrives in anaerobic conditions and is often linked to silage-fed cows.
2. Clostridium sporogenes: This bacterium can cause gas formation in cheese but is less common. It produces spores that survive pasteurisation and grow in low-oxygen environments during ageing.
3. Clostridium beijerinckii: Although rare in cheesemaking, it can cause gas-related defects in dairy products. Like other species, it thrives in high-moisture and low-salt conditions.
4. Clostridium perfringens: While primarily a pathogen associated with foodborne illness, C. perfringens spores can occasionally contaminate milk. It’s not a typical cause of late blowing but may produce gas and spoilage in improperly handled cheese.

Is Clostridium botulinum a risk in cheesemaking?

Clostridium botulinum is a serious foodborne pathogen known for producing botulinum toxin, one of the most potent toxins. While it is more commonly associated with improperly canned or preserved foods, it can pose a risk in cheesemaking under specific conditions.

Conditions for Clostridium botulinum growth

For C. botulinum to grow and produce toxins, it requires:

• Anaerobic environments: Like other Clostridium species, C. botulinum thrives in low-oxygen conditions, such as vacuum-sealed or waxed cheese.
• Moisture: High-moisture cheeses are more susceptible because water activity facilitates bacterial growth.
• Low acidity: C. botulinum struggles to grow in acidic environments (pH below 4.6). Most cheeses fall within a safe pH range after proper acidification.
• Inadequate salt levels: Salt inhibits bacterial growth, but insufficient salting can allow C. botulinum to proliferate.

Is C. botulinum a common concern in cheese?

Clostridium botulinum contamination is rare in cheese because:

• Proper cheesemaking lowers pH to levels that inhibit C. botulinum growth.
• Most cheeses are salted adequately, creating an inhospitable environment for the bacteria.
• Pasteurisation kills vegetative cells, though spores can survive and grow later if conditions allow.

Preventive measures for all clostridium species

Since several Clostridium species can lead to late blowing, it’s vital to adopt broad preventive strategies:

1. Improve milk quality: Use clean, high-quality milk from cows not exposed to silage.
2. Sterilise equipment: Proper sanitation helps minimise all forms of bacterial contamination.
3. Add lysozyme: This enzyme effectively inhibits multiple Clostridium species.
4. Monitor salt and moisture: Low salt and high moisture create ideal conditions for anaerobic bacteria.

By taking these precautions, you can reduce the risk of late blowing caused by any Clostridium species.

Can yeast cause late blowing?

While yeast is not the primary cause of late blowing, certain yeast strains can contribute to similar defects in cheese. Yeast contamination during the cheesemaking or ageing process can lead to gas production, resulting in swelling, cracks or other undesirable changes.

How yeast contributes to late blowing:

• Gas production: Some yeast strains, such as Candida or Saccharomyces species, ferment lactose or residual sugars in cheese, producing carbon dioxide and other gases. This can mimic the effects of Clostridium species, particularly in cheeses with high moisture content.
• Altered microbial balance: Yeast growth can disrupt the balance of the starter culture, weakening the ability of beneficial bacteria to dominate. This may indirectly encourage Clostridium or other harmful bacteria to proliferate.

Distinguishing the contaminants that can cause blowing in cheese

Early and late blowing defects can both cause gas formation and irregular holes in cheese, but their causes and characteristics differ. The most common cause of early blowing is coliform contamination which can cause a defect called spongy coliform.

Let’s take a look at the main differences between late blowing, yeast contamination and spongy coliform.

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Cheeses most commonly affected by late blowing

Late blowing is most frequently observed in hard and semi-hard cheeses. These styles undergo prolonged ageing, providing an ideal environment for gas-producing bacteria like Clostridium tyrobutyricum. Here are some examples of cheeses commonly affected by late blowing:

• Gouda: Gouda is one of the cheeses most associated with late blowing. Its moderate moisture content and long aging process create conditions that can allow Clostridium spores to thrive. This is why lysozyme is often added during Gouda production to prevent the defect.
• Edam: Similar to Gouda, Edam has a semi-hard texture and ages in a low-oxygen environment, especially when waxed. If the cheese is not adequately salted or the milk is contaminated, late blowing can occur.
• Parmesan: Despite its lower moisture content, Parmesan is still susceptible to late blowing due to its extended aging period. Any contamination in the milk or during production can result in unwanted gas production months into ageing.
• Emmental and Swiss-style cheeses: Swiss-style cheeses like Emmental are naturally prone to gas formation due to their propionic acid bacteria, which create desirable holes (or “eyes”). However, contamination with Clostridium can lead to excessive or uneven gas formation, causing defects rather than the controlled eye development typical of these cheeses.
• Cheddar: While less common, Cheddar can also experience late blowing if hygiene during production or ageing conditions are inadequate. The defect is more likely in Cheddars aged for extended periods.

How to handle affected cheese

Cheese affected by late blowing is often unsafe to eat due to the presence of harmful bacteria, such as Clostridium tyrobutyricum. While it may not always cause illness, it is best to err on the side of caution and discard the affected cheese.

Instead of throwing the cheese in the trash, consider composting it. Here’s how:

1. Break it into smaller pieces: This speeds up decomposition.
2. Mix with other compostable materials: Combine with brown materials like leaves or cardboard to balance the nitrogen content.
3. Monitor your compost pile: Avoid adding too much cheese to prevent an unpleasant smell or attracting pests.

By composting, you can reduce waste while giving back to the environment.

Learning from late blowing

Late blowing is frustrating, but it’s also a valuable learning opportunity for home cheesemakers. By carefully reviewing your process, you can identify what went wrong and make adjustments for future success. Here’s how you can turn a setback into a lesson:

1. Keep detailed records

Maintain a cheesemaking journal to document each step of the process, including:

• Milk source and type (e.g., raw, pasteurised).
• Cleaning and sanitation methods.
• Starter culture used and its quantity.
• Temperatures, pH levels, and pressing conditions.
• Salting method and amount.

Comparing records from successful and unsuccessful batches can help pinpoint potential causes.

2. Examine your milk source

Raw milk is more likely to contain Clostridium spores, especially if cows are fed silage. If you used raw milk, consider switching to pasteurised milk or ensuring stricter hygiene practices at the source.

3. Assess your sanitation

Late blowing often stems from contamination. Evaluate whether your cleaning methods were thorough enough. Sterilising all equipment and working in a clean environment can significantly reduce bacterial contamination.

4. Evaluate your starter culture

Weak or insufficient starter cultures might allow harmful bacteria to outcompete the beneficial ones. Next time, consider using a stronger culture or adjusting the quantity.

5. Analyse your ageing conditions

Improper humidity or temperature levels can contribute to late blowing. Double-check your ageing setup to ensure it aligns with the cheese type’s requirements.

6. Experiment with preventive additives

If you frequently make cheeses prone to late blowing, consider adding lysozyme or increasing salt levels to inhibit Clostridium spores.

Conclusion

Late blowing doesn’t have to be the end of your cheesemaking journey. By analysing your process and making informed changes, you’ll become a more skilled cheesemaker—and your next batch will be even better.

Mistakes are part of the learning curve, and every issue resolved is a step toward mastery.

Jonah Kincaid

Cheese lover. Scientist. Created a website and a Youtube channel about cheese science because he could not find answers to his questions online. 

cheesescientist.com

The post Understanding Late Blowing In Home Cheesemaking appeared first on Cheese Scientist.