WHAT CAN CAUSE EARLY BLOW IN PARMESAN CHEESE?
Several microbial groups are known to contribute to early blowing in
Parmesan cheese. These organisms ferment residual substrates in the curd and
release gases—primarily carbon dioxide (CO₂) and hydrogen (H₂)—that
disrupt the compact structure required for this cheese style.
1. Clostridium tyrobutyricum
Although more commonly associated with late blowing, Clostridium
tyrobutyricum can contribute to early defects when conditions allow early
germination of spores.
Mechanism:
* Anaerobic, spore-forming bacterium,
* Ferments lactate into butyric acid,
CO₂, and H₂,
* Gas accumulation causes internal openings and
structural weakness.
Contributing factors:
* High spore load in raw milk (often from silage
contamination),
* Inadequate curd acidification,
* High moisture pockets within the cheese,
* Insufficient salt penetration.
Impact on Parmesan:
* Unwanted openness,
* Cracks and swelling,
* Butyric, rancid, or barny off-flavours.
2. Adventitious Propionibacterium spp.
While Propionibacterium species are intentionally used in
Swiss-type cheeses, their uncontrolled presence in Parmesan is
undesirable.
Mechanism:
* Ferments lactic acid to propionic
acid, acetic acid, and CO₂,
* Even low populations can cause gas formation in
dense cheeses.
Sources:
* Raw milk contamination,
* Poor sanitation of vats and pipelines,
* Cross-contamination from other cheese processes.
Impact on Parmesan:
* Early eye formation or pinholes,
* Disruption of the closed texture typical of
Parmesan,
* Slightly sweet or nutty off-flavours
inappropriate for the style.
3. Heterofermentative Lactobacilli (e.g. Lactobacillus fermentum)
Heterofermentative lactic acid bacteria are a common cause of early
blowing, especially during the first weeks of ripening.
Mechanism:
* Ferment sugars and citrate to produce:
- Lactic acid,
- CO₂,
- Ethanol or acetic acid.
* Gas is produced early, before the cheese body
has fully stabilised.
Risk factors:
* High residual lactose,
* Slow or uneven acid development,
* High moisture curd,
* Elevated ripening temperatures.
Impact on Parmesan:
* Fine, irregular openness,
* Mechanical weakness,
* Acidic or alcoholic flavour notes.
4. Escherichia coli and Coliform Bacteria
Coliforms, including E. coli, are classic indicators of poor
hygiene and are strongly linked to early blowing.
Mechanism:
* Rapid fermentation of lactose,
* Production of CO₂ and hydrogen (H₂),
* Hydrogen gas forms very small, fine openness
or pinholes rather than large eyes.
Sources:
* Contaminated raw milk,
* Inadequate pasteurisation,
* Post-pasteurisation contamination,
* Poor sanitation of equipment or moulds.
Impact on Parmesan:
* Early swelling,
* Fine cracks or sponge-like texture,
* Unclean, gassy, or bitter flavours,
* Serious food safety and quality concerns.
Key Contributing Factors to Early Blow
Early blowing rarely results from a single cause. It is usually linked
to a combination of:
* High microbial load in milk,
* Inadequate milk hygiene and sanitation,
* Slow or insufficient acidification,
* High curd moisture,
* Uneven salt uptake,
* Poor temperature control during early ripening.
Prevention Strategies
To minimise the risk of early blow in Parmesan cheese:
* Use high-quality, low-spore milk,
* Control silage quality at farm level,
* Ensure rapid and consistent acid development,
* Optimise curd cooking and whey drainage,
* Apply correct salting and brining protocols,
* Maintain strict hygiene and sanitation,
* Use well-selected starter cultures to outcompete
spoilage organisms.
Conclusion
Early blowing in Parmesan cheese is primarily caused by gas-producing
bacteria such as Clostridium tyrobutyricum, adventitious Propionibacterium
spp., heterofermentative lactobacilli like Lb. fermentum, and coliforms
including E. coli. Their metabolic activity leads to premature gas
formation, resulting in openness, cracks, and quality defects that compromise
both texture and flavour. Effective prevention depends on milk quality,
microbial control, and precise process management, all of which are
essential for producing high-quality, long-ripened Parmesan cheese.
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