blue mould: meaning, definition, pronunciation and examples
C1Neutral to technical; common in everyday domestic contexts, gardening, and mycology.
Quick answer
What does “blue mould” mean?
A common type of fungus that appears as a bluish-green, fuzzy growth on decaying organic matter, especially food.
Audio
Pronunciation
Definition
Meaning and Definition
A common type of fungus that appears as a bluish-green, fuzzy growth on decaying organic matter, especially food.
1. Specifically refers to Penicillium fungi, some species of which are used in cheese production or antibiotic manufacture. 2. A symptom of spoilage, particularly on bread, fruit, or damp surfaces.
Dialectal Variation
British vs American Usage
Differences
British English predominantly uses 'blue mould' (spelt 'mould'). American English uses 'blue mold' (spelt 'mold'). The organism and concept are identical.
Connotations
Identical in both varieties: overwhelmingly negative, associated with decay, spoilage, and uncleanliness, except in specialised contexts (e.g., cheese-making).
Frequency
Equally common in both varieties within relevant contexts (food, damp environments).
Grammar
How to Use “blue mould” in a Sentence
[Subject: food/surface] + has/gets/develops + blue mouldBlue mould + grows on + [Object]To keep/stop + [Object] + from blue mouldVocabulary
Collocations
Examples
Examples of “blue mould” in a Sentence
verb
British English
- The forgotten tomatoes in the back of the fridge had begun to blue-mould.
American English
- The damp drywall started to blue-mold in the corner.
adjective
British English
- He discovered a blue-moulded crust at the edge of the cheese.
American English
- The blue-molded berries were quickly discarded.
Usage
Meaning in Context
Business
Rare, except in food retail/import (e.g., 'The shipment was rejected due to blue mould contamination.')
Academic
Used in biology, mycology, and food science contexts (e.g., 'Penicillium roqueforti is a blue mould used in cheesemaking.')
Everyday
Very common in domestic settings (e.g., 'I had to throw the strawberries out—they had blue mould on them.')
Technical
Specific in mycology and agriculture (e.g., 'Blue mould of tobacco is caused by Peronospora tabacina.')
Watch out
Common Mistakes When Using “blue mould”
- Spelling: Using 'mold' in a UK context or 'mould' in a US context.
- Countability: Incorrectly using 'a blue mould' for a single instance (usually uncountable: 'some blue mould').
- Confusing with 'blue-green algae', which is not a fungus.
FAQ
Frequently Asked Questions
It depends. The visible mould is a sign of spoilage, and its roots can penetrate deep into food. For soft foods, it's safest to discard the entire item. Some specific, controlled blue moulds are safely used in cheese production (e.g., Roquefort, Stilton).
Yes, for some individuals. While small amounts are common, large infestations (like in very damp buildings) can cause respiratory irritation, allergic reactions, or worsen asthma. It's best to remove mould carefully, wearing a mask if cleaning a large area.
They are different species of fungi with different colours. Black mould often refers to Stachybotrys chartarum, which is typically darker and associated with prolonged water damage. Blue mould is usually Penicillium species, more common on food but can also grow on damp walls. Both indicate unwanted moisture.
The colour can range from bluish-green to greenish-blue depending on the species, age, and surface. The name 'blue mould' is a traditional descriptor for the Penicillium genus, where many species have a distinctive blue or blue-green spore colour under certain conditions.
A common type of fungus that appears as a bluish-green, fuzzy growth on decaying organic matter, especially food.
Blue mould is usually neutral to technical; common in everyday domestic contexts, gardening, and mycology. in register.
Blue mould: in British English it is pronounced /ˌbluː ˈməʊld/, and in American English it is pronounced /ˌbluː ˈmoʊld/. Tap the audio buttons above to hear it.
Phrases
Idioms & Phrases
- “(To be) as welcome as blue mould on bread (intensely unwelcome)”
Learning
Memory Aids
Mnemonic
Think of 'Blue MOULD' as 'MOist, OLD, and Unwanted Leftover Decay'—it's the blue fuzz on old, moist food left too long.
Conceptual Metaphor
DECAY IS INVASION (e.g., 'The blue mould took over the loaf.'), UNCLEANLINESS IS A SURFACE COVERING (e.g., 'A blanket of blue mould.')
Practice
Quiz
In which context might 'blue mould' have a positive connotation?