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Skim Milk Agar (AS-1350) | Casein Hydrolysis & Proteolysis Test
$125.00 AUD
AuSaMicS Life Science • Culture Media
Skim Milk Agar
SMA • Differential medium for detection of casein hydrolysis and proteolytic activity
Skim Milk Agar (SMA) is a differential microbiological medium used to detect protease-producing microorganisms through hydrolysis of casein. The medium contains skim milk as both a nutrient source and differential substrate, allowing clear visualization of proteolytic activity as a zone of clearing around colonies.
AS-1350
Differential Medium
✓ Protease Detection
🧫 Casein Hydrolysis Test
🥛 Substrate: Skim milk / casein
🔬 Use: Enzyme screening, QC, teaching
📄 Available: COA + TDS + SDS
🧬 Proteolysis Screening Medium
🥛 Skim Milk Base - nutrient + differential substrate
⭕ Clear Zones - visible protease activity
🧪 Casein Hydrolysis - easy interpretation
🔬 Broad Utility - food, dairy, research
🎓 Teaching Friendly - strong visual readout
Classic Protease Test Medium
Ideal for casein hydrolysis screening workflows
🔬 Product Overview
Skim Milk Agar is formulated for the differential detection of microorganisms capable of hydrolyzing casein, the principal milk protein. Organisms that produce extracellular proteases digest the opaque milk protein matrix, resulting in a clear zone around the colony.
Because skim milk also supplies proteins, lactose, and minerals, the medium supports growth of a wide range of bacteria and fungi, including organisms relevant to dairy microbiology, food quality control, fermentation studies, and enzyme research.
SMA is widely used for screening protease-producing microorganisms, assessing spoilage potential, comparing enzymatic activity, and demonstrating extracellular hydrolysis in educational settings.
⚗️ Principle of the Medium
Skim Milk Agar uses casein in skim milk as the differential substrate for detecting extracellular proteolytic enzymes:
Microbial growth on skim milk-containing agar
↓
Extracellular protease secreted by positive organisms
↓
Hydrolysis of casein around colonies
↓
Clear or translucent halo = positive proteolysis
Opaque medium unchanged = negative reaction
↓
Extracellular protease secreted by positive organisms
↓
Hydrolysis of casein around colonies
↓
Clear or translucent halo = positive proteolysis
Opaque medium unchanged = negative reaction
Readout advantage: the natural opacity of skim milk provides direct visual contrast, so proteolytic activity is easy to observe without additional indicator reagents.
🧫 Applications
🦠 Protease Screening
Detection of casein hydrolysis by bacteria, yeasts, molds, and other protease-producing microorganisms.
🥛 Dairy & Food Microbiology
Useful in dairy and food quality control for spoilage studies and detection of proteolytic contaminants.
🏭 Fermentation & Enzymology
Applicable in enzymology, fermentation research, and microbial strain evaluation for extracellular protease activity.
🎓 Teaching & Demonstration
Excellent for laboratory teaching and demonstrations of extracellular enzyme activity and substrate hydrolysis.
🔬 Research & Quality Control
Suitable for strain comparison, routine QC, and laboratory evaluation of protein-degrading microorganisms.
📊 Key Features
Skim Milk as Substrate
Provides casein for differential detection and nutrients for microbial growth.
Provides casein for differential detection and nutrients for microbial growth.
Clear Proteolysis Readout
Casein degradation is visible as a transparent zone around colonies.
Casein degradation is visible as a transparent zone around colonies.
Broad Growth Support
Supports many bacteria and fungi, including nutritionally demanding organisms.
Supports many bacteria and fungi, including nutritionally demanding organisms.
Versatile Utility
Suitable for food, dairy, industrial, research, and teaching laboratories.
Suitable for food, dairy, industrial, research, and teaching laboratories.
🧪 Composition (per litre)
Final pH: 6.8–7.2 at 25 °C
🧭 Preparation
- Suspend 120–125 g of medium in 1 litre of purified water.
- Heat with gentle agitation until fully dissolved.
- Dispense into Petri dishes, bottles, or tubes as required.
- Sterilize by autoclaving at 121 °C for 15 minutes.
- Allow plates to solidify at room temperature before use.
💡 Interpretation
Positive Proteolysis
A clear or translucent zone surrounding colonies indicates casein hydrolysis and extracellular protease activity.
A clear or translucent zone surrounding colonies indicates casein hydrolysis and extracellular protease activity.
Negative Reaction
The medium remains uniformly opaque with no visible clearing around growth.
The medium remains uniformly opaque with no visible clearing around growth.
📋 Technical Specifications
| Product Name | Skim Milk Agar |
| Short Name | SMA |
| Catalogue Number | AS-1350 |
| Medium Type | Differential agar medium |
| Primary Use | Detection of casein hydrolysis |
| Differential Substrate | Skim milk / casein |
| Incubation Temperature | 30–37 °C |
| Incubation Time | 24–48 h; up to 5 days for slow growers |
| Final pH | 6.8–7.2 at 25 °C |
| HS Code | 3821.00.00 |
🌡️ Incubation Guidance
- ✓ Typical temperature: 30–37 °C
- ✓ Routine reading: 24–48 h
- ✓ Slow-growing organisms: up to 5 days
- ✓ Read zones of clearing against an opaque background
✅ Typical Use Cases
- ✓ Protease-producing isolate screening
- ✓ Dairy spoilage and food microbiology studies
- ✓ Enzymology and fermentation research
- ✓ Educational demonstrations of protein hydrolysis
❄️ Storage
- ✓ Prepared plates/tubes: 2–8 °C
- ✓ Protect from light and dehydration
- ✓ Recommended use within 3 months
- ✓ Inspect for contamination or syneresis before use
📄 Available Documentation
Technical Data Sheet (TDS)
Certificate of Analysis (COA)
Safety Data Sheet (SDS)
🧬 Related Enzyme & Differential Media
Complementary Media & Workflow Products
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AuSaMicS Pty Ltd • 31 Longview CT, Thomastown, VIC 3074, Australia • ABN 56676640467
Website: www.ausamics.com.au • Email: support@ausamics.com • Phone: +61 412 520 598
For laboratory use only. Not for human, animal, or food consumption. Product suitability should be verified by the user under validated cultivation and interpretation conditions.