Cold water lime bath pasteurization is a simple, effective way to prepare substrates for mushroom cultivation. This method uses hydrated lime (calcium hydroxide) to create a high-pH environment that discourages contaminants, making it ideal for substrates like straw, sugarcane mulch, and wood shavings and wood pellets.

What is Cold Water Lime Bath Pasteurization?

Unlike traditional pasteurization, which requires heat, this method involves soaking the substrate in cold water with a small amount of hydrated lime. This type of lime (also known as slaked lime) quickly raises the pH of the water, helping to neutralize harmful organisms without harming mushroom growth.

Why Use Hydrated Lime?

Hydrated lime (calcium hydroxide) is effective because it significantly raises the pH, helping to reduce the risk of contamination. It is important to use only hydrated lime and not garden lime or quicklime, which are chemically different and may damage the substrate.

Step-by-Step Guide for Cold Water Lime Bath Pasteurization

Follow these precise steps and measurements for effective pasteurization.

Materials Needed:

• Hydrated Lime (Calcium Hydroxide): Ensure it is food-grade or agricultural-grade.
• Water: Enough to fully submerge your substrate.
• Large Container: A plastic bin, barrel, or bucket large enough to hold the lime bath and substrate.
• Substrate: Suitable materials include straw, sugarcane mulch, or wood shavings.

Measurements

Using 0.2% hydrated lime relative to the amount of water ensures the ideal pH for effective pasteurization. Use the following measurements as a guide:

Amount of Water	Hydrated Lime (grams)	Hydrated Lime (pounds)
10 liters	20 grams	0.044 lbs
20 liters	40 grams	0.088 lbs
50 liters	100 grams	0.22 lbs
100 liters	200 grams	0.44 lbs

Instructions

1. Prepare the Lime Bath

   Fill your container with the required amount of water. Add the hydrated lime to the water gradually, stirring to dissolve it completely. Let the solution rest for about 10 minutes.

2. Add the Substrate

   Submerge your substrate in the lime bath, ensuring it is fully covered. Use a weight or clean object to keep it submerged.

3. Soak the Substrate

   Allow the substrate to soak for 12-24 hours to ensure thorough pasteurization. This soaking period allows the lime to act on contaminants, reducing risks while preserving helpful microbes.

4. Drain and Prepare for Inoculation

   After soaking, remove the substrate and drain thoroughly. Avoid rinsing to retain the alkaline environment. Allow the substrate to reach field capacity, where it feels moist but not dripping. It is now ready for inoculation.

Additional Tips for Success

• pH Monitoring: Aim for a pH around 12 in the lime solution for optimal effectiveness.
• Hydrated Lime Safety: Hydrated lime is caustic, so wear gloves and eye protection to avoid irritation.
• Best Substrates for This Method: Cold lime pasteurization works well with fibrous substrates like straw and sugarcane mulch but is less effective for grain-based substrates.

Frequently Asked Questions

1. Can I use other types of lime?
No, only hydrated lime (calcium hydroxide) is suitable. Garden lime (calcium carbonate) and quicklime (calcium oxide) do not provide the same results and can harm the substrate.

2. Can the lime water be reused?
Reusing the lime water is not recommended, as the pH level may drop after soaking, reducing its effectiveness.

3. When should I use the pasteurized substrate?
Use the substrate within one to two days after pasteurization to minimize the risk of recontamination.