Mangrove Jacks M42 New World Strong Ale Yeast 10g

M42 is built for high-gravity beers — specifically beers that push past 8% ABV where standard ale yeasts stall or produce harsh fusel alcohols. Its very high alcohol tolerance and clean neutral profile make it the right choice for barleywines, imperial stouts, and double IPAs.

Best Suited To

• Barleywine, Imperial Stout, Double IPA, Triple IPA
• Strong Ale, Wee Heavy
• Any beer targeting above 8% ABV where fermentation stress is a risk

Specs

• Fermentation temp: 16–22°C (lower end for cleaner high-gravity fermentation)
• Attenuation: High
• Flocculation: High
• Alcohol tolerance: 14%+ ABV
• Pitching rate: 2 sachets per 23L for beers above 1.080 OG; add yeast nutrient

When to Choose M42

Choose M42 when your target OG is above 1.080 or target ABV is above 8%. Standard ale yeasts — US-05, M44, M15 — can stall or produce fusel alcohols in strong beers. M42 is designed for this range.

For standard-gravity beers (under 1.060), use a more expressive strain. M42's strength is alcohol tolerance, not flavour character — a neutral yeast is wasted on a session ale.

Practical Notes

Two sachets per 23L is the correct pitch rate for beers above 1.080 OG. Under-pitching at high gravity is the most common cause of fusel alcohol production and stuck fermentation — do not save money here.

Add yeast nutrient to the wort before pitching. High-gravity wort is fermentation-stressful; nutrients help M42 work cleanly through to full attenuation.

Ferment at 16–18°C to minimise fusel production. For very high-gravity beers above 1.100 OG, oxygenate well before pitching.

Keep refrigerated. Once opened, reseal and use within 7 days.

Reviewed by the AHB Brewing Team — June 2026.