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Imperial Yeast A38 Juice and Imperial Yeast A24 London Fog are the two most popular hazy IPA-specific strains in Imperial’s catalog, and I’ve fermented wort splits with both to understand what distinguishes them in the final beer. Both produce the signature hazy, soft, juicy character that defines the NEIPA style, but with different ester profiles and biotransformation behavior that affect the finished flavor in ways worth understanding before choosing between them.
A38 Juice vs. A24 London Fog: key specifications compared
Imperial Yeast A38 Juice: Hazy IPA and New England IPA strain. Attenuation: 73–77% (moderate, leaves residual body that contributes to hazy IPA mouthfeel). Flocculation: low (produces the characteristic persistent haze of NEIPA through yeast-polyphenol-protein interaction). Alcohol tolerance: up to 10% ABV. Temperature range: 18–22°C (64–72°F). Flavor profile: tropical and citrus-forward, the most prominent ester from A38 is a bright, tropical fruit character (mango, passion fruit, pineapple) with clean orange citrus supporting notes. A38 Juice is Imperial’s flagship NEIPA strain and is one of the most widely used hazy IPA yeasts in American craft brewing. It has exceptional biotransformation activity, when used with tropical and citrus hops (Citra, Galaxy, Mosaic, Ekuanot), the biotransformation reactions during active fermentation convert hop monoterpene alcohols (geraniol, linalool) and transform hop aroma compounds into new aromatic molecules, significantly amplifying the tropical-citrus character beyond what the hop charge alone would produce. The result of A38 + Citra/Galaxy DDH is the archetypical American hazy IPA flavor profile. Imperial Yeast A24 London Fog: English-influenced hazy IPA strain derived from a London ale culture. Attenuation: 71–75% (slightly lower than A38, slightly more residual sweetness). Flocculation: low-medium. Temperature range: 18–22°C (64–72°F). Flavor profile: richer, more stone fruit and peach-forward ester profile compared to A38’s tropical-citrus focus. London Fog produces pronounced stone fruit (peach, apricot, nectarine) esters with a creamy, full mouthfeel that adds thickness to the hazy IPA body. The biotransformation activity is present but somewhat less aggressive than A38, London Fog amplifies peach and stone fruit hop compounds more than tropical-citrus compounds. With Citra and Galaxy, London Fog produces a softer, fruitier, more peach-and-orange character than A38’s bright tropical profile.
Hazy IPA brewing: A38 Juice vs. A24 London Fog in practice
Use A38 Juice when: brewing a bright, tropical-citrus NEIPA where the hop character should lead with maximum punch and the yeast should amplify that tropical direction. A38 with Citra, Galaxy, Mosaic, or Ekuanot produces the most intensely tropical, fruit-forward hazy IPA character achievable with dry yeast. Recipe approach: 70–75% pale malt, 10–15% flaked oats, 10–15% wheat malt; DDH with 3–5 oz/gallon of Citra or Galaxy at terminal gravity; ferment at 19°C for 4 days, add dry hops at terminal, cold crash after 2–3 days contact. A38’s low flocculation and high biotransformation activity make it the standard choice for competition-targeted NEIPAs. Use A24 London Fog when: brewing a softer, creamier, more stone-fruit-forward hazy where a richer, less sharp fruit character is the target. London Fog produces hazy IPAs that taste fuller and creamier than A38 at the same recipe, the stone fruit ester profile softens the hop bitterness perception and adds textural richness. Recipe approach: same grain bill as A38 works well; hop combinations with Sabro, Cashmere, Citra, and Galaxy suit London Fog better than pure tropical-bomb combinations. London Fog also works well in hazy pale ales and hazy session IPAs (3.5–4.5% ABV) where the fuller body from slightly lower attenuation compensates for reduced malt character at lower gravity. Against Verdant IPA and Omega DIPA: The hazy IPA yeast category also includes Lallemand Verdant IPA (based on the Verdant Brewing house strain) and Omega DIPA (OYL-052). Verdant IPA produces aggressive biotransformation and peachy-tropical character similar to London Fog. Omega DIPA targets double IPA body and attenuation. A38 Juice remains the most versatile and widely proven choice across the broadest range of hazy IPA recipes.
Common Questions
What causes the haze in NEIPA and how do I maximize it with these yeasts?
NEIPA haze is not primarily from yeast in suspension, it’s from a protein-polyphenol-yeast cell interaction that creates permanent colloidal haze particles. Understanding this distinction matters for brewing technique. The three contributors to stable haze: (1) High-molecular-weight proteins from raw wheat and flaked oats, these wheat proteins form colloidal particles with hop polyphenols that create stable, light-scattering haze. A grain bill with 20–30% combined wheat and oats provides the protein substrate for good haze. (2) Polyphenols from dry hopping, large hop additions during fermentation (3–5 oz/gallon of finished beer) provide the polyphenol component that complexes with wheat proteins. Dry hopping during active fermentation (biotransformation) vs. post-fermentation both contribute polyphenols but at different stages. (3) Yeast-protein interaction, low-flocculating yeasts like A38 and London Fog contribute suspended yeast cells and cell-wall mannoproteins that stabilize the haze complex. Techniques to maximize haze: use a grain bill with at least 20% wheat malt and 10% flaked oats; dry hop at terminal gravity with 3+ oz/gallon of hops with high polyphenol content; do not fine with gelatin (gelatin strips haze-causing compounds); keep fermentation temperatures at 18–20°C during dry hop contact to maximize biotransformation; package without heavy cold crashing that settles yeast; serve fresh (haze compounds degrade over weeks at serving temperatures). London Fog’s slightly higher flocculation means it produces slightly less yeast-in-suspension than A38, but both produce adequate yeast contribution to haze when combined with proper grain bill and dry hop rate.
