Coffee: Cold Brew — Ratio, pH, and Extended Extraction
Cold brew coffee steeps 12–24 hours in cold water (1:8 concentrate ratio), producing pH 5.3–5.8 — significantly higher than hot-brewed coffee at 4.85–5.10 — and 67% lower perceived acidity.
| Measure | Value | Unit | Notes |
|---|---|---|---|
| Steep time | 12–24 | hours | Refrigerator temp (4°C) tends toward 18–24 hours; room temp (21°C) can be 12–16 hours |
| Brew ratio (concentrate) | 1:8 | Coffee to water by mass; e.g., 100g coffee per 800g water | |
| pH range | 5.3–5.8 | Significantly higher (less acidic) than hot brew at 4.85–5.10 | |
| Serving temperature | 0–4 | °C | Served over ice or chilled |
| Caffeine per 300ml serving | ~200 | mg | Approximate for 1:1 diluted concentrate; varies by bean and grind |
| Concentrate dilution | 1:1 | Typical serving: 1 part concentrate to 1 part water or milk |
Cold brew is defined by temperature: water at 4–21°C instead of 88–96°C. This single variable — extraction temperature — changes the chemistry of what dissolves from coffee grounds, producing a beverage that is measurably different from hot-brewed coffee in acidity, compound profile, and perceived flavor.
Core Parameters
| Parameter | Cold Brew Standard | Notes |
|---|---|---|
| Steep time | 12–24 hours | Longer at refrigerator temp; shorter at room temp |
| Water temperature | 4–21°C | Refrigerator to room temperature |
| Brew ratio (concentrate) | 1:4–1:8 | 1:8 most common; 1:4 for ultra-concentrate |
| pH (concentrate) | 5.3–5.8 | vs. 4.85–5.10 for hot-brewed coffee |
| Serving dilution | 1:1 | Concentrate to water, milk, or plant milk |
| Grind size | 1200–1400 microns | Coarse; similar to French press or coarser |
| Shelf life | 7–14 days | Refrigerated in sealed container |
Cold Extraction Chemistry
Temperature profoundly affects which compounds dissolve from coffee grounds. At cold temperatures:
Acids extract less efficiently. Chlorogenic acids, quinic acid, and citric acid are all less soluble at low temperatures. This is the primary reason cold brew has a measurably higher pH (5.3–5.8) than hot-brewed coffee (4.85–5.10) — it contains genuinely lower concentrations of these acidic compounds, not merely a perception difference.
Caffeine remains highly soluble. Caffeine’s solubility is less temperature-dependent than most acids, meaning cold brew efficiently extracts caffeine despite the low temperature. At the standard 1:8 concentrate ratio, cold brew concentrate can contain 200+ mg caffeine per 100ml before dilution.
Aromatic compounds behave differently. Volatile aromatic compounds, which largely define the bright, floral notes of hot coffee, are less effectively extracted or retained at cold temperatures. Cold brew instead emphasizes lower-volatility sweet, chocolate, and malt notes.
pH Comparison: Hot Brew vs. Cold Brew
| Coffee type | pH range | Perceived acidity |
|---|---|---|
| Hot pour-over | 4.85–5.10 | Bright, sharp |
| Hot espresso | 5.0–5.5 | Concentrated acid |
| Cold brew (concentrate) | 5.3–5.8 | Smooth, low perceived acid |
| Cold brew (diluted 1:1) | 5.5–6.0 | Mild, mellow |
| Iced coffee (hot brew, chilled) | 4.85–5.10 | Full acid profile retained |
Research published on ResearchGate (Mogren et al.) found cold brew coffee had approximately 67% lower perceived acidity than hot-brewed coffee in controlled sensory tests, correlating with its higher pH and lower titratable acid content.
Hot Brew vs. Cold Brew: Compound Comparison
| Compound / Property | Hot brew | Cold brew | Significance |
|---|---|---|---|
| pH | 4.85–5.10 | 5.3–5.8 | Cold brew less acidic |
| Chlorogenic acid | Higher | Lower | Antioxidant; sour contributor |
| Quinic acid | Higher | Lower | Bitterness and sourness |
| Caffeine | Medium | High (concentrate) | Similar after dilution |
| Coffee oils | Depends on filter | High (if unfiltered) | Body and mouthfeel |
| Volatile aromatics | High | Lower | Bright notes reduced |
| Maillard/caramel notes | Standard | Emphasized | Roast character more prominent |
Concentrate Ratios and Dilution
Cold brew is almost always made as a concentrate and diluted before serving. Common ratios:
| Concentrate ratio | Coffee per 1L water | Typical serving dilution |
|---|---|---|
| 1:4 (ultra-concentrate) | 250g | 1:3 (1 part concentrate : 3 parts liquid) |
| 1:6 (strong concentrate) | 167g | 1:2 |
| 1:8 (standard concentrate) | 125g | 1:1 |
| 1:15 (ready-to-drink) | 67g | Serve as-is |
Nitro Cold Brew
Nitro cold brew is standard cold brew infused with nitrogen (N₂) under pressure. Unlike CO₂ carbonation (which creates sharp carbonation), nitrogen produces very fine, persistent bubbles because nitrogen is much less soluble in liquid. The result is a cascading pour effect and a creamy, thick foam head — similar to a stout beer on nitro tap. The mouthfeel is perceived as significantly smoother and creamier than standard cold brew, often without any added milk or sweetener. Nitro cold brew is served without ice to preserve the foam structure.
Room Temperature vs. Refrigerator Brewing
| Factor | Refrigerator (4°C) | Room temp (18–22°C) |
|---|---|---|
| Steep time | 18–24 hours | 12–16 hours |
| Food safety risk | Low | Higher (bacterial growth possible) |
| Flavor | Slightly smoother | Slightly more extracted |
| Acidity | Slightly lower | Slightly higher |
Room temperature brewing extracts more efficiently due to higher temperature, but the warm, moist environment of grounds in water creates conditions for bacterial growth if not handled hygienically. Refrigerator brewing is the recommended approach for both safety and consistency.
Related Pages
Sources
- Mogren L et al. Cold Brew Chemistry. ResearchGate
- SCA Cold Brew Standards
- Toddy Cold Brew System Technical Specifications
Frequently Asked Questions
Is cold brew less caffeinated than hot coffee?
No — cold brew concentrate is often higher in caffeine per ounce than hot-brewed coffee because of the high coffee-to-water ratio (1:8 concentrate vs. 1:15–1:17 for pour-over). After diluting 1:1 for serving, the caffeine content per cup is roughly comparable to hot-brewed coffee, though this varies significantly by bean origin, grind size, and steep time.
Why does cold brew taste less acidic than iced coffee?
Cold brew's higher pH (5.3–5.8 vs. 4.85–5.10 for hot coffee) reflects genuinely lower acid content. At cold temperatures, chlorogenic acids and quinic acid — the primary acidic compounds in coffee — are less soluble and extract at lower concentrations. Iced coffee is simply hot-brewed coffee chilled rapidly; it retains the full acid profile of hot extraction.
Can cold brew be made at room temperature?
Yes. Room temperature cold brew (18–22°C) extracts faster than refrigerator cold brew (4°C) and may be done in 12–16 hours. However, room temperature brewing carries higher food safety risk as it provides ideal conditions for bacterial growth if grounds are not sanitary. Refrigerator brewing is safer and produces a slightly smoother cup.
What is nitro cold brew and how is it made?
Nitro cold brew is cold brew coffee infused with nitrogen gas under pressure, typically dispensed through a stout faucet (like a Guinness tap). Nitrogen creates very fine bubbles — much smaller than CO₂ — that produce a creamy, cascading head and a smooth, almost thick mouthfeel without adding sweetness. It is served without ice to preserve the foam head.