Cold Brew Steeping Time and Flavor Concentration Analysis
Contents:
1. Experiment Setup
2. Analysis & Observations
3. Flavor Compound Release Insights
4. Practical Suggestions & Applications
Cold brew coffee is a method that uses low temperature and long extraction time to gently release the coffee's fruity aroma, sweetness, and smooth texture. To better understand how steeping time affects flavor and concentration, we conducted a three-phase cold brew experiment using Justin Coffee’s Estate Blend — Premium Immersion Coffee: Rich Autumn.
This blend is designed to showcase sweet fruity aromas, berry and peach notes, a balanced sweet-tart profile, and syrupy texture. Each 10g portion of ground coffee is sealed in a ready-to-immerse filter bag, making it ideal for a controlled-variable cold brew experiment to observe how steeping time impacts flavor and TDS.
Experiment Setup
● Coffee Used: Estate Blend – Premium Immersion Coffee: Rich Autumn (10g ground coffee per pack)
● Water Quality & Ratio: 200ml of the same filtered cold water per bag; fixed coffee-to-water ratio of 1:20
● Preparation: Each bag shaken 30 times after submerging to promote initial extraction
● Steeping Method: Immediately refrigerated after prep
● Steeping Durations: 8 hours, 16 hours, and 24 hours
● Sampling: Each bag shaken again 30 times before removal. Liquid filtered with paper filter for TDS measurement (tasting samples used unfiltered coffee)
Analysis & Observations
Although the TDS across the three groups varied only slightly (from 0.90% to 0.94%), the actual flavor differences were striking, suggesting that the key to cold brew flavor isn’t just how much is extracted — but what is extracted.
● 8-Hour Sample: Reached basic concentration, but fruity aroma had not yet emerged. The taste was thin and slightly bitter — likely due to early extraction of hydrophilic acids and caffeine, while sweetness and aroma compounds remained unreleased.
● 16-Hour Sample: Bright fruit aroma and acidity with well-balanced mouthfeel. Likely represents the optimal mid-phase, where aromatic esters and fructose are released in abundance.
● 24-Hour Sample: Most complete and balanced flavor. Clear notes of apricot sweetness and tea-like aftertaste emerged, with a syrupy mouthfeel — likely due to the full release of fat-soluble aromatic compounds and complex sugars.
Flavor Compound Release Insights
Although the TDS difference between the 8-hour and 24-hour samples was only 0.04%, the composition of extracted compounds was clearly different. This confirms that flavor is influenced not just by concentration, but also by the timing and rhythm of flavor compound extraction.
Practical Suggestions & Applications
● To highlight the bright fruity notes and sweetness of Rich Autumn: 16 hours of cold refrigeration is recommended.
● For those who prefer a fuller and rounder body: Steeping up to 24 hours is suitable, but beware of excessive astringency.
● To increase flavor concentration, try a stronger brew ratio (e.g., 10g of coffee to 150ml of water).
This experiment using “Premium Immersion Coffee – Rich Autumn” with three cold steeping durations confirms that even a minor TDS difference (just 0.04%) can lead to significant flavor variation. The true essence of cold brew lies in the gradual release of flavor compounds over time, not merely in chasing higher concentration.
From a practical standpoint, the 16–24 hour cold brew window best expresses the flavor profile this blend was designed for. This reminds us that steeping time should be treated as a precise and adjustable flavor lever — one that can bring out the best in every cup, when used skillfully.
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