Air bukan netral. Mineral content (GH general hardness + KH alkalinity) mempengaruhi extraction massively. Kopi yang sama bisa taste berbeda di Bandung vs Jakarta HANYA karena air keran.

Kenapa Penting

Extraction kopi = melarutkan compound dari beans ke air. Air "keras" (high GH) extract lebih banyak. Air "lunak" (low GH) extract kurang. Alkalinity (KH) buffer pH → mempengaruhi perception asam.

Parameter Kunci

GH — General Hardness (Ca + Mg)

Kalsium + magnesium mempengaruhi extraction efficiency.

<25 ppm: air lunak, kopi watery flat
50-100 ppm: sweet spot specialty
>200 ppm: extract aggressive, scale mesin cepat

KH — Karbonat Hardness (HCO3/CO3)

Alkalinity buffer pH saat brew.

<20 ppm: pH turun ekstrem, kopi sour harsh
40-70 ppm: balance ideal
>100 ppm: pH netralkan asam baik → kopi "flat"

TDS — Total Dissolved Solids

Gabungan semua dissolved = sum GH + KH + Na + Cl + lain-lain. Target: 75-150 ppm untuk brewing.

Rekomendasi Spesialty (SCA Water Chart)

Ca: 17-68 ppm (target ±40 ppm)
Mg: 5-18 ppm (target ±10 ppm)
Total hardness (GH): 50-100 ppm
Alkalinity (KH): 40-70 ppm
pH: 6.5-7.5
TDS: 75-250 ppm

Hoffmann Water Recipe

Resep DIY populer dari James Hoffmann (via Barista Hustle):

1L air distilled/RO/aquadest sebagai base
0.1g Epsom salt (MgSO4) → provide Mg
0.067g baking soda (NaHCO3) → provide alkalinity

Hasil: GH ~60, KH ~50. Balanced default.

Scale untuk 4L jug:

4L aquadest
0.4g Epsom salt (≈ 1/8 sendok teh)
0.27g baking soda (≈ 1/16 sendok teh)

Cara Test Air

TDS Meter (HM Digital TDS-3 Rp 85-150k)

Cukup accurate untuk TDS total. Ukur keran Anda — catat baseline.

GH/KH Test Kit (API Rp 180-280k)

Titration drop kit. Satu botol untuk GH, satu untuk KH. Hitung drop sampai warna berubah.

Rekomendasi Air di Indonesia

Aqua (AMDK paling populer)

TDS ~90 ppm. GH/KH: medium. Fine untuk brewing tapi tidak optimal.

Le Minerale

TDS ~200 ppm. GH: tinggi. Extract kuat tapi cafestol + rasa mineral muncul.

RO filtered + mineral pack (optimal)

Beli RO galon (atau home RO) + sachet mineral dari Third Wave Water / Lotus Water. Konsistensi level professional cafe.

Third Wave Water (TWW)

Classic Light Roast profile — Ca/Mg/Na balanced
Espresso profile — lebih rendah alkalinity
Dose: 1 sachet per galon 5L RO = konsisten

Rp 18-25k per sachet — 5L = 20 brew V60. Worth untuk critical tasting.

Dampak ke Brewing

Air keran jakarta (TDS 250+, alkalinity tinggi)

V60 taste flat, sweetness tidak muncul
Espresso over-extract mudah, bitter
Fix: RO + TWW, atau Aqua + tweak dose

Air keran bandung (TDS 80, alkalinity rendah)

V60 lebih bright tapi bisa sour
Espresso under-extract cepat
Fix: Aqua + baking soda sedikit, atau TWW

Air kemasan pegunungan (Ades, Amidis)

Cek label TDS. Beberapa <50 = terlalu lunak untuk brewing spesifik.

Equipment Rekomendasi

HM Digital TDS-3 Meter (Rp 85-150k) — basic TDS awareness
API GH/KH Test Kit (Rp 180-280k) — GH/KH monitoring
Third Wave Water Classic sachet — most accessible mineral pack
DiFluid R2 Extract (Rp 3.9-4.4 juta) — refractometer untuk TDS seduhan (bukan air)

Common Mistakes

Pakai distilled murni (TDS 0) — extract sangat lemah, kopi flat
Pakai air galon tanpa cek TDS — asumsi "clean"
Mineral pack di air PDAM yang sudah TDS 250 — overload
Lupa descale mesin espresso pakai hard water → scale rusak boiler
Simpan air mineral pack brewing >3 hari → mineral precipitate

Sumber

James Hoffmann — "Water for Coffee" video series
Barista Hustle — Water Compass course
Colonna Smith + Hendon — "Water for Coffee" book 2015
SCA Water Quality Handbook