Sourdough Starter Health + Schedule Predictor — Diagnose State, Predict Peak Time

Why sourdough scheduling is backward-calculation, not clock-watching

Quick answer: "feed once a day" treats sourdough like commercial yeast, but sourdough is a co-fermentation of wild yeast (Saccharomyces) and lactic-acid bacteria (LAB) whose activity is governed by Stevens-grade kinetics: temperature × feed-ratio × flour-substrate. The starter peaks (when CO2 production crosses gluten-retention capacity) at predictable times, and your job is to match that peak to your bake window — not the other way around.

A starter at 18°C peaks roughly twice as slowly as the same starter at 24°C. The same feed schedule that works in summer (24°C kitchen) will leave you with collapsed, sour starter in winter (18°C kitchen) — or rising-but-not-ready starter for an evening bake. The wizard predicts peak time at YOUR temperature and YOUR feed ratio, then tells you when to feed so peak aligns with your dough-mix time.

Visual diagnosis is the single most reliable input

Quick answer: the visual state of the starter right now tells you where in the curve it is — more reliably than the clock. Peaked + domed = within the bake window. Hooch on top = starving (used all flour, now producing alcohol). Pink/orange streaks = contaminated, discard. The wizard's diagnosis decision-tree maps each visual state to a specific recommended action.

The Q10 temperature coefficient — why your starter is "different in winter"

Quick answer: Q10 ~2 means biological reaction rates roughly double per 10°C rise (or halve per 10°C drop). For sourdough at typical kitchen temperatures (18-28°C), this means a 5°C swing roughly halves or doubles peak time. The wizard applies this coefficient to your specific ambient temperature.

This is why bakers who time their starter by the clock alone struggle when seasons change. A summer routine (feed before bed, peak by morning) breaks in winter when the same feed produces under-active starter at the same morning hour.

Feed ratio sets peak time AND flavor profile

Quick answer: tighter feed ratios (1:1:1) peak fastest with lowest sour flavor. Looser ratios (1:5:5, 1:10:10) take longer but allow more LAB activity → more lactic and acetic acid → more pronounced sour flavor. Pick ratio based on BOTH the timing you need and the flavor you want.

What this model does not predict

The Q10 coefficient is empirical — real-world starters vary based on the specific yeast/LAB strain consortium. A starter cultured in San Francisco hosts Lactobacillus sanfranciscensis which has different kinetics than a starter cultured in Singapore. Use the prediction as a calibration starting point — observe your starter for 3-5 cycles to learn its actual behavior at your conditions.

The wizard does not model: (a) inoculum-quality variation between batches, (b) contamination by wild non-LAB bacteria (Acetobacter producing harsh vinegar), (c) starter age effects (very old starters often have more stable kinetics), (d) altitude effects on CO2 retention. For deep starter troubleshooting, use this wizard's diagnosis as triage and consult Maurizio Leo's The Perfect Loaf for case-specific guidance.

Sources and further reading

Maurizio Leo, The Perfect Loaf: The Craft and Science of Sourdough Breads, Sweets, and More (Penguin Random House, 2022) — comprehensive sourdough biology + scheduling. Chad Robertson, Tartine Bread (Chronicle Books, 2010) — starter maintenance and slap-and-fold technique. Harold McGee, On Food and Cooking 2nd ed. (Scribner, 2004), Ch. 10 — microbiology of fermentation. For temperature-coefficient modeling: D. Pyler, Baking Science and Technology, 4th ed. (Sosland Publishing, 2008), Vol. 1 on dough fermentation kinetics.