The art of maintaining a sourdough starter for French country bread is a delicate balance of science and intuition. Among the many factors that influence the character of a mature starter, the ratio of whole wheat flour and the refrigeration cycle stand out as critical elements in acidity management. Bakers who master these variables unlock the secret to achieving that quintessential tangy depth while preserving the starter's vitality over extended periods.

Whole wheat flour introduces a complex ecosystem of microorganisms and nutrients that dramatically alter a starter's fermentation profile. Unlike refined white flour, the bran and germ in whole wheat contain higher levels of minerals, enzymes, and wild yeasts. This richer environment accelerates acid production, particularly acetic acid which contributes to sharper, more pronounced sour notes. However, this intensity comes at a cost - the very components that boost flavor also increase metabolic stress on the culture.

The relationship between whole wheat percentage and acidity follows a nonlinear pattern. Starters maintained with 20-30% whole wheat tend to develop a harmonious balance between lactic and acetic acids, creating the rounded sourness characteristic of good pain de campagne. When the proportion exceeds 50%, acetic acid dominance can lead to overly aggressive sourness that overwhelms the bread's other flavor dimensions. The flour's ash content plays an underappreciated role here - higher mineral content in French-style whole wheat flours buffers acidity differently than their North American counterparts.

Refrigeration transforms the acidity management equation by slowing microbial activity without stopping it completely. A starter kept at 4°C (39°F) will continue developing acids at about 25% the rate of room temperature fermentation, but with a crucial difference in metabolic pathways. The cold environment favors lactobacilli over yeasts, leading to increased lactic acid production relative to acetic acid. This explains why refrigerated starters often yield bread with milder, yogurt-like sourness compared to their tangier room-temperature counterparts.

The duration between feedings during refrigeration significantly impacts acid accumulation. Seven-day refrigeration cycles allow for substantial acid development that requires careful correction during the refreshment phase. Bakers working with this schedule often employ a two-step feeding process - first discarding and feeding with equal parts starter, water and white flour to reactivate the culture, followed by a second feeding incorporating whole wheat after 12 hours. This technique prevents acid shock while still benefiting from whole wheat's flavor contributions.

Shorter refrigeration cycles of 3-4 days create less extreme acidity swings but demand more frequent attention. The sweet spot for many artisanal bakers lies in 5-day cycles, which balance manageable acidity with practical maintenance requirements. During winter months when kitchen temperatures drop, these shorter cycles help maintain starter activity without requiring excessive whole wheat percentages to stimulate fermentation.

Seasonal adjustments prove essential for consistent results. The same starter formula behaves differently in July than in January, not just because of ambient temperature but also due to shifts in flour composition and microbial populations. Smart bakers gradually increase whole wheat proportions during colder months, sometimes by as much as 15%, to compensate for slower fermentation. Conversely, summer maintenance often benefits from reduced whole wheat and more frequent refrigeration cycles to prevent over-acidification.

The water content in the starter interacts profoundly with both whole wheat percentage and refrigeration. Stiffer starters (lower hydration) tend to produce more acetic acid, while wetter starters favor lactic acid production. When working with higher whole wheat percentages, many bakers opt for slightly increased hydration (around 75-80%) to moderate the sharper acetic notes. This adjustment becomes particularly important for refrigerated starters, where the already heightened lactic production from cold temperatures can benefit from this additional balancing effect.

Long-term starter health requires strategic acid management. While acidity preserves the culture by inhibiting pathogens, excessive accumulation weakens yeast populations and enzymatic activity. Periodic "rehabilitation" feedings with white flour help reset the pH balance without losing the flavor benefits built up through whole wheat feedings. Some veteran bakers swear by monthly room-temperature white flour feedings followed by 24-hour fermentation before returning to the regular refrigeration cycle.

The sensory evaluation of a well-maintained starter tells more than pH measurements ever could. A healthy whole wheat-influenced starter fresh from refrigeration should smell sharply fruity with undertones of vinegar, not unpleasantly acidic or cheesy. Its bubbles will appear smaller and more uniform than a white flour starter, with a slightly darker hue from the bran. When removed from cold storage, it should show signs of activity within 4-6 hours at room temperature - slower revival indicates excessive acid buildup requiring adjustment in the feeding regimen.

Bread made from refrigerated whole wheat starters exhibits distinctive qualities beyond mere sourness. The extended cold fermentation allows for more complex starch breakdown, resulting in superior crust coloration and keeping properties. These loaves often display a subtle sweetness beneath their tangy exterior - a hallmark of properly managed acidity. The crumb tends toward a creamier texture with irregular, glossy alveolation that signals excellent gluten development despite the whole wheat's interfering bran particles.

Practical experimentation remains the best teacher in this nuanced aspect of bread craft. Keeping detailed notes on feeding ratios, refrigeration durations, and resulting bread characteristics helps identify patterns specific to one's kitchen environment and flour selection. Over time, bakers develop an intuitive understanding of when to push acidity with more whole wheat and when to pull back with white flour feedings - the mark of true mastery in French country bread traditions.