Question: What happens with the pH is neutral?
About the article "Vegetable", section "Color pigments".

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Anthocyanins can be used as pH indicators because their color changes with pH; they are pink in acidic solutions (pH < 7), purple in neutral solutions (pH ~ 7), greenish-yellow in alkaline solutions (pH > 7), and colourless in very alkaline solutions, where the pigment is completely reduced. 
The pH level of a wine is the measurement of the amount of free (H+) hydrogen ions.
It is related to the titratable acidity level of a wine but differs in significant ways.
Low pH numbers indicate a high concentration of acids in a solution.
While pure water is neutral with a pH of 7, wine tends to be more acidic with a pH between 3 and 4.
As the acid levels in ripening grapes fall, the concentration of acids are lessening which means the pH level is rising.
Yeasts, bacteria, phenolic compounds such as anthocyanins which influence color all have varying tolerance to wines with high pH levels.
In general, wines with high pH value tend to have duller colors and less developed flavors and be more prone to wine faults caused by spoilage organisms which makes monitoring the pH levels of grapes during ripening a priority for viticulturists and winemakers.
While the rudimentary method of testing pH is to expose the grape juice to a pH indicator such as the strips used for a standard litmus test, the results are usually not as detailed and accurate as what is needed to evaluate ripeness.
Therefore, most wineries will us a pH meter that can give readings to an accuracy of plus or minus 0.1.
As with sugars and acids, the ideal pH levels to determine ripeness will vary.
For white wines, winemakers often look for pH readings between 3.1 and 3.2, while would be a maximum of 3.4.
If the pH is too high, it may be a sign that the grapes are overripe (or that the soil has too much potassium which will also influence pH readings).
While there are risks to letting the pH go too high, winemakers can counter high pH by adding more tartaric or malic acid during the winemaking.
However many viticulturists and winemakers uses pH readings as a strong boundary line for when to start the harvest. 
The soil pH is a measure of the acidity or alkalinity in soils.
pH is defined as the negative logarithm (base 10) of the activity of hydronium ions ( or, more precisely, ) in a solution.
In water, it nomally ranges from -1 to 14, with 7 being neutral.
A pH below 7 is acidic and above 7 is alkaline.
Soil pH is considered a master variable in soils as it controls many chemical processes that take place.
It specifically affects plant nutrient availability by controlling the chemical forms of the nutrient.
The optimum pH range for most plants is between 5.5 and 7.0, however many plants have adapted to thrive at pH values outside this range. 
Normal pleural fluid pH is approximately 7.60.
A pleural fluid pH below 7.30 with normal arterial blood pH has the same differential diagnosis as low pleural fluid glucose. 
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