Hi,
I made a single strength juice of red and white grapes using concentrated juice (clarified).
They have same brix value, which is 11, but different total acidity (0.1366 for white, 0.1661 for red)
The white one is much sweeter than the red, when tasted, probably due to the low acid content. But pH of the red (3.88) was higher than the one of white (3.66) though the red has more acids.
So I'm wondering what makes the red grapes to have higher pH....
Do the anthocyanins in the red grape increase pH? Or other reasons??? Please help! :"(
Dear Sel,
acidity is highest in wine grapes just before the start of veraison, which ushers in the ripening period of the annual cycle of grape vines. As the grapes ripen, their sugar levels increase and their acidity levels decrease. Through the process of respiration, malic acid, one of the principal organic acids found in wine grapes, is metabolized by the grape vine. Please be aware that the measure of the amount of acidity in wine is known as the “titratable acidity” or “total acidity”, which refers to the test that yields the total of all acids present, while strength of acidity is measured according to pH. The pH of grape juice may range from about 2.9 to 3.9, depending on the type of grape used. Generally, the lower the pH, the higher the acidity in the wine. However, there is no direct connection between total acidity and pH. It is possible to find wines with a high pH and high acidity (Bellman, R. B.; Gallander, J. F. (1979). "Wine Deacidification". In Chichester, C. O.; Mrak, Emil Marcel; Stewart, George Franklin. Advances in Food Research Vol. 25. Academic Press. p. 3. ISBN 0-12-016425-6.9). So your findings are not too uncommon. You might also wish to look into the composition of the various acids, or the main components of the acids, in the red and white wines under consideration, which might give you a clear answer to your question. Hope this helps.
Wishing you best of success
Johannes
Dear Sel Lee.
This is very common question which is addressed when to start analyze fruit juices and wines too ..... I will try explain...
Please see differences in scales: Between Ph and total acidity (TA)
a. Ph is logarithmic scale not linear. Total acidity is linear.
b. Ph Scale - Less Ph means more acid
TA scale - more TA is more acid
c. TA measures all of the combined acids in the juice (there are many different types) this is more exact and accurate.
but, IMPORTANT The pH is a measure of how acids balance out (Not TOTAL!) against buffering compounds such as Potassium.
So there are many cases, when TA is same, but Ph is different even 3,3 and 3,9 PH..
What we check by testing, If we assume, that TA is same and Ph different...
if Ph 3.3 - means that there are more acidic and have bright fruit flavors,
if Ph 3,9 - means more soft and round...
Best regards,
Zviadi
Thanks so much for the answers...!!!
Yes I just started analyze fruit juices few weeks ago...
So as I understand, total acidity is the amount of total acids. And pH is the power of the acids to neutralize(balance out???) the buffering compounds??
I couldn't find a reference about acid composition in the red and white grape or about the different pH values.... Could you please recommend some references?
Thanks so much again!!!
Dear Sel,
you will find some information here:
https://www.extension.iastate.edu/wine/sites/www.extension.iastate.edu/files/wine/compositionofgrapes.pdf
http://www.bioline.org.br/pdf?cj11057
http://thomson.iqm.unicamp.br/pdf/556.pdf
Hope this helps!
Johannes
Dear Sel,
Just to complete the answers you already received.You should to don't forget that winemakers are always trying to pick-up white grapes with a low acidity level (ph around 3,3) instead for red wines they pick-up grapes in function of the total polyphenols amount and not only using acidity level as a key quality indicator. Even if the acidity still to be a key quality indicator. That is one reason why white wines have almost "always" lower pH than red wines. To sum up : white grapes pick up : aromas+acidity firstly ; to pick up red grapes : polyphenols concentration (anthocyanins+tanins) firstly.
Hope this helps.
- Badges
- Science topic
- Similar topics
- Engineering
- Chemical Engineering