Hi, it depends if you want to know the pH-value of fresh or frozen berries :-)

Dear Mrs Gund,

First of all thank you for your answer.

Based on the literature and when for example you want to measure the rate of berry maturation, berries should be processed and analyzed as quickly as possible. if not, juice have to be extracted and then to be frozen. Before the analysis the samples should be thawed, warmed to x oC, allowed to cool to room temperature and then pH and titratable acidity can be determined.

Is this procedure reliable or not?

Based on other research papers etc, none of the three (pH, titratable acidity and Brix) should be measured on frozen samples.

Hey,

The obvious answer is fresh berries. Frozen berries might dehydrate during freezing and/or will obtain water from the ambient humidity while thawing them. These two lead to a change in the concentrations of both H+ and Organic acids..

In addition, if you do not have the time to measure TA and pH at the day of the sampling, crush them to obtain the must and store in a fridge (4 degrees) for the next day. Do not freeze it, we have noticed a great effect of freezing the must on the pH and TA measured.

If juice or berries are kept at low temp. tartaric acid concetration will decrease becouse K-tartarates will be formed and sedimented. On the other hand if you leave juice samples on room temperature the fermentatin can start very fast and CO2 from it wil afect both TA and pH. You can avoid this if you remove the yeasts (centrifuge) but not for longer time.

Anyway that's why fresh samples are the best sution.

Fresh samples are always better.

Thank you so much for all the information!!!! I really appreciate it..

But what if you have not other choice than to freeze them? I'm talking about 55 samples...