Brehm Frozen

by admin on July 4, 2012

Key Benefits of Brehm frozen grapes and juices

  • High End product for the experienced discerning winemaker
  • Brehm frozen grapes sourcing offers a type of pedigree not comparable to other offerings
  • Control the timing of your winemaking.  Grapes arrive frozen and can be stored frozen until you are ready to make wine.
  • Enhance all juice wines and average your costs by making a second from the skins of the Brehm grapes combined with an all juice product
  • The whites are 20L of 100% pure grape juice
  • The reds are 100% crushed and destemmed grapes.  Normally stems would be about 6% of total grape weight. 
  • Note the actual yield is not as predictable as in the juices when dealing with grapes.  You will need 2 buckets to fill a carboy.
  • Frozen grapes carry all the imprints of the vineyard and vintage. They vary in sugar, acid, etc. from bunch to bunch and vine to vine.
  • True winemakers ability is showcased.  The grapes arrive as they were picked with no additives or adjustment having been made.  The Winemaker has total control over the end product.

Why are the grapes frozen?

Frozen grapes may actually be better than fresh grapes. “After 34 years of experience it has become evident that there are no quality down sides to freezing and a host of advantages, compared to fresh grapes.” Peter Brehm.  

People ask us what the difference is between making wine from fresh grape must and juice and making wine from frozen grape must and juice.  For all intents and purposes, there is no difference.  By freezing our musts and juices, we simply put them in a state of suspended animation.  Once thawed, the musts and juices are almost as they were on the day of processing.

The difference is mainly in the condition of the grapes.  Fresh grapes have been the basis for winemaking over the years.  Shipping fresh wine grapes mandates harvest dates suitable for shipping, not necessarily the harvest for the finest wine.  Shipping over long distances creates severe risks to the grapes.  Frozen grapes can be picked at their optimal ripeness and flavour content as they are processed very soon after harvest.

Note Brehm frozen grapes were always intended on being frozen and they are not an afterthought or because of excess inventory in a fresh form.  Brehm grapes are frozen at the source.

There are a few transitional changes that you should know about when dealing with frozen grape musts and juices.  The freezing process acts as a non-invasive, chemical-free, partial sterilization of the must or juice.  Freezing temperatures will kill most yeast and other microorganisms that are naturally present on the grapes.

Freezing also causes both the red musts and white juices to stratify.  The various components of the musts and juices will form a gradient within the solution of must or juice based on their densities.  Heavier particles that will not freeze completely are driven to the center and bottom during freezing.  Lighter particles freeze and during thawing will rise to the top (float),  A thawed pail left unstirred would be about 7brix at the top, and 45 brix at the bottom of the pail.

The harvest statistics shown on the grape labels of our frozen pails and drums of white grape juice represent samples of the juice taken after pressing the grapes and allowing to cold-settle in a stainless steel tank.  For red grape must, the harvest statistics are taken from vineyard samples that represent the whole vineyard, but not one particular pail necessarily.

The freezing process causes tartaric acid in the musts or juices to form salts and precipitate to the bottom of the pails as cream of tartar.  Because of this precipitation of the tartaric acid, as well as the separation formed by the other components in our frozen grapes we insist that you stir your musts and juices extremely well before doing any analysis.  After stirring your thawed must or juice in the pail, pour this into your fermentor and stir in some more.  Make sure to scrape out and add all the sticky stuff that remains in the pails into your fermentor and then stir your must or juice some more.  Stir, stir, stir.  The tartaric acid will not stabilize until after fermentation.

Total acidity is the concentration of tartaric acid in grams per 100 milliliters of solution.  Tartaric acid is unstable in cold and alcoholic environments.  The ph of your must, juice or wine will be affected by the state of tartaric acid.  If you measure the total acidity and ph of your must soon after thawing your pails, you will see that the TA is low and the ph is high when compared to Brehm vineyard’s harvest stats posted on the grape label of your varietal.

For white juice, the grape label should be accurate, except for the effects of the cold on the tartaric acid.  White juice, after thawing, will show a lower overall total acidity and higher ph due to the instability of the tartaric acid.  This cream of tartar will dissolve during fermentation.

For red grape musts, the freezing process acts as a cold soak both before the must is frozen and while the must thaws.  This process starts to break down the skins of the grapes allowing them to give up some of their color phenolics and juice more easily than fresh grapes fermented immediately after crushing and destemming.  In effect, color extraction and yield is greater due to the must having been frozen.

The ph and sugar readings you initially obtain from fresh red must also change with skin contact.  Zinfandels are notorious for increasing 1 – 3 brix as the raisened berries soak.  The ph invariably rises with skin contact.  Cold soaks as well as skin contact time during red grape fermentation have an effect on the ph of the must solution.

Skin contact in red must, for fresh or frozen grapes, will cause a rise in ph.  This is partially due to the extraction of potassium from the skins into the wine/juice.  The amount of potassium affects the ph of the wine directly without a notieceable effect on the total acidity.  What this means is that the prefermentation ph of must or juice will raise an average of 0.10 to 0.15ph units as a result of skin contact.  This fact is true for fermenation of grapes that were frozen or not. During fermentation, it is normal for the ph to rise even further.

The ph of the wine will again rise due to the conversion of malic acid to lactic acid during malolactic fermentation.  Thus, the pre-fermentation ph of must or juice will rise, on average, a factor of 0.10 to 0.25 ph units as a result of primary and secondary fermentation.