* first of all welcome to Wine Making Talk, you are in hay and berry country, where?
Is the Camden not clearing because of the cool temperature and then the wine yeast is also killed? Did we have some weird mold on the berries that started before freezing and storing them? Is there something else going on with wine chemistry that I just don't understand?
*
ALL fruit will contain all the spoilage organisms that are capable of destroying a wine!
I describe The process of making wine as putting up fences that are capable of selectively farming the family of organism we want. One fence is pH (how acidic) the must is. Another fence is high sugar (osmotic pressure). Another fence is lack of oxygen (aerobic organisms). And our most modern fence is Campden/ potassium metabisulphite. There are more tools that can shepherd the fermentation where you want.
* freezing will not change a microbial population. Freezing will kill insects.
* Do you run pH? As with home canning how acidic the fruit is keeps a lot of organisms out. My goal in making fruit wine is to be between pH 3.2 and 3.5 (water bath canning puts this fence at pH 4.0) , , , (pH testing is done in your local high school chemistry class/ also folks who do salt water fish) It is worth while to find where the next batch is. As in the water bath canner below pH 4.0 there is low risk of food poisoning but risk the wine gets infected and tastes bad.
* Putting metabisulphite in your must can be done while the fruit is thawing. This is a chemical and will react to microbes at 35F as well as 70F. If you are building up contamination on a plastic primary I would suggest doing a double dose as break up fruit off the freezer and add and then once you can stir to get a uniform slurry add a second treatment. Commercial yeast is quite tolerant of SO
2 , ,, meta reacts and drops down to 10ppm fairly fast, ,, your major down side is some pigments as pie cherry red will turn clear, raspberry has a stable pigment.
* Have you had an infection? A floating microbial mat should feel soft/ possibly greasy. Again the local high school will have a microscope and can diagnose if it is a round (cocci/ bacteria) or a long filament (mold family)
* Microbes grow in waves. As with milk a clotting family grows (yoghurt) followed by a proteolitic (bitter break down products). For a modern wine must we put in a known strain which is fast and clean flavor. We want the sacchromyces yeast to over power everything else and get the fence of alcohol up to 5% where the beverage starts to be resistant to infection. It would not hurt to use a starter and help the first wave of microbes.
* dirty hardware? Rubber and plastics which are cracked/ scratched will hold enough residue to inoculate future batches. A heat treatment at 180F can eliminate the risk but most of us get a new plastic pail. Nylon press bags will survive hot water in a kettle.
* Air/ most wine infections require air (ie they grow on the surface). Yeast in the first phase need air to build cell walls but at 1/3 sugar reduction cell reproduction is done and they use anaerobic metabolism. If you are having problems, there isn’t any reason to stay in the open (aerobic) fermentor after 1.050 gravity. I aim for 1.020 since I am looking for fast CO
2 production to create an anaerobic carboy./ keep this fence working.
* The common wine infections do not produce food poisoning toxins. A bad tasting wine gets tossed for flavor not safety. Many infections can be recovered from by adding a double dose of meta. (normal is 50ppm, taste threshold is 100ppm)
* Meta prevents oxidation, I stopped acetaldehyde flavor (oxydized ethyl alcohol) by dosing 50ppm every time I open a carboy.
* you could build higher microbial stability by targeting 13 to 14% alcohol instead of 11%. A natural (unpasteurized) beverage at 5% requires refrigeration to prevent eventual infection.
I will guess you haven’t looked at microbiology. This thread has some basics:
A Course on Wine: INDUSTRIAL WEBINARS by suppliers
