Tuesday, January 29, 2008

Digression: Racking 2006 Cabernet

In July 2007 I used an early prototype of the WinePod to make a batch of 2006 Cabernet Sauvignon from Sonoma County's Windsor Oaks Vineyard. This wine turned out pretty well in my opinion. It was fermented on toasted French oak cubes, and since pressing has been raised in a glass carboy.

I would like to bottle this wine in the next month or so. The wine has been racked once since pressing, when I added SO2, and has dropped about 5 mm of lees in the carboy since then. Today I gave it a second racking and a second addition of SO2. This addition was 30 ppm and I used 2 grams of Efferbaktol granules as the source.

I needed some wine to fill the carboy to replace the volume lost to racking off the lees. Fortunately I have barrels full of 2006 vintage wines available. For topping I used 400 mL of 2006 Tannat out of a new French barrel. Tannat is very dark and spicy, but at about 1.5% of the blend it should effect very little change to the characteristic sensory profile of the Windsor Oaks Cabernet.

Continued Maceration

This morning I made one of the three remaining planned punchdowns on the must. Once again, the Pod's Brix sensor was reading -5° before the punch but returned to a more realistic -2° after mixing. The Provina guys are already working on some mods to the sensor design to help prevent the sensor getting "stuck in the muck" – the heavy lees that settle after fermentation slows.

Late yesterday Vinquiry emailed the results of the malic acid analysis. At this time the wine has 1.01 g/L, which is low compared to average levels – I usually expect somewhere between 2 and 3 g/L in juice. Because of the relatively high level of SO2 added when I filled the WinePod there is little chance that bacterial activity has dropped the malic level. Anyway, with this amount of malic to be converted to lactic I don't expect the pH to rise much above 3.6 after fermentation.

The aroma of the must has changed dramatically from yesterday, and for the better. Where yesterday there was a little funk today there is just sweet jammy fruit. The cap is mostly down but there is a fraction that is still slightly buyoant – likely from the small amount of CO2 produced by the malolactic bacteria. Also, there are a couple of handfuls of whole berries that have refused to pop – they are not hard and green so they should release whatever thay have going on in them at this point (likely lots of carbonic maceration) at pressing.

Monday, January 28, 2008

Inoculated for Malolactic

At the punch this morning the WinePod was reading an unlikely -5° Brix. I will go through the full sensor calibration before the next ferment. Anyway, I felt confident enough that the sugar was gone to go ahead and inoculate the must for malolactic as planned.

After I pulled a wine sample for lab analysis I rehydrated a 2.5 gram pack of Enoferm Alpha bacteria according to directions (resuspend in pure water at 75° F for 15 minutes) and punched it in. Note that this is the smallest pack of one-step malolactic culture avaialble. Even so it is sized to adequately inoculate 66 gallons of wine. I don't expect to have a problem with a slow or incomplete ferment.

Just a few moments ago I received the lab analysis of the wine sample I took in this morning:

Alcohol13.87% v/v
Volatile Acidity0.25g/L
Glucose + Fructose0.02g/L

The alcohol level is consistent with a starting Brix of 24° and the approximately 2-2.5 liters of water I added when making nutrient and acid corrections. The pH is a bit low and confirms that the buffer capacity of the juice was minimal. Again, I'm glad I only added 0.5 g/L before the ferment.

The volatile acidity is very low – this is a good thing, and in my experience is another of the side-benefits to using Uvaferm 43 to conduct the fermentation. Finally, the residual sugar is very, very low – I consider anything under 0.20 g/L to be "dry".

I also asked the lab for a starting malic acid level, but the analysis is still pending. Once I have that number I will have a better expectation of what the final pH on the wine after malolactic will be. Based on average malic levels in 2007, I would expect that the pH might increase to as high as 3.65 in the finished wine.

Sunday, January 27, 2008

Moving Into Extended Maceration

At today's punchdown, -3° Brix at 75° F – no surprise. The cap is still buoyant, but barely. I expect it to be down tomorrow. The plan remains to take a sample to the lab for analysis, and to inoculate for malolactic.

Note that I have done 14 punchdowns so far in this ferment. I plan to do no more than 18 total. It is my firm position that most red wine ferments receive excessive cap manipulation. Three punchdowns a day for ten days? Why? In my experience this kind of over-manipulation just causes problems. With fewer punchdowns I get better color and less harsh tannins.

I consider that this lot started "cold soak" the day after I received the grapes, January 12th. Right now I expect to press it off on February 2nd, after 22 days total of maceration. Malolactic should be complete by then, and the taste should be close to perfect after this amount of time at 75° F.

Saturday, January 26, 2008

Waiting Game

I went in today to punch and check the Brix with a high-precision +5°/-5° Brix hydrometer. The Pod reading on the must after the 4 pm punch was -3° Brix at 75° F.

Unfortunately, the last +5°/-5° hydrometer in the winery has gone missing. Somebody must have broken mine and neglected to tell me about it.

So the backup plan is to get a sample to the lab early Monday morning for enzymatic analysis of glucose+fructose and malic.

Friday, January 25, 2008

Entering Post-Fermentation

This morning the must was reading -2° Brix at 74° F before the punchdown.

After the punch the reading was zero °Brix.

This does not surprise me as the Pod vessel is tall and narrow, and colder towards the top. My scenario is that the ferment stratifies a little, proceeding a little more slowly in and under the cap. Uniformity is re-established by mixing.

Also as I expected and hoped, as the ferment nears completion the hints of sulfide aromas that I noted yesterday are disappearing.

Over the weekend I will be checking the Brix of the must with a precision hydrometer to validate the WinePod's Brix sensor readings. (Note that the Brix goes negative at the end of fermentation because zero °Brix is defined as pure water. The density of the water/alcohol mix in wine is less than that of water, so the value goes negative.)

Once I have verified two consecutive negative Brix readings I am going to inoculate the must for malolactic fermentation, and allow the wine to macerate on the skins for an extended period (until malo is complete) before pressing.

Thursday, January 24, 2008

Fermentation Tapering Off

This morning the must was reading 2° Brix at 77° F at the punchdown. After the punch I dropped the lower temperature setpoint to 75° F, where it will stay through malolactic fermentation.

I finally received the lab analysis of the juice sample I pulled before fermentation:

Disssolved Solids24.0°Brix
Titratable Acidity4.21g/L
Assimilable Nitrogen124mg/L

The sugar is lower than the WinePod Brix sensor was reporting, by 2° Brix. The pH is not particularly high in my experience, but the T.A is a little low. I will be re-evaluating the taste, pH and T.A. after malolactic and pressing to see if there is need (and room) for another tartaric acid addition. The potassium is a bit low.

This is the main challenge of working with frozen fruit: the freezing precipitates most of the potassium bitartrate out of solution before the ferment. In ordinary circumstances, the tartaric acid equilibrium is not established until well after fermentation, and is affected by the alcohol content of the wine.

My training and experience with acid correction in commercial ferments is not of much help with frozen fruit. Some of the tartrate in the WinePod juice will re-solubilize at the higher temperatures of fermentation – it will be interesting to see what the pH and T.A. are after malolactic. Anyway, I'm glad that I added the half-gram of tartaric before inoculation, and gladder still that I did not add more – a larger addition could have driven the pH uncomfortably low.

The nutrient status of this juice was quite low as well. The combined ammonia/nitrogen of 173 ppm is low enough to starve yeast expected to ferment to over 14% alcohol. It turns out that the nutrient additions I made should have added about 140-150 ppm of available N to the must. If I had known that the N was this low early on I probably would have added another 50 ppm of N as DAP to the juice. At any rate, at somewhere around 320 ppm the total N of the must is what I would describe as "barely adequate" to conduct a clean and complete fermentation.

So it's probably not just coincidence that the ferment smelled a little of sulfide this morning.

Wednesday, January 23, 2008

The Critical Phase

Yesterday I did two more punchdowns while the ferment was at its peak temperature: at 1:00 PM it was 15° Brix at 82° F and at 5:45 PM it was 13° Brix at 84° F. It took the WinePod heating unit eight hours to pull the must up from 72° F at 9:30 AM.

At this third punchdown I added another 10 grams each of DAP and liquid yeast extract. This brings the total for each to 46 g/hL. I also raised the lower temperature setpoint to 87° F.

At 5:30 this morning I went in to punch and check on the ferment: 7° Brix at 85° F. Whew - I was worried that the yeast might have tried to rocket through the rest of the sugar overnight. I left the upper temperature setpoint at 90° F and decreased the lower setpoint to 80° F.

At the 2:30 PM punchdown today the sugar was down to 5° Brix at 80° F, so I backed the lower setpointfurther to 78° F.

Ambient temperature in the winery is about 53° F. It's cold but not frigid. The WinePod is very efficient at shedding the heat of fermentation. All this fiddling with temperature setpoints is in an effort to get the ferment in the Pod to track with an idealized commercial fermentation temperature profile.

Tuesday, January 22, 2008

Nutrient Additions

Did a routine punchdown yesterday. The must was 21° Brix at 72° F – the low setpoint on the temperature control.

When I went in this morning to do another punch, the temperature was still at the current low setpoint (72° F) and the sugar was down to 17° Brix.

The fermentation smells great – no suggestions of stress at this point. However since I did not add any water at the beginning of the ferment to bring the sugar down from an initial 26° Brix, the potential alcohol of this lot is over 14% and may be as high as 15%. So I want to add some nutrients at this time to make sure I don't have any fermentation problems on the back end.

It is my regular protocol to try to get all nutrient additions into the ferment before the sugar drops to 8°-10° Brix. This allows the yeast to take up the nutrients during log phase growth – at least before late log phase – when the cells have the ability to do something constructive with the nutrients. Things like making more cell mass, and membranes that are more resistant to high alcohol levels.

From the WinePod starter kit I added 8 grams of Fermaid K nutrient (18-19 g/hL) and 10 grams of diammonium phosphate (DAP, at 23 g/hL), a ready source of nitrogen. This 8 gram addition is all of the Fermaid K supplied with the kit, and is equal to about 75% of the maximum commercially legal addition rate for this product. There is no reason not to add the full legal amount – the kit should come with 10 grams of the Fermaid K nutrient.

The DAP daddition represents about 25% of the maximum commercially legal addition rate of 100g/hL. DAP is one of those things I would like to add as little of as possible – it smells and tastes awful on its own, it raises the pH of the must, and while it is really effective at building yeast cell mass when added at the right stage of fermentation, it also can push the fermentaion rate and temperature up faster than I might want. Since I got this addition in at 17° Brix I have the opportunity to make a second addition before 8° Brix if the must needs it – say if it starts to smell of sulfide, or if the lab analysis comes back showing very low starting nutrient levels in the juice.

And there's the rub – I feel like I am shooting in the dark a bit on this ferment. My timing on filling the Pod could have been better. I did it on Thursday and pulled the juice sample on Friday, but then could not get it to the lab early in the day. I refrigerated it over the weekend, and the lab was open yesterday despite the holiday. But they were unprepared for a juice sample this time of year and needed to make up fresh buffers and standards. I may get results before the fermentation is complete, or I may not. I'm relying on my backup system – a finely-tuned palate, experience and intuition.

To round out the nutrient additions I also added 10 grams of a liquid yeast extract preparation from my commercial production stash. This amount represents about half of the maximum legal addition. I like this material for its positive contrubution to mouthfeel.

After punching this addition into the must I raised the temperature control setpoints to 85° F and 90° F. I plan to make two more punchdowns today and get the ferment through its peak with these setpoints. Once the sugar gets below 2° Brix I will back the setpoints to 72° F and 75° F and complete the cuvaison at these temperatures.

Sunday, January 20, 2008

Inoculation - Cap Up

Today I went in to do my first "real" punchdown on the must in the WinePod, as the cap was up on the yeast I pitched in yesterday.

Yesterday made a small prophylactic addition of tartaric acid to the must of 20 grams (50g/hL). Then I prepped the yeast that was included with the WinePod starter kit. Here begins the gospel according to John, chapter 3 verse 1:

I used 200 mL of purified water at 104° F (it's critically important that the water has no chlorine). Then I suspended 20 grams of GoFerm nutrient in the water. GoFerm is another one of these magical yeast extracts – in this case, one selected for production of a high concentration of the sugar trehalose. This extract helps the active dry yeast to rehydrate with very little loss of viability.

Note that the commercial recommended addition rates are 30 g/hL for GoFerm and 25 g/hL for yeast. It is my confirmed opinion that it is better to over-inoculate than to use too little. My actual rates of addition were 47 g/hL and 37 g/hL, respectively.

Once the GoFerm was thoroughly dispersed, I added 16 grams of the Uvaferm 43 yeast included with the kit. According to Vinquiry's promotional material, Uvaferm 43 is a "[s]train selected for ability to restart stuck fermentations. Isolated in the Rhone valley, has shown consistent properties for adapting to sluggish or stuck fermentation. Alcohol tolerance greater than 18% (v/v), moderate/low nitrogen demand with good fermentation rate after lag time for adaptation to wine conditions. Contributes berry and cherry aromatics and slightly higher glycerol contribution." In my experience this yeast hardly ever "sticks". It also respects wine color and does not put its own stamp on the character of the fruit. Overall I think this is a great yeast to use for avoiding fermentation problems.

After 15 minutes I "proofed" the yeast preparation with a pinch of table sugar and 50 mL of juice from the fermenter. Proofing does two things: first, it confirms to me that the yeast prepartaion is viable (capable of fermentation and growth) and second, helps drop the temperature of the inoculum closer to that of the must, which is good for maximizing yeast viability.

Before pitching the yeast into the must I changed the setpoints on the WinePod temperature control to 70° and 80° F. I waited until the must was close to 70° F before I pitched the inoculum, which was at about 84° F when it went into the Pod.

After the punchdown today I increased the lower setpoint on the temperature control to 72° F to put a little more heat into the must. The sugar has dropped from 26° to 24° Brix.

Friday, January 18, 2008

Preliminary Must Additions

When I checked on the pod this morning I noticed that the thermistor had come loose from the side of the tank – nothing I couldn't fix with a piece of duct tape. The temperature was reading 54°-55° F. Observed no evidence of fermentation.

After using the industrial potato masher supplied with the starter kit to do a punchdown (really just a mix to homogenize the must) I pulled a juice sample to take to the wine lab (Vinquiry) for analysis.

Then it was time for some must additions: tannins, enzyme and yeast extracts. I really don't want to stamp on the natural expression of the vineyard on this fruit so I added only small amounts of tannin, which binds with protein, color, and bitter phenolics that might be released by the seeds during the freeze-thaw cycle. I added 5.0 g/hL (2.0 grams) each of Vitanil AJ-11 (quebracho extract), Sublitan Vinif (grape skin extract) and Oenotan (pure oak tannin extract).

Then I added 2.0 g/100 kg (1.25 grams) of Lallzyme EX-V, an enzyme preparation that helps to release color from the skins early in the fermentation. When I first considered making wine from previously frozen fruit I felt that an enzyme would not provide any benefit. However after seeing how well the skins of these grapes hold up to freezing and thawing I decided enzyme might be a good idea after all. The tannins and enzymes came from my commercial winemaking stash – some day these might be included in the WinePod starter kit.

Finally I added the yeast extract preparations supplied with the starter kit: OptiRed and Booster Rouge, each at about 18 g/hL (8.0 grams). These preparations are selected for enhancing volume and softness on the palate.

All of these were mixed into the must with the potato masher. Then I set the cooling system to start gently heating the must prior to inoculation. The lower setpoint was 62° F and the upper limit for the time being was set at 72° F just in case a "native" ferment takes off at the permissive lower setpoint – I don't want the must to get rocking before I add the desired yeast strain.

Thursday, January 17, 2008

Filled The Pod Today

I am helping Provina, Inc. prototype their exciting home winemaking unit, the WinePod. I have been working with the Pod team for about a year, and this blog starts with my second ferment.

The first ferment, a 2006 Cabernet Sauvignon from the Windsor Oaks Vineyard in Sonoma County, turned out well. I was working with an early alpha WinePod unit, and while it worked acceptably I was able to find its limitations fairly quickly.

This year I am starting with another Cabernet, this time from the Rancho Sarco in the Coombsville region of Napa Valley. The vineyard is Clone 337 Cabernet on gently-sloped and well-drained soil with a permanent cover crop. Yields looked to be a high-quality 3 tons/acre and the berries were really tiny.

Part of the Rancho Sarco vineyard was harvested for Provina and delivered to Brehm Vineyards in Petaluma, where it was destemmed and crushed, packed into 6-gallon food-grade pails, and flash-frozen. Frozen fruit was delivered to my doorstep at 10:30 am on Friday 1/11/08. I left the pails in the winery to thaw over the weekend.

Greg Snell, president of Provina, delivered a new WinePod to me on Tuesday 1/15/08. This beta unit showed really significant re-engineering compared to the alpha prototype from last year! Greg also brought along the WinePod starter kit, which includes basic labware and a set of wine additives sized for the Pod, including: sulfur dioxide granules, tartaric acid, yeast nutrients, yeast, oak cubes, and malolactic bacteria. Excellent!

Today I took the stretch wrap off the thawed pails of fruit and opened them with the handy pail key included in the starter kit. The first thing I noted was that the pails were much cleaner on the outside than last year – a very good thing in terms of keeping the fruit from growing spoilage organisms.

I sanitized the WinePod before filling it – I cheated a little and used my ozone generator insead of the "Star-San" included in the starter kit. When I transferred the crushed fruit from the pails to the unit I added about 10 grams of Efferbaktol - the safe and clean sulfur dioxide preparation provided.

The three pails netted about 138 pounds of fruit. I estimate this should yield about 11.7 gallons of juice. The 10 grams of Efferbaktol was a bit of deliberate overkill as it should be equal to about a 90 ppm addition of SO2 – conservative, but as the fruit had been thawed for several days I really wanted to make sure that any undesirable microbes are killed or inhibited.

Not that I had any strong suspicions that any "native" flora had already started growing - there were no "off" aromas and no evidence that CO2 was pushing up a cap in the pails. In fact, the aromas were wonderful – strongly varietal with hints of tobacco. The juice was already a lovely deep purple. Temperature was 52° F and the integrated sensor was reading 25° Brix.

While I have the unit plugged in I have not yet invoked any temperature control. I'm going to let the must equilibrate overnight and mix it tomorrow before sampling for lab anlysis of the jucie and before making the pre-fermentation additions I have planned.

In the meantime I am going to install the updated WineCoach software on my laptop, which will allow the WinePod to upload fermentation data to the computer wirelessly. Cool, huh.