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Work in Progress: Sous Vide Salami Fermentation

Work in Progress: Sous Vide Salami Fermentation
January 17, 2015 Kyle Hildebrant
Fermenting salami sous vide with an immersion circulator

Is it possible to ferment salami using the sous vide method? And if so, are there any real benefits to doing so, or is it simply a novel, unnecessary approach? These are things I started asking myself about a year ago. It wasn’t until recently that I’ve put these questions to the test.

Note: These ‘Work in Progress’ posts are a way for me to present ideas or concepts that are not yet fully baked. In doing so my hope is to have an open dialog with others who may have input, ideas or experience on the topic at hand. It’s a way for us to learn, together; and its a way for me to document the miscellany of experiments and ideas I have in process. Most of which end up on Instagram, if you’re not following me there.
A Word of Caution: Nitrite is absolutely necessary if attempting to ferment sous vide. Insta Cure #2 contains both sodium nitrite (at 6.25%) and nitrate (at 1%), with the remaining 92.75% being salt. This prevents Clostridium botulinum from producing botulinum toxin, which causes botulism. Some approach making salami in the old-world style with just “salt and time”. Please don’t ferment under vacuum without added nitrites. Moreover, this post is not intended as instruction for beginners. Please do not use sous vide fermentation as your foray into the world of salami making. 

Can you Ferment Salami en Sous Vide?

The answer is yes. It is possible and it works well. But are there any real benefits over traditional fermentation methods? We’ll get to that.

Fermentation Primer

'Nduja post Sous Vide Fermentation; pH 5.03 reached

‘Nduja post Sous Vide Fermentation; pH 5.04 reached

In the traditional method of fermenting, the salami is brought to a desired temperature to encourage the lactic acid producing bacteria to reproduce, eat the sugar (typically dextrose) and produce lactic acid as a byproduct. The amount of acid increases and in turn lowers the pH; typically targeting a pH of 5.3 or a bit lower. The higher acidity environment discourages bad bacteria from growing. Temperatures often range from 70°F/20°C to 115°F/46°C; with the lower temperatures producing old-world-style salami, and higher temps for more assertive and tangy American-style salamis. Humidity is often kept as high as possible, ranging from 75-95% relative humidity. The high humidity prevents the casing from drying out and hardening.

In commercial productions this is accomplished with a purpose-built fermenter, which can be an entire room for larger production, or smaller bread proofers. In home production fermentation can be done a myriad of ways: from lower-temp fermentations in a oven, simply using the heat from the pilot light; to purpose-built boxes or converted refrigerators; to speed racks enclosed by a plastic cover, heated with a space heater and kept humid with a portable humidifier—anything able to maintain a consistent temperature and humidity.

Sous Vide Fermenting

The approach to fermenting salami is no different from cooking anything else sous vide:

  1. Vacuum seal your salami in a bag
  2. Set your immersion circulator to the desired fermentation temperature
  3. Ferment for the amount of time necessary to reach pH 5.3
  4. Then move to dry-curing chamber and dry as usual

The Pros and Cons

The Pros:
Precise temperature control. The reason we cook sous vide is it’s ability to maintain a precise temperature. In home production and without a purpose-built fermenter, it’s often difficult to maintain a constant temperature; fluctuation can range between 5°-10°F. The water bath eliminates this inconsistency.

Humidity is not an issue. The lactic acid bacteria (LAB) that we add through starter cultures are anaerobic and do not require oxygen to survive or reproduce. Therefore the reduced oxygen environment (there’s still a bit left in there) of the vacuum-sealed bag does not pose a problem. Moreover, because the salami is sealed in a bag there is no place for the moisture to escape. This means it’s impossible to over-dry the casing during fermentation, which contributes to “case hardening”.

The Cons:
Mold will not grown under vacuum. In most salami it is desirable to have a covering of good mold. We often do this by inoculating the casing with a mold solution, typically Bactoferm® Mold-600. Inoculation is best done by soaking the casing in the mold solution before stuffing, with a secondary external application during fermentation. The majority of the mold bloom happens in the warm humid environment of fermentation. Mold is aerobic, in that it requires oxygen to grow. When fermenting sous vide—literally “under vacuum”—there is no oxygen for the mold to grow. This precludes inoculation by soaking prior to fermentation and/or application of mold during fermentation. It’s still possible to apply and grow mold post fermentation while drying, though it’s less ideal because the covering is often not as full as when done prior and/or during.

In summary:

  • Precise temperature control allows for better, more predictable fermentation
  • Vacuum sealing eliminates the need to maintain high humidity
  • Mold cannot grow under vacuum and requires application during drying

Method

All trails to date have utilized Bactoferm® F-LC stature culture. I’ve fermented at temperatures ranging from 75°F/24°C to 95°F/35°C.

What to Expect 

My limited trails have found that the salami does not firm up as much during fermentation, at least not in the same way that you would expect with traditional fermentation. This was a bit worrisome at first, but it seems that the firming happens more after fermentation. I’m not sure what causes this. I would assume that it’s due to the fact that there is no water loss during sous vide fermentation, where there is in a traditional approach. I don’t know. There also seems to be less color transformation. Traditionally you’d see a significant change to a darker red as the various enzymatic and bacterial reactions take place. This also seems to normalize post fermentation. Again, I’m also not certain what causes this. More investigation is needed. I would not think that ingredient formulation would have any affect on the outcome of fermentation, outside of time required to reach desired pH.

Summary

Due to the inability to grow mold during fermentation, fermenting sous vide is likely best suited to applications where mold growth is less of a concern. In the photos above I am fermenting ‘Nduja. Due to the large amount of peppers/capsaicin and post fermentation cold-smoking, mold will not grow on ‘Nduja. This makes it perfectly suited to sous vide fermentation. For me it’s also an issue of convenience. It’s much easier for me to drop a sealed salami in a water bath than to babysit a fermenter for several days. While my fermentation setup, consisting of a speed rack, plastic covering, space heater and ultrasonic humidifier, is certainly capable of doing an excellent job of fermentation, it takes a bit of work. I must constantly monitor temperature and humidity and I have to refill the humidifier 3-4 times. If making salami is a full-time affair for you, this is likely not an issue. But when it’s not, a multi-day ferment takes a bit of coordination. With sous vide, I can simply drop it in the bath and take it out when it’s ready.

Our Daily Brine is my personal journal of food exploration and experimentation; covering topics of fermentation, preservation, salumi and all things charcuterie. I appreciate your part in this journey. Please comment, ask questions, offer criticism, or simply say hello.

29 Comments

  1. Author
    Kyle Hildebrant 2 years ago

    Has anyone else fermented sous vide?

  2. Dan W 2 years ago

    A pH of 5.3 sounds high to me. Toxin formation by most bacteria can happen at any pH > 4.4; if you want anything less acidic than that then you really want to be certain that either the nitrite level and / or the water activity (which is broadly similar to salt concentration, in this context) is suitable to control Clostridium botulinum / Staph. aureus growth and toxin production.

    • Author
      Kyle Hildebrant 2 years ago

      Dan, is your experience or perspective from a salami making angle, or purely scientifically?

      As you pointed out, pH 5.3 is not enough acidity alone to prevent bad bacteria growth and toxin production. In salami there are two major phases in production: fermentation and drying. I’m dealing specifically with the fermentation step. I’ve also addressed Clostridium botulinum with 0.25% cure #2, which contains both nitrate and nitrite. Additionally, there is roughly 3% salt content (2.75% added by sea salt, and roughly .25% coming from the sodium nitrate/nitrite). Finally, the water activity is addressed through the second, drying stage. Though I cannot yet afford a $6K+ aW meter, like most I gauge water activity by starting and finishing weight, targeting about a 33% loss of weight in the final product.

      You question does make me think that I should make it abundantly clear to those not familiar with salami production that salt/nitrites are a necessary inclusion, considering that Clostridium botulinum thrives in a vacuum (sous vide).

      Does that alleviate the concern? Or?

      • Reg 5 months ago

        Kyle you have answered the question perfectly. Because the ph is at 5.3 does not mean the process has stopped, it may have slowed somewhat but it does continue during the drying stage and that depends upon the amount of residual sugars (sometimes a good idea to use one or more types) left for the culture to feed on. No sugars then the culture will die off leaving behind enzymes that will continue to produce aromas and flavours, much like in the cheese making process.

        Having said that I should let everyone know that I am home educated on these subjects but have been making cured meats, sausages and cheese for a very long time

        A note on sea salts but this is only my opinion and totally open to discussion. There may be additional nitrite and nitrate in the salt depending on where the salt was collected from. If the salts come from areas close to coral reefs there will be increased amounts of both nitrate and nitrite because of the ongoing ‘life cycle’ on or within the reef. In the open ocean or where no reef exists it is a totally different story

        reg

  3. redzed 2 years ago

    Hi Kyle,

    Very interesting and informative. Using sou vide to ferment salami is something I have been looking at for a time. The perfect temperature control would be great. The thing that has been holding me back is that the more affordable circulators out there heat at a range of 25-99C. That is too warm for the Southern European salami that need to be fermented around 20C. The other issue is that not all bacteria are anaerobic. F-LC, the starter that you used is comprised of staphylococcus xylosus, pediococcus acidilacti, both of which are anaerobic, but the third ingredient, lactobacillus curvatus is a microaerophilic culture that requires free oxygen. According to Chr. Hansen, the pediococcus acidilacti and l. curvatus both contribute in suppressing listeria monocylogenes. So in your experiment only half the job is being done.

    Best wishes

  4. redzed 2 years ago

    Hi Kyle,

    I erred in my assessment of l. curvatus. A microaerophile is a microorganism that requires free oxygen for growth but at a lower concentration than that contained in the atmosphere. So it may be still functioning in the vacuum sealed bag. Most lactobacilli are facultatively anaerobic or facultatively aerobic, meaning that the can grow without or with oxygen. But I would think it’s still important to carefully check the contents of the starter culture we are using.

    If I could purchase a circulator can heat in the 18-99C I would probably switch to fermenting with this method.

    Keep up the good work. I enjoy your blog.

    • Author
      Kyle Hildebrant 2 years ago

      Redzed — First, thank you for taking the time to contribute to the conversation—and thank you for the kind words. To the issue at hand: I’ve been looking into this a bit more since your initial comment. I was able to find a study that may shed a bit more light on the subject. This study deals specifically with the affect of nitrite on “the influence of the gas phase on the growth and bacteriocin production of Lactobacillus curvatus …”. While it’s focus is on the affect of nitrite, it also deals in how oxygen influences nitrites role in it’s growth and bacteriocin (the reason it’s part of the culture). I’ve yet to read the study in its entirety. But what I have read so far seems to indicate that the lack of oxygen actually increases it’s effectiveness as a bacteriocin, in relation to it’s reaction to nitrite, which we add through the cure #2. Am I reading this correctly? Does the anaerobic state actually increase the “bio protective” properties of the culture (considering that nitrite decreases these properties)? I’d love if you read this and gave me your take.

  5. Alan Friedman 2 years ago

    Kyle, I suspect there’s little difference, regarding the oxygen availability, in the sausage using sous vide as compared to traditional fermentation methods. Aerobic and facilitative aerobic bacteria would quickly consume whatever oxygen is available. The solubility of gasses also decrease temperature increase. That’s why Clostridium botulinum, which is a strict anaerobe is such a concern in cured sausage production.

    • Author
      Kyle Hildebrant 2 years ago

      Alan, I appreciate your input on this. I suspect the same.

  6. Tomic 2 years ago

    I am curious if you have tried double bagging, place the salami in a loose sealed bag having some free air then vacuum sealing. I know that all of the meat would not be in direct contact with the bath but since we are talking about a long bath and not cooking would it matter. Would this possibly allow some water loss from the meat mass.

    • Author
      Kyle Hildebrant 2 years ago

      I’m not sure what the purpose of this would be? Moreover, having air makes the transfer of heat from the water bath to meat very difficult. Air is a poor conductor of heat/cold. This is why thermoses and the like have an air barrier as insulation. Further, this method works perfectly fine. I’ve done so about half a dozen times now with the same results. It’s best suited to higher temperature fermentation applications. But it still an excellent way to keep humidity high and control temperature exactly. Long story short: there is application, IMHO.

  7. Michael Mean 2 years ago

    I’m just curious, roughly how long did it take for the meat in the sous vide machine to reach the desired Ph? I’m a screaming novice but I’m curious. Thanks!

    • Author
      Kyle Hildebrant 2 years ago

      Michael, it’s totally dependent on several factors: (1) starting pH of meat, (2) type of bacterial cultures used, (3) amount of sugar, and (4) the temperature. With what I used here, it was around 2 days if I recall correctly.

  8. Brad McLeod 1 year ago

    Kyle , I have developed a salami that I ferment Sous Vide, In Canada CFIA chapter 4, option 3, sausage under 55 mm held at 32C for 6 days is considered cooked under the ecoli cooking requirement we have here. So I used A bio protective Culture, fibrous casing, frozen certified trich free sow meat, vacuumed it and place in 33c water, it took 2 days for the core to reach 32C, but while that was occurring we achieved a PH OF 4.5 in 400 degree hours well under the 650 degree hour requirement, held the salami for 6 more days, at 33C, removed and hung in our drying room for 3 weeks until an Aw of .70 was achieved. An incredible success, plus meeting all regs the limiting factor is the size restriction of 55 mm casing.
    I am planning to do a 55c ecoli kill for 121 min for larger casing salami and see if
    The texture will not be damaged to much.

    • Author
      Kyle Hildebrant 1 year ago

      Brad, been traveling. Sorry for late reply. Thank you for sharing. That’s very interesting. Do you have the ecoli requirement for pork in Canada? Ecoli is only a concern when using beef here in the states.

  9. Brad McLeod 1 year ago

    Hi Kyle
    http://www.inspection.gc.ca/food/meat-and-poultry-products/manual-of-procedures/chapter-4/eng/1367622697439/1367622787568?chap=18

    The operator of establishments which use beef as an ingredient in a dry or semi-dry fermented meat sausage;
    establishments which store or handle uncooked beef on site;
    establishments which obtain raw meat from a supplying establishment which stores or handles uncooked beef on site.
    Then you must cook, or test and small operations can’t afford the test or sampling requirements, but between the shelf stable, degree hour. Trichinosis, and e-Coli requirements there is opportunity to create something new which I am having great success at. And I misprinted in above post it was option 2 that I followed.

  10. simon 1 year ago

    do you think I can use SEL DE PRAGUE (in french, I am not sure if pink salt is the english equivalent..) for the sous vide technique? and i understand that it is time effective but in terms of flavor have you notice any better or less qualities?

    can we hang them to dry like other technique or we really need that mold that forms on the outside that i understand means a healthy maturation?,,,

    thx really enjoy this blog that is new to me, i do everything my self for years but i like new and well explained ideas… not always the case on the net….

    • Author
      Kyle Hildebrant 1 year ago

      Simon, I believe Sel de Prague is the translation for Prague Powder. As long as it’s #1, and NOT #2, you are fine. You are looking for nitrITE, not containing nitrATE. As for flavor, they are exact same thing. Just different marketing names. Yes, just hang to dry as you normally would. This only deals with the fermentation step. Cheers.

  11. Ryan 1 year ago

    I’ve never fermented sausage before. The question I have is, if mold won’t grow in a vacuum…why do you need to vacuum it? With my sous vide, I can use a wire rack to hold a sealed bag under water if it has air in it. Water will still circulate around it and keep the thermal equilibrium.

    Just a thought. I have no experience in sausage making, but would like to start soon. Let me know what you think.

    • Author
      Kyle Hildebrant 1 year ago

      Ryan, it’s a novel idea, yet there are a few issues: (1) Air is a very poor conductor of heat and excellent insulator. This is why insulated products often consist of nothing more than a small chamber of air between an interior and exterior surface. Take double-paned windows, for example. The air between the two is what keeps the house insulated. This is the same reason we evacuate all air possible in sous vide (a term that literally translates to “under vacuum”). Because if there is air surrounding the product, the heat will not be easily transferred to it. (2) There is still a finite amount of air (oxygen, etc.) for the mold to use. I don’t have data one how much air is needed for mold to grow, but I’d venture a guess that it’s significantly more than is present inside of a bag.

      • Ryan 1 year ago

        I have less understanding of mold than you, so I have no idea how much air is needed. I do see that it doesn’t take much to grow the bad kind in my refrigerator…sometimes things I wrap up tightly in plastic wrap end up turning blue-green.

        Although not as quick as in a vacuum bag, a thermal equilibrium will be reached in a bag with air. If air moves it loses its insulating properties…make sure the sous vide pump is blowing on the bag, causing agitation. Also, part of the salami will be in contact with the bag…that part will be not far behind a vacuumed bag.

        I don’t know how quickly a salami must reach a temperature to ferment and grow mold, but within 3-4 hours I’d be surprised if the temperature in the bag isn’t the same as the surrounding water. A vacuumed bag will get their much quicker, but I’m not sure it’s a requirement to ferment.

        I think it’s worth experimenting. I’m going to start my first fermented sausage this month and will give it a shot. I’ll some under vacuum and some with air.

        • Author
          Kyle Hildebrant 1 year ago

          To be clear, and can still grow mold post ferment. Maybe it takes bit longer to take hold, but it still grows well.

          • Mark 1 year ago

            So if the mold is mixed in with the starter culture/seasonings then filled/stuffed and sous vide fermented, the mold will activate once salami is removed from the bag to dry (given correct humidity and temp control)? Cheers
            p.s thanks for sharing this site :-)
            Mark

          • Author
            Kyle Hildebrant 1 year ago

            Mark — I have not tried that yet. I would assume so, but I cannot say with certainty. Seems like a logical conclusion.

  12. Ryan 1 year ago

    What do you think about using the heat and humidity of the sous vide to “power” a fermentation chamber above the water bath? Turn a rubbermaid tub upside down, drill a few holes and suspend sausages from rods inside, and put it overtop of the bath. Adjust the temperature and height above the bath to get the it in the sweet spot.

    Cut a “window” in the side of the tub and adhere a thermometer/hygrometer to the inside so you can get a measurement of what’s going on in there. If the tub is clear enough, a window may not be needed to read a digit display.

    I did a test run last night and it was 93 degrees in the tub above a 140 degree water bath. This was right above the bath. If I drop the sous vide temp, it will lower the fermentation chamber temp above…maybe one for one…

    Thoughts?

    • Author
      Kyle Hildebrant 1 year ago

      Several people have done this if you google it. Seems like a very convicted process, given all the other ways one might control heat (like a light bulb on a thermometer).

  13. André Grassi 6 months ago

    Cool, I Will ferment some Hungarian Salami with T-SPX and i will tra this! Will let you know the resulta!

  14. Jeff Campbell 5 months ago

    I just found your site, after starting to ferment a batch myself! I am very interested in your results. I am using F-RM-52, which has Lactobacillus sakei, which should acidify my salami and prevent pathogenic growth. I had a slight concern that the low oxygen conditions would have an effect, but your results show that is not an issue.

    My recipe called for Prague Powder #2. My understanding is that the lowering pH will convert nitrates to nitrites over time, providing protection from Listeria. Thanks again for the information!

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