Inspired by the Swedish bread blog Pain de Martin which I recently discovered I decided it was time to have a go at sourdough breads! Although one of my favorite types of bread it’s a long time since I gave it a try and even longer since I actually succeeded. Leaving apple peel covered with water for two weeks in a cool place (15 °C) I got a light apple cider which I used to make a starter some years ago. I followed a recipe from the Norwegian artisan bakery Åpent bakeri and it gave a marvelous bread. But since then I’ve tried to repeat this twice without success. No wonder that even Rose Levy Beranbaum in her book “The Bread Bible” writes that she didn’t intend to include a chapter on sourdough at all. There’s no doubt that sourdoughs are tricky, but I was a litte surprised and disappointed that someone who sets of to write a 600+ page book on bread even considered to skip sourdough… Luckily she changed her mind and the introduction has a fascinating nice-to-know fact: 1 g flour contains about 320 lactic acid bacteria and 13000 yeast cells!

I believe one the reasons why sourdoughs seem to live their own lifes sometimes is that they need to be kept in a warm place. My kitchen isn’t that warm so I figured it was time to use my immersion circulator and give sourdough another chance (who says you can only use immersion circulators for sous vide anyway? – I think my next project will be to make yoghurt!). With a thermostated water bath keeping a sourdough starter at constant temperature is as easy as 1-2-3. But surprisingly I haven’t seen any blogposts yet from people using their sous vide water baths for sourdough starters (although some have built their own water baths for this purpose using aquarium equipment).


Fresh apple peel in water. This particular experiment failed – the cider smelled OK, but there was quite a lot of mould on the surface after two weeks so I didn’t dare to proceed …

It was Martin’s post on an apricot starter that triggered my desire for sourdough (but careful – never close your jar with a rubber as shown in his picture!). I got a bag of dried apricots and gave it a try. There was some bubbling and it smelled quite nice, but the bread dough never rose properly. I later found out that in a comment to the first post and a later post on the same topic it was pointed out that the apricots should not be treated with sulfur dioxide or a sulfite (used to conserve the fruit, appears on labels as E220-228 in Europe). That’s very obvious once you think about it, because the sulfur dioxide/sulfite is there to kill microogranisms and increase shelf life. For a sourdough however you want living microorganisms! The solution to this is to use untreated dried apricots. I haven’t been able to find any yet, but I’ll definitely give it a new try once I find some! Other options of course are to use dried or fresh apples, pears, grapes – preferably not treated with pesticides or sulfur dioxide – as the surface of these fruits are host to many yeasts.

A relatively firm rye starter with 150 g water and 200 g whole grain rye flour (left) shows signs of yeast activity after 24h at 28 °C (right).

Having failed with the apricot starter I decided to give a traditional rye sourdough a try, using a recipe from the book “Brød” (=bread) by “Åpent bakeri”. I got a nice bubbling after 1 day, but the starter was pretty dry. As I discarded a portion and fed more flour and water to the starter it seemd as if it died… I (believe) I followed the recipe very accurately (except for the very first day where I opted for a hydration of 75% instead of 60%), but the final dough never rose, so I had to cheat and add bakers yeast in order to actually get the breads baked. Acid production was fine however and the resulting flavor was very delicious and I got the crumb that I desired! However, with all these problems I figured it was time to turn to the scientific litterature and read more on sourdouhs … More on what I found out in a follow up post.

One last thing: Despite my limited experience with sourdoughs I’ve already been a little annoyed by recipes for starters that require one to discard a significant portion of the sourdough every day before feeding the start with more water and flour. One obvious way around would be to start at a much smaller scale so that every feeding can be done without having to waste any sourdough. In fact Kurt Janz already has a post with detailed instructions on a less wasteful sourdough (and he BTW has one of the most comprehensive sites on sourdough I’m aware of including a sourdough calculator). The only reason I could think of why one perhaps would want to use more than a couple grams of flour to start with would be to outnumber any unwanted yeasts or bacteria from the air or the equipment. Is this the case? Are there any other reasons? To circumvent this one would simple have to work very clean and wash all equipment properly.

Since I got my immersion circulator in December I’ve discovered that there are two critical questions that always come up as I hold a piece of meat in my hands, ready to cook it sous vide: At what temperature should I cook this? And for how long? Despite the fact that two books were published on sous vide last fall it is the short yet comprehensive guide “A Practical Guide to Sous Vide Cooking” by Douglas Baldwin that I’ve found most useful to answer these questions. Those who have followed the eGullet thread on sous vide cooking will probably recognize Douglas Baldwin as one of the major contributors alongside Nathan Myhrvold. Out of curiosity and eager to learn more I therefore emailed Douglas and asked if he would be interested in doing an email interview.

ML: From your homepage I see that you are a PhD student in applied mathematics, how did you become interested in sous vide?

DB: I have always loved to cook. Before last January, though, I mainly cooked slow food. That is when I saw sous vide mentioned in one of Harold McGee’s NY Times articles. Wow. Cooking meat at its desired final core temperature is so obvious! As a mathematician, I kicked myself for never asking “if overcooked meat is bad, what temperature should the meat be cooked at?” A question which many mathematician would instantly answer, “just above the temperature you want it to end up at.”

A quick search of the web led me to the massive eGullet thread on sous vide cooking. While the thread contains a treasure-trove of practical information — especially Nathan Myhrvold’s posts — it left me with a lot of unanswered questions. Being an academic, I turned to the scientific literature for answers; as expected, I found many answers and many more questions.

ML: Your excellent sous vide resource, “A Practical Guide to Sous Vide Cooking” has a wealth of information. What drove you to write this article? And have you ever considered publishing it in a peer reviewed journal?

DB: Thank you. I’m very glad to hear you find my guide to be useful.

As a scientist, I am driven by two things: an insatiable curiosity to learn everything I can about a topic and the desire to freely share what I have learned with the world (so others can extend and build on what I have done). After spending hundreds of hours researching sous vide cooking and discovering how much of the information online was incorrect (and potentially dangerous), I felt compelled to write up what I had learned and post it as soon as possible. I am still actively working on my guide, and hope to complete another major revision in February.

I have not submitted my guide to a peer reviewed journal because its intended audience is chefs and foodies. Though I did ask a number of food scientists to review my guide for technical accuracy, and I was recently asked to referee a paper for the Journal of Food Science.

ML: From your viewpoint, what is the biggest advantage of sous vide over conventional cooking?

DB: Control. Precise temperature control gives incredible choice over the doneness and texture of meat, poultry and fish. Tough cuts can be made tender. Tender cuts are the same perfect doneness from edge-to-edge. Fish and light meat are moist and flavorful. Pork and poultry no longer needs to be brined to be juicy (because they can be made safe without being cooked well-done).

ML: Do you think sous vide cooking will ever become so common that the equipment will be available in regular kitchen stores? And if yes – when will that be?

DB: I don’t think sous vide cooking will ever be so common that immersion circulators will be sold next to microwave ovens. But I fully expect them to be as common as smokers in 5–10 years. Like smoking, sous vide cooking requires a little knowledge and planning — an easy request of the average Khymos reader, but a lot to ask of most consumers. This is unfortunate, because I find sous vide cooking to be convenient, energy efficient, and versatile.

ML: What kind of equipment are you using yourself at home for sous vide? And how often do you typically cook sous vide?

DB: I use a Minipack-torre MVS31 chamber vacuum sealer and a PolyScience 7306C immersion circulator for most of my sous vide cooking. I usually attach the immersion circulator to a full-size countertop food warmer with a lexan lid I made — the lid limits evaporative cooling and the food warmer speeds the (initial) heating of the water and limits heat loss from the bottom and sides of the water bath. I also have a couple Iwatani butane blowtorches, a used PolyScience immersion circulator, a couple PID controllers from Auber Instruments, a Ranco ETC temperature controller, a FoodSaver vacuum sealer, and a bunch of thermocouples and meters from ThermoWorks.

I eat food cooked sous vide almost everyday. As a single guy, I batch cook most my meat in single servings pouches, rapidly chill and then freeze them until needed. While this `cook-freeze’ sous vide is very convenient, the freezing and reheating of the meat does causes small, but noticeable, degradation in taste and texture.

ML: Have you compared DIY bagging with zip-lock bags, food saver bags and vacuum chamber packs? I know that liquids are challenging with the food saver, but does the bagging method affect flavor (or even texture)? Does the small amount of oxygen in the DIY version have any effect?

DB: For meat, different bagging methods have little or no effect on flavor and texture. The primary purpose of bagging is to allow the efficient transfer of heat from the water (or steam) to the food (while still keeping the food and water separated). Sealing the food in a bag has the added benefit of preventing evaporative losses of flavor volatiles and moisture. Even when using a chamber vacuum sealer, the majority of bags have high levels of residual oxygen. The main difference between using a zip-lock bag and a chamber vacuum sealer is the extent to which the bags balloon when heated; (when heated over about 65C/150F) both bags will start to balloon because of the vapor pressure of the liquid in the bag, but the zip-lock bag will balloon more because the residual air in the bag will also expand. It is important that the food is kept from floating to the surface of the water to prevent uneven heating.

While meat can easily be cooked in a zip-lock or food saver bag, fruit and vegetable compression requires a chamber vacuum sealer. Moreover, zip-lock and food saver bagged vegetables balloon excessively in the 85C/185F water bath they are (typically) cooked in because it very difficult to remove all the air in the bag.

Liquid in the bag is indeed problematic when using a food saver, but is easily solved by freezing the liquids before bagging. (Although, I might add that freezing often traps air bubbles in the liquid which cause the bag to balloon more than it would have if a chamber vacuum sealer was used.)

ML: What are your favorites cuts of meat for sous vide?

DB: With the faltering global economy in mind, I love showing off sous vide cooking’s ability to transform inexpensive cuts of meat into something amazing. Consider the humble chuck roast, a flavorful cut of beef which is usually relegated to stews and hamburger because of its abundant connective tissue. Vacuum sealing, cooking for 24 hours at 55C/131F, and searing to a beautiful mahogany color transforms this humble cut into something akin to prime-rib! Pork shoulder vacuum sealed with lard and cooked for 24 hours at 68C/155C, torn into bite-sized hunks and fried in a little oil is always a hit at my dinner parties. Even the the lowly chicken breast can be made into something moist and flavorful by pasteurized in a 60C/140F water bath (see my guide for pasteurization times).

ML: Is there any meat that you would prefer not to cook sous vide?

DB: I don’t like some types of fish cooked sous vide. When cooked too slowly, the enzymes in the fish remain active and cause the flesh to become mushy. [This can be mitigated by using a water bath temperature 5--10C/10--20F higher than the desired final core temperature and using a needle temperature probe inserted through closed-cell foam tape to determine when the fish is done heating.] Also, fish which is not extremely fresh will taste too fishy because the flavor volatiles remain sealed in the bag with the fish —this is a particularly irksome problem for me in land-locked Colorado.

ML: Some critics claim that with sous vide, even though you brown the surface, you loose some flavor since temperature is kept so low (I believe this applies especially for pork). Do you share this experience?

DB: It is a very reasonable concern, but can be mitigated by quickly searing the meat before vacuum sealing and cooking. While the initial Maillard reaction occurs noticeably above 150–180C/300–350F, many of the subsequent reactions can occur at the low temperatures used in sous vide cooking. Personally, I feel searing after cooking is sufficient and almost never take the time to pre-sear my meat.

ML: From your experience, what is most difficult to achieve when cooking sous vide?

DB: A great sear without overcooking the meat. While a blowtorch works wonders on beef and (most) pork, it tends to burn poultry. A pan with a little oil over medium heat (so the oil is between 150–180C/300–350F) works fairly well for poultry, but may overcook the meat before the surface is golden brown.

ML: With Keller’s recent book “Under pressure” and your guide (and an extremely long thread at eGullet) being available now: Which areas would you say need further exploration?

DB: Sous vide cooking is still relatively young and there are hundreds of interesting questions yet to be answered! Some of the questions I’m currently interested in are: How long does it take all the soluble collagen to unfold into gelatin at 55–65C/130F–150F? What is the role of enzymes when cooking at low temperatures for long times? Is it better to thaw the meat or cook it from frozen? If cooking from frozen, how long does it take to heat a piece of meat (such as foie gras) stored at -80C/-110F? Which foods can be frozen or refrigerated after cooking (and for how long?) without significantly degrading taste or texture? How and why should fruits and vegetables be cooked sous vide? Why does fish retain so many more of their essential fatty acids when cooked sous vide (compared with conventional cooking methods)? . . .

In addition to the many unanswered questions, there are also many topics which are understood but have yet to be discussed in sufficient detail. For example, many people’s intuition about clamp and chamber vacuum sealers is wrong. The importance of food shape in predicting heating times has not been discussed — spherical and cylindrical foods heat much faster than slab shaped food. The relatively fast onset of warmed-over-flavor after the food is removed from its vacuum pouch is absent. And even how large and powerful the water bath needs to be for a given quantity of food has not been discussed.

Hopefully I, Nathan Myhrvold, or someone else will have the time and resources to answer all these interesting questions.

ML: Thank you very much!

Thomas Keller, known from the French Laundry, Bouchon and per se, has written the book “Under Pressure – Cooking Sous Vide” (the Under Pressure title was also used by NY Times in a 2005 feature article on sous vide). According to the publisher, Keller and his chefs de cuisine have blazed the trail to perfection through years of trial and error and they show the way in this collection of never-before-published recipes from his landmark restaurants.

The book “Sous-Vide Garen im Vakuum” (Sous vide cooking under vacuum) by Viktor Stampfer (known from the Ritz-Carlton in Dubai) has received much less attention, but certainly deserves to mentioned. The title is in German, but do not despair – it seems to be a bilingual edition with German and English text (can anyone confirm this?), but so far it’s only available for preorder from the German Amazon. According to the publisher the book gives an introduction to the equipment used including sealing devices and recommended temperatures for cooking together with numerous recipes.

These are not the first books to appear on sous vide – enthusiasts have probably obtained one or more of the books by Roca, Farber, Ghazala, Leadbetter, Choain/Noël and Calmejane/Barrier – but I’m quite sure that the new books will complement these very nicely, and they will certainly be more available as several of the others have unavailable for some time.

There is however an easier way to make a perfect steak! In restaurants the method has been around since the 70′s and is known under the name sous vide (fr. under vacuum, more info on history of sous vide in this NY Times article). The meat is packed in plastic bags, vacuumed and put into thermostated water baths. This equipment is not (yet?) found in the average kitchen. So here is a simple DIY procedure. You just use a normal plastic bag, leave the meat in the water bath for 30 min (or longer) and then quickly fry both sides to generate the products of the Maillard reaction. You do need a thermometer though to control the temperature of the water bath, preferably one with a dip in probe.

1. Put the meat (I used a rib eye steak for this experiment) in a thick plastic bag. Only put one or two pieces of meat in each plastic bag – this ensures a greater contact surface with the water.

2. Add any spices you like (salt and pepper always works well – for the experiment shown I used curry paste, soy sauce and chili sauce in stead), press (or suck) out the air and close the plastic bag tightly by tying a knot (or use a zip-lock bag). You don’t want any water to enter the bag!

3. Heat a pot of water to the desired temperature (or use hot tap water) and place the plastic bag with meat in the water. Cover with a lid (not shown in the picture) to reduce heat loss. If you use a large pot of water it’s easier to keep the temperature constant. Also, it’s easier to control the temperature with an induction or gas stove top than with an electric plate since there is no additional heating once you turn them off. Regarding the temperature, start with 60 °C (140 F) and experiment from there (or check this table at Wikipedia for doneness temperatures of meat). You should leave the meat in the water for at least 30 minutes – more for a thicker cut. But the good thing is you can leave it for much longer (several hours) provided the temperature does not come above 60 °C (or whatever temperature you decided on). A convenient way to keep the temperature constant for a long time is to put the pan with water into the oven and use the thermostat of the oven.

4. Heat a frying pan, add a fat of you choice, remove meat from plastic bag and brown both sides of the meat. Since you take the meat directly from the water bath it’s already at about 60 °C. Therefore the browning is very fast.

5. A temperature of 60 °C (140 F) gives the meat a pink interior. It’s succulent and juicy. The short frying gives it a nice browned crust and the chewing resistance is perfect. All in all a wonderful combination of taste, aroma, texture and mouth feel!

Note added January 2009:
Since I published this procedure the first time I’ve learnt a lot more about sous vide. The procedure above is a rather crude procedure, but it works. If the meat turns out grey you’ll need to turn the temperature somewhat down. If you’re interested in reading more about sous vide, the best discussion I know of which also includes important safety aspects is Douglas Baldwin’s “A Practical Guide to Sous Vide Cooking”.

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