Posts Tagged ‘yeast’

No-knead bread

Wednesday, December 22nd, 2010

Update: I’ve written up a short post about no-knead bread in Norwegian – Brød uten å kna – to accompany my appearance in the popular science program Schrödingers katt.

I know – since the NY Times article about Jim Lahey in 2006 the no-knead breads have been all over the internet, newspapers and now even appear in numerous books – this is really old news. But the no-knead breads are really tasty as well, so I hope you’ll forgive me! When I give popular science talks about chemistry in the kitchen the one thing I’m always asked about is the no-knead recipe I show, so I thought it was about time to publish a recipe. Surely, everyone can google it – but regrettably many (if not most?) recipes are given in non-metric, volume based units – even Jim Lahey’s original recipe. And for baking this is really a drawback because the density of flour depends so much on how tight you pack it. Oh yeah, and I will also try to explain why and how the no-knead bread works.
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Baking with hefeweizen yeast

Monday, September 6th, 2010

Wheat beers such as hefeweizen, weissbier and wit are all light beers made from a mix of malted barley and wheat. In southern Germany the typical hefeweizen is fermented with a non-flocculating yeast, and it is not filtered before bottling. This gives the beer a yeasty, bread like flavor accompanied by aromas reminiscent of banan, cloves (we’ve encountered that combo before), coriander and citrus. I’ve just begun to read up on brewing and my first batch of a partial mash hefeweizen is bubling along. As I pitched the liquid hefeweizen yeast into the wort I decided to keep a tiny amount for baking. If hefeweizen beer is reminiscent of bread, why not use the yeast for making bread? In particular I was curious whether some of the aroma top notes characterizing hefeweizen beer would stand out in bread made using the same yeast.
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Sourdough work in progress (part II)

Sunday, October 18th, 2009

sd-bread-1
A sourd dough bread made from a spontaneous starter

After 7 days of feeding my sour dough starter “took off” and was ready for baking. Even with a water bath set to 28 °C it took longer than expected. yeast_kinetics I started off with 100% hydration as this is convenient when you have to feed your starter frequently. Using only whole grain rye flour and water, I fed my starter every 12 hours (I’ve included details of the “feeding schedule” at the end of this post). This time interval is based on the growth cycle of yeast, where the yeast after an exponential growth phase reaches a plateau after 8-12 hours. This is the best time for feeding the starter.

There seems to be a consensus that a wet starter (more…)

Sourdough work in progress (part I)

Thursday, May 21st, 2009

apricot-starter
Attempt to make a sourdough starter using dried apricots, using my immersion circulator for temperature control. I got some bubbling yeast activity, but the final bread dough never rose properly.

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).
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Cherry jams with a twist

Sunday, August 3rd, 2008

We have a small garden with a single tree. It’s a sweet cherry tree and this year must have been one of the best ever. In May it was overthrown with flowers. Last year I made some jam which came out OK, but the drawback with sweet cherries is that their taste doesn’t really compare with that of sour cherries. They’re good to eat, but not as good for cooking and jam as their sour cousins. The summer last year was quite wet and cold which could explain the fad taste, but this year however has been quite hot and the cherries grew darker and sweeter as summer proceeded.

I decided to give cherry jam another try. To improve the flavor even further, I was pondering on adding spices. My mom has previously added cloves and cinnamon to plums when making jam. The first place I looked was under cherries in the book “Culinary artistry”. Among the numerous suggestions for flavor pairings it was black pepper and lemon that caught my attention. Who would have thought? I made a small test batch and was quite pleased by the “bite” provided by pepper so I proceeded with a full batch. I used a pre-mixed gelling sugar from Danisco sugar (which contained sugar, pectin, a preservative and an acid), but you could use whatever pectin you have at hand. Just follow the instructions on the pack (more on the science further down).

Having added pepper and a little of the sugar to get an idea of how it would turn out, it almost felt as if ginger was already there so I added a little more to accentuate that. The other spices were added to round everything off. The pepper taste is quite noticeable if you eat the jam by itself, but on buttered bread or toast it’s really nice. I also suggest that you try it with different semi-soft and hard cheeses such as Emmentaler, Jarlsberg, Prästost, Parmesan or Pecorino. My wife thinks it’s a little to much pepper, but for me it’s just perfect. In German this jam would be known as a Herrenmarmelade (a gentleman’s jam). If you’re not very fond of pepper however it’s a good idea to start with half the amount of pepper.

Spicy cherry jam with pepper
3.7 kg depitted sweet cherries
7.0 g black pepper, ground
0.8 g cloves, ground
0.7 g ginger, ground
1.3 g anis seeds, ground
0.8 g star anis, ground
zest and juice from 1/2 lemon
2.2 kg gelling sugar (with pectin and preservative)

Place enough jars in a cold oven and heat to 120-130 °C to sterilize them (this is more convenient than in boiling water). Depit cherries (conveniently done with a cherry stoner) and cut in four (helps you discover those stones that eluded the cherry stoner). Add spices and bring to boil. Remove any remaining pits that float up to the surface. Pureé with immersion blender (hopefully you will not hear the sound of cherry pits being crushed at this stage). Add gelling sugar. Let boil and skim of foam. Fill the hot jars immediately. And remember – as all chemists know – hot glass looks just like cold glass! Use a canning funnel to avoid spilling jam on the sealing surface of the jars. Leave to cool for 10-15 minutes and then screw on lids. I usually wipe the inside of the lids with 40-60% alcohol and then screw them on tightly before the alcohol has evaporated. There’s more at the end regarding the procedure for closing the jars.

This way of canning is very convenient and the jam will keep for several years in closed jars if kept in a cool, dark and dry place. This is due to the high sugar concentration (sugar binds water, and unless water is available, molds won’t grow), the low pH and – if added – the presence of preservatives. A more tedious way is to sterilize the jars after filling by boiling in water. This is no doubt the best way to sterilize the jars, but for jams with a high sugar content and a low pH it’s a little overkill. The National Center for Home Food Preservation in the US has more information about this (but notice that there are different traditions – I wonder if there is a divide between Europe and North America?). There are also many books about this and good place to start would be the “Ball Blue Book of Preserving”, better known as BBB among home canners. If you chose this method you should probably use a little more pectin as the additional heating at low pH will degrade some of the pectin making the jam more runny.

Using black pepper in a jam worked really well so I googled this and found Clotilde’s recipe for a strawberry jam with pepper and peppermint. She got it from Christine Ferber, author of “Mes confitures: The Jams and Jellies of Christine Ferber” which has recipes organized according to season. As mint was also mentioned as a good flavor pairing for cherries in “Culinary artistry” I thought I’d give pepper and peppermint a try.

Cherry jam with pepper and peppermint
2.2 kg depitted sweet cherries
1.3 kg sugar
2.4 g fresh peppermint leaves
2.8 g black pepper, ground
zest and juice of 1/2 lemon
1 pack of Certo fruit pectin*

Depit cherries and cut in four. Add pepper and peppermint and bring to boil. Remove any remaining pits that float up to the surface. Pureé with immersion blender. Add pectin and stir until dissolved. Add sugar. Let boil and skim off foam. Sterilize and fill jars as in the previous recipe.

[ * The Certo pack weighs 70 g and contains sugar (for easier dispersion of the pectin), citrus pectin, citric acid to get the right pH for gelling and a preservative (ascorbic acid). ]

This jam was dominated by peppermint and the pepper could barely be noticed. I found it very refreshing and there is a surprise element as the red color does not suggest the presence of peppermint. Apart from the obvious use as a bread spread, I can imagine that this jam would be very nice with roasted meat, especially lamb, reindeer, elk and perhaps also wild game.

Having experimented with different spices and peppermint, my wife asked me to also make a batch of plain cherry jam which I happily did. But next year I would like to try making cherry jam with red wine!

As you can imagine, I couldn’t do all this without offering the chemistry behind some thoughts. Pectin chemistry is quite complicated though and there are several types available (low methoxyl, high methoxyl and amidated – so far I’ve only included the two first in “Texture – A hydrocolloid recipe collection”). Commercial packs of pectin for home use do normally not specify which type of pectin they contain, but I assume that it is the high methoxyl which gels in the presence of sugar and at low pH (as opposed to the low methoxyl which requires calcium ions to gel). The easiest is probably to follow the instructions that come with the pack you chose. Always add pectin before you add sugar (unless you premix them). The reason for this is that the gelling of high methoxyl pectins is promoted by sugar. If you add sugar before pectin, it will be very diffult to get the pectin properly dispersed and dissolved (it can be done with an immersion blender though – I’ve tried that once). Ready to use pectin is often pre-mixed with an acid to get the pH below 3.5 which promotes gelling. Citric acid is often used, and plain lemon juice will also do the job. Lowering the pH is especially important when using ripe or over ripe fruit as these can be less acidic and also contain less pectin if we are talking about pectin containing fruit. After the pectin and sugar have been added, the jam shouldn’t boil for more than a couple of minutes as pectin is not very heat stable.

There are also a couple of claims found in jam recipes which I have been wondering about:

Skimming: Almost all recipes I have seen for jams call for rapid skimming of the foam which formes when the jam mixture boils. One explanation I’ve seen is that this is done to prevent growth of mold, as these apparently grow more easily in the foam. There are certainly airborn molds, but the bubbles in the foam come from the jam as it boils, so it’s been very hot and presumably sterilized. So I’m simply wondering if the whole skimming is about esthetics – which is is still a good enough reason to me (but then I wish the recipes could state that!).

Turning jars upside-down: One thing that has puzzled me for a time is why recipes recommend that the jars should be turned upside-down. I’ve googled and checked several books and have come up with a couple of explanations (but most recipes only state that it should or shouldn’t (!) be done, without giving any reason). The fun thing is that the suggested time for how long the jars should remain turned upside-down varies from 2 minutes to several hours when the jam is cool and has set.

  • One site claims it is done to prevent larger pieces of fruit from settling to the bottom. This does make sense, and in that case there is no reason to do it if the fruit has been puréed.
  • A blogpost commenter suggests that turning the jars upside-down for 5 minutes makes sure the inside of the lid gets sterilized too. The temperature of the jam at this time is probably somewhere around 95 °C, so it does seem reasonable that it might kill some molds residing on the lid. I’d give this a thumbs up. Any microbiologist who could confirm this?
  • Personally I have speculated whether turning the jars upside-down would allow water (or jam to be precise) to be drawn into the seal by capillary action and that this helps to make a perfect seal, but several sites emphasize that this should not be done to prevent the seal from being broken (these sites assume that a canner has been used – i.e. sterilizing the filled jars with lids in boiling water for 5 to 10 min). I’m not sure, but I wonder if there is a difference here between screw caps and glass lids with rubber bands?
  • A last reason to turn jars upside down would be to prevent the water evaporating from the hot jam to condensate on the lid. If the jars are left to cool upside-down for 10-15 minutes, but turned back before the jam sets this will prevent water to condense on the lid and drip back to the surface of the jam. This water could potentially mean better conditions for growth of molds. This theory is also supported by the suggestion found in old cookbooks where the jars are left to cool completely without lids to let the surface dry and form a skin, and then covered with a filter paper dipped in alcohol before tying them up with pergament paper and string.

The conclusion so far regarding turning the jars upside-down can be summed up as follows. You should chose of the three methods:

  • Cover with lid immediately and turn upside-down until cool enough to handle (~40-50 °C). Then return to upright position. This will prevent condensation of water on the lid, it might help create a better seal and it could possibly knock out some molds on the lid. The jam however will most likely not have set yet.
  • As above, with the only difference that you leave the jars upside-down until cool and set. This means that the air pocket will not be below the lid but at the bottom of the glass when turned back to the upright position.
  • Allow the jam too cool without lids until a skin has formed and the jars are cool enough to handle. This prevents condensation of water on the lid. Wipe the inside of the lids with the highest percentage alcohol available (but do NOT use denatured alcohol!) – typically it would be 40% or 60% – and screw on the lid before the alcohol evaporates. The skin formed will be less suceptible to growth of mold because there is less water present and because of the presence of alcohol.