Posts Tagged ‘pH’

Maximizing Food Flavor by Speeding Up the Maillard Reaction

Monday, June 4th, 2012


Is there a way to speed up the browning of onions? (Photo: Frying onion from Bigstock)

An idea that struck me once was to add baking soda to browning onions. I chopped an onion, melted butter in a frying pan, and added the onions together with a pinch of baking soda. And voilà (as Louis-Camille Maillard himself would have said): the color of the onions changed faster than without the baking soda. The taste of the browned onions was remarkably sweet and caramel-like, and compared with conventionally browned onions, they were softer—almost a little mushy. By the addition of baking soda, I had changed the outcome of an otherwise trivial and everyday chemical reaction, and the result seemed interesting from a gastronomic perspective!

The idea of the baking soda addition was not taken out of the blue but based on (more…)

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…)

Speeding up the Maillard reaction

Friday, September 26th, 2008


Ever thought about how pretzels and salt sticks get their nice brown color?

The products of the Maillard reaction provide tastes, smells and colors that are much desired and lend their charachteristics to a variety of foods. In this post I will focus on the factors that influence how fast the Maillard reaction proceeds. And more specifically I’ll give examples on how the Maillard reaction can be speeded up. This is not about fast food, nor is it about saving time. It’s more about controlling the browning reaction by speeding it up or slowing it down in order to get a desired end result.

The Maillard reaction is, to put it simple, a reaction between an amino acid and a sugar (there’s more on the chemistry at the end of the post). To speed it up you can do one or more of the following:
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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.