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Whenever we make butter chicken, or just tandoori chicken, we marinate the meat in yogurt. Even though it is only in the marinade for 30 minutes or so, it makes the meat beautifully soft and tender. If you leave it in the marinade for too long, it can even become overly soft.
For a lot of marinades it doesn’t seem to matter that much for how long you marinade them for. One of the big exceptions there though, in my experience, is the use of those yogurt marinades. A yogurt marinade seems to actually transform your meat quite well. So, why is it that yogurt marinades work so well?
Composition of yogurt
As you will have learned from our post on making your own yogurt, yogurt is made from just yogurt cultures (which are bacteria) and milk. Those are the only two ingredients. The bacteria in the culture live and grow in the milk. During their growth they use lactose (the sugar in milk) as a fual and along the way transform is into lactic acid.
The lactic acid increases the acidity of the milk, making the yogurt sour. Because of the lower pH-value, the proteins in the milk will start behaving different (similar to when you make cheese) and the yogurt thickens. The yogurt forms a gel.
This gel though isn’t very stable. If you dilute it only slightly you will see that the structure breaks up quite quickly. This is because you haven’t really added a thickener, you have just had the milk do the work itself.
When you use yogurt in a marinade or a dip you will notice this as well, all of a sudden it’s a lot more watery.
pH-value of yogurt
Yogurt is acidic, but it is moderately acidic only. The pH-value (a measure for the acidity) of yogurt tends to be around 4.2-4.6, where 1 is very acidic and 7 is neutral. For comparison, the pH of lemon juice and vinegar tends to go down as low as 2, quite a lot more acidic.
Greek style yogurt
There are a lot of yogurts that are a lot thicker than a naturally gelled yogurt. This can be due to various reasons, the first is the addition of thickeners (eg. starches or gums) to the yogurt. A second way though is to straining the yogurt. By getting rid of more of the water of the yogurt the gel can thicken even more.
How meat turns softer
There are roughly two ways to tenderize meat: chemical (e.g. using acid or enzymes) or mechanical (e.g. with machines or by using a meat hammer). Most of the research you can find has been done on the mechanical method it seems. That is pretty common for food science research. The research tends to focus on the food manufacturer’s challenges as opposed to those of a chef.
We won’t look into mechanical tenderization, we’ll focus on the chemical method since that is how yogurt tends to do its job. It is worthwhile to say that this is one of those other food phenomena that no-one seems to completely understand! There’s still so much to learn in the world of food science.
The role of acid
Acids can change the properties of a meat quite drastically. Remember, meat is a muscle from an animal so it will respond to its environment. Lowering the pH-value of meat will help the meat to absorb more moisture and it can also help to convert some of the collagen in the meat into gelatin. This is especially important for stews where the meat contains a lot of connective tissue and collagen that needs to be broken down slowly.
As we read for ceviche, where acidity can be used to actually ‘cook’ fish, acidity can really transform the proteins and therefore texture of a meat. Leaving a meat in a very acidic for a long period of time can actually make it less tender.
Power of enzymes
The major component of meat, after water, is protein. Meat contains a very high content of proteins. You can tenderize the meat by breaking down some of these proteins.
Such a chemical reaction can be catalyzed by enzymes. Enzymes don’t take part in the chemical reaction, but they help them occur more easily. A specific group of enzymes, proteases, is especially good in catalyzing the breakdown of proteins. For meat tenderization two naturally occurring enzymes are commonly used: bromelain (comes from pineapples!) and papain (from the papaya).
Enzymes are also very good in tenderizing meat, but they can be overused more easily, turning the whole meat into mush.
How yogurt tenderizes meat
So why does yogurt work? There are several explanations available, not all of which researchers are clear on how they work and what their impact is.
The one thing most people agree on is that the fact that yogurt is acidic, makes it a good ingredient of a marinade. Since yogurt is not that acidic it doesn’t over-tenderize meat as easily (although it definitely can, I speak from personal experience, I prefer not leaving yogurt marinated chicken in the fridge for more than a couple of hours).
Other theories also mention the fact that heating yogurt will result in different flavours. Once you heat the marinated meat the proteins in the yogurt will react. I wasn’t able to find a good explanation of this but I can well understand that adding yogurt will impact flavour, as does the addition of most other ingredients.
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The last interesting theory I read, but for which again I couldn’t find a lot of proof, is the role of calcium. Yogurt, just like milk, contains reasonable amounts of calcium. Some claim that this will help some enzymes tenderize the meat, but proper proof is hard to find here.
Now that you know how yogurt marinades (might) work, it’s time to bring it to life. This tandoori chicken uses a yogurt marinade for a great soft texture (and plenty flavour).
Ashie, I.N.A, Sorensen, T.L., Nielsen, P.M., Effects of Papain and a Microbial Enzyme on Meat Proteins and Beef Tenderness, 2006, Journal of food science, link
Bon appetit, Yogurt marinating is the best marinating, 2018, link
Epicurious, For a Better Marinade, the Secret’s in Your Breakfast Bowl, 2015,
Goli, T., et. al., Influence of sodium chloride and pH during acidic marination on water retention and mechanical properties of turkey breast meat, 2014, Meat science
the Kitchn, Make Better Chicken in 15 Minutes, Thanks to Greek Yogurt, 2017, link
PBS, Learn three techniques for tenderizing meat, 2012, link
Popular science, Yogurt marinades make meat perfectly tender—here’s why, 2018, link
Science learning hub, Fruit tenderizes meat, link