RL 140609 Lecture 11: Proteins Part II [continued...]

Remembered 2 weeks ago when we entered the topic proteins, we were talking about wheat gluten (plant proteins). This week, we wrapped up the lecture with animal proteins, milk and egg proteins. Then I just realised that Dr. Chong left us a couple of questions unanswered, so I'm making use of this post to answer the questions as a form of revision. =)

RL 140609 Lecture 10: Clearing my debt....

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1. What are the wheat flour alternatives? Which are gluten-free, which are non gluten-free?

How well do you know your flour?

As I mentioned before,  gluten is a big big concern for celiac disease patients. So while they can't exposed to a tiny bit of gluten, they still want to enjoy wheat flour products such as cakes, breads, noodles, and pastries. In these cases, wheat flour have to be substituted by other kinds of flour. These substitutes can be totally free of glutenin and/or gliadin, which makes it totally gluten free, while others have a different ratio compared to wheat. All these could affect texture of a food, lesser in cakes and pastries, but more in breads and noodles. Functions and effects aside, what are the examples of gluten-free flour and non gluten-free flour?

Generally, grains are the items to watch out for gluten, while other parts of a plant such as tubers (potatoes), roots (tapioca) and legumes (soybeans, mung beans, etc) are gluten-free.

Most grains, including corn, buckwheat, and rice are totally 'gluten-free', which leaves a minority of grains to be non gluten-free (eg. wheat, barley and rye). Hence, celiac disease patients should totally avoid those grains. Oat is a special case where oats itself is gluten-free, but cross-pollination between wheat and oats are so common that some oats became capable of producing glutenin and gliadin, making it non gluten-free. Same goes to soybeans. For a more extensive explanation and examples, you could refer here. 

2. Whipping cream vs light cream vs half-and-half vs heavy cream?

Difference is in the fat content!

Half-and-half is the lightest of all, containing 12% fat, followed by light cream, 20%, then whipping cream 35%, and lastly heavy cream 38%. The higher the fat content, the creamier is it, and the more stable is also the foam formed. Hence, baking recipes (requires foaming) often call for heavy cream, while lighter cream is sufficient for cooking/beverage recipes (which does not requires foaming). 

More reading: here and here. 

3. Why does mustard has emulsifying properties?

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Mustard seeds has equal amount of fats, carbohydrates and proteins, and contains mucilage, a kind of plant glycoprotein. Mucilage is a polar molecule and is also able to interact with both water and fats, giving it the ability to form suspension. More details here.

4. Factors affecting coagulation of egg proteins...

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Promoting factors:

1. Salt: Salt forms ions in water and interact with ionic functional groups. This increases the ionic interaction between the polypeptide chain (salt bridge/attraction force) bringing them closer together, hence increasing the tendency of forming disulphide bonds.
2. Number of eggs: Increased number of eggs increased the concentration of egg protein, hence increased interactions, and thus easier to form dispulphide bridge. 
3. Vinegar/lemon juice: decrease pH, bringing the proteins towards the isoelectric point, causing the proteins to coagulate.

Obstructing factors:

Sugar: Sugar can react with the polar side chains of proteins by forming hydrogen bonds, making the side chains unavailable to react with another protein. As a result, the association of protein molecules is delayed.

5. Duck egg vs chicken egg...

It's said that duck eggs are more flavourful than chicken egg.. what say you?

Duck egg and chicken egg, what makes them different? Basically, the genetic composition would be different, since it's from two different species. Other than that, the chemical composition of the two are similar. The yolk contains majority fats, with duck having more than chicken, while the whites are just water and albumin. But there're still people who prefers duck egg more than chicken egg, cause they said it's richer and 'saltier'. Well, the saltiness might be because of the higher sodium content in duck egg, but I think it's basically just a myth since duck eggs are always preserved with salt. However, I can't deny that duck egg is much flavourful since it contains more fat, which could give the richer and creamier sensation. So, I guess it shouldn't be a big problem to substitute chicken egg with duck egg in a recipe. It might have a shorter texture and tastes richer and more moist. Bear in mind duck eggs are bigger than chicken eggs, it might not be advisable to substitute one-to-one. =)

That's about all for this week's reflective learning...

So long till the next post!
Dong

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RL140526 Lecture 9: Proteins

Staring at the computer screen for a solid 20 minutes, typing words and deleting it. Okay, I have a confession to make, I didn't know what to write for this week's reflective, plus I almost forgot to write this too.. *sheepishly hiding myself away* Yeah, not sure for what reason, this week, I wasn't really in a focus mode, I found it hard to concentrate in class. It's not about the tight schedule (in fact, this is the free-est I've had in this semester) , or even about the uncompleted assignments other classmates are worrying about (I've completed mine way looong before the holiday ends). Anyway, there's nothing to dwell into, and I shall move on and get going...

RL140526 Lecture 9: Gluten, nothing to be afraid of...

We started a new chapter on proteins. Dr. Chong forgot to upload the notes, and I didn't remind her too.. my bad.. Felt kinda uneasy as I didn't have a hard copy to refer to when I needed to jot down some notes. But I think this is a better way for me, as there will be less distractions, so I'll pay full attention during the class, and I could remember better too. So now, it's time to test my memory and understanding, let's recap on what we've learnt: *I've not printed the set of notes yet so I've nothing to refer to

The focus of the lecture was on gluten: What makes wheat flour unique and different from other flour is gluten? It is the protein network formed from the interaction between wheat storage proteins (gliadin & glutenin) and water, when kneading is introduced. As gluten develops, it gives structure and chewiness to the product. In other words, wheat flour technically contains no gluten if it has not been interacting with water AND kneaded. Hah! Smell something fishy? Who knows how would some unethical manufacturers label their normal flour as gluten-free, and get away with it? Awareness, guys! Though I'm at total opposition of this whole "gluten=toxin" mindset (the power of marketing and consumer's ignorance, once again), it still matters for those who are allergic to gluten. 

Gluten free products are getting more popular in Asia, thanks to the influence from the West.

What's the big fuss about gluten anyway? In case you haven't known about the relationship between celiac disease and gluten, you can read it here. Though it can be quite fatal, it's not a prevalent disease in Asia, so why care about that when gluten has so many usage in food, especially when the staple food in Asia very much depends on it? Trust me, a gluten-allergic can't survive in Asia, cause gluten is everywhere...

Even in McDonalds!!! *kay fine, bad example.. their buns already contains gluten, just wanna show something Asian... =X

So, as you can see, gluten is not only important in making bread, as most of us understood. It also plays important roles in all kinds of wheat flour products. Different composition, ratio of gliadin to glutenin, and processing method also affects the performance of flour. Low protein flour are used to make cakes and biscuits, medium protein flour are used to make noodles, pastries, etc, while high protein flour are used to make bread. While the gluten network in breads is formed by kneading, the one in noodles/dumpling wraps are formed upon resting. This gives a difference in the texture, whereby the one bread is more nicely formed, thus, higher elasticity, and the one in noodles are more compact and not as elastic. However, the springiness of noodles can actually be improved by adding lye water. 

Vegetarian meat is also mostly made of gluten. It's even the protein source for vegetarians...

All in all, gluten a very important protein structure in determining the texture of wheat flour products. It needs water and kneading to develop, while the way it forms can be manipulated by different processing methods or additives, or simply using different kind of flour. Gluten is just as common as rice to us. Just stop this whole gluten-paranoia already.. 

Had enough of gluten already? Let's have something gluten-free... *wink*

Google wishes everyone a happy Dragon Boat festival!!! xD

Cheers!

Dong

  

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