Friday, May 14, 2010

Food Science Friday and Seared Yellowfin Tuna

This week's Food Science Friday paper:
'Effect of Debraching & Heat Treatments on Formation & Functional Properties of Resistant Starch from High-Amylose Corn Starches' - By Serpil Ozturk et al., European Food Research & Technology, 2009 229:115-125

This was one of those kinda sleepy reads for the non-science enthusiast. Me, I found it somewhat stimulating, but I won't bore you with the details. Instead, I think I'll talk about High-Amylose Corn Starches.

We've all heard of starches, and most of us use them in our everyday cooking lives... natural starches are found in tons of vegetables and fruits - potatoes and corn being the big ones here.

But with so many different starches out there, what's the difference? We won't go into the different varieties, but just High-Amylose corn starch, which is used in a plethora of settings, manufacturing of textiles, gum candies, cosmetic products, pharmaceuticals, biodegradable plastic products, and used as an additive in food products to increase dietary fiber and lower the rate of energy release.

Most scientists and food industries are highly interested in this type of starch. Why? Well, it contains a high rate of RS, or Resistant Starch. Resistant starches are less susceptible to digestion than regular starches and this is major because it helps lower our Glycemic Index. A lowered glycemic index helps promote long term health and reduces risk of heart disease and diabetes. This is also key to sustainable weight loss.

There are 4 different types of RS:
  1. RS1 - physically inaccessible starch locked within cell walls
  2. RS2 - native granular starch
  3. RS3 - retrograded or crystalline starch
  4. RS4 - chemically modified starch
During food processing, RS1 and RS2 are both destroyed due to heat and moisture. However, RS3 is possibly formed, but not always.

So basically, what this study tried to accomplish, is to find a way to produce more RS3 during the food processing. Crystalline structures take into consideration numerous factors and one of those factors is debranching. The high degree of debranching, the more opportunity amylose chains would be able to align and aggregate to form perfectly crystalline structures - leading to more RS3. In order to accomplish the debranching, they used a debranching enzyme - Pullulanase, which is used more often in starch conversion processes.

The study concluded by saying that the debranching treatments, indeed, increased the RS3 levels and improved functional properties of amylose corn starches. The results are suitable for use in food products - most of which require high water binding capacity, high cold viscosity, or good emulsion properties.

What do I take from this study? High-Amylose corn starches are good for you. They help lower your glycemic index and promote good health. So the next time I'm buying a product, I may have to look at the ingredients list and see if high-amylose corn starch is listed.

Your comments? Concerns? Is this blasphemy? I want to hear it!

Here's a simple and healthy tuna recipe:

Adapted from Now Eat This! - Seared Tuna w/ Green Beans, Lemon, & Wasabi

2 3 oz. sushi-grade yellowfin tuna steaks
salt and pepper, to taste
1 tablespoon olive oil
12 oz. haricots verts, trimmed
juice and zest from 1 lime
1 garlic clove, minced
1 tablespoon wasabi paste
4 scallions, sliced thin
black sesame seeds, for garnish

Bring a large pot of salted water to a boil.

Heat olive oil in a large skillet under medium high heat. Season tuna with salt and pepper. Add to skillet and cook for 2-3 minutes per side. If you want a nice medium rare, I'd go a little under 2 minutes. As you can see from the picture above, I went a little over and got a small margin of rarity. Let tuna rest on cutting board for 5 minutes.

Meanwhile, add the haricots verts to the boiling water and cook until tender, about 3-5 minutes. Drain.

In a small bowl, mix together the lime juice, lime zest, garlic, and wasabi. You may have to add a little water also if there's not enough liquid. Add mixture to the haricot verts, along with the scallions.

Thinly slice tuna and serve with haricot verts. Top with black sesame seeds!

This was pretty refreshing. Next time, I think I'll do it a little rarer, but all in all, a great dish! Enjoy!

1 comment:

  1. I love tuna...and seeing your plate makes me want to pick some up for tonight. I love your food science fridays...they are so informative! Thank you for sharing!