Food Composition and Taste

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Potatoes

Potatoes are a common food that many people eat on a regular basis. From French fries to potato chips or even potato salads, this delicious food is a popular dish worldwide. However, most of the times, the nutrition contribution of this delectable good is overlooked. Yes, potatoes can be very delicious, but what makes them more special is what they’re made of.

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Some people fear that the potato is full of empty starch calories which tend some people to avoid eating them. But don’t worry! Potatoes contain a generous amount of fiber, vitamin C, several B-group vitamins, and potassium, along with carbohydrates, the primary source of energy for the body. And when baked or boiled, they are virtually a fat-free food.

Below, you can take a look at the different nutrient values of a potato based on its preparation.

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Preparation methods are able to change the chemical and nutrient contents of a potato because of things like temperature and cooking time. For example, water-soluble vitamins and minerals such as B vitamins, vitamin C, and potassium leech out from the potatoes when boiled in water. However, if you boil a potato with its skin on, it greatly reduces the loss of the nutrients.

In addition to the preparation styles, the chemical content and nutritional value of a potato can also change depending on how it is stored and how long it is stored. For example at temperatures around 40 degrees Fahrenheit, enzymes break potato starches down into simpler sugar molecules, which result in a sweeter tasting potato.

In the end, potatoes are a good food to eat because it provides lots of energy for the body with carbohydrates (chemicals made of carbon, hydrogen and oxygen).  In addition to this, it is a relatively quick source of energy as well. This is due to the fact that the complexity of the molecule determines the carbohydrate’s function.  Potato starch is slightly more complex than sugar (the smallest and simplest carbohydrate which provides quick energy) but still simple enough that it provides the same function.  Lastly, a good thing to keep in mind is that an advantage of obtaining carbohydrates from potatoes is that you will be getting a considerable amount of micronutrients as well. So the next time you eat a potato, don’t feel guilty, but enjoy every bit of it.

 

 

Author: Jennifer Lee

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Sulfur Dioxide in your Food?

The process of food preservation can be dated back about 5000 years ago in ancient Mesopotamia. The process of food preservation can be found in the history of many civilizations for it is an essential tool for successful population growth. Preservation usually involves the means of preventing the growth of bacteria, fungi, and other microorganisms. Traditional food preservation includes drying, refrigeration, freezing, salting, curing, sugar, smoking, pickling, canning and bottling, and etc. Although the processes described above indeed contain elements of chemistry, there are a lot more chemistry involved in the preservation of food today, since chemical additives are now being added for stronger and more prolonged effects.

Chemical preservatives are essential for modern day food industries and human health concerns. Chemical preservatives are not meant to fully substitute processes such as commercial sterilization, which annihilates all enzymatic and bacterial activity. Therefore, chemicals are more effective when used to slow spoiling and maintain the population of microorganisms. Chemical preservatives can be categorized into three general types: antimicrobials; antioxidants; anti-enzymatic. Antimicrobials prevent the development of bacteria, yeasts or molds on food. Antioxidants slow air oxidization of fats and lipids, which eventually can lead to rancidity. Finally anti-enzymatic inhibits the natural ripening and enzymatic processes that would naturally occur after harvest.

One great example of a chemical additive that serves all three functions is Sulfur dioxide. Sulfur dioxide or SO2 (figure 1) can be found in many household items such as sundried tomatoes, dried fruits, vinegar, juice, and syrup. Sulfites are also commonly found in wine preparation to prolong the life of fruit juice, which will allow the process of fermentation to carry-on for a greater amount of time. According to Hassan Gourama, an associate professor of food science at Pennsylvania State University, sulfites are able to react with the energy currency of the cell, adenosine triphosphate to inhibit metabolic pathways. By blocking cellular transport systems within the cells of the food, Sulfur dioxide greatly prolong the enzymatic processes of the cells, and minimalize the development of bacterial colonies.

Fig. 1 Molecular structure of SO2

From left to right, the difference between using commercial food preservatives, Sulfur Dioxide, and just letting it dry…

 

Author: David Zhang


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A Cup of Coffee

The luring smell of coffee can drag sleepers from beds and pedestrians into cafés, but this seemingly everyday beverage is actually very chemically complex. The myriad of compounds that affect taste, smell, and texture have been researched greatly in order to produce the extremely popular coffee that so many people wake up to. Food scientists must study the reactions that occur in coffee beans and in the beverage itself, starting from the roasting of the beans and ending with the final concoction.

A thousand volatile compounds have been found in coffee, but only a few dozen were shown to contribute to the smell. They include β-damascenone (which has an aroma like cooked apples), 2-furfurylthiol (sulfury, roasty), 2-isobutyl-3-methoxypyrazine (earthy), guaiacol (spicy), 2,3-butanedione (buttery), and 4-hydroxy-2,5-dimethyl-3(2H)-furanone (caramel-like). These chemicals react in a multitude of chemical reactions, including the Maillard reaction, caramelization, polyphenol degradation, polymerization of carbohydrates, and pyrolysis. The important thing to note here is that these compounds are necessarily volatile so that they can easily evaporate to quickly deliver the attractive aroma.

During roasting of the beans, the added heat input causes the decomposition of many compounds into more reactive subunits. Many of these contribute to the somewhat bitter taste of coffee. The aroma molecules in the beans are susceptible to degradation when exposed to heat, so fresh coffee that is heated for too long can have a noticeably different smell and taste only minutes after initial preparation. Some of the flavoring compounds are shown in the following diagram:

In expresso coffee, there is usually a reddish-brown froth on the surface called crema. These tiny gas bubbles are encased in thin films, and they keep in much of the flavor and aroma. These important substances are actually dispersed in emulsions, a type of solution composition, of tiny oil droplets.

The following diagram displays the optimal extraction time of expresso that will lead to the most aromatic coffee. Happy coffee making!

coffee

Author: Jonathan Yu


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Ever tried Coconut Milk?

In modern Western civilizations, almost everyone drinks dairy milk their entire life after possibly relying on their mother’s milk during infancy. Surprisingly, this is actually strange in the rest of the world; coconut milk is a very popular food ingredient in Southeast Asia, especially in Thailand, Malaysia, Indonesia, Singapore, and the Philippines. In China and Taiwan, sweetened coconut milk is common drink during the spring and summer. In this post, we’ll go over some different to things you should know about coconut milk.

Fresh coconut milk derived from the meat.

First, let’s discuss coconut milk, since it is much less well-known than is dairy milk. Coconut milk is derived from the meat of coconuts, and its color and rich taste are the results of a high oil content. The meat is soaked in warm water and then squeezed through a cheese cloth to extract what is known as thin coconut milk. In addition, coconut milk contains a very wide range of minerals and vitamins, and is also a good source of protein. You can look at a more detailed nutrition breakdown in the following table:

Nutritional value per 100 g
Carbohydrates 2.81 g
Fat 21.33 g
-saturated 18.915 g
-mononunsaturated 0.907 g
-polyunsaturated 0.233 g
Protein 2.02 g
Water 72.88 g
Vitamin C 1 mg (1%)
Calcium 18 mg (2%)
Iron 3.30 mg (25%)
Magnesium 46 mg (13%)
Phosphorus 96 mg (14%)
Potassium 220 mg (5%)
Sodium 13 mg (1%)
Zinc 0.56 mg (6%

Even better, coconut milk can be an alternative for people with lactose intolerance because, unlike dairy milk, coconut milk does not contain lactose. Furthermore, it is unique in that it contains lauric acid, which is anti-microbial, anti-fungal, and anti-protozoal. Therefore, drinking coconut  milk can be another everyday way to protect against infections and viruses. Lastly, coconut milk has many antioxidant properties, which also means that it takes longer to go bad.

While both dairy milk and coconut milk are high in saturated fats, there is a key difference in this comparison. Coconut milk mostly contains medium-chained fatty acids, which are easier for the body to metabolize quickly. Dairy milk, on the other hand, contains a lot of long-chained fatty acids, which are more difficult for the body to break down.

By Jonathan Yu


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Pineapple Jello

At the supermarket, you can find all sorts of delicious Jell-O and even ones with bits of fruit in them. Jell-O is simply a brand name for gelatin, so we’ll try to refer to it as gelatin from now on. The chemical structure of gelatin is basically a mixture of peptides, or short polymers of amino acids, and proteins. Gelatin is a processed version of the protein collagen, which is found in the hooves, bones, and connective tissue of cows, horses, and pigs. The 3-D protein mesh that composes gelatin is fairly organized, and the holes of the mesh are filled with water. The result is a “jelly”-like substance, or something that is soft enough to cut yet rigid enough to hold its shape.

For desert, you might happen to want to eat a gelatin dessert with some fresh fruit. This certainly sounds delicious, but be careful about what fruit(s) you use! If you don’t want your gelatin dessert to dissolve into a puddle of colored water, don’t use pineapples, mango, or kiwi. All of these fruit contain the enzyme bromelain, which is a member of a special class of proteins called proteases. These proteins essentially eat through other proteins. Because the structure of gelatin is a protein mesh, mixing gelatin and bromelain leaves you with a soupy mess instead of an enjoyable treat.

You might even see this warning on Jell-O packets, such as the one below:

Fresh pineapples will certainly have bromelain proteins to break down the proteins in gelatin. Why not frozen ones though? Fresh frozen pineapples never lost their proteolytic abilities; the bromelain was still active, just frozen away temporarily. Canned pineapples are good though! Why? Because in their manufacturing preparation, the enzymes were denatured in order to enhance preservation. With these tips in mind, have fun making a successful and delicious jello!

Enjoy your dessert! (:

Author: Jonathan Yu


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Soft-serve or Hard-serve Ice cream?

Have you ever wondered what the difference is between soft-serve and hard-serve ice cream (other than the obvious soft vs hard)? It seems as if outdoor ice cream stands only sell soft-serve ice cream, while supermarkets and ice cream shops tend to sell hard-serve ice cream. And if both are ice cream, why is one soft enough to lick with your tongue while the other is hard enough to require metal ice cream scoopers?

Both choices are delicious, so what’s the difference?

Ice cream can be categorized as different types of colloids. It is an emulsion, which is when both the dispersed substance and the dispersing medium is liquid. Molecules of fat are suspended in a water-sugar-ice structure. Hard-serve ice cream is generally more of an emulsion than is soft-serve ice cream because it has many more dissolved substances. For example, hard-serve ice cream has 10 to 18% fat content while soft-serve only has 3 to 6%. It is also a foam, which is when the dispersed substance is gas while the dispersing medium is liquid. The most important foam property of ice cream is the air content. Soft-serve ice cream is much lighter and softer than hard-serve ice cream because its air content is significantly higher.

Soft-serve ice cream is much more convenient when you’re on-the-go since it melts very fast, due to the high air content, so that you can eat it quickly. Hard-serve ice cream, on the other hand, can hold those small bits of dried fruit or chocolate to make this more expensive option even tastier! There’s no clear winner on which to choose, so we’ll leave it up to you depending on the occasion (:

Author: Jonathan Yu


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Well-done? Medium rare? Rare?

Eating steak at a high-end restaurant isn’t something many people do on a regular basis, so when you do get the opportunity, you should be ready. In this post, we’ll go over the differences between the levels that the meat can be cooked: from very rare to medium rare, to well done.

We’ll start off with a table that shows the basics of each level:

Term (French) Description Temperature range
Extra-rare or Blue (bleu) very red and cold 46–49 °C 115–120 °F
Rare (saignant) cold red center; soft 52–55 °C 125–130 °F
Medium rare (à point) warm red center; firmer 55–60 °C 130–140 °F
Medium (demi-anglais) pink and firm 60–65 °C 140–150 °F
Medium well (cuit) small amount of pink in the center 65–69 °C 150–155 °F
Well done (bien cuit) gray-brown throughout; firm 71–100 °C 160–212 °F

Chemical composition:

Meat is generally made up of proteins, fats, carbohydrates, minerals, and water (moisture). On average, three-quarters of meat is water. However, this number can change significantly after cooking; the more the moisture is evaporated off, the harder the meat will become. The rest is mostly protein and fat, while carbohydrates make up only a small percentage. At around 140 °F, fat in the steak begins to dissolve and dissipate. This is crucial because it releases the flavor into the meat.

Meat Texture:

Meat texture is highly dependent on the extent of proteolytic changes, or changes related to breakdown of protein, that occur during cooking. High cooking temperatures, as used for well done steak, can reduce tenderness. Long cooking times with a slightly lower temperature can tenderize meat that contain large amounts of connective tissue by converting them into gelatin. The chemical composition of meat is also extremely important in determining texture; large amounts of fat will make the meat more tender since fat is softer than muscle. The pH of the environment in which the meat is cooked in has also been determined to have a clear relationship with meat texture. High pH values favor proteolysis, helping to break down the muscle fibers in the meat and making it more tender.

Meat Quality:

Meat quality is a subjective topic, but it can assessed objectively in a few ways. For example, tenderness is usually the most desirable. This is reflected in the fact that fillet steak is both the most tender and the most expensive cut of beef. In addition, juiciness can range from dryness to succulence. Dry meat can be the result of reduced “water-holding capacity” as a result of chemical changes due to heating or low  levels of fat. Flavor is usually determined by the water-soluble constituents of the meat, while the odor is usually determined by the fat-soluble, volatile components.

To finish off this post, we’ll present a picture of the different cooking levels of steak to help you decide which one you’ll order:

Author: Jonathan Yu