Beavers and Vanilla

Why flavorings smell and taste the way they do

By Mark Sabini, Justin Yu, and James Lee

Imagine a cave of darkness lined with white pearly stalactites and stalagmites. On the ground is an organic carpet of living red, and there is an uncomfortable dampness in the air. Liquid flows all over the ground, making navigation difficult. Now imagine moving to another location with two doorways, side by side, carrying breezes of air in and out. They both look the same, mirror images of each other. Peering inside, you see what seems to be a grass of some sort, except that it grows all around the surface of the doorway, not just on the ground. You step inside, into a tunnel of blackness, and then whoosh! A strong breeze sucks you in, into oblivion. Now reflect on where you have just been: a human mouth and a human nose. Working together, these organs make up 40% of the five senses, and give flavor to food and aroma to flowers. How exactly do these marvels of nature function?

Taste and Smell

Taste relies on the transformation of chemicals from food (tastants) into nerve signals. The tongue’s mucous membrane is lined with tiny bumps called taste papillae. These little sensors responsible for taste perception consist of taste buds with sensory cells. The sensory cells form a little “cup” (see picture), which contains taste hairs. The proteins on the surface of the taste bud bind the chemicals from the food to the sensory cells for tasting. Then, the sensory cells transform the chemical signals into electrical signals that travel along nerves to the brain. Contrary to popular beliefall parts of the tongue are equally sensitive to the five tastes, sweetness, sourness, umami, bitterness, and saltiness, except the back of the tongue. The cells there are more sensitive to bitterness, most likely as a natural defense against swallowing bitter plants containing poisons.

Figure 1: Diagram of a typical taste bud
Figure 2: Video about taste

Smell works slightly differently from taste, but still employs the same basic principle: the transformation of chemical signals to electrical signals. At the top of every person’s nasal passage is a patch of neurons that is exposed to air. The neurons have small hairlike projections called cilia, to which volatile food chemicals (odorants) bind and cause transmission of electrical signals along the neurons to the olfactory bulbs on the underside of the frontal lobe. As a result of this mechanism, only volatile compounds will have smells. While they might seem unrelated, taste and smell work hand in hand. The data from the two senses is merged in the insula, a part of the brain, to put together what we know as flavor. This is why you cannot sense flavor when your nose is blocked – the smell component of flavor is missing.

Figure 3: Diagram of the Olfactory System. The patch of neurons located at the top of the nose feed into the olfactory bulb which sends signals directly to the brain.

The Chemistry of Flavorings

Esters are a class of organic compounds that have distinctive tastes and smells, and are used widely in the food industry.The ester octyl acetate, for example, is responsible for the characteristic citrus smell and taste of oranges. Esters can be prepared through Fischer-Speier esterification, in which a carboxylic acid and alcohol are reacted in the presence of an acid catalyst. The strong smell of esters is attributed to their volatility and the functional groups attached to the ester group. A list of commonly-used esters and their tastes and smells is shown below.

Figure 4: Fischer Esterification Figure 5: Chemical structures of some common esters

Other flavoring ingredients come from more natural sources, albeit quite strange ones. One example is castoreum, a brown, slimy secretion from the castor sacs located near a beaver’s anal glands. It has a vanilla taste after some processing, as it is originally mixed in with beaver urine and other impurities from the animal. Castoreum contains chemicals such as phenols and ketones, all contributory towards the smell and taste. According to MSU flavor chemist Susie Bautista, castoreum is not used much (since it is not kosher), but greatly enhances vanilla flavor. A similar chemical to castoreum is vanillin, a phenolic aldehyde. Vanillin is a component in both natural and artificial vanilla flavoring. Occurring in natural vanilla pods, vanillin can be extracted from the natural source. Otherwise, it can be synthesized from a chemical called guaiacol and glyoxylic acid. Chemical synthesis accounts for the vast majority of vanillin production in the world.

Figure 6: Left: Castor sacs from a beaver and castoreum. Right: Vanilla Pod
Figure 7:Vanillin and4-Ethylphenol1,2-dihydroxybenzene, and 3-hydroxyacetophenone: three components of castoreum; there are clear similarities between the chemical structures which accounts for their similarity in taste/odor

Figure 8: Chemical synthesis of vanillin from guaiacol

Another chemical that has gained much publicity is monosodium glutamate, MSG for short. MSG contains around 80% glutamic acid and contributes to the taste ‘umami,’ which is a taste found in cured meats, mushrooms, and cheeses. MSG is used as a flavor enhancer to greatly improve the flavor of many foods. It does so by providing glutamic acid to bind to the glutamate receptors on the tongue, allowing food to taste “meatier”, and therefore tastier. However, its wondrous properties do not come without negative effects. MSG can lead to eye damage, depression, and a whole host of other problems, as well as cause “Chinese Restaurant Syndrome,” which affects MSG over consumers with headache and asthma. This chemical is one example of why are chemical food flavorings require careful scrutiny. The benefits of taste may be outweighed by the health related downsides.

Figure 9: Structure of glutamic acid, a major component of MSG.

Conclusion

Smells and tastes are caused only by the chemical binding of compounds to receptors in the tongue and nose. In order to be smelled, a chemical must be volatile, or no odor components will enter the nose. Many chemicals play important roles in tastes and smell. For example, esters are a class of organic compounds with strong smells commonly found in fruits such as bananas and apples. Other flavor compounds include vanillin and castoreum, which are both used as vanilla flavorings. While both compounds emulate the same flavor, vanillin, a phenolic aldehyde, is found naturally in vanilla pods, while castoreum, a mixture of phenol and ketones, is produced in beaver castor glands. These compounds easily highlight the ability to “fool” the taste buds. Finally, monosodium glutamate, MSG, is a chemical responsible for the umami taste in foods. Its numerous adverse effects show the potential dangers of using flavorings and the need for in-depth analysis of the effects of flavor compounds on humans. The complexity of flavors highlights the need for humans to scrutinize the additives in their food. Who knows – the next vanilla iced coffee you drink might not actually have vanilla.

The Chemistry of Digestion: Exposing the True Secrets of the Stomach and Intestines

Digestion can be simply put as a catabolic process of breaking down the foods we eat, filtering out nutrients necessary in the body, and expelling waste material. This process is important because it provides all of the energy we use to function daily. even when organisms consisted of a mouth and anus with an esophagus connecting the two, digestion was crucial in providing the organism with energy, eventually allowing organisms to develop more complicated features. 95% of nutrients get absorbed in the small intestine. Digestion takes on average about 53 hours, with around 40 hours spent in the large intestine.

The different processes of digestion for types of biomolecules

The Chemistry of Digestion

There are many chemicals that play crucial roles in digestion in order to break down food and separate the nutrients our body needs to absorb from the waste material which will eventually be removed from the body. Digestion can be broken down into mechanical and chemical digestion. They occur in conjunction at certain times, and alternately at other times. The major components of mechanical digestion are the chewing of the teeth, peristalsis in the intestines, churning of the stomach, and the separation of fat by bile in the small intestine. Initially, the mouth performs mechanical digestion, or mechanically breaks down the foods we eat by using the teeth to chew them into smaller pieces.The food is also exposed to saliva in the mouth, which contains amylase.This catalyzes the reaction that breaks down starch into sugars. This could form smaller disaccharides such as maltose, or even monosaccharides such as glucose. Whatever the case, this enzyme consists of three domains, where the A domain the hydrolysis of starch.

Hydrolysis

This is the use of a water molecule to break bonds. In the stomach, multiple enzymes are added which break down the food, around 400-800 mL of stomach acid per meal. This “gastric” juice consists of hydrochloric acid at concentration 0.1M, as well as some sodium chloride and potassium chloride. One of the most critical of these enzymes is pepsin, which is initially added as pepsinogen by the “chief cells” and converted to pepsin as the pH is lowered to around 2 by hydrochloric acid released by the parietal cells, which also stops the activity of amylase. This is important since pepsin is initially secreted as a zymogen, an inactive form. Otherwise, the enzyme would digest parts of your body. Thus, it is only activated when inside the confines of the stomach where the pH is low enough to turn pepsinogen into pepsin.Thus chemical reactions not only help digest the food, but also control when and where it occurs.

Caption: Pepsinogen and Pepsin

Salivary amylase

Bile AcidsParietal cells also release the protein intrinsic factor, which aids the large intestine in the absorption of Vitamin B12. Other cells secrete mucous which protects the cells lining the stomach from activity of pepsin.

Yet another class of chemicals that aid in digestion are the bile acids. Found naturally in bile, a digestive fluid produced by the liver that helps the small intestines digest lipids, the bile acids play two important roles in digesting food: Bile acids are amphipathic, meaning that they can both donate and accept protons due to the bile acids. One known effect of bile in the digestive process is the “emulsification of lipid aggregates.” Here, similar to how washing detergent acts, the bile acids break fat molecules down into microscopic droplets. Another astounding property of bile acids is their ability to solubilize a great variety of lipids. Essentially, the bile acids solubilize normally insoluble compounds by surrounding them similarly to the chemical structure of a  micelle. Thus, bile acid is extremely important as it aids in digestion in more ways than one.

The Intestines

In the small intestine, wrinkles in the walls called villi release intestinal enzymes which finish the digestion of proteins and carbohydrates. In the duodenum, the first part of the small intestine, sodium bicarbonate from the pancreas neutralize the pepsin, chyme (basically food stuff mixture), and HCl from the stomach while watery mucous released by the duodenum protects the intestine. Bile from the liver emulsifies or break down fat molecules until fat-digesting enzymes (Lipase) can act upon them and also help neutralize the acids from the stomach. Other intestinal enzymes (Protease-proteins, amylase-carbohydrates, maltase sucrase lactase -sugars, peptidase -peptides, nuclease – nucleic acids in sugars) break down sugars and peptides, eventually finishing the digestion of carbohydrates and proteins. Hormonal secretions are released in the intestine in order to control the flow of food and ensure all of the nutrient can be absorbed. Secretine, released by the duodenum and triggered by food passing into the small intestine, controls the secretion of sodium bicarbonate and stops the addition of stomach content into the intestine until the previous content can be neutralized, protecting the intestine from the stomach’s acidic conditions. Gastrin in the stomach is triggered by proteins entering the stomach and triggers the addition of gastric enzymes into the stomach. Cholecystokinin (CCK) in released by the small intestine and triggers the release of bile and pancreatic enzymes into the small intestine.

Finally, in the large intestine, any remaining nutrients such as vitamins and any water is absorbed, and the waste material is expelled from the body as bowel movement.

The different parts of the digestive system


Conclusion

https://www.youtube.com/watch?v=v2V4zMx33Mc

From the moment food enters your mouth, to the moment it leaves your body as waste material, a large variety of chemical reactions are occurring. Mechanical and chemical digestion break down the food you consume, allowing for it to be used by your body. Food is broken down, increasing the total surface area, allowing for contact with the enzymes. Nutrients and minerals are absorbed through various processes, made possible by the cohort of enzymes catalyzing reactions. Without the well-coordinated series of chemical processes that must happen, food would merely pass through your body without acting as sustenance.

Molecular Gastronomy The Science Behind the Cooking of Food

When cooking an egg, you often notice that the egg white (albumen) changes from a clear, runny liquid, to a firm, opaque, solid. Why does this happen? Similarly, why does yellow, unbaked bread dough, turn brown when put in the oven? These questions are answered in a branch of food science called molecular gastronomy. While this two-word phrase may seem intimidating, it simply refers to the study of the physical and chemical changes that happen to ingredients during cooking. The term was created by Hervé This and Nicholas Kurti in 1988 as the title of a series of workshops aimed at exploring the science behind the cooking of ingredients. The pivotal moment in molecular gastronomy came in 1969, when Kurti held a presentation called “The Physicist in the Kitchen” for the Royal Society of London, in which he performed food-based science experiments, including making meringue in a vacuum chamber (previously unheard of since meringue involves beating air into egg whites) and using pineapple juice to digest protein. In this blog post, we will explore three major applications of molecular gastronomy: spherification using alginate, transglutaminase meat glue, and sous-vide cooking. As will be seen, understanding the chemistry behind food allows for exotic and unique culinary creations to be realized.

Spherification with Alginate

One of the great wonders of molecular gastronomy is the process of reverse spherification, which allows one to create balls of liquid encapsulated in long-lasting, gelatinous shells, similar to caviar. How exactly does spherification work? The secret lies in the chemicals involved.

The first of two main components is alginate, which can be extracted from brown seaweed. Alginate is an anionic polysaccharide, and is often obtained as a sodium salt. It is important to know that alginate is not the only compound capable of performing the same role, as chemist and food enthusiast Martin Lerschasserts – a whole list can be found here. The large carbohydrate chains of alginate allow it to act as a thickening agent, but the real magic happens when the second of the main components is present – calcium ions. In contrast to alginate, it is preferred that the calcium ions already be present in the liquid being spherified. In the case that calcium is not already present, calcium lactate or calcium lactate gluconate can be added. What exactly happens between the alginate and the calcium ions that allows for the formation of liquid-filled spheres? The calcium ions fit between the strands of alginate, allowing them to interlock, creating a net of tangled polymers and form ing a gel. After knowing the chemistry behind spherification, the process is quite simple – the flavored liquid, containing calcium ions, is simply “dropped” using an eyedropper into a solution of sodium alginate.

 Left: Alginate, Right: Calcium lactate gluconate

However, before spherification can be guaranteed to happen, there is one parameter left to tweak – density of the flavored liquid. This physical property is extremely important due to surface tension, the net effect of the intermolecular forces between liquid particles at the surface. An underly dense liquid will not be able to penetrate the surface of the sodium alginate solution, while an overly dense one will not bead up into a sphere.

Spherification has had many creative applications to molecular gastronomy over the years. A popular experiment is to encapsulate tiny drops of fruit juice, creating “fruit caviar.” However, using larger drops allows one to also simulate many foods, like green olives and cheese.

Various examples of spherification to create exotic foods

Provided here is a video demonstrating the spherification of foods

Transglutaminase Meat Glue

One of the topics in the field of molecular gastronomy that has generated heated discussion is a material colloquially called, “Meat Glue”. Chemically, meat glues are referred to as transglutaminase. Transglutaminase is an enzyme naturally found in blood which catalyzes the formation of a covalent bond between a free amine group and an acyl group which are found on the ends of proteins. These enzymes aid in the formation of strong protein bonds which do not degrade easily. These enzymes are frequently used to connect different pieces of protein-rich food stuff, mostly meats, together.

Schematic of bonding involved in use of transglutaminase

No US law requires chefs to disclose whether they use meat glues. However, many customers look down upon the practice, worried whether the meat they eat is actually one piece or a mixture of scrap meats. Another concern of critics is that by “gluing” pieces of meat together, the pathogen-covered surfaces of the meat, which are usually seared to kill these pathogens, are left unfettered and pose a health hazard to the consumer. In 2001, the USDA stated that any meat products produced through the use of meat glue must have it clearly marked on the label.

However, chefs defend the use of meat glue, stating that meat glues help reduce waste and allow them to create creative culinary masterpieces, making it possible to design foods with patterns and combine different types of foods together to create never before seen

Transglutaminase, aka meat glue, is sold under its brand name Activa. It is sold as a powder which can directly be applied to the surfaces of the foodstuffs that are being combined. After adding a little water, placing the conglomerate in a vacuum bag, and letting it set in a freezer overnight, the transglutaminase will form bonds. It is sold by the Ajinomoto company, the same company which produces other products such as the commonly utilized neurotoxin food additives, aspartame and MSG (monosodium glutamate). The U.S. Food and Drug Administration lists transglutaminase as “generally recognized as safe.” However, many people are hesitant of eating meat glue because they fear transglutaminase may also possess toxic properties. Transglutaminase is produced by cultivating bacteria using vegetable and plant extracts in the blood plasmas of pigs or cows. However, manufacturers are not required to share the exact method of synthesis, adding to the uncertainty and fear consumers hold regarding this product.

 Left: Meat-glued chicken and beef. Center: Meat-glued salmon and tuna. Right: Meat-glued lamb and scallops.

 

Production process of food using transglutaminase meat glue

Sous-vide Cooking

The last molecular gastronomy technique that will be discussed is sous-vide cooking. So what exactly is sous-vide cooking? This is a technique where food is vacuum packed in a plastic pouch and cooked a closely controlled temperature in a water bath. This allows for a great deal of control and the ability to cook food with extreme consistency. Many recipes can make use of this technique. So why spend the money on such expensive equipment in the first place?

Firstly, sous-vide involves vacuum packing the food product. This allows the carefully controlled temperature, usually around 122 to 149 degrees Fahrenheit to evenly cook the food in polyethylene bags.Polyethylene is a common plastic polymer that is generally regarded as safe for use with food.

Polyethylene

Another benefit of using the bag is that it allows, for example, meat to retain its juices while cooking. Volatile flavors are also saved. Sous-vide also prevents the development of odd flavors from oxidation. Since it is vacuum packed, the amount of oxygen in contact with the food greatly decreases, as does the chance of oxidizing the cooking oil when the oil nears its boiling point. Meat begins to turn to a red color and then to a grayer color when in contact with oxygen as myoglobin is oxidized to oxymyoglobin and then metmyoglobin. Bacteria may also begin to grow. These effects are greatly reduced by vacuum pack-cooking the food, since aerobic bacteria will not proliferate. This can also help reduce the need for adding nitrites, an anti-oxidizing agent

Left: Fresh meat which has not been oxidized. Right: Meat that has turned grayer after coming into contact with oxygen.

Conclusion

By implementing molecular gastronomy in cooking, exciting new kinds of food can be created. Shapes, textures, and even flavors can be generated using a variety of techniques such as spherification, sous-vide cooking, and meat-glue. Although some may stick to more traditional methods, the new wave of approaches to cooking give a contemporary spin on food. Many restaurants and chefs around the country have adopted molecular gastronomy such as Grant Achatz and Wylie Dufresne. Molecular gastronomy truly gives a glimpse into the kitchen of the future.

The Oil about Oils: Structure, Smoke Point, and Health Effects of Cooking Oils

By Mark Sabini, Justin Yu, & James Lee

Fig. 1. Types of oils with their precursors displayed inside

Oils often get a bad rap. People frequently view them as trademarks of obesity and unhealthiness, where some people go so far as to nearly eliminate them from their diets. However, the set of oils contains a plethora of different compounds, each with its own unique qualities. One subset of oils is the cooking oils. Found in virtually every household and type of world cuisine, cooking oils are used to give food flavor and aid the cooking process. Every oil is different, and with different molecular structures comes different chemical properties.

Background on Oils

The introduction of vegetable oils into the American food industry began in the early 1900’s. Before then, oil was primarily derived from animal fats. In the mid 1800’s, farmers realized that vegetables such as corn held higher nutritional value than their animal counterparts and also were cheaper to grow. This led to a sharp increase in the production of corn and other vegetables, and later on, the production of vegetable-based oils.

Fig. 2. Formation of oil products from raw materials

 Vegetable oils were favored because they were less saturated than those derived from animals due to the amount of double bonds in their structure (See Fig. 7. below). This meant that they were much more fluid and much less likely to clog blood vessels, making them healthier for the body and easier to process. A process called fractionation is used to purify oils by cooling the oil until some of it crystallizes into fat and filtering that fat out so only pure oil is left, removing any impurities in the oil. This process is widely used in the manufacturing of cooking oils in order to ensure the oil is safe to consume.

Fig. 3. Oil consumption trends

 Before chemical properties of oils can be examined though, physical properties must be set straight. A common belief is that pure fats and oils have color, taste, and odor. However, this is not true! Pure fats and oils have none of the three aforementioned characteristics. For example, the bitter taste of extra-virgin olive oil is produced by several polyphenols, including oleocanthal and oleuropein. In addition, the color of olive oil depends on the color of the olives themselves, as black olive oil comes from olives that fall off the branches of trees. It is important to distinguish between pure fats and oils, and “mixed” oils such as olive and canola oil.

File:Oleocanthal.pngFile:Oleuropein.png
Fig. 4. Left: Structure of oleocanthal. Right: Structure of oleuropein
Fig. 5. Classification of Fats and Oils

 Cooking oils vary in the components that make them up. Cooking oils are generally split up into three different categories, vegetable oils, animal-derived oils, and synthetic oils. These oils differ in their chemical composition because they come from different sources. Vegetable oils, for example, are derived from the triglycerides in plants, primarily extracted from plant seeds. Some common vegetable oils include sesame oil, olive oil, peanut oil, and coconut oil.

Fig. 6. Comparison of Average Fatty Acid Values of Dietary Fats

Smoke Point of Oils

Oils, as well as other chemical compounds, decompose when heated because at a certain temperature, enough heat is absorbed to break the chemical bonds that hold the compound together. The amount of energy needed to break the bonds in an oil and therefore decompose it is determined by the oil’s structure. Thus, the smoke point of an oil is the temperature at which it begins to give off smoke, due to the thermal decomposition of the oil into glycerol and free fatty acids.

Fig. 7. Oil beginning to smoke

 In addition, the smoke point marks the start of nutritional and flavor degradation. Temperatures above the smoke point of an oil are undesirable, as the acrolein starts to be produced, and the oil goes rancid. Several factors determine the smoke point of an oil. Saturated fatty acids provide stability and are more resistant to high heat, while polyunsaturated fats are more sensitive to both light and heat. This means that excessive heat can cause production of heat free radicals and harm the body if consumed.

The smoke point for a single batch of oil does not stay constant. As an oil is used more and at higher temperatures, the smoke point decreases. In addition, foreign entities (such as batter and bread crumbs) in the oil can cause the smoke point of an oil to decrease more rapidly. That being said, there are several ways to stop the smoke point of an oil from lowering too quickly and therefore prolong the oil’s life. The first is to use a more refined oil. Oils that are more refined (such as safflower oil) tend to have higher smoke points than say, lards. According to Ohio State University food scientist Sam Vance, another way to prolong the life of an oil is to mix it with oil that has a higher smoke point. Finally, reducing the amount of salt in deep-fried food as well as ensuring that excess bread crumbs and batter do not enter the oil help stop the oil from going rancid.

 

Health Effects of Cooking Oils

Cooking oils, as evidence shows, come in many types. Thus, naturally, their nutritive values and health effects should be just as diverse. Oils are comprised of fats, which fall into two main groups, saturated and unsaturated. Saturated fats have as many hydrogens bonded to carbons as possible, and thus result in straight molecules. These straight molecules can be packed tighter, so solid fats like butter are composed mostly of saturated fats. Cooking oils contain a mix of saturated and unsaturated fats.

Fig. 8. Structure of fatty acids

 Fats such as palm oil, which contains 52% saturated fat, are not heart healthy due to the possible adverse health effects. Since saturated fats clump more easily, they can form deposits in blood vessels and cause atherosclerosis. In fact, unsaturated fats with trans bonds are much straighter than those with cis bonds, and therefore less healthy for the reasons mentioned.

Fig. 9. Examples of types of fatty acids

 However, there are alternatives that can in fact be healthy. Omega-3 fatty acids have been getting a lot of good press lately, and for good reason. Omega-3’s can help prevent heart diseases and strokes, according to Cleveland Clinic. Oils like walnut and hemp oil are good sources of this type of polyunsaturated fatty acid (a fatty acid with more than one double bond).

Conclusion

Cooking oils have many properties that differentiate them, and the huge variety can make choosing one difficult. However, each oil has its advantage, whether it be its higher smoke point or high level of Omega-3 fatty acids. Compromises must be made, since there is no perfect oil. However, with a better understanding of each oil and the chemistry behind it, one can make more informed decisions when cooking, taking into consideration the multi-faceted characteristics of cooking oils.

Blanching, Canning, and Freezing

Keeping Food Fresher, Longer

In the modern age, the movement from a self-sustaining life on the farm to a lifestyle reliant on supermarkets for food has changed the way people shop, eat, and live. One of the challenges of this lifestyle is maintaining the nutritive value and freshness of products as they are transported from producer to consumer. Several methods have been devised to remedy this: canning, blanching, and freezing, allowing supermarkets the freedom of selling products that are not in season, like apples in the winter. This maintains a constant food supply for consumers around the world, and also gives them flexibility with the food they eat.

Blanching

The first food processing method to be discussed, blanching, is a common precursor to canning and freezing.  It utilizes high temperatures at carefully timed intervals to preserve the nutritional, aesthetic, and textural properties of produce. Heat denatures enzymes that might otherwise spoil the food and kills many of the spoilage-inducing microbes. The exact temperature is carefully controlled, as under-blanching could actually shorten the longevity of the food through stimulation of the enzymes, while over-blanching is akin to boiling and alters many of the properties that blanching is supposed to preserve. The high heat of blanching also kills most, if not all, of the spoilage-inducing microbes.

There are several methods of blanching, including water, steam, microwave, and gas blanching, the first being the most commonly used technique. This involves an apparatus called a blanching basket, which submerges the fruits or vegetables in boiling water. Regardless of the initial step, the produce is always shocked in ice-water after heating, using about one pound of ice per pound of vegetables. This is very important as it immediately halts the cooking process.

Blanching Basket

The effects of blanching can be seen both qualitatively and quantitatively. Qualitatively, blanched food appears fresher, more vivid, and more appetizing than unblanched preserved foods. Blanched vegetables are also softer than unblanched ones, helping to reduce the likelihood of freezer burns. Because blanched foods are softer, they are easier to pack and consume. In addition, when blanching  is done correctly, it can prevent total loss of a nutrient, such as ascorbic acid (Vitamin C) in immature sweet peas blanched for 1 minute at 96ºC.

Freezing

Freezing foodstuffs in order to preserve them has been a commonly practiced procedure for centuries. Even in ancient times, people were aware of the effect of temperature on the activity of bacteria and enzymes, which break down and spoil food. People created cool, dark cellars beneath the ground in order to lower the temperature of food and keep foods as fresh as possible. The ice industry skyrocketed in the 19th century as the use of ice to preserve food increased. People realized that ice floating in the ocean could be captured and sold for use in food preservation. Soon, every household had an icebox where people would place ice bought from a vendor and store their food in order to prevent it from spoiling.

Icebox

A review by the Food Processing Center, part of University of Nebraska’s Food, Science, and Technology Department, showed that foodstuffs kept at temperatures below -18ºC are able to last a year without spoilage, foods kept at -10ºC can last 8 months, and foods kept at -2ºC spoil in less than two months. This information has led to the conclusion that -18ºC is an upper limit for food preservation using freezing. Any lower temperatures would prove to be more harmful than helpful for the following reasons:

Freezing in produce with a high water content causes the water to form large ice crystals that puncture the cell walls and destroy the cellular structure of the food. When food that has undergone this phenomenon is thawed out, it is limp and unpalatable. In order to solve this problem, Clarence Birdseye created a process called quick freezing, similar to the fish preservation method of the Eskimos. In quick freezing, food is frozen quickly, preventing large ice crystals from forming and damaging the cells of the food.

Quick Freezing vs. Slow Freezing

Canning

Canning is a process that is well-established as a method for food preservation. The process that frequently precedes it, as mentioned before, is blanching. A common misconception is that canned fruits and vegetables are not nearly as healthy as fresh ones. However, as seen with blanching and freezing, further processing does not necessarily mean further loss of nutrients. In fact, canning does a good job of preserving many of the nutrients in the foodstuff. However, the marked increase in shelf-life might not be outweighed by the potential loss of benefits of the product.

Canned Foods

One study examined the presence of various nutrients after canning. Different nutrients behave differently when subject to canning. Vitamin C, generally found in fruits as well as spinach and asparagus, is mostly retained in heat treatment. In fact, the amount of this vitamin is relatively stable even after storage for two years. The same holds true for Vitamin A, which is not water soluble and thus less likely to escape from the produce. Lycopene, a specific type of Vitamin A found in tomatoes, seems to have better anti-prostate cancer effects when consumed in canned form. Other nutrients that withstand canning well are potassium, dietary fiber, and protein. Canning not only preserves vitamins and nutrients – it also kills potentially harmful microbes. Due to the process’s excellent benefits, canned fruits and vegetables are excellent alternatives to their fresh counterparts.

Conclusion

The three methods of blanching, freezing, and canning go hand-in-hand to prolong the freshness, nutritive value, and natural appearance of food. Blanching before canning prevents degradation during its storage, while blanching before freezing prevents re-growth of microbes after thawing.  At the end of the day, no matter how elaborate the process, food will always wilt, wither, and decay. However, using the techniques of canning and freezing in coordination with blanching, nutritious foods can survive the long journey from the fields of farmers to the mouths of hungry consumers.