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Why are vegetables either red or yellow?

Why are vegetables either red or yellow?


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Have you ever wondered why these two colors occur so often? Take these: onion waltnut potato carrot/parsley and even cabbage which can be green or red.

Why these two pigments? Or is it just one pigment and it's just its concentration that makes the difference?

Thanks for any explanations!


As many plants do, many of vegetable do photosynthesis. For photosynthesis, chlorophylls, which are green, and carotenes, which are yellow to red, play important roles. When chlorophylls get less, you might see yellow to red color due to carotene. When chlorophylls are degraded, they get light brown. In some vegitable, such as tomatoes, lycopene, which is an intermediate of carotene synthesis, is accumulated.

https://en.wikipedia.org/wiki/Lycopene

Another popular pigment is anthocyanin, the color of which is red to purple. Various functions of anthocyanin are suggested from sun-shade, to an antioxidant, to attracting birds in fruits.

https://en.wikipedia.org/wiki/Anthocyanin


A lot of fruit and veg are green when unripe and become brightly coloured when they are ready to eat (obviously not true for all, but most fruit/veg does).

This is probably deliberate as a mechanism to signal to birds and animals that it is ready to eat, so that they can disperse the seeds inside.

Red and Yellow are bright colours not usually seen on plants except of fruit/veg, and flowers (which are brightly coloured to attract bees and whatnot), so it makes sense these could be used as signals.

http://www.rosincerate.com/2015/07/colour-changing-fruits-and-veggies.html


Anthocyanins

Britt Burton-Freeman , . Indika Edirisinghe , in Nutraceuticals , 2016

Abstract

Anthocyanins are natural plant pigments imparting red, blue, and purple colors to flowers, leaves, fruits, and some vegetables. In addition to fruits and vegetables baring these colors, other sources of intake include dietary supplements and natural colorants of food and beverages. Anthocyanins have a complex metabolic fate that includes extensive presystemic metabolism giving rise to a wide range of metabolites. Anthocyanins modify the expression and activity of cellular and tissue targets influencing various systems associated with health benefits, including anticancer, vascular, metabolic, and neuronal health. Assessments of anthocyanin safety and toxicology indicate that acute toxicity is very low in animals and there are no reports indicating adverse health effects in humans with consumption of anthocyanins at usual dietary intake levels. Currently, there is no recommended intake level of anthocyanins for optimal health or to avoid adverse effects however, future research and continued consumer interest will undoubtedly present opportunities for pursing dietary guidance recommendations.


Related terms:

General Information about Lutein

Lutein is a xanthophyll , or hydroxycarotenoid (C 40H56O2, Figure 23.1 ). Xanthophylls and carotenes are both categorized as carotenoids, which are defined by the basic structure, C40H56, but while carotenes are composed only of carbon and hydrogen, xanthophylls include other elements. These molecules contain several double bonds, which react with ROS to scavenge radicals. Carotenes are transformed to vitamin A in the body, and are therefore called pro-vitamin A [4] . However, lutein’s properties are considerably different from those of carotenes.

FIGURE 23.1 . Chemical structure of lutein.

Lutein is categorized as a xanthophyll carotenoid, and has the chemical composition C40H56O2.

Lutein is a phytochemical, which are plant-derived compounds that are not essential nutrients for sustaining life. Because phytochemicals have pigments, fragrance, or a bitter taste, they are generally thought to help protect plants against external threats, such as ultraviolet light, pathogens, or creatures that eat them. Plant enzymes synthesize lutein from lycopene and α-carotene ( Figure 23.2 ) [5,6] .

FIGURE 23.2 . Biosynthetic pathway of lutein in plants.

Overview of lutein biosynthesis. Several steps are omitted for simplification. Briefly, lutein is synthesized through a series of intermediates that include lycopene and α-carotene.

In contrast to plants, animals cannot synthesize lutein. Humans and other animals obtain lutein from foods therefore, lutein is called a food factor. Some vegetables, such as kale, spinach, and broccoli, and the marigold flower which is used as a source for supplementary micronutrients, can provide lutein. Egg yolks also contain high levels of lutein, which is obtained by the female bird as part of her diet and deposited in the yolk.

The lutein ingested by an animal is incorporated into micelles and absorbed from the intestinal epithelium into the blood by enterocytosis. Lutein then circulates systemically to reach the liver, lung, and retina [3,7,8] . In the human retina, lutein is concentrated in the macula, the most central region ( Figure 23.3 ), so it is called a macular pigment. The analysis of stereoisomers of this macular pigment revealed two stereoisomeric carotenoids with identical properties to lutein and zeaxanthin, another xanthophyll [4] . Lutein is also present throughout the retina, at lower concentrations then in the macula [8] . Although the concentration of both pigments is highest in the macula, there is more zeaxanthin than lutein in the macular region, while more lutein than zeaxanthin in the peripheral retina [9,10] .

FIGURE 23.3 . Macula of the human fundus.

Human fundus photograph (A) and cross-sectional image of the macula by OCT (B). Lutein is rich in the macula but is also present in the peripheral retina. (A) The macula is the central part of the fundus. (B) ∗ indicates NFL, OPL, ONL, and RPE, in order from top to bottom. OCT, optical coherence tomography NFL, nerve fiber layer, consisting of the axons of retinal ganglion cells OPL, outer plexiform layer, consisting of the synapses between photoreceptor cells and downstream neurons ONL, outer nuclear layer, consisting of photoreceptor cells RPE, retinal pigment epithelium.

Within the retina, resonance Raman imaging has shown that lutein is most abundant in the neuronal network layer (the outer plexiform layer [OPL]) that connects the photoreceptor cells (the outer nuclear layer ONL) to the secondary neurons [11] . Because lutein is a yellow-pigmented crystal, it has long been thought to act as a blue light filter, to protect retinal tissue from the high-energy end of the visible spectrum. The fact that lutein is abundant in the OPL, which is closer to the vitreous side of the retina than to the photoreceptor cell layer, is consistent with the idea that lutein filters light before it reaches the photoreceptor cells, to prevent harmful cellular events and vision loss. Lutein is also found in the photoreceptor outer segments (OSs), where light stimuli are received, and in the retinal pigment epithelium (RPE), where OSs are phagocytosed and recycled. The level of lutein in photoreceptor cells is reported to be twice that in the RPE [11,12] .

Recently, a lutein-binding protein in the retina was reported [13] . This protein was identified as steroidogenic acute regulatory domain 3 (StARD3), which is expressed in both the retina and RPE. In the monkey retina, StARD3 localizes to all the retinal neurons in the macular area, especially the cone inner segments and axons, but it is not found in Müller glial cells [13] .


Types of Carotenoids

Xanthophylls

There are two main types of carotenoids, the xanthophylls and the carotenes. Xanthophylls are easily recognized by their yellow coloration, and are present in high quantities in leaves. In the fall, these carotenoids are responsible for yellow leaves. Xanthophylls also give color to fruits and vegetables like papaya, squash, and peaches. The macula lutea in the human retina gets its coloration from these carotenoids, which play a significant role in vision. They help protect the retina from blue and ultraviolet light, which tends to cause radical ions in the tissue.

Carotenes

Beta-Carotene

Beta-carotene is a specific carotenoid found plants and fruits. It has a red-orange coloration when isolated. Beta-carotene is the most common carotene found in plants. In humans and other animals, beta-carotene becomes a precursor for vitamin A, and must be consumed in the diet for survival. Beta-carotene is found in carrots, pumpkins, sweet potatoes, and even leafy greens like spinach and kale. Over consumption of beta-carotene, while not expressly harmful, will leave the skin with an orange coloration, as the carotenoid is stored in the fat layer just under the skin.

Lutein

Lutein is a xanthophyll, found in leafy green plants. Lutein is a yellow colored pigment. It bestows yellow color to egg yolks, and yellow carrots. Like all carotenoids, it is synthesized in plants. Animals can store the pigment in fat, and recent studies have shown that it may have some function in the human eye. Diseases like macular degeneration may be caused by the body’s inability to incorporate and use carotenoids like lutein.

1. The puffin is a sea-faring bird, which survives mainly on a diet of small bait fish. The bait fish survive mainly on krill, which eat mostly algae. Puffins have bright orange patches on their beaks, caused in part by the build-up of carotenoids. Which link in the food chain provides these carotenoids?
A. The krill
B. The algae
C. The baitfish

2. Flamingos are pink because of the extra carotenoids they store in their feathers. They eat tiny brine shrimp, which in turn accumulate carotenoids from the algae they eat. What would happen if flamingos were fed a diet with no carotenoids?
A. They would become red
B. They become white
C. They would die immediately

3. What would happen to a plant without carotenoids?
A. It would be able to absorb a wider range of specific frequencies
B. Photosynthesis would break down
C. Carotenoids essentially do nothing for the plant


Vegetable Seedling Identification: Pictures and Descriptions

Here’s a quick visual guide to some of the easiest vegetables to grow from seed.

Beans (Pole and Bush)

The bean seedling’s first seed leaves often appear to be heart-shaped. Its true leaves will be smooth-edged and arranged three to a stem, with two opposite each other and one above. Learn how to grow beans.


Bean seedling

Beets

With proper watering, beet seedlings will emerge in five days to two weeks after planting. Young beets put forth smooth, oblong green leaves on red or pinkish/purple stems. Because several seedlings can grow from one beet “seed,” you may need to thin them by snipping some off at ground level. Learn how to grow beets.


Beet seedlings. Photo by Tepeyac (Own Work) via Wikimedia Commons.

Broccoli (and Cauliflower)

Broccoli and cauliflower seedlings produce two kidney-shaped seed leaves before their true leaves, which are more rounded and may have vaguely serrated edges. Learn how to grow broccoli and cauliflower.


Broccoli seedling. Photo by Chris Burnett.

Carrots

Carrot seedlings in the earliest stages may be mistaken for grass because their seed leaves, unlike some other vegetable cotyledons, are tall and thin. A young carrot’s true leaves, shown below, have a distinctive, fern-like shape. Learn how to grow carrots.


Carrot seedlings. Photo by Victor M. Vicente Selvas (Own Work) via Wikimedia Commons.

Cucumbers

The oval seed leaves of emerging cucumber and squash plants look very much alike, but the cucumber’s true leaves will be triangular and lobed with a fuzzy surface and serrated (toothy) edges. As the cucumber vine develops, its delicate-looking but tenacious tendrils will grip and climb anything in their path. Learn how to grow cucumbers.


Cucumber seedling

Kale comes in many varieties, with true leaves that may be either smooth or fancily ruffled. Its seed leaves may peek above the soil in about a week and the plants should be thinned to a foot apart when they reach five inches tall. The benefit of thinning kale is that you can enjoy the snipped seedlings in a salad! Learn how to grow kale.


Kale seedlings. Photo by Forest and Kim Starr via Wikimedia Commons.

Kohlrabi

Kohlrabi—a Brassica—initially resembles seedlings of other members of this family, like broccoli, cauliflower, and kale. Until its first true leaves appear, it may be hard to recognize it! True leaves will have deeply serrated edges (more so than broccoli) and its leaves will be more pointed than rounded.


Kohlrabi seedling. Photo by Chris Burnett.

Lettuce

The many varieties of looseleaf and head lettuce are characterized by their leaves. Depending on whether the leaves will become soft or stiff, loose or bunched, lettuce seedlings will vary in appearance. Lettuce seedlings respond well to consistent watering and cooler temperatures and, if started indoors, will need to be hardened off before being planted outside. Learn how to grow lettuce.


Lettuce seedlings. Photo by Tepeyac (Own Work) via Wikimedia Commons.

You won’t see seed leaves emerging from pea seedlings because, unlike those of many other vegetables, pea cotyledons remain underground. Peas like to climb and will form oval leaflets with tendrils that readily wind around supports. Learn how to grow peas.


Pea seedlings. Photo by Rasbak (Own Work) via Wikimedia Commons.

Pumpkins

Pumpkin, squash, watermelon, and cucumber seedlings may be hard to tell apart because they belong to the same family, the cucurbits. A pumpkin’s seed leaves will be large, flat, and rounded, looking a little like small elephant ears. As it grows, a pumpkin will form huge leaves and its vines may eventually cover a lot of territory. Learn how to grow pumpkins.


Pumpkin seedling

Radishes

Radishes have smooth, heart-shaped seed leaves that soon give way to elongated and scalloped or gently serrated true leaves. Radishes are fast-growing, and those planted in the cool days of spring may be ready to eat in just three or four weeks. The nutritious radish leaves, or “tops,” may be eaten as well as the roots. Learn how to grow radishes.


Radish seedlings

Squash (Summer and Winter)

While all squash will emerge with rounded cotyledons, squash seedling leaves will vary by type the more that they grow. A summer squash will develop prickly, semi-triangular, jagged-edged leaves. A winter squash leaf will generally be broader and more rounded and, while hairy, not prickly. Learn how to grow squash.


Squash seedlings. Photo by Belmargo2014 (Own Work) via Wikimedia Commons.

Swiss Chard

Like beets (a close relative), chard typically produces 1 to 3 seedlings per seed cluster. Seedlings have narrow seed leaves and—depending on the type of chard—red, white, yellow, or orange stems. Learn how to grow Swiss chard.


Swiss chard seedlings. Photo by Chris Burnett.

Tomatoes

The seed leaves of tomato seedlings are long and narrow, while the true leaves tend to have asymmetrical lobes, very similar to the leaves of the adult plant. Look for three connected (or nearly connected) leaves at the end of each branch, with one or two smaller leaves farther down the branch. The seedlings’ stems and leaves may also be lined with small hairs. Learn how to grow tomatoes.


Tomato seedling

Learn More About Gardening

For more information on growing vegetables, herbs, flowers, and more, check out our library of Growing Guides.


What Exactly is a Food Colorant?

May as well go straight to the FDA, which refers to them as color additives: “A color additive is a dye, pigment, or other substance made by a process of synthesis or similar means, or extracted, isolated, or otherwise derived, with or without intermediate or final change of identity, from vegetable, animal, or other sources, that when added to a food imparts color to it.”

That is not the exact wording, and the definition also includes drugs and cosmetics, but that should do for a working definition. Other sources, you ask? Well, you can get colors from minerals, and one authorized color additive comes from an insect! We’ll get to that.

Food coloring chemicals fall generally into three categories:

  • synthetic organic compounds (which are the FD&C) colors)
  • mineral or synthetic inorganic colors (like iron oxide)
  • natural coloring from vegetables or animals (vegetable and fruit juices, or color extracts).

Why do they put coloring in foods?

Well, it’s not just “they” who do it, we all do. Why do we add tomato paste to a sauce or soup? Won’t tomatoes do the job? We add tomato paste, not only for a concentrated tomato flavor but to get a deeper, richer looking ‘tomato’ color. Why? It makes the food look more appetizing, and our eyes inform our stomachs as much as smell and taste does. Our eyes provide us the first judgment and if the food doesn’t pass this first test, we may not eat it. Color counts, pure and simple.

Think about it. From an early age we learn what colors go with what foods, and furthermore, we learn to associate the vividness of these colors with the quality of said food. If a dark green vegetable looks grayish green and “lifeless” we know it’s not fresh or of good quality. When a sliced apple turns brown, we know it has been sitting around for awhile. We even figure an egg with a rich dark yellow yolk will be tastier than one with a light and dull yellow yolk. And what’s more, we’d probably be correct. But those are the colors of single foods as they come to us from nature. Once we start combining foods together in the presence of heat, acids, etc. the colors change, and not always for the better.

All sorts of things are added to common home recipes for the purpose of adding color, it is not just the province of manufactured foods. What you may not realize is that if coloring were not added to many of the foods you buy, you might tend to think they were of low quality, owing to an inconsistency in color, or the colors being muted or dull. Paprika and turmeric do as much for color as they do for taste. And one of the most expensive food ingredients you can buy, saffron, is prized as much for the rich yellow color it imparts as for the flavor it brings.

Color additives, therefore, make food more attractive and appetizing. They even help us to identify the foods we buy and eat. Are the bright, deep colorants that are used in today’s food really necessary? Of course not, and it can be difficult to justify, especially when the colors come from a lab instead of from nature. But you must realize that the uniformity and attractiveness you have grown to expect in manufactured foods would not be possible without them.

Can you imagine M&M’s without food dyes? You would have grown up being unable to enjoy saving all the green ones for last! But, let’s be more pragmatic. We expect a product that tastes, for instance, like a strawberry, to be the color of a strawberry. This is purely instinctive. In reality, it is not logical for a drink flavored with strawberries to be the exact color of a strawberry, but we identify the color with the fruit, and so “strawberry colored” soda, for example, may be more appealing than clear strawberry soda. This is changing as clear drinks come on the market with the word “natural” attached to them, but this has entailed its own marketing campaign.

Try your own experiment and infuse a drink with a fruit flavor. It is not reasonable to expect it to be the original color of the fruit, but it is no more reasonable to expect it to appear as clear as water! Each instance is a manipulation, whether the product’s color is exaggerated through dyes, or whether the flavor is completely artificial and no color is imparted to the product. Neither is “natural” in any true sense of the word if there is a true sense. The soda maker may try to use a “naturally occurring” pigment, but these have many failings as they are not stable in all conditions. A consistent color would be very difficult to come by, and regardless how much consumers cry out for ‘natural’ products, they expect consistency in those products!

The reason that food colors are added to foods is the same reason that professional chefs pay close attention to how food is arranged on a plate and the balance of colors in a dish. Flavor and color perception are closely linked. When colorants are used correctly, they are there to enhance the appearance of food that is already of good quality and safe to eat. Colorings should never be used to cover up bad food! However, the idea that the only purpose of food colorings is to provide aesthetic appeal to foods overlooks to close link between the coloring of food and our perception of its quality and healthfulness. No matter the importance, though, it is hard to argue that the large range of colorings, some of which may have unknown effects on the body, is essential.

What are natural food colors?

It is almost impossible to define “natural” food colors in one consistent way. For instance, caramel, an absolute workhorse of a food color, comes from organic sugars, amino acids, or amides. These could be called natural in that they are produced by biological systems, in nature. But the caramel color itself does not come from these systems. Instead, the sugars or proteins are modified to produce the color.

Indigo blue, perhaps one of the most important and well-known plant dyes in history (gives the blue color to blue jeans) is natural, or at least it was, coming from a plant glycoside, indican. But indican is colorless! The leaves of the plant had to be processed, hydrolyzed and oxidized, to turn the indican a blue color.

Therefore, when it comes to colors coming from biological organisms, the definition has to be expanded or the word natural will lose all meaning. Pigments may come from living (or dead) cells, but may be altered in some way to affect their usefulness.

Natural colors could be said to come from minerals, as well. In the 19th century, colorants derived from minerals were introduced into food products, and they led to very serious health problems. Lead chromate and copper sulfate, used to color candies and sauerkraut, were contaminated with arsenic and other toxins, causing deaths. Some mineral colors are no longer permitted to be used for food coloring, such as calcium carbonate (allowed in drugs), carbon black, ferric chloride, and ferrous sulfate. By the same token there are some naturally occurring food colorings of plant origin that are permanently banned.

Natural substances that have been used for food coloring include carmine, paprika, saffron, turmeric, carrot oil, beet extract and vegetable and fruit juices. Also, some natural nutrients can also be used to color food, such as riboflavin and beta-carotene. Several natural food colorants that were used in the past have been banned from use in the United States:

Banned Natural Food colors

  • Alkanet: dyers’ bugloss, Alkanna tinctoria of the borage family, used for a red dye
  • Cudbear: Orcein, also archil, orchil, lacmus, Citrus Red 2, and C.I. Natural Red 28, dyes from orchella weeds, a species of lichen
  • Logwood (chips and extract): Haematoxylum campechianum, a tree with a dark heartwood, from which a purplish-red dye is obtained
  • Safflower: Carthamus tinctorius, also called American saffron or bastard saffron, the flowers make red and yellow dyes

The FDA Does Not Classify Food Colors as Artificial versus Natural

The public is very quick to attack anything synthetic and embrace that seen as natural, but the FDA does not actually recognize any type of food colorant as natural because the addition of any type of color to food results in an artificially colored product. This is not to say that the agency does not differentiate synthetically produced colors from those derived from natural sources, only that all colorings are subject to safety standards and approval for use.

Definition of Artificial Colors

This, in fact, is a cause for general confusion. People speak of “artificial colors” while thinking of “colors made in a lab” but in reality any time a food is intentionally colored beyond that which is present naturally in the food, it is artificially colored, and this is really what is meant by something being artificially colored. It is the process of intentionally changing the color of food beyond its original appearance, regardless of where the colorant comes from. When caramel color is added to Coca Cola® it is being artificially colored, although caramel coloring is derived from natural sources. Therefore, the term artificial color simply means a color that is used to artificially add color to a food. As stated above, the term artificial is often used interchangeably with synthetic, but his usage is not technically correct.

Whatever they are called, there are certain natural colors that are exempt from certification and permanently listed for food use. This does mean that “natural” colors are not subject to some type of premarket approval process, only that these particular colors do not have to be batch certified by the FDA. The FDA classifies colors as either certified or exempt from certification. According to the agency:

Certified colors are synthetically produced (or human-made) and used widely because they impart an intense, uniform color, are less expensive and blend more easily to create a variety of hues. There are nine certified color additives approved for use in the United States Certified food colors generally do not add undesirable flavors to foods.

Colors that are exempt from certification include pigments derived from natural sources such as vegetables, minerals or animals. Nature-derived color additives are typically more expensive than certified colors and may add unintended flavors to foods. Examples of exempt colors include annatto extract (yellow), dehydrated beets (bluish-red to brown), caramel (yellow to tan), beta-carotene (yellow to orange) and grape skin extract (red, green).

Why is the term Artificial Color So Important?

You may be thinking that calling all synthetic colorings “artificial” and calling naturally derived colors “not artificial” makes perfect sense, despite the above. Let’s imagine a scenario in which food labeling permits this use of the term artificial. Say a soda maker uses “natural” caramel coloring and perhaps beet coloring. Therefore they declare on the label: No Artificial Colors! This soda maker, confused, thinks that the lack of artificial colors means that he does not need to mention that color additives were used in his product. Now, you, the consumer, are not informed as to the true ingredients in the product. No artificial colors, in this instance, is ambiguous, since its general connotation would be taken to mean that no color, whatsoever, was added to the product, when in fact there was. It is simpler to simply say that all added colors are color additives and therefore should be considered “artificial.”

This brings us to how colors can be listed on food labels. For certification exempt food colors, similar to flavors, specific colors may or may not be added to the ingredient list. If ONE specific color is listed, then all colors must be listed. However, all specific colors do not have to be listed and an “appropriate statement” can be used, such as “color added.” Under the FD&C act:

  • Section 403(k) of the FD&C Act states that if a food contains an artificial color it should bear labeling “stating that fact. Specifically, the terms “Artificially Colored,” “Artificial Color Added,” *”color added,”* or an equally informative statement should be used which clearly indicates the addition of a color to a food, except where regulations require specific declaration of the color by common or usual name. FDA will not insist upon the use of the word “artificial” with the declaration of color as an ingredient *when* the declaration identifies the color by specific common or usual name and by function. Thus, terms such as “colored with _” or “_ (color)” (the blank being filled with the specific color name such as annatto, beet powder, beta carotene, etc.) is considered satisfactory.
  • Section 403(i)(2) of the FD&C Act permits a color to be listed on a food label as such without naming specifically the color used.
  • 21 CFR 74.705(d)(2) states that all foods, including butter, cheese, and ice cream that contain FD&C Yellow No. 5 shall specifically declare the presence of this color additive in the list of ingredients.

Food color added, natural color or any similar terms that contain the words food or natural cannot be used. These terms could be taken to mean that the color is a naturally occurring color in the food. If you think about it, you can understand that someone might take the term “food color,” for instance, to mean that the color IS A FOOD. Likewise, if a labelled simply bared the declaration “natural colors,” a consumer might think that the manufacturer was simply saying that “only the natural color of the food is present”. That is, that the colors are natural as opposed to coming from added colors! The FDA considers all added colors to result in artificially colored food, and so objects to any added color being declared “natural” or “food.” 4

Certified color additives, such as FD&C Blue No. 1, FD&C Yellow No. 6, etc. must ALL be listed in the ingredients. However, an abbreviation can be used, such as “Blue No. 1” for FD&C Blue No. 1 or “Yellow no. 1” for FD&C Yellow No. 6. However FD&C has a special proviso: “Foods for human use that contain FD&C Yellow No. 5, including butter, cheese, and ice cream, shall specifically declare the presence of FD&C Yellow No. 5 by listing the color additive as FD&C Yellow No. 5 among the list of ingredients.” 1 5

Certified Natural Food Colorings

The list below gives the naturally derived colors that are exempt from certification. Certain of these colors are listed because they are used as a color additive in feed for chickens, salmon, in order to impart a certain color characteristic to the the skin or flesh, or colors used in cat and dog foods. There are regulations as to the total amount that can be used, but those numbers are not included. See amounts here

  • Algae meal, dried – Chicken feed only
  • Annatto extract – GMP*
  • Astaxanthin – Salmonid fish feed only
  • Astaxanthin dimethyldisuccinate – Salmonid fish feed only
  • Beet juice (as vegetable juice) – GMP
  • Beet powder (Dehydrated beets) – GMP
  • Beta-Apo-8′-carotenal – General use
  • Beta carotene, natural and synthetic – GMP
  • Canthaxanthin – General use
  • Caramel – GMP
  • Carmine – GMP
  • Carrot oil – GMP
  • Cochineal extract – GMP
  • Corn endosperm oil – Chicken feed only
  • Cottonseed flour, toasted partially defatted cooked – GMP
  • Ferrous gluconate -Ripe olives only – GMP
  • Ferrous lactate – Ripe olives only – GMP
  • Fruit juice – GMP
  • Grape color extract – Nonbeverage food only
  • Grape skin extract (enocianina) – Still and carbonated drinks and ades, beverage bases and alcoholic beverages
  • Haematococcus algae meal – Salmonid fish feed only.
  • Synthetic iron oxide – Sausage casings for humans cat & dog food
  • Lycopene, tomato extract or concentrate – GMP
  • Mica-based pearlescent pigment – 1.25% by weight in cereals, confections and frostings, gelatin desserts, hard and soft candies (including lozenges), nutritional supplement tablets and gelatin capsules, and chewing gum.
  • Paprika & Paprika oleoresin – GMP
  • Paracoccus pigment – Salmonid fish feed only
  • Phaffla yeast – Salmonid fish feed only.
  • Riboflavin – GMP
  • Saffron – GMP
  • Sodium copper chlorophyllin – Citrus-based dry beverage mixes only
  • Tagetes (Aztec marigold) meal and extract – Chicken feed only
  • Titanium dioxide – = 1.0% by wt. of food
  • Turmeric & Turmeric oleoresin – GMP
  • Ultramarine blue – Salt for animal feed only
  • Vegetable juice – GMP

* GMP Stands for Good Manufacturing Practices. This designation as to use, means that the color can be generally used in amounts required to gain a desired effect, as consistent with good manufacturing practices

Where do those pretty colors in vegetables and fruits come from, anyway?

When things go right, it’s true, nature can make foods of a more pleasing color than the Jelly Belly people could ever hope to. Despite this, there is a synthetic food dye, Citrus Red No. 2 that is permitted for use solely to color the skins of oranges, as long as those oranges are not going to be processed in any way. Incidentally, this is the only synthetic colorant that the Center for Science in the Public Interest did not petition to be banned. Apparently, CFSAN is not aware of all the hyperactive kids with an orange peel licking habit!

So, besides the occasional cheat, where do the real colors in fruits and vegetables come from? The green colors in plants come from chlorophylls, which are pigments in leafy vegetables, fruits, algae, and photosynthetic bacteria (cyaonbacteria) which absorbs light and uses the energy to synthesize carbohydrates from carbon dioxide and water. IT can also impart color to food and when isolated is a deep green.

Carotenoid pigments, such as carotenes and xanthophylls have color ranging from yellow to a dark, almost crimson red. They give yellow and orange colors to fruits and vegetables. Beta carotene, perhaps the most well known, is what makes carrots orange. Perhaps less familiar, astaxanthin gives the flesh of salmon its pink color, derived from the algae that the salmon eat. Lycopene is another carotenoid, found in tomatoes and red peppers. Over 100 different types of carotenoid have been isolated and identified but only three are commonly used for food coloring: beta carotene, apocarotenal (shown above as Beta-Apo-8′-carotenal), and canthaxanthin. Most of these used for food coloring are synthetically manufactured and do not need to be batch certified. In fact, today, more than 90% of colors added to foods are synthetic.

  • Beta carotene – orange to yellow color, general use.
  • Apacarotenal – comes from spinach and citrus fruits, is a precursor to Vitamin A like beta carotene but 50% less pro-vitamin activity. Orange to orange red color. Tends to be used along with annato in fat based foods such as margarine, salad dressing, dairy products, etc.
  • Canthaxanthin – the active substance in tanning pills, it builds up in the panniculus gives quite a fake looking a golden orange color to the skin. This use and the build up of the substance in the retinas called its use in foods into question, but the amounts used in tanning pills is much, much greater, and the crystal build up is reversible after cessation of tanning pill use. Permitted for general food use in the U.S. In the U.K, it’s only permitted for use in Saucisses de Strasbourg, as well as poultry feeds. Red color.

Red, violet, and blue colors come from anthocyanins. These are polyphenolic compounds in flowers, fruits, and vegetables. Lots of anthocyanins are present in berries like blueberries, blackberries, raspberries, strawberries, and grapes, and black currants. Besides being famed, along with carotenoids, for their antioxidant properties, they are used widely to color candies and soft drinks.

Part of the names of many substances are prefixs or suffixes that imply a certain color. For instance chloro- in chlorophyll comes from the Greek chloros meaning a yellow-green color. The -cyanin suffix in anthocyanin comes from the Greek kyanos meaning a blue color. The xanth in xanth- in xanthophyll comes from the Greek xanthos meaning a yellow color.

Some other color words you may be familiar with:

  • Flavin : As in riboflavin, from the Latin flavus meaning pale-yellow.
  • Mela– : As in melanin, from the Greek melas meaning black (although not all melanins are black).
  • Lute– : As in Lutein, from the Greek word luteus meaning a yellow color.

What are the problems with these colors?

Chlorophylls are unstable to heat and insoluble in water. So, chlorophyll, usually as copper chlorophyllin, also sold as a dietary supplement, is only useful as an added color, not a primary one.

Anthocyanins are unstable outside an acid pH range. Carotenoids, always associated with chlorophyll, are unstable pigments and are sensitive to light, oxygen, and peroxide. Some are soluble in water, the lychromes, but others, lipochromes, are not. Likewise, some are stable in acid and some are not, etc. Besides their stability and uniformity, naturally derived colors may also add an undesired flavor to food.

Synthetic colors are stronger, give more intense colors, and they can be used in smaller quantities to give the same effect. They are also often less expensive. When this is taken into account with the stability and lower cost, it is no wonder they are used so extensively over naturally derived colorings.

What about that food color from an insect?

That would be the infamous Cochineal extract, as well as carmine. These are derived from the dried female insect, Dactylopius coccus costa, which is commonly known as the chochineal. These beetles live on certain cacti, mostly in Peru but also in Chile, Bolivia, and the Canary Islands. They are manually harvested twice a year, sun dried, and crushed. The color is extracted with an aqueous alcohol solution to derive a cochineal extract which can be made into different products both powder and liquid. Or, it can be further processed to produce carmine. The active pigment in cochineal extract and carmine is carminic acid. This coloring imparts a red, orange or pink color to foods and are used in meat, candies, beverages, ice cream, dairy products, and cosmetics.

There are some people who are sensitive to cochineal extract, carmine, or carminic acid. Although for most natural colorings, it is not necessary for labels to name the specific color, a new rule was made for cochineal extract and carmine on January 5, 2009, requiring the declaration by name of both colors on all food and cosmetic labels sold in the United States. The ingredients list of products containing these colors must use the common names, “cochineal extract” or “carmine.” These and any other colors that require specific declaration must be declared separately and not as “artificial color” etc.

Starbucks recently fell under fire because of its use of cochineal extract in its Strawberries and Creme Frappuccino, which enraged vegetarians, since the company had claimed that frappucinos could be made vegan with the simple addition of soy milk. The company responded that the coloring was used as part of a drive to get away from artificial ingredients and although the strawberry base is not a vegan product, it helps to move away from artificial dyes.

Here we see, again, the inappropriate use of the word ‘artificial’ as cochineal extract IS an artificial coloring. What the company means is synthetic dyes.

Although the reports of allergic reaction to these extracts are real, opponents and fear mongers, in their usual disingenuous way, wrongly report that “crushed up beetles” are being added to food, which is far from the truth, and a bit ridiculous.

What was the first food to which color was officially added in the U.S.?

Most likely, butter. The coloration of dairy products, in general, was the first to be subject to governmental regulation. Butter does not always come out the same color. Due to the cow’s feed butter color changes from winter to summer. In the winter, when the cow’s eat dried grains, the color will tend to be a pale yellow, while in the summer, when they eat green grasses, it will be a deep yellow. Margarine, on the other hand, is always a pale, bland, white, unless a color is added. You may have guessed, and rightly, that the summer butter (actually “spring butter”) has a better flavor. So coloring added to butter makes all butter look like spring butter, even though all butter is not created equal.

An annatto color (see achiote) is added to butter to give a consistent product, and most of us expect a deeper yellow color. When yellow color was added to margarine, then called oleomargarine (some people still call margarine oleo), the dairy industry was threatened as margarine then became indistinguishable from butter to most consumers. The butter industry charged that colored margarine was nothing more than a way to defraud consumers by disguising the margarine as butter (this was not the only charge..safety and sanitation was also challenged). Thus began one of the most telling examples of the power and importance of added colorings in foods.

There is no doubt that margarine would have never had such success had it remained colorless, a fact not lost on the dairy industry. In 1886, Congress enacted a statute that levied a special tax on margarine. The reason given was that oleomargarine was an ‘artificial substitute’ for natural butter, and was a serious danger to health. Although many charges were made against margarine, it is obvious that the actual purpose of the legislation was to protect the dairy industry against competition, which had only recently begun to process milk and cheese in factories on a large scale technological basis. By the law, manufacturers, wholesalers, and retailers of oleomargarine had to be licensed and were made to pay an annual tax of $600,000, $480,000 and $48.00, respectively. Not only that but margarine itself was taxed at 2 cents a pound. Later, in 1902, colored margarine scared the pants off the dairy people, and the act was amended so that any margarine that was artificially colored yellow was taxed at 10 cents a pound while if the margarine was left uncolored or colored a different color, it was taxed only 1/4 cent. Yes, you read right, if you colored your margarine green, they taxed it much less.

Despite the handicaps that margarine was given, it still ended up being consistently cheaper than butter and was not subject to the shortages the dairy industry was. Especially during World War II, butter was in short supply and there were price controls on dairy products. Also, the dire health warnings about margarine never came to pass (people were supposed to drop dead by the dozens). After the war, some consumer groups lobbied for removal of the taxes on margarine. In March, 1950, the licensing fees and taxes were repealed, but certain requirements were put in place. The original bill had been prefaced with:

“Yellow oleomargarine resembles butter so closely that it lends itself to substitution for or confusion with butter and in many cases cannot be distinguished from butter by the ordinary consumer. The manufacture, sale, or serving of yellow oleomargarine creates a condition conducive to substitution, confusion, fraud, and deception, and one which if permitted to exist tends to interfere with the orderly and fair marketing of essential foods in commerce.”

So, although the Bill allowed the use of yellow margarine in private homes, it said:

“..the manufacture, transportation, handling, possession, sale, use, or serving of yellow oleomargarine in commerce, or after shipment in commerce, or in connection with the production of goods for commerce, or which affects, obstructs, or burdens commerce or the free flow of goods in commerce, is declared unlawful.”

This was just about as vague as it could get, but the Bill underwent some changes so that:

  • All licensing fees and taxes were removed, but
  • All yellow margarine sold must be packaged and each package must cleary identify itself as margarine “in type or lettering at least as large as any other type or lettering on such label.”
  • When colored margarine was to be served in a restaurant, the establishment must display a notice “prominently and conspicuously” that margarine was being served
  • Each margarine serving in public eating establishments must be kept in triangular packages that were labelled as margarine

The enforcement of these provisions was placed under jurisdiction of the Food and Drug Administration and the Act was signed by President Truman on March 16, 1950. Many probably thought that the repeal of the taxes came about because the federal government came to its senses and realized it had overstepped its bounds, but it was more the changing power of competing interest and public opinion, which had no problem with cheap, yellow, margarine.

How Does the FDA Classify Colors?

The FDA classifies color additives as either straight color dyes, lakes, or mixtures. Straight colors are color additives that have not been mixed or chemically reacted with any other substance (for example, FD&C Blue No. 1 or Blue 1).

Dyes dissolve in water and come in the form of powders, granules, liquids or other special-purpose forms. They are be used in beverages, dry mixes, baked goods, confections, dairy products, pet foods and a variety of other products.

Lakes are formed by chemically reacting straight colors with precipitants and substrates (for example, Blue 1 Lake). Lakes for food use must be made from certified batches of straight colors. (One exception is carmine, which is a lake made from cochineal extract.) Lakes for food use are made with aluminum cation as the precipitant and aluminum hydroxide as the substratum.

Lakes are the water-insoluble form of the dye. Lakes are more stable than dyes and are ideal for coloring products containing fats and oils or items lacking sufficient moisture to dissolve dyes. Typical uses include coated tablets, cake and doughnut mixes, hard candies and chewing gums.

Mixtures are color additives formed by mixing one color additive with one or more other color additives or non-colored diluents, without a chemical reaction (for example, food inks used to mark confectionery).

For food colors, white, black, and grey are also considered colors. Also, a chemical that added to a food and which reacts with another substance to form a color may also be considered a color additive. For example, dihydroxyacetone (DHA), when applied to the skin, reacts with the protein of the skin to impart color. Even though DHA is colorless, it acts as a color additive when used for this purpose and is regulated as a color additive.

What are synthetic food dyes?

In 1856, W.H. Perkins derived synthetic colors from coal tars, and opened the first synthetic coloring factory, to make a mauve or aniline purple color. Others soon made similar dyes and they quickly came to be used to color foods, drugs, and cosmetics. Because these dyes were first produced from by-products of coal processing, they were known as “coal-tar colors or coal-tar dyes. Later in 1860, came a major breakthrough when Peter Geis discovered the diazonium coupling reaction. Soon a great number of colors were being made from coal tar and other petroleum derivatives, such as para red, lithal red, and hansa yellow. These began to be used in food by the start of the 1900’s. Red No. 3 (now infamous) was introduced in 1905.

By 1938, about 200 synthetic colors were listed by the FDA on a provisional basis. Most of these remained until 1960. In all there are about 700 of these coal-tar dyes.

What are FD&C colors?

FDA regulations apply to not only food but to dietary supplements, drugs, and cosmetics. Since color dyes are also used in drugs and cosmetics, as well as food, and not all the same dyes are permitted for use in all regulated products, there must be some way to separate the colors into definable categories.

Therefore, FD&C colors are coloring compounds which are approved for use in food, drugs, and cosmetics. D&C colors are permitted to use in drugs meant for internal use and for cosmetics which may come into contact with mucous membranes. And then there are external D&C colors, which can only be used for externally applied drugs (and for cosmetics) but not for use on lips or that may come into contact with mucous membranes.

What are some synthetic FD&C Colors that have been banned through the years?

The following chart lists some of the FD&C colors that were originally provisionally listed and then delisted later on.

FD&C Color Common Name Year Listed Year Banned
Red No. 1 Ponceau 3R 1907 1961
Red No. 2 Amaranth 1907 1976
Orange No. 1 Orange 1 1907 1956
Yellow No. 1 Napthol Yellow S 1907 1959
Green No. 2 Light Green SD Yellowish 1907 1966
Yellow No. 3 Yellow AB 1918 1959
Green No. 1 Guinea Green B 1922 1966
Red No. 4 Ponceau SX 1929 1976
Yellow No. 2 Napthol Yellow S 1939 1959
Orange No. 2 Orange SS 1939 1956
Red No. 32 Oil Read XO 1939 1956
Violet No. 1 Benzyl Violet 4B 1950 1973

In addition to these, numerous D&C colors have banned from use.

What Synthetic Colors are Now Allowed?

Currently, there are 12 permanently listed colors for use in food, of these, notice there are actually only seven basic certified dyes. The others are lakes of these dyes. In addition, are citrus Red No. 2 which is only allowed to be used on the skins of oranges, and orange B, which is only allowed in sausage and hot dog casings. These last two, then, have limited use restrictions. All together, this makes 9 certified colors, of which 7 are permitted for general use. Most of these colors are also listed for use in drugs and cosmetics, although most cannot be used for the eye area, (exceptions noted). A link is provided to a further overview of some of the colors below.

    – Food, drugs and cosmetics, including drugs and cosmetics for eye area – GMP
  • FD&C Blue #1 Aluminum Lake – Drugs and cosmetics for eye area – GMP – Food and ingested drugs – GMP, sutures
  • FD&C Blue #2 Aluminum Lake on alumina – Bone cement
  • FD&C Green #3 – Food, drugs and cosmetics – GMP
  • FD&C Red #3 – Food and ingested drugs – GMP May no longer be used in cosmetics, external drugs, and lakes
  • FD&C Red #40 and its Aluminum Lake – Food, drugs and cosmetics, including drugs and cosmetics for eye area – GMP. Other lakes for food, drugs and cosmetics are also permanently listed
  • FD&C Yellow #5 – Food, drugs and cosmetics, including drugs and cosmetics for eye area – GMP
  • FD&C Yellow #5 Aluminum Lake – Drugs and cosmetics for eye area – GMP – Food, drugs and cosmetics – GMP
  • Citrus Red #2 – Skins of mature oranges – ≤ 2 ppm by wt. of whole fruit, Orange B – Surfaces and casings of frankfurters or sausages – ≤ 150 ppm by wt. of finished product 12
  • FD&C Lakes – Provisionally listed. May be prepared from any of the above certified FD&C colors, except FD&C Red #3 – GMP

The chart below gives the approximate shade of each of the 7 certified dyes.

Color Shade
FD&C Red 3 Pink shade
FD&C Red 40 Red shade
FD&C Yellow 5 Yellow shade
FD&C Yellow 6 Orange shade
FD&C Blue 1 Blue shade
FD&C Blue 2 Dark Blue shade
FD&C Green 3 Bluish green shade

How do they Mix FD&C Certified Colors to make Other Desired Colors?

There are blend formulas, by weight, used to make commonly desired shades, such as black, lime, strawberry, or orange. Of all the colors, black is probably the hardest to make, as even slight variations in the blend can throw off the shade. And yes, “black” and “white” are considered colors when it comes to food additives.

Blends of Blue No. 1 and Yellow No. 5 will make almost any shade of green. Blends of Yellow No. 6, Yellow No. 5, and Red No. 40 will produce almost any shade of orange. Increasing the amount of Yellow No. 5 in the blend will give a lighter and yellower shade and increasing the Red No. 40 will cause the shade to become a deeper red.

Blends of Red No. 2 and Blue No. 1 will produce almost any shade of grape. To make almost any shade of red, Red No. 2, Red No. 3, and small amounts of Yellow 6 and Blue 1 can be used. The following table gives a listing of certified color blends by weight.

Color Shade Blue No. 1 Red No. 2 Red No. 3 Red No. 40 Yellow No. 5 Yellow No. 6 Blue No. 2
Black 12.3 7.3 26.8 53.6
Deep Blue 60 40
Caramel Brown 5 26 49 20
Chocolate Brown 7.5 28 26.5 38
Medium Green 35 65
Mint Green 45 55
Lime 1 99
Medium Orange 3 27 70
Amber/Orangeade 100
Bluish Grape 15 85
Reddish Grape 10 90
Grape/wine 12 59 30
Cherry Red 60 40
Strawberry 83 3 14
Pink 95 14
Egg Yellow 1 86 14
Lemon Yellow 100

Adapted from Reineccius, 1994.

What kinds of food are most likely to use food colors?

The following list gives the foods that use the highest amount of food colors, including a brief description of their use.

Beverages

The beverage industry is probably the number one user of food colorants, and the certified FD&C colors are by far the main types of colorings used, except for colas and root beers, which use caramel coloring. The table below lists the typical FD&C colors that might be found in some common flavored beverages. When two colors are listed, such as “yellow no. 6 and red no. 40”, it means that these two colors are combined to produce the desired color of the beverage. Cola and root beer, as mentioned, use caramel coloring and are not included in the table.

Beverage Flavor Typical FD&C Colors Used
Orange Yellow No. 6 or Yellow No. 6 and Red No. 40
Cherry Red No. 40 and Blue No. 1
Grape Red No. 40 and Blue No. 1
Strawberry Red No. 40
Lemon Yellow No. 5
Lime Yellow No. 5 and Blue No. 1

Bakery Products

Bakery products use combinations of certified and natural colors to obtain their colors. Doughs, cookies, sandwich fillings, icings, coating, and ice cream cones may all employ colorings.

Candy

Candy uses many certified and natural colors, sometimes mixed to obtain a certain hue or because the candy comes in different colored pieces. For instance, Hershey’s Good and Plenty candies use the above-mentioned carmine and Red 40.

Dairy Products

Just about all ice creams and sherberts contain artificial colors. Remember, the term “artificial color” refers to any coloring added to a food. Chocolate ice cream may be the most common exception. Butter, margarine, and some cheeses use annatto beta-carotene.

Dry Mixes (such as baking mixes)

Although you probably aren’t surprised to find that powdered gelatins and puddings use artificial colors, you may not have realized that cake and pancake mixes often use them as well.

Pet Foods

Pet food are under the jurisdiction of the FD&C Act. Iron oxide has been used traditionally. And certified colors are often used in dry extruded pet foods.

What are the food colors I get at the grocery store made of?

Most grocery stores sell little boxes of assorted liquid food colors. They are made with combinations of the seven certified synthetic dyes that are allowed to be used in foods. Typically, there are four colors: green, yellow, red, and blue, in an aqueous solution

The red color will likely be Red No. 40 and Red No. 3, for a “regular red” color. A deeper red, like “cherry red” might be only Red. No. 40.

The yellow might be a mixture of Yellow No. 5 and Red No. 40 or just Yellow No. 5 for a less orange shade.

The green color might be Yellow No. 5 and Blue No. 1. Blue might be Blue No. 1 and Red. No. 40.


What is Carotene

Carotene is one of the two types of carotenoids present in plants responsible for the orange color of the plant. Generally, carotenoids are organic pigment only produced by photosynthetic organisms including plants, algae, and bacteria. The main function of carotenoids is to serve as accessory pigments in photosynthesis. Although animals cannot synthesize carotenoids inside their body, these compounds play a key role as antioxidants and anti-inflammatory molecules.

Figure 1: Orange Color in Carrots

Furthermore, the main structural feature of carotenes used to distinguish them from xanthophyll is the absence of any oxygen atoms in the molecule. Also, there are four main types of carotenes as β-carotene, α-carotene, and lycopene. Mainly, β-carotene and, to a certain extent, α-carotene are responsible for the synthesis of vitamin A inside the animal body. Looking at the sources, β-carotene occurs in cantaloupe, mangoes, papaya, carrots, sweet potatoes, spinach, kale, and pumpkin while α-carotene occurs in pumpkin, carrots, tomatoes, collards, tangerines, winter squash, and peas. Whereas, lycopene occurs in watermelons, tomatoes, guavas, and grapefruit.


Green

Chlorophyll pigments give plants their green color, and several changes happen when a green vegetable goes into boiling water. First, a brighter green color develops, caused by the expansion of gases and their escape from spaces between plant cells. The collapse of these rather cloudy pockets of gas reveals the bright-green chloroplasts within the cells. A second color change occurs in response to acidic water: The magnesium ion in the center of the chlorophyll molecule is replaced with a hydrogen atom, causing the green to dull. Chlorophyll-a becomes gray-green pheophytin-a, and chlorophyll-b turns into yellowish pheophytin-b. If the boiling water is slightly alkaline, then chlorophyll stays greener. Fried vegetables change to a duller green color when temperatures reach 140 degrees Fahrenheit. The heat damages chloroplasts, releasing natural cell acids to turn green into olive-green.


Using Yellow Watermelon

There are many uses for yellow watermelon, largely the same as red watermelon. [5]

  • The consistency is the same, as is the summary nature of this fruit, making it a popular addition to fruit salads and fruit smoothies.
  • You can also juice yellow watermelon for a nutrient-dense and powerfully sweet beverage .
  • They are good to eat raw, or as a base for a light, refreshing salad.
  • You can also cut these watermelons up and serve slices at your next summer party!

Why the confusion?

In the United States, firm varieties of sweet potatoes were produced before soft varieties. When soft varieties were first grown commercially, there was a need to differentiate between the two. African slaves had already been calling the ‘soft’ sweet potatoes ‘yams’ because they resembled the yams in Africa. Thus, ‘soft’ sweet potatoes were referred to as ‘yams’ to distinguish them from the ‘firm’ varieties.

Large sweet potatoes are ploughed up for migrant workers to pick and sort according to size at Kirby Farms in Mechanicsville, VA. U.S. Department of Agriculture, 2013. USDA Flickr Photostream.

Today the U.S. Department of Agriculture requires labels with the term ‘yam’ to be accompanied by the term ‘sweet potato.’ Unless you specifically search for yams, which are usually found in an international market, you are probably eating sweet potatoes!

Field workers evaluating high yielding yam varieties in a research farm. External link International Institute of Tropical Agriculture (IITA) Image Gallery.

Published: 11/19/2019. Author: Science Reference Section, Library of Congress



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