Why do peas change colour?

Why do peas change colour?

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I am doing an experiment on preservation of peas.

The first notable change to the peas over a period of one week is that they have changed colour from bright green to a dull colour… Why is this so?

The only test tube which did not have peas which changed colour was the one which was kept at 4 degrees Celcius in a fridge, so it probably has some relation to temperature…

Many thanks

N.B.: I know that the bacteria reproduce and could use the pea as their source of food, but how do they have any relation to the colour of the pea? I also put the tag "bacteria" and "thermodynamics" as I couldn't find any other related tags.

Chlorophyll is a dye that makes leaves green, it plays a key role in photosynthesis. It is present also in unripe fruits, young peas etc. Maybe I should say chlorophylls, because it is a group of similar chemicals. They get degraded by heat.

(No assistence of microbes needed).

Bonus: Chlorophyll contains magnesium at the molecule core, which facilitates the green color. There were some creative people, who were upset, that the canned cucumbers are not green enough, so they added some copper-containing molecule during canning. It replaced magnesium and was more stable, so beautiful bright green cucumbers were on the market for a while. However, they turned out to be slightly poisonous and are not sold anymore.

Bonus 2: Most varieties of peas change color also naturally as they rippen. The seeds become yellow. The chlorophyll gets degraded in plant metabolism. The chloroplasts, i.e. the cell organelles responsible for photosynthesis change function to become storage organelles called leucoplasts.

(Edit: Ooops, I first wrote that chlorophyll supposedly contains iron. That was wrong, it is magnesium. Iron is present in a similar die called heme, which makes blood red. Probably I am getting too old :-) )

What causes color changes in home-canned foods - and how to prevent it

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Law of Independent Segregation

Mendelian genetics is based on three laws that dictate how certain traits are transferred from parents to offspring. These three laws are: the Law of Dominance, Law of Independent Segregation, and Law of Independent Assortment. These three laws were proposed by Mendel in 1865 in his paper &lsquoExperiments on Plant Hybridization&rsquo, which he submitted to the National Science Society in Brno (now in the Czech Republic). In this article, we&rsquore going to focus on the Law of Independent Segregation.

Pea Plant Characteristics Studied

Mendel focused on the different traits, or characters, that he noticed pea plants exhibiting in a binary manner. That is, an individual plant could show either version A of a given trait or version B of that trait, but nothing in between. For example, some plants had "inflated" pea pods, whereas others looked "pinched," with no ambiguity as to which category a given plant's pods belonged in.

The seven traits Mendel identified as being useful to his aims and their different manifestations were:

  • Flower color: Purple or white.
  • Flower position: Axial (along the side of the stem) or terminal (at the end of the stem).
  • Stem length: Long or short.
  • Pod shape: Inflated or pinched.
  • Pod color: Green or yellow.
  • Seed shape: Round or wrinkled.
  • Seed color: Green or yellow.

Sorry, Fresh Peas. Frozen Peas are Just Better.

I've always liked the idea of fresh peas. So beautiful and round and green, so lovely in their crisp shells. And every now and then, when the peas are picked at freshly picked and eaten at just the right moment, a fresh pea is pure joy. But those moments are all too rare. There are too many variables that have to be just right in order for a fresh pea to actually taste good, and often they're just starchy and mealy and not sweet.

I recently tried to make a spring chowder with fresh English peas in it, and the soup was a weird, mushy mess until I switched to frozen sweet peas. My first go at this braised leeks and peas dish for Easter was a disaster because I tried to be fancy and use fresh peas—and again once I switched to frozen peas, everything was better.

Yes, those are frozen peas in there and they're the secret to the success of this dish.

Photo by Chelsea Kyle, Prop Styling by Beatrice Chastka, Food Styling by Frances Boswell

I've been disappointed by fresh peas so many times, in fact, that I've decided to go ahead and declare my loyalty to Team Frozen Peas henceforth. Frozen peas, which are always picked and flash-frozen at the exact peak moment of ripeness, will never let you down. A bag of frozen peas (here's a list of our favorite ones) can sit in your freezer for months and still taste delicious, crisp, and sweet when you defrost them.

The key to preparing meals with frozen peas is to be sure not to overcook them. This is crucial. Frozen peas are flash-steamed before they're frozen, so they're already ready to eat—you just want to warm them very quickly so they maintain their slight bounce and bright color. Despite what their packages say, if you cook frozen peas for longer than a minute, they lose their sweetness and that delicious pea "pop."

Sometimes I defrost my frozen peas before using them so they don't cool down whatever I'm stirring them into, like that leek-and-lettuce braise or the spring chowder. To do so, I just run frozen peas under cool water in a strainer until they're no longer frozen—it doesn't take long. If I'm cooking them in boiling water, I don't bother defrosting them at all: I dump the peas directly from frozen into the boiling water, give it a stir, and then immediately strain.

Taste Test: Frozen Peas

This is a great trick for adding peas to pasta: as soon as the pasta is about to be done cooking, add frozen peas to the pot along with the pasta, and then drain everything together and bingo bango your one-pot pasta dinner is ready to go. When I'm feeling even more clever, I add asparagus a few minutes before the peas for a one-pot spring pasta dinner.

So, hey, I'm sorry, fresh peas. You should know that I really did want to love you. You're so pretty and romantic in the spring. But I need a dependable partner in the kitchen, so from now on, frozen peas are it for me.

Have students prepare the solutions for the activity.

Explain to students that they will first make their solutions for the activity. Either go through each step with them or have them follow the procedure described on their activity sheet.

Teacher Preparation

Students will need small amounts of sodium carbonate and citric acid for the activity.

  • Label two small plastic cups citric acid and sodium carbonate for each group.
  • Place about ¼ teaspoon of citric acid and sodium carbonate in the labeled cups.
  • Distribute the cups with universal indicator solution to each student group.

Materials for Each Group

  • 2 clear plastic cups
  • 3 droppers
  • Masking tape and pen or permanent marker
  • Universal indicator in cup
  • Water
  • Graduated cylinder
  • Sodium carbonate
  • Citric acid
  • 2 flat toothpicks


Label your equipment

Use masking tape and a pen to label one cup citric acid solution and another cup sodium carbonate solution.

Use a small piece of masking tape and a pen to label one dropper citric acid solution and the other dropper sodium carbonate solution.

Make a citric acid solution

Use your graduated cylinder to add 5 mL of water to the cup labeled citric acid.

Use a flat toothpick to pick up as much citric acid as you can on the end of the toothpick as shown.

Add this citric acid to the water in the citric acid cup. Gently swirl until the citric acid dissolves.

Make a sodium carbonate solution

Use your graduated cylinder to add 5 mL of water to the cup labeled sodium carbonate.

Use a flat toothpick to pick up as much sodium carbonate as you can on the end of a toothpick.

Add this sodium carbonate to the water in the sodium carbonate cup. Gently swirl until the sodium carbonate dissolves.

Color-changing bacterium inside the pea aphid

The green aphid (left) and red aphid (right) have identical genetic backgrounds. The body color of the green aphid was generated by Rickettsiella infection of a previously red aphid. Credit: Tsutomo Tsuchida

A bacterium that can live symbiotically inside the pea aphid, Acyrthosiphon pisum, is able to change the insect’s body color from red to green, a RIKEN-led team of molecular entomologists has found. Because body color affects how other animals are attracted to aphids, infection with the bacterium is expected to impact on interactions with other symbiotic organisms, predators and parasites. Studies of the molecular mechanism behind the color change could lead to technologies for generating pigments more efficiently, and also for changing the appearance of some organisms, the researchers say.

Both red and green forms of pea aphid occur in natural populations. Previous research by other workers has shown that body color is correlated with the presence or absence of a single gene, and that red is dominant. Ecologically, the balance between the colors is maintained because the most important predators, ladybug beetles, preferentially eat red aphids, while parasitoid wasps attack the green form.

While screening aphids collected in France, Tsutomu Tsuchida from the RIKEN Advanced Science Institute in Wako, together with colleagues from France, and from other Japanese research institutions, found several strains of green aphids with red young that turned green as adults.

Studies by Tsuchida and other researchers have demonstrated that symbiotic bacteria play a role in the adaptation of pea aphids to particular varieties of plants and to high temperature, as well as in the development of resistance to natural enemies. On investigating the symbiotic bacteria in Western Europe, the researchers found that about 8% of pea aphids are infected by a previously unrecognized species of Rickettsiella bacteria. Measurements of growth rate, body size and fecundity of infected aphids showed no negative impact on fitness.

By generating separate lines of aphids infected and uninfected by Rickettsiella, Tsuchida and his colleagues were able to show that uninfected red aphids always retained their color, as did all green aphids. Not all infected red aphids turned green, but the color change from red to green was always associated with Rickettsiella. In fact, the intensity of green color depended on the level of infection. The researchers thus concluded that the color change depended on an interaction between the Rickettsiella and aphid genomes.

“We are now extensively analyzing the genome sequence of the symbiotic bacterium and symbiont-induced gene expression of the host aphid,” Tsuchida says. “These analyses should show us the molecular and metabolic interplay that leads to the body color change.”

How (and why) animals change color with the seasons

Quick, name a color-changing animal. Did you say octopus ? Chameleon ? Cuttlefish ? Excellent work — but there are a lot more. And they may only change color once a year.

And now, two mimic octopuses making sweet, sweet love

We love ourselves some mimic octopodes, and they certainly love each other. In fact, here are two…

Chameleons Use Color to Communicate, Not Hide

Though most people believe chameleons use their color-changing abilities for camouflage, a new…

And now, three minutes of Flamboyant Cuttlefishes resembling acid trips

If you don't have tickets to Laser Floyd at your neighborhood planetarium tonight, just watch 199…

The ability to change colors is one of the most useful adaptations in the animal kingdom. Color can camouflage, hiding you from predator and prey alike. Color can communicate, signaling to potential mates that you're open for business. Color changes can occur swiftly, or they can change with the seasons. Different situations call for different color-changing skills and nature has selected for these traits as necessary across an impressive array of species.

Different animals do this in different ways. Cephalopods, for example, depend on chromatophores — pigment containing cells that can change colors on a millisecond-to-millisecond basis, typically in response to the contraction and relaxation of muscles surrounding the cell. Chameleons achieve a similar effect through rapid molecular signaling within and between cells. Meanwhile, animals at extreme latitudes often change colors with the seasons, as colder temperatures and shorter days trigger hormonal changes that give rise to dense, white coats. Take the stoat, for example.

Stoat (Mustela erminea) aka Ermine

Closely related to weasels, stoats, like snowshoe hare, adopt a predominantly white coat in the winter months (save for their characteristically black-tipped tails). This cold-weather coat is also more densely packed, and softer than the brown fur worn the rest of the year. Perhaps not surprisingly, soft, fluffy and white are all popular features in the fur industry, where stoat coats, harvested by trappers, are referred to as ermine.

NB: Stoats look every bit as conniving in a white coat as they do in a brown one.

Snowshoe Hare (Lepus americanus)

Snowshoe hare are the perfect example of a prey species that relies on camouflage to keep from being eaten. Unlike the stoat, which ecologists suspect may rely on camouflage to hide from prey and predators, snowshoe hare depend on their coat primarily to avoid lynx, coyotes, fox and birds, as well as for warmth.

Ptarmigan (Lagopus muta)

Like the stoat and the snowshoe hare, the ptarmigan is commonly found in northern latitudes, and therefore exhibits seasonal camouflage. By now you've recognized the pattern common to these northern species: come winter, the ptarmigan will trade its "normal" plumage for a set of uniform, downy feathers. Side note: is it me, or do all these species look noticeably more adorable in their winter white? Not saying the Ptarmigan's mottled plumage isn't cool-looking or functional on the contrary, the speckled feathers of ptarmigan do an admirable job of blending in with the rocky mountainsides where the bird tends to hang out.

But not all color-changing animals do so seasonally. Many species of amphibians, reptiles, fish and insects can change their colors relatively quickly, and reversibly. This is due mostly to the fact that they don't need to grow an entirely new coat, or set of feathers, to undergo a dramatic shift in color. Take the goldenrod crab spider, for instance, or Peron's tree frog:

Goldenrod Crab Spider (Misumena vatia)

Goldenrod Crab Spiders, as their name suggests, are often found stalking prey along the petals of intensely yellow goldenrod flowers. When hunting against such a vibrant backdrop, it pays to blend in with one's surroundings, what ecologists refer to as "cryptic mimicry.: Consequently, goldenrod spiders have evolved the capacity to change colors reversibly from white to yellow. The change from white to yellow takes about two to three weeks, and is thought to be triggered by visual feedback, while changing back takes a little under a week. Interestingly, while a few chemical precursors important to the color change have been identified (namely 3-hydroxykynurenine), much of the biochemistry responsible for cryptic mimicry in crab spiders remains a mystery .

Peron's Tree Frog (Litoria peronii)

Peron's tree frog is native to Australia, where it's also known as the Laughing Tree Frog or the Maniacal Cackle Frog. Because. well, because of this:

It's also capable of undergoing a variety of color changes with incredible speed — shifting from a pale, greenish grey color to a reddish brown with green flecks, to almost completely white, with black and yellow markings on its thighs — as its surroundings, the temperature, and the time of day dictate.

There are plenty of other examples, of course. Wikipedia's got a pretty extensive (if incomplete) page dedicated to color-changing animals. Conspicuous in their absence are the arctic fox and various species of chameleons (seriously).

Sexual Selection

Males and females of certain species are often quite different from one another in ways beyond the reproductive organs. Males are often larger, for example, and display many elaborate colors and adornments, like the peacock’s tail, while females tend to be smaller and duller in decoration. Such differences are known as sexual dimorphisms (Figure 3), which arise from the fact that in many populations, particularly animal populations, there is more variance in the reproductive success of the males than there is of the females. That is, some males—often the bigger, stronger, or more decorated males—get the vast majority of the total matings, while others receive none. This can occur because the males are better at fighting off other males, or because females will choose to mate with the bigger or more decorated males. In either case, this variation in reproductive success generates a strong selection pressure among males to get those matings, resulting in the evolution of bigger body size and elaborate ornaments to get the females’ attention. Females, on the other hand, tend to get a handful of selected matings therefore, they are more likely to select more desirable males.

Sexual dimorphism varies widely among species, of course, and some species are even sex-role reversed. In such cases, females tend to have a greater variance in their reproductive success than males and are correspondingly selected for the bigger body size and elaborate traits usually characteristic of males.

Figure 3. Sexual dimorphism is observed in (a) peacocks and peahens, (b) Argiope appensa spiders (the female spider is the large one), and in (c) wood ducks. (credit “spiders”: modification of work by “Sanba38″/Wikimedia Commons credit “duck”: modification of work by Kevin Cole)

The selection pressures on males and females to obtain matings is known as sexual selection it can result in the development of secondary sexual characteristics that do not benefit the individual’s likelihood of survival but help to maximize its reproductive success. Sexual selection can be so strong that it selects for traits that are actually detrimental to the individual’s survival. Think, once again, about the peacock’s tail. While it is beautiful and the male with the largest, most colorful tail is more likely to win the female, it is not the most practical appendage. In addition to being more visible to predators, it makes the males slower in their attempted escapes. There is some evidence that this risk, in fact, is why females like the big tails in the first place. The speculation is that large tails carry risk, and only the best males survive that risk: the bigger the tail, the more fit the male. This idea is known as the handicap principle.

The good genes hypothesis states that males develop these impressive ornaments to show off their efficient metabolism or their ability to fight disease. Females then choose males with the most impressive traits because it signals their genetic superiority, which they will then pass on to their offspring. Though it might be argued that females should not be picky because it will likely reduce their number of offspring, if better males father more fit offspring, it may be beneficial. Fewer, healthier offspring may increase the chances of survival more than many, weaker offspring.

In both the handicap principle and the good genes hypothesis, the trait is said to be an honest signal of the males’ quality, thus giving females a way to find the fittest mates— males that will pass the best genes to their offspring.

What Is the Protein and Biuret Colour Change Reaction?

The protein and biuret color-change reaction is a reaction in which the charge of copper ions in the biuret reagent change from a +2 to a +1 in the presence of the peptide bonds that hold amino acids together. This alteration causes a color change from blue to purple.

Biuret reagent is an alkaline mixture consisting of potassium hydroxide and copper sulfate. It is often used to test for protein in human urine or in the human bloodstream. A significant reaction of biuret reagent with protein in human urine analysis can indicate problems with the function of the kidneys, diabetes, heart disease or other health problems. It may also be an indication of pregnancy. A significant reaction of biuret reagent with protein in the bloodstream is often used to diagnose dehydration, inflammation or infection.

Proteins are made up of amino acids connected to each other by peptide bonds. Though there are 50 amino acids in the human body, only 20 amino acids are used to make proteins. The amino acids are connected by peptide bonds in various combinations to create the many different proteins that are essential for cellular processes. At least two peptide bonds must exist for biuret reagent to indicate the presence of a protein.