What makes the Tarocco blood orange turn color?

wizzard419January 21, 2012

Hi all,

I was just curious about something. I know the Taroccos need cold weather to produce the red pigment within their flesh but I was always curious. Does the tree itself (with fruit on it) need to reach that cold to produce the compounds that create the red flesh or do the oranges (on or off the tree) just need to get cold to do that?

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hoosierquilt USDA 10A Sunset 23 Vista CA(10b Sunset 23)

Well, from what I understand about how anthocyanins work, it is first found in the leaves and stems of the plant. And the fruits mature, the pigments move up and into the fruit. They begin accumulating in the vesicles at the edges of the segments and at the blossom end of the fruit, and will continue accumulating in cold storage after harvest (to some limited extent, depending upon how much anthocyanin is in the peel).

Yes, climate plays a very significant role in the production and deposits of the anthocyanin pigment. Where I live in the coastal S. California area, we don't have quite the optimal temperature variations to get really good coloration, although it's not too bad so far for me since I'm about 6 miles from the coast, especially since we're on our 3rd pretty chilly winter. Plus, you may find that the oranges on the north side of the tree will be more pigmented than the oranges hanging on the south side of the tree. And, Tarocco's tend to taste and perform the best of the 3 anthocyacin blood oranges you can commonly purchase (Tarocco, Moro and Sanguienello), although they are not the most pigmented of the three (Moro is).

The lycopene blood oranges, like Cara Cara and Vaniglia Sanguigno also do well here for sure and their coloration is not dependent upon temperatures. My Cara Cara was distinctly pink and exceptionally sweet. But then, it's a navel orange and a sport of the Washington navel, which do very well here (just about everyone that has citrus in their yard here has Washington Navel orange tree). Plus, another cool feature of Cara Cara is the tendency for variegate sport branches. And, the fruit off those variegated branches ends up with variegated skin! Very fun tree. Pink grapefruits get their color as well from lycopene.

For me, the Moro's get the most pigmented, then the Tarocco, but the Tarocco's do tend to taste better out here. Moro's can develop an off flavor if they stay on the tree too long sometimes, but it doesn't bother me like it does for other folks. For me, the Tarocco doesn't get very pigmented skin The Moro is variable. The Sanguinello has the most erratic pulp pigmentation, but the skin is more pigmented than either the Tarocco or Moro.

Perhaps some of our more knowledgeable members (Dr. Manners??) can add more info about this very interesting phenomena. The great thing about blood oranges besides the cool color and unique flavor, is the amount of great anti-oxidants you get from the pigment. In both the anthocyanin as well as lycopene blood orange varieties! It's like good and better - citrus with extra anti-oxidants, yumm! A sidebar - anthocyanin is what makes Pomegranates red, purple cabbage purple, and red/purple grapes reddish to purple. Lycopene is what makes tomatoes and watermelosn red, and carrots & papayas orange-ish :-)

That's what you get when you ask a nurse I guess!!

Patty S.

    Bookmark   January 22, 2012 at 7:29PM
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I love it when I get tons of info (I'm actually in coastal OC myself) I was surprised that is theoretically possible that cold storage, off the tree, may actually be able to impact the production. Last year was the first crazy bumper crop (over 200 off a semi-dwarf tree).

I was thinking about getting a Moro, but opted against it. While I do like how those are deep red inside, their flavor isn't as special (from what others say).

I probably already overload on anti-ox and lycopine since I have a pom tree, and grow tomatoes all year round.

    Bookmark   January 22, 2012 at 8:14PM
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hoosierquilt USDA 10A Sunset 23 Vista CA(10b Sunset 23)

Actually, I like the Moro orange, Wizzard! I'm in Vista, and in the hills, but I grew up in Huntington Beach just a few blocks from the ocean, small world!! We do get just cold enough to get some nice color in our blood oranges. And I do really like the taste of the Moro. It can taste a little "winey" if it sits around too long, but personally, I don't think it is off tasting to me. It's not bad, just different. And it's pretty sweet with what I think is a very good balance of sugar to acid. I was also prepared to not like them, based on what I was hearing. Glad I planted one and glad I've bought them at our local Farmer's Market (which is what prompted me to plant one.) And you think the Tarocco is a prolific producer, Moro's are really, really prolific. I have twice as many oranges on my Moro right now, than on my Tarocco (but it had the Attack of the Slugs, so had a bit of a wee set back last spring.)

And you can't get too much lycopene or anthocyanin :-) Good for you! I have 7 varieties of poms planted, and hoping for some nice fruit this year. If I can keep the squirrels out of my tomatoes, I'll have more of those this year, too, lol!!

Patty S.

    Bookmark   January 22, 2012 at 8:37PM
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I might get one, it mostly depends on what I want to grow. Right now the sugar cane crop is getting ready to emerge and if it doesn't do well I might uproot it and replace it with oranges.

    Bookmark   January 22, 2012 at 9:43PM
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pgde(Tucson Zone 9)


If you are going to uproot your sugar cane would you like to ship it to me here in Tucson? Would be happy to pay shipping or other costs....

I also have a Moro (although it is too young to bear yet, maybe one or two more years). However, it survived the fr**ze of last year with some frost protection (unlike my Valencia and Grapefruit). I try not to use the "f" word in conjunction with citrus. And, it seems to be growing rather vigorously -- right now it is probably about 5 feet high and 4 feet across. I think last winter retarded its normal growth cycle. But, being in coastal OC, I don't think you have to worry about that .

Good luck!


    Bookmark   January 22, 2012 at 11:29PM
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I'll send you an email about getting some cuttings.

Last year was quite chilly, though nothing outside of some tomato plants were affected.

    Bookmark   January 23, 2012 at 2:03AM
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Hoosierquilt -- do you have a reference for the movement of anthocyanin from leaf to fruit? I'm not sure I believe that; rather, I would think the anthocyanin is made on site, likely in the individual plant cell where it will stay. That's certainly the case in blackberries, etc., and I'd think it true for citrus too. I know of only one plant that has significant anthocyanin in its stem sap, and that's a bizarre rose called 'Basye's Purple', which bleeds what looks like grape juice when you cut a stem. But even there, I suspect it is just making a lot of anthocyanin in those individual stem cells, and they are released when you cut the stem.

    Bookmark   January 23, 2012 at 10:39AM
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Lycopene pigmented citrus probably should not be called "blood".

Cut the sugar cane between the nodes and use it to mulch your citrus. It has lots of potassium and the plants like sugar too. It is one of the best mulches I've used, and I've tried a lot.

    Bookmark   January 24, 2012 at 11:40AM
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hoosierquilt USDA 10A Sunset 23 Vista CA(10b Sunset 23)

I did just read that, Dr. Manners, but it may have been the precursor components of anthocyanin that move up the stem to the fruit. Let me see if I can find the article I was reading. I believe the red basils also have anthocyanin in their stems and leaves (bad memory, but pretty sure that's what I read). What I find very interesting, is why some blood oranges end up with very pigmented skin, but not pulp, while others, like the Moro, have strikingly pigmented pulp, and not so much the skin. and tantanman, yes, technically I agree with you, but most folks just lump all pigmented citrus into the "blood" category. I agree, but it's hard to make folks do the logical, sometimes :-) You'll see Cara Cara and Vaniglia Sanguigno often categorized as blood oranges, but how they get pigmented is different. Just how some folks categorize colored oranges - not my choice.

Patty S.

    Bookmark   January 24, 2012 at 11:48AM
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hoosierquilt USDA 10A Sunset 23 Vista CA(10b Sunset 23)

Dr. Manners, went back and did more reading on the biosynthesis of anthocyanins, and you are indeed correct. Although the components that produce the end product - anthocyanin are of course transported to the site (pulp and peel for citrus), they are "assembled" for lack of a better word, on site in the vacuoles of the cell where the pigment is displayed. Actually, (shockingly?), Wikipedia has a very nice synopsis of the biosynthesis of anthocyanin, and the entry is well-referenced. Now, that all being said, my biochemistry is OLD (can we say 1980?), so pretty rusty, but yes, you're quite correct - happens in the peel and pulp, and the anthocyanin can travel to the pulp from the peel, even after picking. And since there are several enzymes responsible for the creation of anthocyanin, there can be any number of genetic or environmental factors which can affect anthocyanin synthesis. So, some years you may get very pigmented oranges, and other years, not so much, even from a tree with good anthocyanin "genes". What I found very interesting as an aside, is that pretty reddish tint you see in a rose's new growth is caused by juvenile anthocyanin. I wonder where it goes though, after the leaves mature and turn green? Or does it NOT go anywhere, but is "overruled" by chlorophyll?? Travel to the red petals of the flower (red/dark pink roses have much redder new leaves). Guess that's another topic for another forum, lol!! I will always defer to your expertise, I am no biochemist for sure!!

Patty S.

    Bookmark   January 24, 2012 at 12:09PM
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That is interesting, so the reason that my oranges were more red towards the end (in some cases they looked almost as red as a moro) was simply due to post picking chilling?

I would give my oranges the sugar cane but I usually juice it or eat it, so I might give them the left overs.

    Bookmark   January 25, 2012 at 9:56PM
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hoosierquilt USDA 10A Sunset 23 Vista CA(10b Sunset 23)

Could be, wizzard. Perhaps whatever anthocyanin was left in the peel migrated to the pulp?

Patty S.

    Bookmark   January 25, 2012 at 11:31PM
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