Analyzing and comparing satsuma sweetness

[mar3]

The University of California Riverside maintains records of various features such as brix and acidity for a number of satsuma varieties. This is a great resource, and they've made freely available online. I'm sure most of you folks are already aware of it. I was curious about the sweetness of different varieties of satsumas, so I used it to compare listed varieties with trees over around 4 or 5 years old.

The ratio:  soluble solids concentration (SSC) / total acid (TA) is the most common formula that I've seen used, and some states that have a satsuma industry use it to grade their product quality. At least one study has shown that an alternate method called "BrimA" better predicted how much consumers would like a fruit. You calculate BrimA by: SSC - k * TA Here, "k" is some coefficient used to weigh acidity more than SSC, since the idea is that acidity will have a greater impact on flavor. To me, subtracting weighted acidity from SSC makes sense for satsumas. For example, if you have a very low acid satsuma that is not very sweet, it can still score relatively well with SSC / TA (e.g. when it has an TA of ~0.5). But some might say it lacks richness and has a watered down flavor. But by instead using subtraction, you must have a high SSC in order to get a high brimA. If the SSC is high enough, and even if you have acidity, you can still beat out lower acid fruits (getting a sweet + tart flavor). This article mentions California switching to this method in 2012 for grading navals. For this post, I used brimA with a k-value of 3.

UCR's entries have info such as dates, SSC, TA, exterior color, and % juice. Different varieties ripen at different times. I wanted a more objective way to find a "ripe enough" date than something like taking an average of when they happened to pick fruit. I've noticed that many varieties will decline in juiciness as time goes on and that UCR tends to stop picking them when values fell below 40%, roughly. My guess is that after this point, the fruit is perceived to be poorer quality and "dry," despite the fact that sweetness continues to increase and acidity decrease. I did a linear regression on date and juice % and solved for the latest date at which juiciness was still at least above 40%. A couple of varieties never really went above that point, and so I excluded them. A few high quality, late ripening varieties never really fell below 40%, so for those I used the last harvest date in the dataset. These ripeness dates are mostly from Riverside CA. Disclaimer: I'm just guessing that 40% is a good value to use here and don't have any actual firsthand knowledge of it. Please let me know if this needs changing.

I then did a linear regression for brimA against date, as well as for exterior color. I solved for those variables on the ripeness date at which juiciness is probably above 40%. I believe this is a more robust way to compare varieties than simply finding averages, since there's a good deal of variation between fruit. The regression takes all the information and gives a good estimate of what you're likely to see on a given date. I've seen it done on various papers that study fruit quality against other variables.

Unfortunately, I couldn't find a color chart reference on the UCR's website. I think it's a safe bet that probably 0 = green, 10+ = red/orange, and yellow is in the middle somewhere. I've provided this color information since not all varieties have a ripe-looking color at the time that they reach the minimum juiciness threshold.

Note: this only tries to find "sweetness." Taste is subjective, and obviously some people prefer milder satsumas, some more tart, etc. Also, there are many other important features when choosing a tree, such as yield, susceptibility to disease, cold-hardiness, etc. That said, here are the results:

Code: [Select]

BrimA Date Color Variety
(k=3) cutoff   at
cutoff

11.26 December 13 7.56 Okitsu Wase
10.05 December 13 9.23 Frost Owari (AKA "Owari")
9.85 December 13 11.79 Clausellina
9.22 November 27 9.95 Lange #3
9.12 November 14 8.21 Kuno Wase
8.94 November 17 8.83 Miho Wase
8.68 November 17 8.76 Miyagawa
8.39 November 27 9.21 Lange #2
8.25 November 18 6.27 Dart North
8.21 November 17 5.80 Aoshima
7.90 November 10 6.95 China S-9
7.89 November 17 7.42 Xie Shan
7.80 November 18 4.94 Road 164 Satsuma
7.78 November 18 5.50 Dart South
7.65 November 08 7.27 Armstrong
7.63 November 18 5.80 Lange #1
7.49 November 17 6.20 China S-2
7.46 November 17 6.63 Silverhill
7.45 November 17 5.72 Iveriya
7.29 November 12 4.32 Agudzera
7.16 November 17 5.32 China S-7
7.15 November 17 4.90 China S-6
7.10 November 18 6.72 Mc Ewen
7.06 November 10 4.90 Dungan
6.57 November 10 7.34 China S-1
6.24 November 10 7.46 China S-11
6.02 November 10 4.30 China S-3
5.95 October 26 5.56 China S-5
5.83 November 18 6.27 China S-15
5.24 October 07 4.40 China 6-22
4.92 October 16 5.21 China S-18
4.21 September 27 3.76 China S-20
3.89 October 18 4.18 China S-12


[brian]

Your approach is interesting, but I personally agree with the UCR's opinion you infer, that as fruit becomes drier it is less appealing.  I like juicy+sweet+sour and am disappointed by overly sweet and dry mandarins.  Often oranges and mandarins become somewhat bitter as they age also, at least with grocery store fruit - I haven't noticed this with fruit I have grown myself

[slopat]

I still like the Owari the most but i enjoy most of the others, just not too sour and/or dry... frost damage or overripe (fermenting) are just nasty. Im also partial to peeling the segments and Owari seems the easiest. Maybe I should build a brick wall north of my tree or somehow trap more heat for sweet!

After "researching" [reading Brian, Millet, Steve, and Kaz's posts] I think I'll just enjoy eating and not think too hard about it     

Thanks for the synopsis and postingthe table.  Anyways, based on the posts read, I did finally buy Fukushu and Marumi kumquat trees, easier decision  as the local farm supply had it marked down - broken limbs? Seems like prices for the fruits are going up everywhere! (I'll still buy pummelos at farmer's market from the farmers growing Exeter!)

[brian]

the truth is we are spoiled with so many excellent citrus varieties and you really can't got wrong with any of the popular ones.  'Owari' was one of the first mandarins I grew and is still one of my favorites.  It has been a fun ride trying a little of everything, though.

Fukushu and Marumi are both great (and I can barely tell them apart).  You will be very happy with them if you like sweet+sour fruits.  Kumquats have a tingling effect like szechuan peppercorns, which is interesting.

[sc4001992]

Brian,

I have the Marumi, Meiwa, and Nagami, and like them all. Isn't the fruits of the Fukushu larger than the others. I like the Meiwa and Nagami since one is sweet (skin & flesh) and the other is sweet (skin) and sour (flesh) but didn't see my advantage in growing the Fukushu.

Also for mandarins, the satsuma and clementines are all done now, but I like the Gold Nugget and Yosemite Gold because the fruits are still hanging on the trees and ripe but not over ripe. Gives me some good mandarins to eat in April-May. My Florida murcott mandarins are also just ripening (Feb-April) so I get good tasting fruits from them. My Tango is ok to eat now, but has not fully ripen yet. My large fruits on Sumo is still getting big fruits and it can be eaten now but it is still not fully ripe yet (neck/bump is still green).

Mar3, I grew most of the China satsuma offered from UCR, didn't like any so got rid of them. I have not heard of Lange #2 & #3, Clausellina, but did grow most of the rest on your list. My unknown satsuma (lost my tag) is the sweetest one I have, gets lots of fruits in cluster (last season it had 24 fruits on one branch). It is very sweet with just a little tartness. I liked it better than the Xie Shan.

[brian]

Fukushu and Marumi are basically identical except Fukushu seems to have a more pronounced dimple on the bottom of the fruit.  Fruit size and taste has been the same for me.  I wouldn't have even noticed they were different cultivars if it weren't for the labels.  I wouldn't bother growing Fukushu if you have Marumi. 

One thing I can say is that in my greenhouse I often get crops of totally seedless Fukushu, almost certainly because my Fukushu is in my greenhouse year-round while the Marumi (and other container Fukushus) rotate outside where they see pollinators.  It is certainly possible that Marumi can be seedless also if no pollination, not sure.   

All of my sweet citrus have been picked and eaten for at least a month now   Not sure if they are on an earlier schedule than you due to greenhouse.  I only have grapefruits left on the tree.

I have been watching the MadisonCitrus site for new trees are available, I see they just listed "China S2 Satsuma", I don't know anything about the China types. I think I am done growing new mandarins unless something revolutionary comes along, the ones I have are so good I can't imagine how they could improve!

[sc4001992]

Thanks for the reply Brian.

Yes, I'm through with new madarins and citrus for now. There is another new one from Japan called "BENI-MADONNA (seedless)" which is supposed to be sweet and nice looking but I'm sure it will not  have any major taste difference from all the rest we have here.

[Millet]

There is  a a citrus variety that is rarely ever mentioned.  It is a variety of the blond oranges, and is named Bitter Sweet..  I grow the tree.  I has a seductive   taste different from most of the  commonly grown citrus.  The taste is really quite alluring, sort of like "what is this - I like it".  It is a great variety to have in ones collection.