What is carb content of 100g cooked celeriac?

I want to replace potatoes and rice with celeriac for a 20g carb per day keto diet, but I am not sure what carb value to use for cooked celeriac.

Tesco: https://www.tesco.com/groceries/en-GB/products/255932007
Asda: https://groceries.asda.com/search/celeriac
does not say if for cooked or raw
Sainsburys: values similar....
energy 25kcal
carb 2.3g
fibre 3.7g
protein 1.2g

CoFID Composition of Foods Integrated Dataset (CoFID) GOV.UK
(I dowloaded data 3-4 years ago)
cooked
energy 15kcal
carb 1.9g
fibre ??
protein 0.9g
CoFID raw
energy 18kcal
carb 2.3g
fibre ??
protein 1.2g

Swedish Food Agency
cooked
http://www7.slv.se/SokNaringsinnehall/Home/FoodDetails/5864
energy 25kcal
carb 2.7g
fibre 2.9g
protein 1.0g
raw
http://www7.slv.se/SokNaringsinnehall/Home/FoodDetails/292
energy 32kcal
carb 4.4g
fibre 3.1g
protein 1.0g

USDA Fooddata Central
https://fdc.nal.usda.gov/fdc-app.html#/food-details/342022/nutrients
cooked
energy 44kcal
carb 7.7g
fibre 1.9g
protein 1.6g
USDA
https://fdc.nal.usda.gov/fdc-app.html#/food-details/170400/nutrients
raw
energy 42kcal
carb 7.4g
fibre 1.8g
protein 1.5g

The USDA carb value for cooked celeriac is 7.7g and the others are 1.9-2.7g. That is a very big difference. Why? Have I made a mistake?

I would not use celeriac daily if the carb value is 7.7g, so it is important
to know.

Would be grateful for advice.

In my post above I went to the USDA FoodData Central website, searched on celeriac and obtained matches. The first was:
'celeriac, cooked Survey (FNDDS) ...' with nutrients
Carbohydrate, by difference 9.63g
Fiber, total dietary 1.9g

making the carb-only value 9.63-1.90 = 7.73g = 7.7g
That is the value I wrote in my first post above.

Matches 2,3,and 4 were of type SR Legacy and I should have chosen one of these, for example the fourth:
'Celeriac, cooked without salt SR Legacy...' with nutrients
Carbohydrate, by difference 5.9g measured before 8/1/1984
Fiber, total dietary 1.2g measured before 4/1/1996

making carb-only value 5.9 - 1.2g = 4.7g.

The USDA carb content for cooked celeriac is 4.7g and CoFIDs value is 1.9g and that is still a very big difference. If the variety of celeriacs are similar I think the measurement values would be similar too.

Here is a link to differences between FNDDS aand SR:
https://esha.zendesk.com/hc/en-us/articles/360019493512-USDA-SR-Database-vs-FNDDS-Database

Just checked fatscecret.com (original fatsecret site?) and the UK fatsecret.co.uk and both show 9.62g carbs+fibre /100g for cooked celeriac.

The USDA FoodData Central site at https://fdc.nal.usda.gov/ shows the value 9.62g carb+fibre (7.7g carb-only) for Celeriac cooked Survey(FNDDS) type, so it is likely Fatsecret obtained the celeriac data from USDA. This value is way too high for a 15g carb/day keto-diet that I would like to try.

I will not stop eating celeriac as dinner potatoes and rice replacement hoping that CoFID's celeriac carb 1.9g/100g is the correct one.

I sent an email yesterday to USDA and asked about the USDA's and CoFID's carb values. I received a response today. This wordbrick:

Thank you for your inquiry regarding carbohydrates values. In FoodData Central carbohydrate is determined as the difference between 100 and the sum of the percentages of water, protein, total lipid (fat), ash, and, when present, alcohol and is referred to as “Carbohydrate by difference”. Values for carbohydrate by differeence include total dietary fiber. Available carbohydrate, which is used in some countries, can be calculated if desired by the user, by subtracting the sum of the percentages of water, protein, total lipid (fat), ash, total dietary fiber, and alcohol (when present) from 100. Total dietary fiber content is determined by enzymatic-gravimetric methods 985.29 or 991.43 of the AOAC (2012). Total sugars is the term used for the sum of the individual monosaccharides (galactose, glucose, and fructose) and disaccharides (sucrose, lactose, and maltose). Analytical data for individual sugars were determined by liquid chromatography (AOAC 982.14). Starch is analyzed using the AOAC method 966.11 or 979.10 (2012) or by a polarometric method (The Feedings Stuffs Regulations 1982). Because the analyses of total dietary fiber, total sugars, and starch are performed separately and reflect the analytical variability inherent to the measurement process, the sum of these carbohydrate fractions may not equal the carbohydrate-by-difference value. I hope this information is helpful.

which explains how to calculate carbs with or without fibre.

Carb-nofibre formula: 100 - (water+ash+protein+fat+dietfiber) where the input nutrients and the output carb nutrient are for 100g food.
Disclaimer: have never seen or done this before so I am guessing.
Correct me if I am wrong.

I used this formula and calculated carb-nofibre for cooked celeriac for some national nutrient databases:

France https://ciqual.anses.fr/#/aliments/20025/celeriac-cooked
Water 90.1g
Ash Ash (g/100g) 0,82
Protein (g/100g) 1,3
Fat (g/100g) 0,86
Fibres (g/100g) 2,6
Carbohydrate available (g/100g) 4,6
My Carb-nofiber: 100 - (90.1 + 0.82 + 1.3 + 0.86 + 2.6) = 4.3g

Italy http://www.bda-ieo.it/wordpress/en/?page_id=23
Water 88.0g
Ash: ?g 0.9g guessing
Total protein 1,9g
Total fat 0,1g
Dietary total fibre 5,1g
Available carbohydrates 3.8g
My Carb-nofiber: 100 - (88.0 + 0.9 + 1.8 + 5.1) = 4.2g

Sweden http://www7.slv.se/SokNaringsinnehall/Home/FoodDetails/5864
Water 92.0g
Ash: 0.91g
Protein 1,00g
Fat 0,50g
Fibre 2,90g
Carbohydrates available 2,70g
My Carb-nofiber: 100 - (0.91 + 1.0 + 0.5 + 2.90) = 2.69g

Australia
https://www.foodstandards.gov.au/sc...nts/afcd/Pages/fooddetails.aspx?PFKID=F002383
Moisture 85.6g
Ash 1.5g
Protein 1.7g
Fat 0.2g
Dietary fibre 5.5g
Available carbohydrate 3g
My Carb-nofiber: 100 - (85.6 + 1.5 + 1.7 + 0.2 + 5.5) = 5.5g (was hoping for a value closer to 3g - maybe the value
of input nutrient 'moisture' is too low)

UK CoFID https://www.gov.uk/government/publications/composition-of-foods-integrated-dataset-cofid
Water 90.3g
Ash not avail? guess 0.9g
Protein 0.9g
Fat 0.5g
Fibre not avail? guess 3.0g?
Carbohydrates available reported by CoFID 1.9g << why this?
My Carb-nofiber: 100 - (90.3 + 0.9 + 0.9 + 0.5 + 3.0) = 4.4g

USDA by FoodData Central
Water 92.3g
Ash 0.64g Protein 0.96g
Total lipid (fat) 0.19g
Fiber, total dietary 1.2g
Carbohydrate, by difference 5.9g
Carb available = 5.9-1.2 = 4.7g
My Carb-nofiber: 100 - (92.3 + 0.64 + 0.96 + 0.19 + 1.2) = 4.71g


The value reported by the databases range from 1.9 - 4.7g per 100g celeriac. That is big difference caused by different quantities of water and dietary fibre of the celeriac used when calculating.

I do not know if US celarics always contain high quantities of water and Italian celeraics contain lower amounts, or if the quantity simply depends on how the celeriacs have been grown, stored and transported and on their age when being used/tested.

Differences in carb values like these only matter for very low carb (keto-)diets, e.g. 15g carb/day.

My average carb-nofiber: 4.3+4.2+2.7+5.5+4.4+4.7 = 3.7g/100g celeriac
Maybe I can choose 3.2g as a compromise celeriac value...