The food weight conversion factor in NPS-DSS 2019-2020, NPS Wave 5
The food weight conversion factor
The household recorded the amount of food items consumed in the last 7 days using various units such as KILOGRAMS, GRAMS, LITRES, MILLILITRES, and PIECES. It is generally recommended to use metric units such as grams (g), milligrams (mg), or micrograms (µg). Since food is typically consumed on a fresh weight basis and only the edible portion is eaten, food composition data is usually reported as ‘per 100 g edible portion on a fresh weight basis’.
To convert KILOGRAMS to GRAMS, the conversion factor of 1000 was used, as 1 KILOGRAM equals 1000 GRAMS.
Liquid food conversion
For liquid food items, LITRES and MILLILITRES were used. To convert LITRES to GRAMS, the density of the liquid (in g/ml) was taken into account, and the conversion was done using the following formula:
LITRE * Density (g/ml) * 1000 = GRAMS
To convert MILLILITRES to GRAMS, the density was multiplied by the volume in MILLILITRES as follows:
MILLILITRE * Density (g/ml) = GRAMS
To convert liquid volumes to weight, the following steps should be followed:
Calculate the mean values of liquid density using food items listed in the FAO/INFOOD Density Database that are commonly consumed in Tanzania. It is important to select food items that are representative of the local diet to obtain accurate conversion factors.
*Honey, syrups, jams, marmalade, jellies, canned fruits Honey is not listed in the FAO/INFOOD Density Database. Therefore, the liquid density of honey needs to be calculated separately. Use other references, for example, The “Weights, Measures, and Conversion Factors for Agricultural Commodities and Their Products” produced by the U.S. Department of Agriculture https://www.ers.usda.gov/webdocs/publications/41880/33132_ah697_002.pdf provides the necessary information; see page 13 - using this information, the liquid density of honey can be calculated (1 gallon = 3.785 litres) and included in the calculation of the mean liquid density value of the other food items.
Food items that reported by LITRE and MILLILITRE
itemcode
N
Food item in FAO/INFOODS
Liquid density
COOKING OIL
978
Oils and fats
Calculate the mean of liquid density including oils commonly use in Tanzania.
Determine the weight of the food item based on its size in pieces. You can either use the mean value or the median size of the food item (e.g. using the weight of a standard or medium-sized piece if it is commonly used).
*COCONUTS - There is no available reference value for the weight of whole coconuts. Do you know any reference value in weight in Tanzania?
Food items that reported by PIECES
itemcode
N
Food item in Tanzania Food Composition Tables
Mean conversion factor
EGGS
206
#307 (Std 70)
70
COCONUTS (MATURE/IMMATURE)
32
No whole coconuts - any reference?
CHICKEN AND OTHER POULTRY
28
#554 (S 50, M 100, L 200; A 200)
SWEETS
16
e.g. #532 African donuts?
MAIZE (GREEN, COB)
1
#13, 14 (S 100, M 350)
RIPE BANANAS
1
#102 (S 50, M 115, L 175)
CITRUS FRUITS (ORANGES, LEMON, TANGERINES, ETC.)
1
#114 Orange (S 120, M 170, L 200), #109 Lemon (Std 70), #124 Tangerine (S 40, M 70, L 100)
MANGOES, AVOCADOES AND OTHER FRUITS
1
#112 Mango (S 120, M 155, L 270), #101 Avocado (S 150, M 200, L 500), Other fruits?
WILD BIRDS AND INSECTS
1
?
(To get the list - see the R script below.)
R scripts - Listing up the food items
open dataJ1
library(tidyverse)
Warning: package 'tidyverse' was built under R version 4.2.2
Rows: 71040 Columns: 13
── Column specification ────────────────────────────────────────────────────────
Delimiter: ","
chr (11): interview__key, sdd_hhid, itemcode, hh_j01, hh_j02_1, hh_j03_1, hh...
dbl (2): hh_j02_2, hh_j04
ℹ Use `spec()` to retrieve the full column specification for this data.
ℹ Specify the column types or set `show_col_types = FALSE` to quiet this message.