Stability of Vitamins and Minerals in Coated and Extruded Fortified Rice Kernels Stored under Real-Life Conditions over Two Years and Implications for Standards

doi:10.1016/j.rsci.2026.03.007

Abstract

Abstract:

Rice fortification is a cost-effective intervention to address and prevent micronutrient deficiencies in contexts where rice is a staple food. The stability of such added micronutrients is of critical importance, especially when rice is stored under harsh storage conditions. Coated and extruded fortified rice kernels (FRKs) containing vitamins A, B1, B3, B6, B9, and B12, zinc, and iron, as well as bulk rice fortified with these kernels, were stored in different packaging materials over periods of 24 and 26 months, respectively. Blending, final packaging, and storage were conducted in Madhya Pradesh, in central India, which experiences a subtropical monsoon climate condition. Large variations in the analytical results were observed for the fortified rice samples, mostly due to non-homogeneous distribution of the FRKs within the bulk rice. Consequently, to reduce analytical variation, results were correlated with the concentration of vitamin B3 as an internal standard. Vitamins B3, B6, B9, and B12, zinc, and iron remained stable in both coated and extruded FRKs throughout storage, while vitamin B1 stability was higher in coated FRKs, with results consistent across packaging materials. The decay of vitamin B1 followed zero-order kinetics in extruded premix kernels stored in metallized paper bags and in rice fortified with these kernels across all packaging types, with half-lives of 20 and 34 months, respectively. Vitamin A decay followed first-order kinetics in both rice fortified with coated and extruded kernels, with half-lives of 6.8 and 15.1 months, respectively. In FRKs, vitamin A decay was best described by mixed-order kinetics, with half-lives of 6.5 months (coated) and 5.5 months (extruded). This study informed major revisions to the World Food Programme fortified rice specifications, including the removal of vitamin A due to its instability during storage, while confirming the stability of B vitamins, zinc, and iron, and highlighting the critical role of blending and analytical control practices.

Key words: vitamin A, B-complex vitamins, zinc, iron, industrial blending, coated fortified rice kernel, extruded fortified rice kernel

Werner Nader, Deblina Sarkar, Melas Adoko, Saskia de Pee, Elise Ivarsen, Vitalii Shkliar, Sabine Meng Jensen, Johannes Hein. Stability of Vitamins and Minerals in Coated and Extruded Fortified Rice Kernels Stored under Real-Life Conditions over Two Years and Implications for Standards[J]. Rice Science, 2026, 33(4): 559-570.

Figures/Tables 9

Fig. 1. Concentrations of vitamins A, B1, B3, B6, B9, and B12 in premix kernels during storage over 24 months. A, C, E, and F, Results for vitamins A (A), B3 (C), B9 (E), and B12 (F) stored in laminated metallized and polyethylene (PE) inner liners were combined and plotted as mean values. B and D, Results for vitamins B1 (B) and B6 (D) in extruded fortified rice kernels (FRKs) are plotted separately for the two packaging types: PE inner liner bags and laminated metallized bags. Error bars represent data variability due to measurement uncertainties (Table 1). Power trend lines were fitted to the vitamin A results, and linear trend lines were fitted to the other vitamins. The specified minimum and maximum concentration ranges are delimited by red dotted lines.

Fig. 2. Zinc and iron concentrations in extruded and coated fortified rice kernels (FRKs). Results of both packaging types were combined and plotted as mean values. Error bars represent data variability due to measurement uncertainties (Table 1). The horizontal dotted red (zinc) and green (iron) lines indicate the upper and lower specification limits.

Table 1. Relative expanded measurement uncertainties for analytical methods and propagated uncertainties for measurements related to vitamin B3 as internal standard. %

Parameter	Measurement uncertainty	Measurement uncertainty related to internal standard vitamin B3
Vitamin A	16	23
Vitamin B1	16	23
Vitamin B3	14	Not applicable
Vitamin B6	14	21
Vitamin B9	14	21
Vitamin B12	20	26
Iron	16	23
Zinc	16	23

Fig. 3. Concentrations of vitamins A, B1, B3, B6, B9, and B12 in rice fortified with coated and extruded fortified rice kernels (FRKs) during storage over 26 months in 90-µm polyethylene (PE), polypropylene woven (PP), and United States Agency for International Development provided hybrid (Hybrid) bags. Mean values from duplicate tests are plotted, with error bars indicating the range of measurement uncertainties (Table 1).

Fig. 4. Concentrations of vitamins A, B1, B6, B9, and B12 in rice fortified with coated and extruded fortified rice kernels (FRKs), corrected using vitamin B3 as the internal standard, during storage over 26 months in 90-µm polyethylene (PE), polypropylene woven (PP), and United States Agency for International Development provided hybrid (Hybrid) bags. Results were corrected using a factor calculated from the internal standard, vitamin B3. Mean values from duplicate tests are plotted, with error bars indicating the range of measurement uncertainties (Table 1).

Fig. 5. Concentrations of vitamins A, B1, B6, B9, and B12 in fortified rice, corrected with vitamin B3 as the internal standard, during storage over 26 months. Results from storage in polyethylene (PE), polypropylene woven (PP), and United States Agency for International Development provided hybrid (Hybrid) bags were combined and plotted as mean values. Error bars indicate the range of measurement uncertainties (Table 1).

Fig. 6. Concentrations of zinc and iron in rice fortified with extruded and coated fortified rice kernels (FRKs), without correction (A) and after correction (B) using factor calculated from internal standard vitamin B3. Results from storage in polyethylene (PE), polypropylene woven (PP), and United States Agency for International Development provided hybrid (Hybrid) bags were combined and plotted as mean values. Error bars represent data variability due to measurement uncertainties (Table 1). The horizontal dotted red (zinc) and green (iron) lines indicate the upper and lower limits of the specifications.

Table 2. Moisture contents of extruded and coated fortified rice kernels (FRKs) and rice fortified with these FRKs.

Packaging	Moisture content (%)
Packaging	Extruded FRKs	Coated FRKs
PE inner liner paper bags	11.1 ± 1.1	11.9 ± 0.1
Laminated metallized bags	12.7 ± 1.0	12.3 ± 0.1
	Rice fortified with extruded FRKs	Rice fortified with coated FRKs
PE 90 µm bags	11.8 ± 0.4	12.1 ± 0.4
PP woven bags	12.0 ± 0.9	11.8 ± 1.0
USAID hybrid bags	11.9 ± 0.3	12.0 ± 0.4

Table 3. Concentrations of vitamins, zinc, and iron in the extruded and coated kernel (FRK) defined by the World Food Programme (2025).

Nutrient	Fortificant	Specified content (mg/kg)			Specified content at beginning (mg/kg)
Nutrient	Fortificant	Minimum	Maximum		Coated FRK	Extruded FRK
Vitamin A	Retinyl palmitate	195	312	363 ± 58		292 ± 47
Vitamin B1	Thiamine mononitrate	650	975	1 115 ± 178		742 ± 119
Vitamin B3	Niacinamide	9 100	10 920	10 700 ± 1 498		11 350 ± 1 589
Vitamin B6	Pyridoxine hydrochloride	780	1 170	961 ± 135		849 ± 119
Vitamin B9	Folic acid	169	254	242 ± 34		180 ± 25
Vitamin B12	Cyanocobalamin	1.3	2.0	1.6 ± 0.32		1.4 ± 0.28
Iron	Ferric pyrophosphate	4 000	4 800	4 700 ± 752		4 100 ± 656
Zinc	Zinc oxide	6 000	7 200	7 100 ± 1 136		5 950 ± 952

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