ETH Zürich, Department for Health Sciences and Technology (D-HEST), Institute of Food, Nutrition and Health (IFNH), Laboratory of Human Nutrition, Zurich, Switzerland.
ETH Zürich, Department for Health Sciences and Technology (D-HEST), Institute of Food, Nutrition and Health (IFNH), Laboratory of Food & Soft Materials, Zurich, Switzerland.
J Nutr. 2022 May 5;152(5):1220-1227. doi: 10.1093/jn/nxab435.
Hot extrusion is widely used to produce iron-fortified rice, but heating may increase resistant starch and thereby decrease iron bioavailability. Cold-extruded iron-fortified rice may have higher bioavailability but has higher iron losses during cooking. Thus, warm extrusion could have nutritional benefits, but this has not been tested. Whether the addition of citric acid (CA) and trisodium citrate (TSC) counteracts any detrimental effect of high-extrusion temperature on iron bioavailability is unclear.
Our aim was to assess the effects of varying processing temperatures on the starch microstructure of extruded iron-fortified rice and resulting iron solubility and iron bioavailability.
We produced extruded iron-fortified rice grains at cold, warm, and hot temperatures (40°C, 70°C, and 90°C), with and without CA/TSC at a molar ratio of iron to CA/TSC of 1:0.3:5.5. We characterized starch microstructure using small- and wide-angle X-ray scattering and differential scanning calorimetry, assessed color over 6 mo, and measured in vitro iron solubility. In standardized rice and vegetable test meals consumed by young women (n = 22; mean age: 23 y; geometric mean plasma ferritin: 29.3 μg/L), we measured iron absorption from the fortified rice grains intrinsically labeled with 57ferric pyrophosphate (57FePP), compared with ferrous sulfate (58FeSO4) solution added extrinsically to the meals.
Warm and hot extrusion altered starch morphology from native type A to type V and increased retrograded starch. However, extrusion temperature did not significantly affect iron solubility or iron bioavailability. The geometric mean fractional iron absorption of iron from fortified rice extruded with CA/TSC (8.2%; 95% CI: 7.9%, 11.0%) was more than twice that from extruded rice without CA/TSC (3.0%; 95% CI: 2.7%, 3.4%; P < 0.001).
Higher extrusion temperatures did not affect iron bioavailability from extruded rice in young women, but co-extrusion of CA/TSC with FePP sharply increased iron absorption independently from extrusion temperature. This trial is registered at www.clinicaltrials.gov as NCT03703726.
热挤压广泛用于生产铁强化米，但加热可能会增加抗性淀粉，从而降低铁的生物利用度。冷挤压铁强化米可能具有更高的生物利用度，但在烹饪过程中铁损失更高。因此，温热挤压可能具有营养益处，但尚未对此进行测试。柠檬酸（CA）和柠檬酸三钠（TSC）的添加是否能抵消高温挤压对铁生物利用度的不利影响尚不清楚。
我们的目的是评估不同加工温度对挤压铁强化米淀粉微观结构以及铁溶解度和铁生物利用度的影响。
我们以冷、暖、热温度（40°C、70°C 和 90°C）生产挤压铁强化米，同时在摩尔比为铁与 CA/TSC 为 1:0.3:5.5 的情况下添加 CA/TSC。我们使用小角和广角 X 射线散射以及差示扫描量热法来表征淀粉微观结构，在 6 个月内评估颜色，并测量体外铁溶解度。在年轻女性（n=22；平均年龄 23 岁；几何平均血浆铁蛋白 29.3μg/L）中标准化的米饭和蔬菜测试餐中，我们测量了从用 57 铁焦磷酸（57FePP）内在标记的强化米粒中吸收的铁，与添加到餐中的硫酸亚铁（58FeSO4）溶液进行比较。
暖温和热挤压将淀粉形态从天然 A 型转变为 V 型，并增加了回生淀粉。然而，挤压温度并未显著影响铁溶解度或铁生物利用度。用 CA/TSC 挤压的强化米中，铁的几何平均分数铁吸收（8.2%；95%CI：7.9%，11.0%）是未添加 CA/TSC 的挤压米的两倍多（3.0%；95%CI：2.7%，3.4%；P<0.001）。
在年轻女性中，较高的挤压温度不会影响挤压米中铁的生物利用度，但与 FePP 共同挤压的 CA/TSC 可独立于挤压温度显著增加铁的吸收。该试验在 www.clinicaltrials.gov 注册为 NCT03703726。
