Influence of grain quality characteristics and basic processing technologies on the mineral and antinutrient contents of iron and zinc biofortified open-pollinated variety and hybrid-type pearl millet

The present study aimed at determining whether mineral biofortified pearl millets will continue to maintain significantly higher iron and zinc contents after processing, and the effects of decortication, steeping/fermentation and parboiling on mineral, phytate and total phenolic contents in eight varieties of pearl millets (two biofortified hybrids, Dhanashakti and ICMH 1201, five improved varieties with high iron content and one traditional variety) were also investigated. The hybrids showed higher iron and zinc contents after processing compared to the improved varieties, for example, 17–51% and 10–26% higher iron and zinc contents, respectively, after steeping/fermentation followed by decortication compared to the best varieties. Phytate:mineral ratios also indicated that iron bioavailability was higher in the hybrids after processing, several times above the critical 1:1 ratio. Across all the types, iron content after processing was positively correlated (P ≤ 0.05) with high kernel weight, large kernels, and high fat content, and zinc content was positively correlated with high fat content. These kernel characteristics should aid in the selection of high iron and zinc pearl millet types.     

Modulation of chelating factors,trace minerals and their estimated bioavailability in Italian and African sorghum (Sorghum bicolor (L.) Moench) porridges

Factors able to modulate chelating factors, trace minerals and their bioavailability were investigated in porridges of five sorghum (Sorghum bicolor (L.) Moench) varieties: from Nigeria, Senegal, Burkina Faso and two from Italy. Effects of variety and traditional fermentation and cooking were assessed on iron‐binding phenolic groups, phytates and iron and zinc content and bioavailability. Chelating factors, trace elements as well as the effect of processing (mainly fermentation) were modulated by variety. Fermentation decreased iron‐binding phenolic groups until 49% and phytate content until 72% as well as increased phytase activity 3.4–16.4 fold, leading to enhancement of iron and zinc estimated bioavailability. Cooking alone had almost no effect. The lowest chelating factors content and the highest trace minerals bioavailability were shown by fermented Senegal landrace, whereas the Italian varieties overall showed the worst results. The results indicate that selection of traditional varieties and appropriate processing methods can improve sorghum nutritional value.     

Iron content and availability studies in some Sri Lankan rice varieties

Thirty‐eight rice varieties, grown in Low Country Wet Zone, during Yala (2006) and Maha (2006/2007) seasons were screened for stable high iron rice varieties and were statistically analysed. Iron contents ranged 1.89–3.73 mg 100 g^?1 and varied significantly (P < 0.05) with variety and season. Selected fifteen high iron rice varieties, at degree of polishing 8–10% were analysed for iron, zinc and phytate. High iron contents in endosperm were observed in Suduru Samba (0.47 mg 100 g^?1), Basmati 370 (0.37 mg 100 g^?1), Kalu Heenati (0.42 mg 100 g^?1), Rathu Heenati (0.44 mg 100 g^?1) and Sudu Heenati (0.37 mg 100 g^?1). Phytate contents of polished rice varieties ranged from 200–300 mg 100 g^?1. Large reduction in iron content (84.5–93.6%) was observed in polished rice while the reduction in phytate content (18.9–40.8%) was low. Percentage dialyzability of iron in selected endosperm high iron rice varieties ranged from 1.73 to 8.71. Dialysability of iron in cooked polished rice did not show a relation to the phytate content in raw rice.     

Bioavailability of iron and zinc from multiple micronutrient fortified beverage premixes in Caco-2 cell model

Abstract: Iron and zinc deficiencies are the most prevalent nutrient deficiencies worldwide. They often coexist as the dietary factors, especially phytate, which impairs iron absorption also affects zinc absorption. Therefore, suitable strategies are required to control multiple micronutrient deficiencies in populations that subsist on high‐phytate foods such as the whole wheat flour based Indian bread (chapatti). The objective of the study, therefore, was to test the bioavailability of iron and zinc in 2 multiple micronutrient beverage premixes in the absence and presence of chapatti. The premix‐1 contained iron, zinc, and vitamin A while premix‐2 contained all micronutrients in premix‐1, plus folic acid and ascorbic acid. Ferritin induction and ⁶⁵Zn uptake were assessed using coupled in vitro digestion/Caco‐2 cell line model as the surrogate markers of iron and zinc bioavailability, respectively. The results show that iron bioavailability from premixes‐1 and 2 was similar in the absence of chapatti. However, premix‐2 showed significantly higher iron bioavailability compared to premix‐1 in the presence of chapatti. In contrast, the zinc uptake was similar from both premixes‐1 and 2 in the absence or presence of chapatti. These results suggest that both the premixes provide bioavailable minerals, but premix‐2 appears to be promising in the presence of foods that have high phytate.     

Effects of Phytases and Dehulling Treatments on In Vitro Iron and Zinc Bioavailability in Faba Bean (Vicia faba L.) Flour and Legume Fractions

ABSTRACT: In vitro digestions were performed on faba bean flours with decreased phytate contents and on 2 dephytinized or nondephytinized faba bean fractions, a dehulled faba bean fraction, and a hull fraction with low and high fiber and tannin contents, respectively. In vitro bioavailability iron and zinc was defined as the relative amount of iron and zinc that became soluble after enzymatic treatment. Faba bean samples were sequentially digested with enzymes, including amylase, pepsin, pancreatin, and bile, under certain conditions following the enzymatic degradation procedure. Iron and zinc in vitro bioavailability of whole faba bean flours were significantly improved by phytate degradation, even if the phytate were not all degraded. Total dephytinization of dehulled faba bean led to an obvious increase in iron and zinc in vitro bioavailability, but that of hulls had no effect on either iron or zinc in vitro bioavailability. Fibers and tannins other than phytate are more important in chelating a high proportion of iron and zinc in faba bean hulls.     

Combating Mineral Malnutrition through Iron and Zinc Biofortification of Cereals

Iron and zinc are 2 important nutrients in the human diet. Their deficiencies in humans lead to a variety of health‐related problems. Iron and zinc biofortification of cereals is considered a cost‐effective solution to overcome the malnutrition of these minerals. Biofortification aims at either increasing accumulation of these minerals in edible parts, endosperm, or to increase their bioavailability. Iron and zinc fertilization management positively influence their accumulation in cereal grains. Regarding genetic strategies, quantitative genetic studies show the existence of ample variation for iron and zinc accumulation as well as inhibitors or promoters of their bioavailability in cereal grains. However, the genes underlying this variation have rarely been identified and never used in breeding programs. Genetically modified cereals developed by modulation of genes involved in iron and zinc homeostasis, or genes influencing bioavailability, have shown promising results. However, iron and zinc concentration were quantified in the whole grains during most of the studies, whereas a significant proportion of them is lost during milling. This makes it difficult to realistically assess the effectiveness of the different strategies. Moreover, modifications in the accumulation of toxic elements, like cadmium and arsenic, that are of concern for food safety are rarely determined. Trials in living organisms with iron‐ and zinc‐biofortified cereals also remain to be undertaken. This review focuses on the common challenges and their possible solutions related to agronomic as well as genetic iron and zinc biofortification of cereals.     

Effects of legume processing on calcium,iron and zinc contents and dialysabilities

Legumes are a good source of calcium, iron and zinc, but are also a source of phytates and dietary fibre components that can negatively affect the bioavailability of these minerals. To estimate the latter, an in vitro dialysis method can be applied that gives the dialysability of a mineral as an estimate of its availability for absorption. Calcium, iron and zinc contents and dialysabilities in three legumes (beans, chickpeas and lentils) and the effects of cooking treatments and industrial processing on these parameters were studied. Beans had the highest calcium content (1.54 g kg^?1 dry matter (DM)) and chickpeas the lowest iron content (46.9 mg kg^?1 DM), whilst the zinc contents were similar in all three raw legumes (33.7–36.9 mg kg^?1 DM). Traditional and microwave cooking reduced the mineral contents by 9.7–36.4% for calcium, 14.2–31% for iron and 11.1–28.9% for zinc. The dialysabilities of calcium with respect to the values for the raw products were also reduced by these cooking techniques. Industrially processed legumes had higher dialysabilities of calcium, iron and zinc than traditionally or microwave cooked legumes. © 2001 Society of Chemical Industry     

Iron,zinc and phytic acid content of selected rice varieties from China

Rice is the major Chinese staple food (per capita approx 250 g day^?1) and, as such, is an important source of essential minerals. However, due to a number of factors the bio‐availability of these minerals is limited. In this study, the variation of phytic acid (PA), iron (Fe) and zinc (Zn) levels in 56 varieties of Chinese rice was investigated. The samples included in this study were collected in proportion to the importance of the rice‐growing regions in China. Fe levels showed the biggest variation (9–45 mg kg^?1) and were not related with PA content or grain shape although growing locations were identified yielding higher (25.2 mg kg^?1) and lower (14.2 mg kg^?1) Fe levels. Zn showed a moderate variability (13–39 mg kg^?1), which was narrower than for Fe, while broader than for PA (7.2–11.9 g kg^?1). Zn content is correlated (R² = 0.5; P < 0.01) with PA content, and shows a relation with growing region and kernel shape. Variation of PA content is the least among the three components. Molar ratios of PA to Fe and Zn ranged from 15 to 105 and 27 to 67, respectively. The results of the mineral contents and PA content can be interpreted in terms of expected bio‐availability. This study shows that the mineral bio‐availability of Chinese rice varieties will be <4%. Despite the variation in mineral contents, in all cases the PA present is expected to render most mineral present unavailable. We conclude that there is scope for optimisation of mineral contents of rice by matching suitable varieties and growing regions, and that rice products require processing that retains minerals but results in thorough dephytinisation. Copyright © 2006 Society of Chemical Industry     

Effects of yeast and bran on phytate degradation and minerals in rice bread

ABSTRACT:  Rice bread is a potential alternative to wheat bread for gluten-sensitive individuals. Incorporation of rice bran into bread made from white rice flour adds flavor but also phytic acid, which can reduce the bioavailability of minerals. Breads with varied amounts of defatted bran and yeast were prepared to determine their effects on the phytate and mineral contents of the bread. A completely randomized factorial design was used with bran levels of 3.7%, 7.3%, and 10.5% of the dry ingredients and yeast levels of 1.6%, 3.2%, and 4.7%. Increasing the amount of bran decreased the phytate degradation from 42% at the lowest level of bran to 10% at the highest, and the amount of yeast had no significant effect. The bran contributed substantial amounts of magnesium, iron, and zinc. Breads with the lowest level of bran had phytate-to-zinc molar ratios between 5 and 10, which suggest medium zinc bioavailability. Rice bread is a tasty and nutritious food that is a good dietary source of minerals for people who cannot tolerate wheat bread.     

Losses of nutrients and anti-nutritional factors during abrasive decortication of two pearl millet cultivars (Pennisetum glaucum)

Losses of nutrients such as starch, lipids, proteins, iron and zinc as well as phytase activity and of recognised anti-nutritional compounds (some insoluble fibres, iron-binding phenolic compounds and phytates) were determined following abrasive decortication of grains from two pearl millet cultivars (Gampela and IKMP-5) with different composition cultivated in Burkina Faso. In both cultivars, abrasion of the starchy endosperm started when about 12% of the dry matter had been removed from grains but lipid and protein losses followed the loss of dry matter. Zinc loss (%) was lower than that of iron; however, both were higher than dry matter losses. By contrast, phytate loss was lower than dry matter loss. Interestingly, decortication led to significant losses in fibres and iron-binding phenolic compounds with different level depending on the cultivar. Changes in phytase activity also differed in the two cultivars (42% and 11% losses of phytase activity in grains from Gampela and IKMP-5 cultivars, respectively, at 12% of abrasion). Hence, decortication of pearl millet grains does not decrease lipid and protein contents but does considerably decrease some anti-nutritional factors (part of the fibres and iron-binding phenolic compounds). However, as mineral contents and particularly iron content decreased while phytate content remains high, decortication may be insufficient to increase Fe and Zn bioavailability.     

Assessment of iron bioavailability from twenty elite late‐maturing tropical maize varieties using an in vitro digestion/Caco‐2 cell model

An in vitro digestion/Caco‐2 cell model was used to assess iron bioavailability of twenty elite late‐maturing tropical maize varieties grown in three diverse agroecologies in West and Central Africa (WCA). Kernel‐iron concentration of the varieties, averaged across locations, varied from 19.2 to 24.4 mg kg^?1, while mean kernel‐zinc concentration ranged between 19.4 and 24.6 mg kg^?1. Significant differences in iron bioavailability were observed among varieties, but the environment had no significant effect. Mean bioavailable iron ranged between 14% below and 43% above the reference control variety, TZB‐SR. Variety DMR‐LSR‐Y with the highest concentrations of kernel‐iron and ‐zinc of 24–25 mg kg^?1 across the three locations had a similar quantity of bioavailable iron as the reference control, TZB‐SR. In the long run this variety could be potentially effective in reducing iron deficiency because of its high kernel‐iron. The most promising varieties were Mid‐altitude STR synthetic and ACR91SUWAN‐1‐SRC1. They had kernel‐iron and ‐zinc levels of 22–24 mg kg^?1 and bioavailable iron 24–36% higher than the reference control, TZB‐SR. Additional research is necessary to determine if the increases in kernel‐iron concentration and bioavailable iron observed in this study can significantly improve the iron status of individuals in WCA at risk for iron deficiency. Copyright © 2004 Society of Chemical Industry     

Use of soaking to enhance the bioavailability of iron and zinc from rice‐based complementary foods used in the Philippines

Complementary foods used in the Philippines are predominantly rice‐based, although enrichment with mung beans and sesame seeds is recommended despite their high content of phytic acid, a potent inhibitor of iron and zinc absorption. We have investigated the effect of soaking on the inositol penta‐ (IP5) and hexaphosphate (IP6) (analysed by HPLC), zinc, iron and calcium (via AAS) content of rice‐based complementary foods with and without the addition of mung beans and sesame seeds. Soaking rice flour for 1, 6 and 12 h at 30 °C reduced the content of IP5 + IP6 by 60, 65 and 98% respectively, with only slight changes in zinc, iron and calcium. Levels of IP5 + IP6 were reduced by 10 and 47% by soaking mung bean flour, but not whole beans, for 1 and 6 h respectively. In conclusion, soaking can be used to reduce the IP5 and IP6 content of complementary foods based on mung bean flour and/or rice flour and thus enhance the bioavailability of iron and zinc. © 2002 Society of Chemical Industry     

Zinc and iron bioavailability of genetically modified soybeans in rats

ABSTRACT:  The aim of this work was to evaluate zinc and iron bioavailability of UFV-116, a new variety without 2 lipoxygenases, with better taste and flavor than a commercial variety OCEPAR 19, containing all 3 isozymes. To evaluate zinc absorption using ⁶⁵Zn whole body retention and femur ⁶⁵Zn uptake, rats were given 3 g of a ⁶⁵ZnCl₂ labeled test meal (0.25 μCi). The 2 varieties were tested at the level of 9 and 30 ppm of zinc as defatted soy flour. Two other groups (control) received egg white as source of protein and ZnS0₄.H₂0 as the zinc source. To evaluate iron absorption, using ⁵⁹Fe whole body retention, animals were given a 3 g ⁵⁹FeCl₃ labeled test meal (0.2 μCi). The 2 varieties were tested at 12 and 25 ppm iron as defatted soy flour. Whole fat soy flour of variety 1 (UFV-116) was higher ( P < 0.05) in Ca, K, Mg, phytic acid, and oxalate than variety 2 (OCEPAR-19). No difference was observed among the soybean varieties ( P > 0.05) for femur ⁶⁵Zn retention, at different levels of zinc. However, whole body retention was lower ( P < 0.05) for UFV-116 than for OCEPAR-19. Femur ⁶⁵Zn uptake was correlated with the whole body retention; however, whole body retention was more sensitive. Whole body ⁵⁹Fe retention from UFV-116 was lower ( P < 0.05) than from OCEPAR-19. Zinc and iron bioavailability was lower for UFV-116, possibly due to its higher content of antinutrient factors, especially phytate.     

Changes in mineral absorption inhibitors consequent to fermentation of Ethiopian injera: implications for predicted iron bioavailability and bioaccessibility

Possible changes in mineral bioavailability during processing of different types of injera sampled in Ethiopian households were assessed using different methods: phytic acid/mineral molar ratio, absorption prediction algorithm and in vitro availability measurements. Most foods analysed were rich in iron, but most of the iron likely resulted from soil contamination. The highest iron, zinc and calcium contents were found in teff–white sorghum (TwS) injera and flour. The lowest phytic acid/Fe and phytic acid/Zn molar ratios were found in barley–wheat (BW) and wheat–red sorghum (WrS) injeras. Although ideal phytic acid/Fe molar ratios (<0.4) were found in BW and WrS injeras, no significant difference between in vitro iron bioaccessibility and algorithm predicted absorption was observed. In injera, phytic acid degradation alone is unlikely to improve iron bioavailability, suggesting interactions with other absorption inhibitors. The use of phytic acid/Fe molar ratios to predict bioavailability may thus be less appropriate for iron‐contaminated foods.     

Comparison of enhancement in bioaccessible iron and zinc in native and fortified high‐phytate oilseed and cereal composites by activating endogenous phytase

In developing countries, iron and zinc deficiencies are mostly attributable to poor bioavailability of iron and zinc. The study aimed at enhancing the bioaccessibility of minerals in high‐phytate oilseed and cereal flour mixes by activating the intrinsic phytase of wheat flour. The flour mixes were fortified with iron and zinc separately for comparison. The flour mixes were incubated at optimum conditions of temperature and pH for phytase activation. Phytase activation enhanced bioaccessible iron by 43–162% in native and 40–168% in fortified wheat–soya, 83–192% in native and 97–240% in fortified wheat–groundnut flour mixes in relation to control flour mixes. Bioaccessible zinc was enhanced by 87–183% in native and 30–113% in fortified wheat–soya, 31–65% in native and 61–186% in fortified wheat–groundnut flour mixes. Endogenous phytase activation was effective in enhancing bioaccessibility of iron and zinc in native and fortified flour composites economically.     

In vitro bioaccessibility of iron and zinc in fortified fruit beverages

Iron and zinc bioaccessibility was estimated in the in vitro gastrointestinal digests of six different fortified fruit beverages (Fb) containing iron and/or zinc and/or skimmed milk (M). Solubility values can be used to establish trends in relative bioavailability of iron and zinc, as the first stage towards mineral bioavailability comprises solubility in the intestinal tract. FbFe, FbFeM and FbFeZnM samples showed iron bioaccessibility above 88%, differing ( P  < 0.05) from those of FbFeZn (53%). In turn, FbZn, FbFeZn and FbZnM samples presented higher zinc bioaccessibility (above 68%), differing ( P  < 0.05) from those of FbFeZnM (48%). The presence of milk-derived caseinophosphopeptides (CPPs) formed during gastrointestinal digestion in dairy samples does not increase iron or zinc bioaccessibility in FbFeM or FbZnM vs. FbFe or FbZn, but it is hypothesised that the negative interacting effect of zinc upon iron bioaccessibility when co-supplemented in these fruit beverages is overcome in the presence of CPPs, which favour iron solubility more than in the case of zinc.     

Dephytinisation of Sangak and Barbari bread made from different extraction rate flours increases iron and zinc bioaccessibility in Caco‐2 cells

Bread is a staple food in many countries and an important source of iron and zinc. The bioavailability of these minerals is generally low because of the content of phytic acid. Traditional Iranian breads were prepared with flours of different extraction rates, Sangak at 93% and Barbari at 82%. Breads were dephytinised by addition of Aspergillus niger phytase during in vitro digestion. The effect upon iron and zinc bioaccessibility in the Caco‐2 cell model was investigated. The cellular uptake of iron and zinc was lower from Sangak, compared to Barbari, despite higher mineral content in Sangak. Dephytinisation of both breads increased iron uptake in the Caco‐2 cells (0.65 vs. 1.64 in Sangak and 0.77 vs. 1.97 ng mg^?1 protein in Barbari). Zinc uptake increased from 0.98 to 2.8 in Sangak and from 1.4 to 2.9 ng mg^?1 protein in Barbari. Thus, dephytinisation substantially improves iron and zinc bioaccessibility.     

The effect of roasting on the nutritional and antioxidant properties of yellow and white maize varieties

Maize varieties (yellow and white) were roasted for 17 min; and allowed to cool, and later milled into powder. The nutritional evaluation (proximate composition, mineral and antinutrient content determination) and antioxidant properties investigation (reducing power, free radicals scavenging ability and Fe²⁺ chelating ability) of the product was subsequently carried out. The result of the study revealed that roasting caused a significant increase (P < 0.05) in the crude fat, carbohydrate, Ca, Na, Mg and Zn content. Conversely, a significant decrease (P < 0.05) was observed in crude protein, crude fibre, Fe and K content. A significant decrease in the phytate content was also observed. However, the reduced phytate content did not have sparing effect on Zn bioavailability. Roasting significantly (P < 0.05) reduced the extractible phenol and flavonoid content of the maize varieties. The antioxidant properties (1,1‐diphenyl‐2‐picrylhydracyl free radical scavenging ability and Fe²⁺ chelating ability) followed the phenolic content pattern. However, roasting caused a significant increase in the ferric reducing antioxidant power of the maize varieties. Thus, roasting reduced the protein content of maize but also increased the energy value and antioxidant capacity as exemplified by high reducing power.     

Nutritional evaluation of some Nigerian wild seeds

Some wild seeds, namely Parkia biglobosa, Tetracarpidum conophorum, Pentaclethra macrophylla, Irvingia gabonensis, Afzelia africana, Prosporis africana and Monodora myristica, were randomly collected from various parts of Nigeria and analyzed with regard to their proximate, mineral, antinutrient composition and zinc bioavailability. The results revealed that the seeds had high protein (6.5-24.2%), fat (19.0-58.5%), mineral (Mg, Fe, Zn, Mn, Ca, Na, K, P) and phytate (1043.6-2905.2 mg/100 g) contents, while the cyanide content was low (3.7-6.4 mg/kg). However, Co, Pb and Ni were not detected in all the samples. The calculated [Ca] [phytate]/[Zn] molar ratios (which is the best index for predicting Zn bioavailability) for all the seeds revealed that Parkia biglobosa, Irvingia gabonensis and Prosporis africana had a calculated molar ratio above 0.50 mol/kg (critical level), thus indicating reduced bioavailability of Zn to a critical level. In view of the high fat, protein, mineral and low cyanide contents, the high phytate content would not be expected to reduce bioavailability of Zn in some of the wild seeds (Afzelia africana, Pentaclethra macrophylla and Monodora myristica). These wild seeds could be good nutrient sources if integrated fully into human and animal nutrition. However, further studies will be carried out on the protein quality and toxicological potentials of these wild seeds.     

In-vitro iron dialysability from legumes: Influence of phytate and extrusion cooking

In-vitro iron dialysability from five Italian legumes (mottled bean, white bean, faba bean, chickpea, lentil) and the influence of phytate and extrusion cooking on it were evaluated. Iron dialysability was 2·3 and 2·4% in mottled and white bean respectively, 1·2% infaba bean, 2·7% in chickpea and 1·1% in lentil. After extrusion cooking the flours showed a marked iron contamination and a decrease in iron dialysability, but these changes were significant only for mottled bean. Enzymic phytate removal induced an increase in iron dialysability > 100% in all the raw legumes except mottled bean which showed an increase of only 57%. This finding indicates that, although phytate consistently modifies iron dialysability, it is difficult to identify a quantitative relationship between phytate content and iron dialysability.