Effect of phytate and iron-binding phenolics on the content and availability of iron and zinc in micronutrients fortified cereal flours

Iron deficiency anaemia is highly prevalent in Tanzania—affecting predominantly children and women. Fortification of cereal flour with micro-nutrients is being carried out as a strategy for combating micro-nutrient deficiencies. Four different cereal flours were fortified with micro-nutrients and evaluated for total and bioavailable iron and zinc, iron binding polyphenolics, phytate content and ascorbic acid. The extractable total phenolics ranged from 1.3 (maize) to 19.4 (redsorghum) mg catechin equivalent (CE) g-1. Catechols ranged from 1.1 (maize) to 11.7 (red-sorghum) mg CE g-1. Red sorghum was the only flour that contained ahigh amount of galloyls (4.0 mg tannic acid equivalent (TAE) g-1). All samples contained high amounts of phytate (10.7 ± 1.0 ìmol g-1). The average total iron was 42.26 ± 10.26 mg kg-1 in the unfortified and 52.67 ± 10.19 mg kg-1 in the fortified cereal flours and the average in vitro available iron was 1.03 ± 0.30 mg kg-1 and 1.65 ± 0.31 mg kg-1 respectively. The average zinc content was 21.4 ± 3.10 mg kg-1 and 25.9 ± 2.84 mg kg-1 in the unfortified and fortified flours respectively andthe average available zinc was 0.30 ± 0.12 mg kg-1 and 0.53 ± 0.16 mg kg-1 respectively. No ascorbic acid was detected in any of the unfortified flour, and a little amount was detected in the fortified red sorghum (4.5 mg kg-1), compared to the white sorghum (11.1 mg kg-1), finger millet (15.8 mg kg-1) and maize (29.6 mg kg-1). There was no significant increase of in vitro available iron (0.02 mg kg-1) and zinc (0.06 mg kg-1) availability in the red sorghum. The in vitro available iron increased by 3.8 % in finger millet, by 9.2 % in white sorghum, and by 10.1 % in maize four—compared to respective total iron content as a result of fortification. In vitro available zinc increased by 7.9 % in finger millet, by 4.8 % in white sorghum and by 5.9 % in maize flours, compared to respective total zinc content as a result of fortification. It was concluded that other dietary modification strategies that are being carried out for the improvement of native iron and zincbioavailability (processing for decreasing inhibitory factors, consumption of fruits and green leafy vegetables for enhancing absorption and nutrition education) should accompany fortification of flours with micro-nutrients. The red sorghum is not recommended as a good vehicle for food fortification with iron and zinc

Effects of Genotype and Growth Temperature on the Contents of Tannin, Phytate and in vitro Iron Availability of Sorghum Grains

Background: It has been predicted that the global temperature will rise in the future, which means crops including sorghum will likely be grown under higher temperatures, and consequently may affect the nutritional properties. Methods: The effects of two growth temperatures (OT, day/night 32/21°C; HT 38/21°C) on tannin, phytate, mineral, and in vitro iron availability of raw and cooked grains (as porridge) of six sorghum genotypes were investigated. Results: Tannin content significantly decreased across all sorghum genotypes under high growth temperature (P ≤0.05), while the phytate and mineral contents maintained the same level, increased or decreased significantly, depending on the genotype. The in vitro iron availability in most sorghum genotypes was also significantly reduced under high temperature, except for Ai4, which showed a pronounced increase (P ≤0.05). The cooking process significantly reduced tannin content in all sorghum genotypes (P ≤0.05), while the phytate content and in vitro iron availability were not significantly affected. Conclusions: This research provides some new information on sorghum grain nutritional properties when grown under predicted future higher temperatures, which could be important for humans where sorghum grains are consumed as staple food

Bioavailability of Iron, Zinc, Phytate and Phytase Activity during Soaking and Germination of White Sorghum Varieties

The changes in phytate, phytase activity and in vitro bioavailability of iron and zinc during soaking and germination of three white sorghum varieties (Sorghum bicolor L. Moench), named Dorado, Shandweel-6, and Giza-15 were investigated. Sorghum varieties were soaked for 20 h and germinated for 72 h after soaking for 20 h to reduce phytate content and increase iron and zinc in vitro bioavailability. The results revealed that iron and zinc content was significantly reduced from 28.16 to 32.16% and 13.78 to 26.69% for soaking treatment and 38.43 to 39.18% and 21.80 to 31.27% for germination treatments, respectively. Phytate content was significantly reduced from 23.59 to 32.40% for soaking treatment and 24.92 to 35.27% for germination treatments, respectively. Phytase enzymes will be activated during drying in equal form in all varieties. The results proved that the main distinct point is the change of phytase activity as well as specific activity during different treatment which showed no significant differences between the varieties used. The in vitro bioavailability of iron and zinc were significantly improved as a result of soaking and germination treatments

Phenolic content in cereals and legumes. Influence of processing and effect on in vitro availability

Iron deficiency anaemia is highly prevalent in Tanzania, and one of the major causes is the low bioavailability of iron in the plant food staple diet. Cereals and legumes contain large amounts of compounds that inhibit iron absorption, e.g. phytate and phenolic compounds including phenolic groups such as galloyls (trihydroxyl) and catechols (ortho-dihydroxyl). Several processing methods are also known to reduce the amount of phenolic compounds, but little is known about their effect on specific phenolic groups. Dephytinization has been shown to increase the bioavailability of iron from several cereals, but this treatment alone is not sufficient to increase the bioavailability in high-tannin grains. This study was conducted to determine and characterize the amount of phenolic compounds in some cereals and legumes commonly consumed in Tanzania and to study the effect of traditional processing methods in combination with polyphenol oxidase on phenolic groups and on in vitro available iron.Total phenols, resorcinols and potential iron-binding phenolic groups (galloyls and catechols) were determined in the food grains using different colorimetric methods. Grains were subjected to community processing methods including dehulling, soaking, cooking, germination or fermentation. Phenolic compounds were oxidized by incubating phytate-reduced cereal slurries with polyphenol oxidase (PPO) or adding PPO during the fermentation processes. The in vitro available iron was measured as iron solubility at physiological conditions. The methods used for the determination of phenolic compounds were reproducible and the sum of different phenolic groups correlated to the amount of total phenols (r2 = 0.97;

Phenolic content in cereals and legumes. Influence of processing and effect on in vitro availability

Iron deficiency anaemia is highly prevalent in Tanzania, and one of the major causes is the low bioavailability of iron in the plant food staple diet. Cereals and legumes contain large amounts of compounds that inhibit iron absorption, e.g. phytate and phenolic compounds including phenolic groups such as galloyls (trihydroxyl) and catechols (ortho-dihydroxyl). Several processing methods are also known to reduce the amount of phenolic compounds, but little is known about their effect on specific phenolic groups. Dephytinization has been shown to increase the bioavailability of iron from several cereals, but this treatment alone is not sufficient to increase the bioavailability in high-tannin grains. This study was conducted to determine and characterize the amount of phenolic compounds in some cereals and legumes commonly consumed in Tanzania and to study the effect of traditional processing methods in combination with polyphenol oxidase on phenolic groups and on in vitro available iron.Total phenols, resorcinols and potential iron-binding phenolic groups (galloyls and catechols) were determined in the food grains using different colorimetric methods. Grains were subjected to community processing methods including dehulling, soaking, cooking, germination or fermentation. Phenolic compounds were oxidized by incubating phytate-reduced cereal slurries with polyphenol oxidase (PPO) or adding PPO during the fermentation processes. The in vitro available iron was measured as iron solubility at physiological conditions. The methods used for the determination of phenolic compounds were reproducible and the sum of different phenolic groups correlated to the amount of total phenols (r2 = 0.97;

Phenolic Compounds, Phytate, Citric Acid and the In-vitro Iron Accessibility of Cowpeas, Mung Beans and Four Varieties of Kidney Beans

Iron deficiency anaemia is highly prevalent in Tanzania affecting predominantly children and women of childbearing age. One of the major causes is the low iron bioavailability from vegetarian diets mainly due to the presence of various antinutritional factors that interfere with non-heme iron absorption. Cereals and legumes constitute the main ingredients of diets in the country providing proteins, carbohydrates, minerals and vitamins. Certain varieties of these grains contain large amounts of polyphenolics and phytate that are known to inhibit iron absorption. Varieties of legumes; cowpeas (Vigna unguiculata) and mung beans (Vigna radiata L.) and kidney beans (Phaseolus vulgaris L.) were analyzed for the polyphenolics and phytates. The total and in vitro accessible iron, and the citric acid were also quantified and their nutritional consequences discussed. Phenolic compounds varied widely in the analysed legumes ranging from 3.37 to 9.14 mg catechin equivalent/g and they associated negatively with in vitro accessible iron (r = - 0.367; p = 0.054). The catechol and resorcinol phenolics ranged from 1.58 to 3.51 and 1.41 to 5.37 mg catechin equivalent/g respectively and were relatively higher than galloyls that range from 0.10 to 1.52 mg tannic acid equivalent/g). Phytate ranged from 8.46 to 13.18 mg/g, total iron from 3.58 to 7.55 mg/100g and in vitro accessible iron from 0.45 to 1.04 mg/100g. Citric acid ranged from 70.8 to 205.2 mg/100g and was associated positively with in vitro accessible iron (r = 0.845; p = 0.006). Proper processing of legumes to reduce antinutritional factors to relatively lower levels is important in order to render the iron and other nutrients readily available for absorption. Keywords: Phytate; phenolic compounds; galloyls; catechols; resorcinols; citric acid; in vitro accessible iron Résumé COMPOSES PHENOLIQUES, PHYTATES, ACIDE CITRIQUE ET LE FER ACCESSIBLE IN-VITRO DE NIEBES, HARICOTS MUNGO ET QUATRE VERIETES DE HARICOTS ORDINAIRES L'anémie ferriprivée est fortement répandue en Tanzanie touchant principalement, les enfants et les femmes en âge de procréer. L'une des principales causes est le faible bio-disponibilité en fer des régimes végétariens due principalement de divers facteurs antinuritionnelles qui empêchent l'absorption de fer-non-hémique. Les céréales et les légumes constituent la source principale d'alimentation dans ce pays. Ils fournissent les protéines les hydrates de carbone, les minéraux et les vitamines. Les variétés de légumes ; des niébés, (vigna unguiculata) et haricots mungo (vigna radiata L) et des haricots ordinaires (phaseolus vulgaris L ) ont été analysées pour voir leur contenance en polyphénoliques et phytates. L'ensemble le fer accessible in-vitro et l'acide citrique ont été également quantifiés et leur impact nutritionnel discuté. Les résultats de l'analyse ont indiqué que les composés phénoliques ont largement varié allant de 3,37 à 9,14 mg équivalent/g de catéchine et ils se sont associés de façon négative au fer accessible in-vitro (r=-0,367; P=0,054) La contenance en catéchol et résorcinol (composés phénoliques) ont varié respectivement de 1,58 à 3,51 et de 1,41 à 5,37mg de catéchine équivalent/g respectivement et étaient des taux relativement plus élevés que celui de galloys qui a varié de 0,10 à 1,52mg d'acide tannique/g. Les phytates ont varié de 8,46 à 13,18mg/g, le fer total a varié de 3,58 à 7,55 mg /100g et le fer accessible in-vitro de 0,45 à 1,04 mg / 100g. La teneur en acide citrique a varié de 70,8 à 205,2 mg / 100g et a été associé positivement avec le fer accessible in-vitro (r= 0,845g;p=0,006) Il est important qu'un traitement approprié des légumes soit réalisé pour réduire les facteurs anti-nutritionnels à des niveaux relativement bas afin de faciliter l'absorption du fer et d'autres nutriments. Mots clefs: phytates, composés phénoliques, galloys, catéchols, résorcinols, acide citrique, fer accessible in-vitro. (Af. J. of Food, Agriculture, Nutrition and Development: 2003 3(1): 53-59

Adoption of mechanized postharvest cassava processing technologies, and the determinants of high quality cassava flour (HQCF) processing in Tanzania

Open Access JournalIn this study, the factors influencing the adoption of mechanized technologies for processing cassava into a value-added high quality cassava flour (HQCF) by rural households in Tanzania were examined. A structured questionnaire was used to collect data from 400 households in villages which carry out both mechanized and non-mechanized cassava processing activities. The questionnaire focused on the households' socio-economic characteristics and their adoption parameters. Data were analysed using descriptive statistics and the double-hurdle model. The study revealed a positive correlation between the level of awareness of mechanized cassava processing technologies and their rate of adoption. In addition, the adoption decisions made by the households were significantly influenced by a number of factors, such as the gender of the processors, the distance of the processing sites to the nearest tarmac road, and the cost of capital required to invest in HQCF processing technology. The amount invested by households in the processing of HQCF was influenced by the number of adult females in the household, the education level of the processors, farming experience and the distance from the processing plant to the nearest product market. This suggests that mechanized post-harvest processing of HQCF at the household level was influenced by access to product market. Therefore, the study recommends increased promotion of postharvest processing technologies, access to capital and enhancedinfrastructures, especially rural roads to facilitate improved access to markets for HQCF in Tanzania