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Review of related literature of string beans

Wirth Find articles by James P. Received 2014 Nov 27; Accepted 2015 Jan 29. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution license http: This article has been cited by other articles in PMC.

Abstract Common beans are a staple food and the major source of iron for populations in Eastern Africa and Latin America. Bean iron concentration is high and can be further increased by biofortification. A major constraint to bean iron biofortification is low iron absorption, attributed to inhibitory compounds such as phytic acid PA and polyphenol s PP.

We have evaluated the usefulness of the common bean as a vehicle for iron biofortification. PA concentrations in beans are high and tend to increase with iron biofortification. Short-term human isotope studies indicate that iron absorption from beans is low, PA is the major inhibitor, and bean PP play a minor role.

Multiple composite meal studies indicate that decreasing the PA level in the biofortified varieties substantially increases iron absorption.

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  • Received 2014 Nov 27; Accepted 2015 Jan 29;
  • Review of literature the literature pertinent to the present investigation entitled, effect of integrated nutrient management on yield 1992 conducted a green house experiment to study the effect of graded.

Beans are a good vehicle for iron biofortification, and regular high consumption would be expected to help combat iron deficiency ID. The annual global bean production is approximately 12 million metric tons, with 5. The highest producer is India at more than 4 million metric tons per year [ 9 ]. The highest apparent per capita consumption is found in Burundi, Kenya and Rwanda [ 3 ], ranging from 31 kg to 66 kg per year [ 48 ], equivalent to 180 g per capita and day.

However, bean consumption and production tend to be underestimated because beans are often intercropped and consumed in remote rural areas [ 10 ] where dietary intake data are often incomplete or inexistent [ 11 ]. Thus, estimations of bean consumption as high as 200 g and 300 g per capita per day have been reported in Rwanda and certain regions of the DRC, respectively [ 1213 ].

One potentially sustainable strategy to combat ID in bean-eating populations is iron biofortification. Beans exhibit sufficient genetic variability in iron concentration, which is the basic requirement for biofortification.

In order to successfully introduce a biofortified crop in to the food system, other human and environmental factors have to be properly addressed. Sensory and cooking qualities have to be maintained and studies assessing consumer preferences must be undertaken in different cultural settings [ 11 ]. The new variety also has to be accepted and cultivated by the farmers, and must exhibit high agronomic yield and resistance to pathogens and other environmental stresses; in short, it must be as or more profitable than local varieties.

Review of related literature of string beans

To augment the sustainability of biofortification in general, and beans in particular, breeders have to take into account the impact of climate, soils and agronomic practices on iron concentration [ 2324 ].

In some countries e. They show good micronutrient retention after processing, and equal or increased agronomic yield, indicating that the common bean may be a promising crop for iron biofortification [ 28 ]. However, successful bean iron biofortification might be constrained due to the reported low iron bioavailability associated with high concentrations of PA [ 2930 ] and PP [ 1431 ], two potentially potent iron absorption inhibitors in common beans [ 3233343536 ].

Recent human stable isotope iron absorption studies, conducted with black and brown biofortified bean varieties, [ 3738 ] reported that the additional iron bred into biofortified beans review of related literature of string beans of low bioavailability and the authors questioned whether biofortified beans could make a useful contribution to filling the gap between current iron intake and requirements [ 28 ].

This review evaluates the potential of the common bean as a vehicle for iron biofortification, with a focus on human studies of iron absorption from beans and bean-containing meals and the impact of compounds present in beans PA; PP; proteins on bean iron absorption.

Methods Due to the broad scope of the review, key words related to the overarching topics were searched in PubMed and Web of Science to identify published literature related to bean consumption, bean production and iron in beans including iron biofortification, iron speciation, iron absorption inhibitors and human studies conducted with beans and bean containing meals. The key-word search was conducted in September 2014, and included the following words and expressions: Additional sources published and unpublished were identified through a reference review of key publications and theses [ 394041 ] and following discussions with researchers at HarvestPlus and ETH Zurich.

Sources not pertaining to the aforementioned topics review of related literature of string beans. Results and Discussion 3. Iron in Beans 3. Genetic Variability of Iron Concentrations in Beans Iron in beans is present in higher concentrations than in cereal staples, and is almost completely retained through harvest and processing [ 1442 ].

Much data are available on the iron content of beans, but the most complete overview and reliable information is provided by two independently conducted studies screening the common bean core collection of CIAT, which is a systematic sample of the germplasm available and contains more than 1000 genotypes.

It is not clear to what extent these very high iron concentrations are due to iron contamination from soil or other sources, but this is a potential source of apparent variability that should be investigated. There is no correlation between geographic distribution and iron concentration in beans, although beans from the Andean gene pool tend to have higher iron concentrations than Mesoamerican beans [ 14 ].

However, variability of iron concentration in beans was not only ascribed to bean variety, but was also influenced by the planting site and season [ 46 ]. Iron Speciation in Beans Storage iron in legumes is sequestered in ferritin, which is the major iron storage protein.

It is abundant in legumes and has been reported in beans, soybeans, lentils and peas [ 49505152 ]. Hoppler and colleagues [ 53 ], using their isotope dilution technique [ 52 ] subsequently reported that ferritin concentration in beans is independent of iron concentration and that as the iron concentration in beans increases, there is an increase in the non-ferritin bound iron Figure 1. They further observed a correlation between non-ferritin bound iron and phytate and suggested that this might be the reason for the low iron bioavailability reported from biofortified beans.

In colored beans, it is also possible that iron in the seed coat [ 54 ] is bound to PP as little PA is located in the seed coat.