Discovery of natural waxy cassava starch. Evaluation of its potential as a new functional ingredient in food

Cassava starch is a functional ingredient largely used in the food industry. This work reported the discovery of the first natural waxy cassava genotype (AM206-5) in CIAT, Cali, Colombia. SDS-PAGE demonstrated abnormality in the GBSS enzyme in the starch AM206-5. No change in starch granule size or shape was observed in comparison with normal cassava starch. Colorimetric and DSC amylose content for AM206-5 showed (3.4%; 0%) in comparison with normal cassava starch (19.7%; 19.0%) respectively. Paste clarity (61% vs 50%). Wavelength of maximum absorption (?max), (535 nm vs 590 nm), Pasting properties (RVA 5%): Pasting temperature (67.4°C vs 63.9°C) ; Maximum viscosity (1119 cP vs 954 cP) ; breakdown (631 cP vs 479 cP). swelling power ( 54.7% vs 40%), solubility(8.8% vs 7.3%), at 90°C. All analysis reported converge to support the hypothesis that genotype AM206-5 has amylose-free (waxy) starch. The evaluation of gel stress resistance was also compared with other industrial roots, tubers and cereal starches. Acid, alkaline, and shear resistance of waxy cassava starch were similar to normal cassava except for alkaline pH, at which it showed a lower effect. Gels from normal root and tuber starches (potato, cassava) after refrigeration and freeze/thaw had lower syneresis than cereal starches (maize, rice). Gels from waxy starches (except for potato) did not present any syneresis after 5 weeks of storage at 4°C. Waxy cassava starch was the only one not showing any syneresis after 5 weeks of storage at -20°C. Natural waxy cassava starch is, therefore, a promising ingredient to formulate refrigerated or frozen food. CIAT is producing new waxy genotypes especially for Thailand, and Brazil the biggest world cassava starch producers. In a recent selection 25% of large segregating populations (>11 500 genotypes) were waxy. Agronomic evaluation is underway for a release of a waxy starch variety for Thailand. (Résumé d'auteur

Evaluation of industrial potential of novel cassava starches with low and high amylose contents in comparison with other commercial starch sources

The industrial starch market is undergoing major expansion, but certain specific industrial uses cannot be satisfied by native starches and, therefore, chemical or physical modification is necessary. These modifications are often harmful to the environment and generate additional costs. Mutations in the cassava starch biosynthesis pathways were recently discovered at CIAT, Cali, Colombia. CIRAD, in partnership with CIAT, carried out a study on the physicochemical and functional properties of these starches, which could result in interesting industrial applications and create new market for cassava starch. Among the new cassava starch types, two new mutant cassava starches with extreme amylose contents (0% and 31%) have been recently reported. These mutants are drastically different from normal cassava starch whose amylose content typically ranges between 15-25%. The new mutants were compared with normal cassava starches and commercial versions of amylose-free or normal potato, rice and maize starch. The structure of cassava amylopectin was not modified by the waxy mutation and waxy cassava starch exhibited properties similar to the ones of waxy maize starch. On the contrary, the higher-amylose mutations induced by gamma rays radiation in cassava deeply modified the branching pattern of amylopectin as well as other starch characteristics and properties. These modifications resulted in changes in starch granule ultrastructure (e.g. decreased starch crystallinity), a weak organized structure, and increased susceptibility to mild acid and enzymatical raw starch hydrolysis (fastest and most efficient hydrolysis of all studied native starches). This mutation could offer interesting advantages for the production of bioethanol. Gels from normal root and tuber starches (potato, cassava) after refrigeration and freeze/thaw had lower syneresis than cereal starches (maize, rice). Gels from waxy starches (except for potato) did not present any syneresis after 5 weeks of storage at 4°C. Waxy cassava starch was the only one not showing any syneresis after 5 weeks of storage at -20°C. The distinctive properties of the new cassava starches suggest new opportunities and commercial applications for tropical sources of starch. Supporting information: Journal of Agricultural and Food Chemistry (2007), 55(18): 7469-7476. http://dx.doi.org/10.1021/jf800603p; Journal of Agricultural and Food Chemistry (2008), 56(16): 7215-7222. http://dx.doi.org/10.1021/jf800603p; Journal of Agricultural and Food Chemistry (2010), 58(8): 5093-5099. http://dx.doi.org/10.1021/jf1001606; Food hydrocolloids (2012), 27(1): 161-174. http://dx.doi.org/10.1016/j.foodhyd.2011.07.008. (Texte integral

Realizing the promises for high-value Cassava: root quality traits. [SP12-09]

A decade ago CIAT began the search of what it called "High-Value Cassava". What was then only a promise has gradually became a reality. In the area of starch quality traits an amylosefree (waxy) mutation was identified and has now been successfully introgressed to be released as commercial varieties. Part of this work is financially supported by the private starch sector. A small-granule mutation was also identified and found to be particularly suitable for processes requiring starch hydrolysis (e.g. sweeteners and ethanol). Moreover, CIAT has also identified a high-amylose genotype with as much as 42% amylose (whereas cassava starch typically has around 20%). Breeding methodologies to exploit these traits have been developed and tested. On the nutritional side, during the past decade, the increases in carotenoids content in the roots have been remarkable, and there seems to be no plateau in the progress made. Protocols for efficient selection in carotenoids have also been made. These results demonstrate that Manihot esculenta has many useful traits waiting to be found and also that this crop is capable of rapid responses if proper breeding methodologies are employed. Future work will concentrate on developing herbicide resistance and improving the protocol for assessing post-harvest physiological deterioration in roots. (Résumé d'auteur

Novel cassava starches with low and high amylose contents: Structural and macro-molecular characterization in comparison with other commercial sources

Cassava (Manihot esculenta Crantz) is one of the most important sources of commercial production of starch along with potato, maize and wheat particularly for tropical and subtropical regions of the world. It is the third most important source of calories in tropics, after rice and maize. Natural mutation, and induced ones in cassava starch have recently been reported leading to new starches with low and high-amylose contents (0 and 30-31 %). These mutants are drastically different from normal cassava starch whose amylose content typically ranges between 15-25 %. The aims of this study were to have an overview of the structural variability among the recently discovered cassava mutants comparatively to normal and amylose-free potato and maize starches. The macromolecular features, the crystallinity, the granule sizes, and the thermal properties of these new mutants were compared with five normal cassava starches (ranging from 16.8 to 21.5 % amylose) and commercial versions of amylose-free or normal potato and maize starch. The structure of cassava amylopectin was not modified by the waxy mutation and waxy cassava starch exhibited properties similar to the ones of waxy maize starch. Waxy cassava and maize amylopectins show similar molar masses and radii of gyration (from 408×106 g mol-1 to 520×106 g mol-1; and from 277 to 285 nm, respectively). Waxy potato amylopectin exhibit lower molar mass and size. Inversely, the higher-amylose mutations induced by gamma rays radiation in cassava, modified deeply the branching pattern of amylopectin as well as the starch characteristics and properties: molar masses and radii of gyration decreased, while branching degree increased. These modifications resulted in changes in starch granule ultrastructure (lowered starch crystallinity), a weak organized structure, and increased susceptibility to mild acid hydrolysis. The distinctive properties of the new cassava starches demonstrated in this article suggest new opportunities and commercial applications for these tropical sources of starch. (Résumé d'auteur

A reappraisal of nitrogen-to-protein conversion factors in cassava roots. [S10-05]

A study was conducted comparing the amino acid profiles of 10 commercial varieties (COL) and 15 clones with the highest levels of nitrogen (HIN) over two years of harvests. The highest nitrogen values detected in roots to date are close to 1.30%. The conversion factors of total nitrogen into protein calculated from amino acid profiles was 3.6 ± 0.9 for COL and 2.8 ± 0.2 for HIN. 53.7% of the total nitrogen is measured from protein with no difference between COL and HIN. The remaining 46.3% corresponds to ammonium ions, nucleic acids, or other nitrogenous non-protein molecules. Nitrogen content is 15.1 ± 1.2 and 19.1 ± 0.6% of the protein for COL and HIN, respectively. This difference is explained by a high content of arginine (4 nitrogen atoms per arginine molecule) in HIN clones. For COL, the proteins contained, on average: 23.3% glutamic acid, 15.7% proline, 14.3% arginine, 7.9% aspartic acid, while for HIN: 23.5% glutamic acid, 2.3% proline, 35.5% arginine, 7.9% aspartic acid. A linear correlation was found between the total nitrogen content and the level of arginine in cassava roots. Root protein content based on amino acid profile varied between 1.0% and 2.8% in the clones analyzed. Screening of varieties by the total nitrogen content leads to identify clones that are richest in arginine and not necessarily the richest in protein. Nitrogen alone, therefore, is not adequate to predict protein content. (Résumé d'auteur

Potential of the small-granule starch mutation for the Bioethanol Industry.

The industrial starch market is undergoing major expansion, but certain specific industrial uses cannot be satisfied by native starches and, therefore, chemical or physical modification is necessary. Mutations in the cassava starch biosynthesis pathways were discovered at CIAT (Cali, Colombia) few years ago. A starch mutation induced by gamma rays radiation resulted in a deeply modified branching pattern of amylopectin as well as other starch characteristics and properties. These modifications include changes in starch granule ultrastructure (e.g. decreased starch crystallinity), a weak organized structure, and increased susceptibility to mild acid and enzymatic raw starch hydrolysis (fastest and most efficient hydrolysis of all studied native starches). This mutation could offer interesting advantages for the production of bioethanol. Surprisingly this mutation also results in increased proportion of amylopectin. Hydrolysis was more dependent on granule morphology than on starch chemical composition. Recent crosses produced segregating progenies whose starch had the small-granule characteristics, but amylopectin content ranged from 19 to 42%. Rapid viscoamylograms of the latter starch showed very distinctive patterns. (Résumé d'auteur