Understanding and Influencing Starch Biochemistry (original) (raw)
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STARCH IN FOOD. STRUCTURE, FUNCTION and APPLICATIONS
Journal of Texture Studies, 2005
This comprehensive review on starch chemistry and technology applied to food is divided into four parts and 21 chapters. The first part of the book covers starch analysis and modification. In Chapter 1, J. Preiss reviews starch synthesis in plants. The author describes a pathway of starch synthesis suggesting specific functions for starch synthesis and branching enzymes. The paper points to the possibility of producing modified starches through molecular biology techniques. Chapter 2 deals with the analysis of starch structure. E. Bertoft reviews analyses of starch structure focusing on amylopectin as the main substrate, and using enzymic methods. The author stresses the need for improved technology for routine starch component characterization. In Chapter 3, A. Blennow reviews progress in starch bioengineering, emphasizing cross disciplinary approach for starch modification. Bleenow points to the huge potential that biotechnology offers in producing starch with customized functionalities, at low cost and in an environment-friendly way. In Chapter 4, D.P. Butler et al. deal with starch-acting enzymes. The chapter reviews starch-hydrolyzing enzymes and their use for functional changes in starch and starch-based foods. The paper also describes molecular biological strategies used to obtain enzymes with new applications in starch modification. A.M. Donald in Chapter 5 reviews starch structure and functionality, highlighting the role current technology can play in understanding and modifying the structure of starch granule. The chapter by M. Peris-Totajarda in Chapter 6 is about measuring starch in food. Perris-Totajarda reviews regulations pertaining to starch analyses and describes classical and modern methods of analyzing starch in food. The second part of the book deals with the various sources of starch. H. Cornell in Chapter 7, provides a comprehensive review on the functionality of wheat starch. Wheat starch manufacturing, structure and functionality are described. Rheological properties of wheat starch paste and gels are covered, as well as wheat starch modification for application in food industry. In Chapter 8, W. Bergthaller offers a succinct review of developments in potato starch, stressing its unique functional properties. The paper covers rheological properties of potato starch, production techniques and ways to improve potato starch for food applications. The reviews ends with a brief look at future trends, especially in breeding, genetic engineering, organic potato starch and the potential offered by small potato starch granules.
Form and functionality of starch
Food Hydrocolloids, 2009
Starch is a macro-constituent of many foods and its properties and interactions with other constituents, particularly water and lipids, are of interest to the food industry and for human nutrition. Starch varies greatly in form and functionality between and within botanical species, which provides starches of diverse properties but can also cause problems in processing due to inconsistency of raw materials. Being able to predict functionality from knowledge of the structure, and explain how starch interacts with other major food constituents remain significant challenges in food science, nutrition, and for the starch industry generally. This paper describes our current understanding of starch structure that is relevant to its functionality in foods and nutrition. Amylose influences the packing of amylopectin into crystallites and the organization of the crystalline lamellae within granules, which is important for properties related to water uptake. Thermal properties and gel formation appear to be influenced by both amylose content and amylopectin architecture. While amylose content is likely to have an important bearing on the functional properties of starch, subtle structural variations in the molecular architecture of amylopectin introduces uncertainty into the prediction of functional properties from amylose content alone. Our ability to relate starch granule structure to suitability for a particular food manufacturing process or its nutritional qualities depends not only on knowledge of the genetic and environmental factors that control starch biosynthesis, and in turn granule morphology, but also on how the material is processed.
Causal Relations Among Starch Biosynthesis, Structure, and Properties
Springer Science Reviews, 2014
Starch, an important carbohydrate with widespread applications in human foods, animal feeds, and many industrial products, is synthesized by plants by the action of a complex system involving many enzymes. The differing activities of these enzymes contribute to variations in starch structure among different plant species, botanical organs, and genetic backgrounds, and thus affect the physicochemical properties and end-use functions of starch. The demand for starches with particular functional properties is increasing, but the ability to produce novel starches is still limited. Starches with specific properties can potentially be produced by biotechnical modification of the starch biosynthetic pathway; however, this requires further understanding of the starch biosynthesis-structureproperties relationships. This review summarizes the state of the art in the understanding of these causal relationships: the roles of the main starch-synthesizing enzymes on starch structure, hierarchical structure of starch, advanced molecular structure characterization methods, and impact of starch structure on some functional properties. A better understanding of these relationships among starch biosynthesis, structure, and properties provides direction for genetic modification and targeted breeding programs to produce starch with desired characteristics.
Food Hydrocolloids, 2005
Potato starch was modified in planta by antisense of the starch branching enzyme I (SBE I), and the starch branching enzyme II (SBE II) both simultaneously and individually generating B group starches. Another group of starches, G group starches, was generated by over expression of the E. coli glycogen branching enzyme (E. coli glgB). The content of covalently esterified phosphate increased in the B group starches and decreased in the G group starches. The content of phosphate correlated with length of debranched amylopectin chains measured by HPAEC-PAD, and with gelatinisation mid temperature (T m ) and change in enthalpy (DH) measured by differential scanning calorimetry (DSC). Freeze/thaw stability measured by 1 H pulse-NMR and cohesiveness measured by texture profile analysis (TPA) was in the same range in all starch samples, whereas gel hardness was inversely correlated to phosphate content. No correlations between the pasting properties measured by rapid visco analysis (RVA), gel strength (G 0 ) measured by small deformation oscillation testing or any structural parameter could be revealed. The data set was mined using multivariate statistics. Based on this data starch samples could be separated into the two groups B and G, in accordance with their original transformation strategy. q
Starch biosynthesis and modification of starch structure in transgenic plants
Macromolecular Symposia, 1997
Starch is synthesised through the ADP-glucose pathway, involving the three enzymes ADP-glucose pyrophosphorylase, starch synthase and starch branching enzyme. ADP-glucose pyrophosphorylase is the key enzyme of the pathway, determining the flux of carbon into starch. It generates ADP-glucose, which is the substrate for the starch synthases, from glucose-1-phosphate and ATP releasing pyrophosphate. The enzyme is stimulated by 3-phosphoglycerate and inhibited through inorganic phosphate. The starch synthases, which catalyse the transfer of glucose from ADP-glucose to the nonreducing end of a growing a-1,4glucan, are divided into two classes, the granule-bound starch synthases (GBSS) and the soluble starch synthases (SS). In both classes several isoforms have been described from many different plant species. The branching enzyme, which introduces branchpoints into the amylopectin, can also occur in different isoforms. Other enzymes present in plants, which also act on a-1,4-glucans, such as the starch phosphorylases, disproportionating enzyme and different starch hydrolases, might also be important for dertermining the starch structure and, therefore, its processibility. Many aspects of starch synthesis are not fully understood to date. Starch metabolism can be manipulated through genetic engineering, either by the ectopic expression of different heterologous genes, or through the repression of the expression of endogenous genes using antisense RNA technology. This not only allows the functional analysis of starch biosynthetic proteins, but also the manipulation of starch structure in order to widen its industrial applications. In this way many different potato lines have been generated, containing either different amounts of starch, or which synthesize a structurally modified starch. These structural changes relate to the amylose content, the phosphate content, or the gelatinisation and gelation characteristics of the starch.
Chemical Modifications of Starch; A Prospective for Sweet Potato Starch
Jordan Journal of Agricultural Sciences
The current review presents the potential chemical modifications and applications of sweet potato starch in food and non-food industries. Native starch in general and particularly sweet potato starch characteristics have several functional features and applications in biomedicine as well as in the food industry. Modified starch is expected to enhance such characteristics as discussed in this review. For instance, due to the polymeric and branching nature of starch; the starch is usually less soluble, absorbs less water and oil, and shows a strong ability to bind to iodine. Also, native starches have significantly lower digestibility values under enzymatic treatment. Starch modifications, therefore are designed to enhance one or more of the above-mentioned limitations; thereby, modification of starch can alter the physicochemical characteristics of the native starch to improve its functional characteristic. Starches can be modified using physical methods (annealing, heat moisture tre...
The Plant Journal, 1999
A chimeric antisense construct has been used to generate transgenic potatoes (Solanum tuberosum L.) in which activities of both of the main starch synthases responsible for amylopectin synthesis in the tuber (SSII and SSIII) are reduced. The properties of starch from tubers of these plants have been compared with those of starches from transgenic plants in which activity of either SSII or SSIII has been reduced. Starches from the three types of transgenic plant are qualitatively different from each other and from the starch of control plants with unaltered starch synthase activities, with respect to granule morphology, the branch lengths of amylopectin, and the gelatinisation behaviour analysed by viscometry. The effects of reducing SSII and SSIII together cannot be predicted from consideration of the effects of reducing these two isoforms individually. These results indicate that different isoforms of starch synthase make distinct contributions to the synthesis of amylopectin, and that they act in a synergistic manner, rather than independently, during amylopectin synthesis.
2014
Morphology, molecular structure, and thermal properties of potato starch granules with low to high phosphate content were studied as an effect of mild acid hydrolysis (lintnerization) to 80% solubilization at two temperatures (25 and 45 C). Light microscopy showed that the lintners contained apparently intact granules, which disintegrated into fragments upon dehydration. Transmission electron microscopy of rehydrated lintners revealed lacy networks of smaller subunits. The molecular composition of the lintners suggested that they largely consisted of remnants of crystalline lamellae. When lintnerization was performed at 45 C, the lintners contained more of branched dextrins compared to 25 C in both low and intermediate phosphate-containing samples. Highphosphate-containing starch was, however, unaffected by temperature and this was probably due to an altered amylopectin structure rather than the phosphate content.