Starch thermal modification

Zweifel, C., Conde-Petit, B., and Escher, F. 2000. Thermal modifications of starch during high-temperature drying of pasta. Cereal Chem. 77, 645-651. 

Depolymerizing modification of starch usually involves the use of enzymes, acid- (and less frequently base-) catalyzed hydrolysis, and thermolysis alone and thermolysis combined with acid-catalyzed hydrolysis (see a recent survey in this Series2). Despite several studies, the physical treatment of starch has not yet resulted in major practical applications. The aim of this Chapter is to review physical methods as tools for the treatment of starch which deliver amounts of energy suitable for depolymerizing starch to target products. It should be noted that the duration of such processes does not need to exceed that for conventional, namely enzymic, chemical, and thermal modifications. Moreover, a potential advantage of nonconventional physical treatments is the fact that they generate no waste products. 

What is a resistant starch Why are resistant starches considered as nutra-ceuticals List the four types of resistant starches, indicating the types produced via thermal modifications. 

Another special type of t. by thermal modification is Zulkowsky starch which is used in the same applications as Lintner starch. 

DSC studies have shown that modification alters thermal transition temperatures and the overall enthalpy (AHgei) associated with gelatinization (Tables 10.13 and 10.14). Upon hydroxypropylation, the reactive groups introduced into the starch chains are capable of disrupting the inter-and intra-molecular hydrogen bonds, leading to an increase in accessibility by water that lowers... 

Starch modifications can be classified as physical modifications, chemical modifications and genetic modifications.45 Physical modification of cassava starch involves application of shear force, blending and thermal treatment. A combination of thermal treatment and shear force has been widely used to produce many extruded products and snacks. Well-known physically modified cassava starch products are alpha starch or pregelatinized starch and heat-moisture treated starch. 

The modification of cellulose with alkaline carbon disulfide to introduce xanthate groups has been extensively exploited in the industrial production of viscose. Early work on the preparation and properties of starch xanthate has been discussed. Xanthate derivatives of cellulose and starch have been discussed with respect to general xanthate chemistry, and the xanthation of cellulose in homogeneous medium is known to be a second-order reaction. Cellulose xanthate shows some potential as a matrix for enzyme insolubilization, " and stable derivatives of this xanthate may be prepared by transesterification. Thermal decomposition of cellulose allyl- and benzyl-xanthates gives 5,6-cellulosene. Some thiocarbonyl derivatives of polysaccharides have been prepared. "... 

Modifications of the native starch form can be made by means of thermal and mechanical treatments where the amount of water has an essential role. Referring to Equation 2.1, when starch is heated at a water volume fraction above 0.9 a pure gelatinization phenomenon (and afterwards gelation and retrogradation) or jet-cooking occurs. On the contrary, when the water volume fraction is low (e.g. below 0.45), a real melting of starch crystallites occurs [11,27] and thermoplastic starch can be obtained [27]. 

In the previous section, it was outlined how the thermal stability of bio-nanocom-posites is more related to the type and to the modification of the nanopaiticle dispersed within the hiopolymer, than to do with any reinforcement effect attributable to the nanoparticle. Different nanoparficles have different effects on the thermal stability of biopolymers. Nanoclay can greatly enhance the thermal stability of a number of different biopolymers—PLA [48,63], POL [67], starch [68,69] and PHBV [65]. As... 

A wide range of modification mechanisms of starches are known (Yalpani, 1988). These include self-association (induced by changes of pH, ionic strength, or physical and thermal means) and complexation with salts and covalent cross-linking. 

However, increasing cellulose fiber content and time of photo-irradiation led to decreasing elongation (%) values. Other research on the use of thermoplastic starch without further modification (i.e., changes in experimental conditions) include the work of Lu et al. (2006), Ma et al. (2007), Fama et al. (2009), Kaushik et al.(2010), Liu et al. (2010), Guimaraes et al. (2010), and Kaith et al. (2010). These studies show a significant increase in tensile and thermal properties of thermoplastic starch when the matrix reinforced with nanofibers. 

Modifications in order to improve starch matrix-starch nanoparticles nanocomposites were also proposed. For example, Ma et al. (2008c), proposed the fabrication and characterization of citric acid-modified starch nanoparticles/plasti-cized pea starch composites. In dynamic mechanical thermal analysis, the introduction of CA-S-NP could improve the storage modulus and the glass transition temperature of pea starch/CA-S-NP composites. The tensile yield strength and Young s modulus increased Irom 3.94 to 8.12 MPa and from 49.8 to 125.1 MPa, respectively, when the CA-S-NP contents varied fiom 0 to 4 wt%. 

Chakraborty S, Sahoo B, Teraka 1, Miller LM, Gross RA (2005) Enzyme-catalyzed regioselective modification of starch nanoparticles. Macromolecules 38 61-68 Chartoff RP (1981) Thermal characterization of polymeric materials. In Turi E (ed) Academic Press, San Diego, p 526... 

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