Structural and physicochemical property changes during pyroconversion of native maize starch

Functionalization Methods of Starch and Its Derivatives: From Old Limitations to New Possibilities

It has long been known that starch as a raw material is of strategic importance for meeting primarily the nutritional needs of people around the world. Year by year, the demand not only for traditional but also for functional food based on starch and its derivatives is growing. Problems with the availability of petrochemical raw materials, as well as environmental problems with the recycling of post-production waste, make non-food industries also increasingly interested in this biopolymer. Its supporters will point out countless advantages such as wide availability, renewability, and biodegradability. Opponents, in turn, will argue that they will not balance the problems with its processing and storage and poor functional properties. Hence, the race to find new methods to improve starch properties towards multifunctionality is still ongoing. For these reasons, in the presented review, referring to the structure and physicochemical properties of starch, attempts were made to highlight not only the current limitations in its processing but also new possibilities. Attention was paid to progress in the non-selective and selective functionalization of starch to obtain materials with the greatest application potential in the food (resistant starch, dextrins, and maltodextrins) and/or in the non-food industries (hydrophobic and oxidized starch).

A Comparative Study of Resistant Dextrins and Resistant Maltodextrins from Different Tuber Crop Starches

The anti-digestibility of resistant dextrin (RD) and resistant maltodextrin (RMD) is usually significantly affected by processing techniques, reaction conditions, and starch sources. The objective of this investigation is to elucidate the similarities and differences in the anti-digestive properties of RD and RMD prepared from three different tuber crop starches, namely, potato, cassava, and sweet potato, and to reveal the associated mechanisms. The results show that all RMDs have a microstructure characterized by irregular fragmentation and porous surfaces, no longer maintaining the original crystalline structure of starches. Conversely, RDs preserve the structural morphology of starches, featuring rough surfaces and similar crystalline structures. RDs exhibite hydrolysis rates of approximately 40%, whereas RMDs displaye rates lower than 8%. This disparity can be attributed to the reduction of α-1,4 and α-1,6 bonds and the development of a highly branched spatial structure in RMDs. The indigestible components of the three types of RDs range from 34% to 37%, whereas RMDs vary from 80% to 85%, with potato resistant maltodextrin displaying the highest content (84.96%, p < 0.05). In conclusion, there are significant differences in the processing performances between different tuber crop starches. For the preparation of RMDs, potato starch seems to be superior to sweet potato and cassava starches. These attributes lay the foundation for considering RDs and RMDs as suitable components for liquid beverages, solid dietary fiber supplements, and low glycemic index (low-GI) products.

Effect of Continuous and Discontinuous Microwave-Assisted Heating on Starch-Derived Dietary Fiber Production

Dietary fiber can be obtained by dextrinization, which occurs while heating starch in the presence of acids. During dextrinization, depolymerization, transglycosylation, and repolymerization occur, leading to structural changes responsible for increasing resistance to starch enzymatic digestion. The conventional dextrinization time can be decreased by using microwave-assisted heating. The main objective of this study was to obtain dietary fiber from acidified potato starch using continuous and discontinuous microwave-assisted heating and to investigate the structure and physicochemical properties of the resulting dextrins. Dextrins were characterized by water solubility, dextrose equivalent, and color parameters (L* a* b*). Total dietary fiber content was measured according to the AOAC 2009.01 method. Structural and morphological changes were determined by means of SEM, XRD, DSC, and GC-MS analyses. Microwave-assisted dextrinization of potato starch led to light yellow to brownish products with increased solubility in water and diminished crystallinity and gelatinization enthalpy. Dextrinization products contained glycosidic linkages and branched residues not present in native starch, indicative of its conversion into dietary fiber. Thus, microwave-assisted heating can induce structural changes in potato starch, originating products with a high level of dietary fiber content.

Molecular structure of different prepared pyrodextrins and the inhibitory effects on starch retrogradation

Pyrodextrins with different molecular size were prepared by dry heating native corn starch with and without hydrochloric acid (HCl) at 180 °C for 0.5, 3, and 5 h. Those with HCl treatment displayed much smaller molecular size, narrower size distribution, and higher proportion of the chains with the degree of polymerization (DP) ~24-400 than the counterparts without HCl treatment. Pasting and rheological tests showed that the addition of pyrodextrins with HCl treatment displayed lower overall and setback viscosity, and reduced gel development and gel strength in comparison of those without HCl treatment. Differential scanning calorimetry (DSC) and wide-range X-ray (WXRD) data suggested that the pyrodextrin sample prepared by heating native starch with HCl at 180 °C for 5 h (A₅) displayed the most effective inhibition on starch long-term retrogradation. This study could supply a pathway by applying pyrodextrins to both increase nutrition value and retard starch retrogradation for bakery and beverage industry.

Structural comparisons of pyrodextrins during thermal degradation process: The role of hydrochloric acid

Hydrochloric acid (HCl) is widely used to prepare pyrodextrins, especially the water-soluble pyrodextrin. In this study, the structural difference between pyrodextrins as affected by HCl is compared by characterizing the molecular size, chain-length distributions (CLDs), crystallinity, and solubility. It is found that: 1) dry heating of starch granules without HCl mainly degrades long-amylose chains while slightly affects amylopectin branches; 2) the presence of HCl during dry heating decreases the degree of polymerization (DP) range of amylose chains upon degradation from DP ~ 833-1267 to DP ~ 206-432, suggesting that the presence of HCl accelerates the breakdown of long-amylose chains; 3) both pyroconversion processes have slight effects on A-(DP ~ 6-12) and B₁- chains (DP ~ 12-24), which might explain the retained granular and crystalline structure during the process. This study could improve the understanding of the role of HCl in affecting the structure and property during pyroconversion of native starch.

Dual modification of various starches: Synthesis, properties and applications

The problems associated with native starches (NSs) and single modified starches were stated in order to justify dual modification of various starches. Broadly, there are two types of dual modification, i.e., homogeneous dual modification and heterogeneous dual modification. The combination of two physical modifications, e.g., (extrusion/annealing); two chemical modifications, e.g., (succinylation/cross-linking) and two enzymes modification (α-amylase/pullulanase) falls under the former classification and the latter classification is the combination of two of each of the differently stated modifications, e.g., acetylation/annealing, extrusion/succinylation, and microwave-assisted phosphorylation, etc. The classification, synthesis, properties and applications of dually modified starches were discussed. There is an attempt to elucidate the problems of each of the single modification in order to justify dual modifications. In dual modifications, the order of reactions, the reaction conditions, the medium of reaction, and the botanical sources of the various starches are very important parameters.