Comparative chemical modification of starches as a function of their origin: synthesis and analysis (original) (raw)
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Starch - Stärke, 2013
Starch is, after cellulose, the most abundant organic compound in nature. Modification of starch is carried out to enhance the positive attributes and to eliminate the shortcomings of the native starches. Various methods have been developed to produce a range of modified starches with a variety of characteristics and applications. Physically modified starches are simple and inexpensive because they can be produced without chemicals or even biological agents. In contrast, chemical modification is possible due to ubiquitous hydroxyl groups in starches that have been exploited for over a century, principally in the preparation of starch esters and ethers, but also in more subtle alterations, e.g., in order to tune the structure of starches for specific applications. All these techniques tend to alter the highly flexible starch polymer with changed physicochemical properties and modified structural attributes of high technological value for the food and non-food industries. Modification of starch is an ever evolving industry with numerous possibilities to generate novel starches which includes new functional and value added properties as demanded by the industry. This review aims to summarize the latest developments and recent knowledge regarding physically and chemically modified starches. This paper covers physical modification methods (pre-gelatinization, hydrothermal, and non-thermal processes), some chemical modifications and a combination of both.
Physical and Chemical Modifications in Starch Structure and Reactivity
Chemical Properties of Starch, 2020
Starch is a naturally occurring glucose homo-polysaccharide of nutritional, pharmaceutical, and industrial importance. The complex polymeric structure and poor solubility of native starch in water limits their importance at pharmaceutical and industrial level. The structure, reactivity, and functionality of the native starch can be modified by physical, chemical, enzymatic, and biotechnological methods. Various physical modifications techniques, including the thermal, radio-thermal, freezing and thawing, annealing, high-pressure, ultrasonic, and pulsed electric field treatment, and chemical modifications, including oxidation, etherification, esterification, cationization, cross-linking, and graft polymerization, have been found to change the surface properties, polarity and linearity of the molecular chains, the degree of substitution, the polymeric, granular, and crystalline structure, amylose to amylopectin ratio, solubility, viscosity, pasting, gelatinization, swelling, water absorption, and emulsifying properties of starch. The structural changes have resulted in the improvement of thermal and freeze-thaw stability, viscosity, solubility, water binding capacity, swelling power, gelling ability, and enzymatic digestibility of starch. The exposure of reactive functional groups after physical or chemical modification modifies the reactivity of starch toward water, oil, acids, enzymes, and other chemical species. These modification techniques have led to some revolutionary changes in reactivity, functionality, and application of starch in various fields.
Food Hydrocolloids, 2007
Effect of some common chemical modifications such as acetylation, hydroxypropylation and cross-linking on the physico-chemical, morphological, thermal and rheological properties of starches from different botanical sources have been reviewed. The distinguishing factors that affect the efficiency of modification are the starch source, amylose to amylopectin ratio, granule morphology, and type and concentration of the modifying reagent. The extent of alteration in the starch properties reflects the resistance or the susceptibility of a starch towards different chemical modifications. Modified starches with desirable properties and degree of substitution can be prepared by critically selecting a suitable modifying agent and a native starch source.
Advances in chemical modifications of starches and their applications
Carbohydrate Research, 2019
Starch is a homopolysaccharide made up of glucose units which are linked together via a glycosidic linkage. This biopolymer is well known for its low cost, biodegradability, renewability and easy availability. In spite of all these beauties, starch has some problems with their solubility in water, retrogradation, loss of viscosity due to rupturing of glucosidic bond when subjected to treatment and absence of some groups of primary importance like different functional groups especially carboxylic group, ester group, ether group and amino group.In order to overcome these shortcomings and enhance its applications, starch must be modified. The modification can be done chemically, physically and enzymatically, but noteworthy one is the chemical modification. In this review article, we focused on the recently used ways of chemical modification such as acid hydrolysis, cross-linking, acetylation/esterification, dual modification, oxidation and grafting of starch, and their properties.This review article highlighted the application of modified starch as an adsorbent for the removal of ammonia, phenol, heavy metals,and dyes.
Novel starch hybrids containing acrylamide (Aam) moieties in monomeric (i.e carbamoylethyl groups) and polymeric (poly acrylamide) forms were synthesized. Thus, starch was first polymerized with acrylamide to yield poly (Am)-starch composite and poly (Aam)-starch graft copolymer which represent the total polymerization products before and after removal of the homopolymer, respectively. The composite and the copolymer were then carbamoyethylated via reaction with Aam. Beside the carbamoylethyl groups, carboxyethyl groups were inevitably formed during carbamoylethylation. This and the onset of such modification on the rheological properties of the so synthesized starch hybrids signify the following. a) The extents of carbamoylethylation of the composite and the copolymer were much lower than native starch; b) The magnitude of poly(Am) content in the form of graft or homopolymer adversely affects the carbamoylethylation reaction; c) before carbamoylethylation, the composite, the copolymer and native starch exhibited non-Newtonian thixotropic behavior. , d) after carbamoylethylation the etherified products were characterized by pseudoplastic behavior. The apparent viscosity of starch, starch composite and starch copolymer decreased significantly after carbamoylethylation but with the certainty that the apparent viscosity increased by increasing the carbamoylethyl and carboxyethyl groups in these starch hybrids.
Chemical modification of Grains’ starch for Improved Functionality
2018
Article History Received: 04.06.2018 Accepted: 25.06.2018 Published: 30.06.2018 Abstract: Grain starch in general has wide array of applications in industry, food preparation, paper surface coating and textiles. Many of the important functional properties of starch including the emulsion capacity, water and oil absorption, least gelation concentration and foaming capacity can be substantially improved from physical and chemical modifications. In this review, current and advances in grain starch modification technology was examined and the functional properties compared with the unmodified sample. Chemical modifications such as crosslinking starch granules with variety of cross-linkers such as citric acid improved the functional properties of acha starch significantly. The least gelation concentration (LGC) increased from 6% to 8% and the pasting viscosity also decreased to 25Cp Other chemical modification techniques examined include oxidation and acid treatment or mild hydrolysis. S...
2003
Grafting of N-tert-butylacrylamide (BAM) onto starch in aqueous medium initiated by ceric ammonium nitrate ion has been studied under N 2 atmosphere. The optimum conditions with respect to monomer concentration, initiator concentration, polymerization temperature, polymerization time and material to liquor ratio were studied in terms of percent of grafting efficiency (%GE) and percent of grafting yield (%GY). The optimum conditions obtained for the grafting of BAM on 1.0 g starch were: [BAM] = 0.020 mol/L, [CAN] = 0.91 × 10 −3 mol/L, Temperature = 30 • C, and Time = 240 min. Starchg-BAM copolymer was characterized by FTIR, TGA for thermal stability, X-ray diffraction (XRD) for the crystallinity and scanning electron microscope (SEM) for surface morphology of the copolymer. Acid hydrolysis and viscosity average molecular weight (M v ) of copolymer were evaluated for the copolymer. Hydrogels prepared by grafting of BAM onto gelatinized starch showed maximum water uptake and moisture retain of 162% and 63% respectively.
Isolation, Modification and Characterization of Tiger-Nut, Maize, Cassava and Potato Starch
Journal of Applied Sciences and Environmental Management, 2018
Four different sources of starchy foods were used for the isolation of starch using commercially cheap and readily available chemical-hypo (3.5 % active Chlorine). The isolated starch was modified through NaIO4 oxidation under mild reaction conditions. Carbonyl functional group test was employed for confirmation of the success of oxidation. FT-IR and Scanning Electron Microscopy (SEM) were used for functional group identification and morphological examination of both modified and native samples to further confirm the success of modification. The appearance of the carbonyl band at 1747-1746 cm-1 and 1647-1637 cm-1 indicated the successful synthesis of oxidized starch. Proximate results showed that the isolated starches were rich in mineral content: 0.25-2.13; crude fibre: 0.85-3.31; fat: 0.23-0.28 and energy: 1331-1410. The study showed that commercial hypo could be a useful replacement for metabisulphite for starch isolation without side effects on starch properties. SEM images showed that morphological architecture of granules was not destroyed during surface functionalization. Characteristic and nutritional features of the oxidized starch showed that it could find useful applications in food and pharmaceutical industries.
Application of Starch and Starch-Based Products in Food Industry
Journal of Science and Technology
Starch is an edible polymer derived from plant basis. It is commonly used in food industry as it offers good stabilising effect. Moreover, starch can be easily modified either physically or chemically making it a very versatile source. For instance, its capability to be easily modified and coming from low cost source making starch as one of the most important ingredient in food preparation. There are currently varieties of commercially modified starch available in Malaysian market. For example, potato, corn, wheat and tapioca starch are presently on the top list. However, there are also numbers of unexplored native starch for example from fruits processing waste. Besides, these fruit by-products are considered as underutilised source of starch. Although there are few existing reported studies on starch extracted from fruits seed and other waste products, more new sources are believed to be explored in future according to particular starchbased products industries and demands. Therefore, this review discusses current starch based-products developments and application of unconventional starch in food industry.