Preparation and Application of Starch Graft Poly(vinyl) Copolymers as Paper Coating Adhesives

A series of starch graft copolymers were prepared from commercial cornstarch products and vinyl monomers and were evaluated as adhesives in pigmented paper coatings. Hypochlorite oxidized (HO), acid modified (AM), and hydroxyethlated acid modified (HEAM) starches were reacted separately with acrylamide (AAm), acrylic acid (AAc), and acrilonitrile (AN) using ceric ammonium nitrate as the polymerization initiator to yield copolymers containing 2–45% synthetic polymer. Pigmented coating mixtures with 6–14 parts co-polymer/100 parts clay and 40–50% total solids were prepared and applied on one side of the paper stock using a hand-drawn doctor blade. Viscosities, adhesive strength, and wet-rub resistance of the coating adhesives and mixtures were determined. Adhesive strength of starch graft polyacrylamide (S-g-PAAm) copolymers containing as little as 12% PAAm was considerably superior to the commercial starches as paper coating adhesives. Adhesive strength of S-g-PAAc copolymers was similar to that of the HO and HEAM commercial starches, whereas adhesive strength of the S-g-PAN copolymers was poor. Copolymers that were prepared from the HO starch were slightly superior to those prepared from the AM and HEAM starches. Wet-rub resistance of the pigmented copolymer coatings was not improved over that of the coatings containing the commercial starches.     

Effect of different starches on rheological and microstructural properties of (I) model processed cheese

A range of processed cheese spread samples containing starch were prepared on a Rapid Visco Analyser (RVA). The starches used were waxy cornstarch, high‐amylose cornstarch, rice starch, potato starch, wheat starch and acid‐converted starch. Incorporation of the starches at different levels produced marked differences in the rheological, microstructural and functional properties of the processed cheese spreads. Rheological attributes such as complex modulus and viscosity increased; the extent of increase depended on the starch type and the starch level. Starch incorporation at reduced protein levels demonstrated the possibility of maintaining satisfactory rheological properties at lower ingredient cost.     

Influence of Heat‐Moisture Treatment and Acid Modifications on Physicochemical,Rheological, Thermal and Morphological Characteristics of Indian Water Chestnut (Trapa natans) Starch and its Application in Biodegradable Films

Water chestnut starch was subjected to acid modification and heat‐moisture treatment. Hydrochloric acid was used for acid modification at three different concentrations (0.25 M, 0.5 M and 1 M) for 2 h. Modifications did not alter the granule morphology. Heat‐moisture treatment (HMT) resulted in slight reduction in the granular size of the starch granules. Acid modification lowered the amylose content, swelling power, water‐ and oil‐binding capacity but improved the solubility of starch to a considerable level. Light transmittance of acid‐modified (AM) starches improved significantly. A significant reduction in peak, trough, final and setback viscosity was observed by acid‐thinning. In case of heat‐moisture treated starch the final viscosity (F_v) was found to be even higher than the peak viscosity (P_v). Native water chestnut starch exhibited a lower onset temperature (T_o) and peak temperature (T_p) of gelatinization than the corresponding acid‐treated starches. Starch films prepared from native starch exhibited excellent pliability, whereas those prepared from AM and HMT starches showed good tensile strength. Starch films prepared from acid‐treated starches provided better puncture and tensile strength.     

Behaviour of Oxidized Starches Towards Cyanoethylation

Starch of different molecular sizes brought about by oxidation of maize and rice starches were cyanoethylated under identical conditions. The degree of cyanoethylation, expressed as % N, was found to depend mainly on the molecular size of starch irrespective of its kind. As the molecular size decreases the degree of cyanoethylation increases. Cyanoethyl starches are water soluble and can be precipitated by ethanol. It was also found that the rheological properties are determined by the nitrogen content of cyanoethyl starch. When the latter acquires low nitrogen content, it exhibits non-Newtonian pseudoplastic behaviour. On the other hand, cyanoethyl starches with higher nitrogen content are characterized by non-Newtonian thixotropic. At constant rate of shear, the apparent viscosity of cyanoethyl starches is directly related to its molecular size. Storing of pastes prepared from these cyanoethyl starches for 7 d exerts considerable influence on rheological properties and apparent viscosity of these derivatives.     

Acid-Modified Wheat Flours. Pasting and Dispersion Properties

Acid-modified (AM) and hydroxyethylated acid-modified (HEAM) wheat flours were prepared with viscosities suitable for use as tub-sizing agents and as coating adhesives for paper. The pasting characteristics and dispersion properties of both these flours were compared with those of commercial products now used in such applications. Effects were determined of time, temperature and solids concentration on pasting characteristics, paste viscosity and dispersion properties. Paste viscosity behavior of the modified flours, prepared under dry-state reaction conditions, was more like that of hypochlorite-oxidized (HO) starch than either AM or HEAM starches. Dispersibility of the modified flours was comparable to that of AM starch, but it was somewhat lower than dispersibility of HEAM and HO starches. Pastes of modified flours and starches, stored and periodically tested, varied little in dispersibility values for flour dispersions, whereas progressively less dispersible material was found in starch pastes.     

Synthesis and Characterization of Hypochlorite Oxidized Starches

Egyptian rice and maize starches were treated with sodium hypochlorite at different concentrations. The oxidized starches so obtained were monitored for carboxyl content and rheological properties. In addition, the extent and rate of the oxidation reaction was assessed by investigating the chlorine consumption. Results indicated that the extent and rate of oxidation of rice starch, expressed as chlorine consumption, are much higher than those of maize starch. The opposite holds true for the carboxyl content. Pastes of rice and maize starches before and after oxidation exhibit non-Newtonian thixotropic behaviour but their apparent viscosity decreases by increasing the hypochlorite concentration. At any event, however, the apparent viscosity of rice starch is substantially higher than that of maize starch. Storing the pastes for 24 h adversely affect the apparent viscosity particularly with oxidized starches prepared using higher hypochlorite concentrations.     

Hydrothermal Modifications of Tropical Tuber Starches. 1. Effect of Heat‐Moisture Treatment on the Physicochemical,Rheological and Gelatinization Characteristics

Cassava, sweet potato and arrowroot starches have been subjected to heat‐moisture treatment (HMT) under different conditions using a response surface design of the variables. A comparative study was performed on the pasting properties, swelling behaviour and the gelatinization properties of the modified starches and also on the rheological and textural properties of their pastes. X‐ray diffraction studies have shown that cassava starch exhibited a slight decrease in crystallinity, whereas sweet potato and arrowroot starches showed an increase in crystallinity after HMT at 120ºC for 14 h with 20% moisture. The swelling volume was reduced and the solubility was enhanced for all three starches after HMT, but both effects were more pronounced in the case of arrowroot starch. The decrease in paste clarity of the starch after HMT was higher in the case of cassava and sweet potato starches. Viscosity studies showed that the peak viscosity of all three starches decreased after HMT, but the paste stability increased as seen from the reduced breakdown ratio and setback viscosity. Studies on rheological properties have shown that storage and loss moduli were higher for the starches heat‐moisture treated at higher moisture and lower temperature levels than the corresponding native starches. Storage of the gel at ‐20ºC resulted in a significant increase in storage modulus for all the three starches. All the textural parameters of the gels were altered after the treatment which depended on the nature of the starch and also the treatment condition.     

Rheological/textural properties of starch and crude hsian‐tsao leaf gum mixed systems

The Effects of hsian‐tsao leaf gum (HG) on the rheological/textural properties of non‐waxy starches were studied. Pronounced interactions between starch and HG were observed. The rheological properties, including pseudo‐gel viscosity in the rapid visco‐analyser test, storage and loss moduli in the dynamic rheological test, as well as firmness in the texture analyser test, of the mixed gels generally improved with increasing gum concentration to a certain level, then deteriorated with further increase in gum concentration. The critical gum concentration for the development of optimal rheological properties depended on the starch type and concentration. Within the concentration range studied, mixed systems with wheat starch could generally reach the highest pseudo‐gel viscosity, firmness, and storage modulus if the starch/HG ratio was appropriate, followed by those with corn and tapioca starch. Copyright © 2003 Society of Chemical Industry     

颗粒状冷水可溶淀粉糊性质的研究

在常压下,用醇解法制备了不同溶解度的颗粒状冷水可溶淀粉系列,并对玉米、木薯和马铃薯原淀粉及其不同溶解度的颗粒状冷水可溶淀粉糊的性质进行了研究。试验证明,相对于原淀粉糊,醇解法制备的颗粒状冷水可溶玉米淀粉糊的表观粘度和冻融稳定性有所提高,凝沉性降低;颗粒状冷水可溶木薯和马铃薯淀粉糊的表观粘度、凝沉性和冻融稳定性均降低。三种颗粒状冷水可溶淀粉糊的透明度大大提高,且随着溶解度提高其透明度增大。     

The Combined Effect of Oxidation and Carbamoylethylation on the Rheological Properties of Maize and Rice Starches

The combined effect of oxidation and etherification on the molecular structure of starch was investigated. Maize and rice starches were used. Oxidation was effected using sodium hypochlorite while etherification was performed by reacting starch with acrylamide in presence of sodium hydroxide; this reaction is known as carbamoylethylation. The extent of the latter, expressed as % N, was found to increase by decreasing the molecular size of starch through oxidation. The carbamoylethyl starches so obtained could be precipitated by ethanol and they are soluble in water irrespective of the kind of starch. On the other hand, results of rheological properties indicated that they are governed mainly by the molecular size of starch. Oxidized starches with relatively high molecular size exhibit thixotropic behaviour. The degree of thixotropy decreases and changes into pseudoplasticity as the molecular size of starch decreases. The results also indicated that at constant rate of shear the apparent viscosity of carbamoylethyl starches decreases as the molecular size decreases. Furthermore, the rheological properties of carbamoylethyl starch pastes undergo considerable changes and so does the apparent viscosity when these pastes were stored for 3 days.     

Preparation and Properties of Physically Modified Banana Starch Prepared by Alcoholic‐Alkaline Treatment

Granular cold‐water‐soluble (GCWS) starches were prepared from banana starch treating it with 40 and 60% aqueous ethanol at two controlled temperatures (25 and 35 °C). GCWS starches prepared at 25 °C and with 40 and 60% aqueous ethanol had the lowest cold‐water solubility, that prepared with 40% aqueous ethanol at 35 °C and stored at room temperature showed low tendency to retrogradation, as assessed by transmittance. Solubility and swelling profiles were similar for GCWS starches and the freeze‐thaw stability of GCWS starches was increased as compared with native starch. The apparent viscosity of GCWS banana starches was higher than that of its native starch counterpart.     

Physicochemical Properties of Waxy and Normal Maize Starches Irradiated at Various pH and Salt Concentrations

Waxy and normal maize starches of various pH values and salt contents were prepared, irradiated with gamma rays (5–20 kGy) and their molecular structure, pasting viscosity and rheological properties determined. Average molar mass and size of both waxy and normal maize starches decreased considerably by irradiation from >338.0×10⁶ to <39.4×10⁶ g/mol and from >237.5 to <125.2 nm, respectively. Adjustments of pH had little influence on the average molar mass and size of irradiated starch, whereas incorporation of salt greatly reduced the molar mass and size of irradiated waxy and normal maize starches. As the pH increased from 4 to 8, the pasting viscosity of the irradiated starches decreased from 1032 to 279 mPa s in waxy and from 699 to 381 mPa s in normal starches. Pasting viscosity of both irradiated waxy and normal starch decreased from 689 to 358 mPa s and from 327 to 184 mPa s as the salt concentration increased from 1 to 5%. The G′ of gels, determined during cooling from 90 to 10°C or storage for 8 h, decreased in irradiated waxy and normal starches by pre‐conditioning at pH 8 and in irradiated waxy starches by pre‐conditioning at 5% NaCl. With 5% NaCl, G′ of irradiated normal maize starch during cooling increased up to the irradiation level of 10 kGy, and increased during storage for 8 h at all levels of irradiation. Incorporated salt prior to irradiation appears to induce incremental modifications in the molecular structure, rheological and retrogradation properties of starch by boosting the degradation of molecules.     

颗粒冷水可溶亲脂性玉米淀粉的制备及性质研究

该研究以玉米淀粉为原料,首先利用酒精-碱法对其α-化,在此基础上,以辛烯基琥珀酸酐(octenyl succinic anhydride,OSA)为酯化剂,在干法条件下制备出颗粒冷水可溶亲脂性淀粉,所得产品取代度最高可达0.0192。通过分析试验制备的颗粒冷水可溶玉米淀粉和颗粒冷水可溶亲脂性玉米淀粉的透明度、冻融稳定性、凝沉性、黏度、流变学特性,并进一步探索这些特性与产品取代度之间的关系。结果表明:这两种淀粉的性质比原淀粉有显著的改善,后者又比前者具有良好的性质,随着取代度的增大,颗粒冷水可溶亲脂性玉米淀粉的透明度增强,冻融稳定性提高,凝沉性降低,表观黏度增加;流变学分析显示两种淀粉呈现出假塑性流体的性质,表观黏度随着剪切速率的增加而降低。     

Noodle quality affected by different cereal starches

To investigate the effects of starch characteristics on the quality of noodle making, white salted noodles (WSN) made from reconstituted flours, in which the wheat starch was substituted by different cereal starches, including waxy and non-waxy rice starches, waxy wheat starch and waxy corn starch, were prepared. The rheological properties of raw WSN were mainly influenced by the size of starch granules, where the small starch granules, such as for rice starches, exhibited high amounts of water absorption during dough preparation and a dense packing of starch granules inside a thin gluten-strand network. The rheological properties of cooked WSN were mainly dominated by the amylose content and fine structure of the amylopectin, which resulted in the differences in water absorption and cooking time required for cooked WSN.     

Physicochemical properties of new starches isolated from Dioscorea opposita Thunb. bulbils

Morphological, crystal, and physicochemical properties, such as AM content, swelling power, solubility, and pasting properties of starches isolated from three different Shanyaodou (the bulbils of Dioscorea opposita Thunb., named Huaishanyao, Xichangmaoshanyao, and Maoshanyao, respectively) were investigated. The yield of starches was in the range 12.5–20.8% (dry starch/fresh whole bulbils). The AM content of Shanyaodou starches ranged from 33.3 to 36.7%. The shape of the three bulbils starch granules varied from round to oval or elliptic. The mean particle diameter of starch granules varied from 20.17 to 26.34 µm. Shanyaodou starches exhibited a C‐type XRD pattern and the degree of crystallinity was in the range 31.0–34.9%. The pasting peak viscosity, trough viscosity, and final viscosity of Shanyaodou starches ranged from 291.1 to 414.7, 210.8 to 227.0, and 350.0 to 359.2 rapid visco units (RVU), respectively, and the pasting temperature was in the range 83.6–87.3°C. The results showed that some of the Shanyaodou starches could be used in foods production as a thickening agent. The simple method of extraction and the high yield of starch from Shanyaodou might be attractive for production of Shanyaodou starch.     

Morphological,thermal, rheological and noodle‐making properties of potato and corn starch

A comparison between the morphological, thermal, rheological and noodle‐making properties of corn starch and potato starches separated from five different potato cultivars was made. The granule size and shape of all starches differed significantly. Potato starch granules were comparatively larger than corn starch granules, while the transition temperatures were found to be higher for corn starch. Consistency coefficients and flow behaviour indices measured by back extrusion were higher for potato starches than for corn starch. Stickiness of cooked starch pastes was observed to depend upon their consistency coefficient. The gels made from all potato starches showed higher gel strength than those from corn starch. The gel strength of starches from both corn and potato increased during refrigerated storage. The amylose content, swelling power, solubility and light transmittance values of potato starches were significantly higher than those of corn starch. Noodles made from potato starches had higher cooked weight and cooking loss than corn starch noodles. Texture profile analysis revealed that potato starch noodles also had higher hardness and cohesiveness than corn starch noodles. Hardness of cooked noodles from all starches increased and cohesiveness decreased during storage. Noodles made from starches of higher viscosity exhibited higher hardness and cohesiveness. Textural differences among cooked starch noodles appeared to be associated with morphological, thermal and rheological properties of corn starch and potato starches. © 2002 Society of Chemical Industry     

Cross-linking of wheat starch improves the crispness of deep-fried battered food

Wheat starches with different degrees of cross-linking were used to study the effect of starch gelatinization in the batter and crust characteristics of deep-fried battered food. Pasting properties, viscosity and batter pick up as well as moisture and oil content and crispness of the fried crusts were evaluated. In batters prepared with a constant solids/water ratio, the cross-linked starches increased batter viscosity and consequently the batter pick up. Batters, with comparable viscosity were prepared by varying the solid/water ratio which gave the same batter pick up.The pasting properties of cross-linked starches showed that the higher the cross-linking the more resistant was the starch to gelatinization and granule disintegration. In batters with a constant solids/water ratio, batter with high cross-linked starch had more water loss during frying. Cross-linked starches had lower moisture content after storage and less oil was retained after frying. Crispness, measured instrumentally as sound intensity, was the highest for the high cross-linked starch at 1 and 20 min after frying.Batters prepared with the same viscosity were used to study the effect of cross-linked starches when the pick up was the same. To obtain comparable viscosities between the batters, the batter with native starch was prepared using the lowest mixing water content and the one with high cross-linked starch with the highest. The batter with the high cross-linked starch, although it had the highest addition of water, had the best crispness after frying.In conclusion, high cross-linking of wheat starch enhances crispness perception of deep-fried battered food.     

Physicochemical and functional properties of fern rhizome (Pteridium aquilinum) starch

Starch isolated from fern rhizome was studied for physicochemical and functional properties. The recrystallization method was used for separation and purification of AM and AP from the starches. The fern rhizome starch contained 25.38 ± 0.40% AM. XRD studies showed that fern rhizome starch exhibited a C‐type diffraction pattern. SEM showed that granule shape was oval mostly, and the size ranged from 7 to 28 µm. The gelatinization temperature was from 58.94 ± 0.11°C to 71.73 ± 0.22°C, and the melting enthalpy was 12.86 ± 0.53 J/g. According to the viscosity measurement with Brabender viscograph, fern rhizome starch presented higher peak viscosity, which showed that it had more swelling power. Compared with corn and potato starches, fern rhizome starch had a lower transparency. The RS in the fern rhizome starch vermicelli prepared with extrusion method was around 10.49 ± 0.46%.     

Starch of diverse Mexican rice cultivars: physicochemical,structural, and nutritional features

Structure‐function relationship of rice starch is scarce in the literature. Starch was isolated from diverse Mexican rice varieties and their swelling power (SP), soluble solids (ss), thermal and pasting properties, XRD pattern, in vitro starch digestibility, and AP chain‐length distribution were evaluated. Rice starches with low SP at 60°C had higher temperature and enthalpy of gelatinization. The peak viscosity of rice starches ranged between 2426 and 3519 cP, and the samples presented high values for setback due to the AM content. Rice starches presented the typical A‐type XRD pattern with crystallinity values between 32.7 and 36.3%. Rice starches presented high amounts of short chains (A and B1), and differences were found among the cultivars. AM content for rice starches ranged between 18.4 and 22.9%, and the main fraction recorded by HPSEC was the Fraction III (short chains) with values around 60%. The uncooked rice starch samples presented high values of slowly digestible starch (SDS) and rapidly digestible starch (RDS), and differences were found among the cultivars. In cooked samples decreased SDS and increased RDS and RS. Onset temperature and enthalpy of gelatinization were correlated with the percentage of A‐chains and an opposite pattern was found with the percentage of B1 chains. AP structural characteristics affect the functional, physicochemical, and digestibility properties of rice starches.     

Influence of Lipids Isolated from Soybean Seed on Different Properties of Cassava Starch

The effect of lipids isolated from soybean seeds on the properties of cassava starch was investigated. Both polar and non‐polar lipid fractions were complexed with starch and the physicochemical and rheological properties were examined. The FTIR spectra of the complexed starches showed all the absorption bands characteristic of native starch with an extra minor peak at 2355 cm^‐1.The complexes prepared using the polar lipid fraction in diethyl ether as solvent exhibited a swelling volume of 32.5 mL/g compared to 36.9 mL/g for petroleum ether as solvent. A similar effect was observed with the non‐polar fraction. The apparent amylose content of the complexes was found to be lowered as a result of complexation. Total and soluble amylose contents and water‐binding capacity of the complexes were higher while their enzyme digestibility was noticeably lowered. The peak viscosity of the complexes was suppressed as a result of complexation. The polar layer exhibited a greater influence on the viscometric properties of the complexes with a higher breakdown ratio and hence higher stability. When compared to native starch, the percentage light transmittance of the complexes was noticeably reduced. The results indicate a considerable influence of the isolated lipid fractions on starch properties which can be useful in food and industrial applications.