Oxidation of Maize and Rice Starches Using Sodium Chlorite Along with Formaldehyde

Maize and rice starches were independently oxidized with sodium chlorite in absence and presence of formaldehyde. The treatment was carried out under different conditions including sodium chlorite and formaldehyde concentrations and duration. Since the treatment involves degradation of starch via oxidation, the treated starch samples were monitored for carboxyl and carbonyl contents as well as apparent viscosity at different rates of shear. Results obtained indicated that with both starches the percent chlorite decomposed increases as the formaldehyde concentration increases within the range studied (0.0–0.3 g/100 starch). The same holds true for the duration of oxidation (15–90min). The apparent viscosity of starch before and after oxidation decreases as the rate of shear increases. Maize starch is more susceptible to oxidation than rice starch. When applied as sizing agents for cotton textiles oxidized starches derived from maize and rice starch display better performance than the unoxidized starch but with the superiority of the sizeability and desizeability of oxidized maize starch.     

Partial Characterization of Tamarind (Tamarindus indica L.) Kernel Starch Oxidized at Different Levels of Sodium Hypochlorite

The effects of different levels of sodium hypochlorite (1–4 g/100 g dry solids active chlorine) on the physicochemical, pasting, and structural properties of tamarind kernel starches were investigated. The isolated starch had low traces of non-starch components, such as protein, fat, and ash, indicating its purity. Both the carboxyl and carbonyl contents in the oxidized starches increased significantly with the increase in chlorine concentration. The introduction of carboxyl and carbonyl groups resulted in significantly lower amylose content. The swelling power of oxidized starches was significantly lower than native starch and the solubility values increased when the chlorine concentration increased at all the measured temperatures. The percentage of light transmittance increased progressively after oxidation. Pasting properties showed that in treatments at high active chlorine concentrations, the peak viscosity decreased more drastically than in treatments at low chlorine concentration, indicating a greater degradation of starch. The morphology of the starches was not altered after oxidation. After oxidative treatment no change in the X-ray diffraction pattern was observed but intensity of the peaks increased. Therefore, tamarind kernel being underutilized raw material, has a great potential as a non-conventional source of starch and desirable properties of this starch can be enhanced by oxidation for applications in food industry.     

Characterization of Different Starches Oxidized by Hypochlorite

The effects of starch origin (potato, corn, and rice starches) and hypochlorite level (NaOCl, 0.8% and 2% w/w) on the structures and physicochemical properties of oxidized starches were investigated. Carboxyl and carbonyl group contents of oxidized starches increased with increasing NaOCl level, with potato starch having the highest and corn starch having the lowest carboxyl groups content at both NaOCl levels. Oxidation generally reduced the pasting temperature and viscosity of native starches as demonstrated by using a Rapid Visco Analyser. The peak viscosities of oxidized rice and corn starches were higher than those of their native counterparts at 0.8% NaOCl. The morphology of starches was not altered and X‐ray diffraction patterns of all the starches remained unchanged after oxidation. Oxidized starch batters exhibited greater adhesions than did native starch batters, with rice starch batter exhibiting the greatest adhesion. Carbohydrate profiles by high‐performance size‐exclusion chromatography indicated that both amylopectin and amylose were degraded during oxidation. The level of oxidation was largely dependent on the degree of crystallinity of starch and the degree of polymerization of amylose, whereas the adhesion property of oxidized starch was mainly attributed to its granular size and shape.     

Factors Affecting the Technological Properties of Starch Carbamate

Starches having different molecular sizes were obtained by subjecting rice starch and maize starch, independently, to oxidation with aqueous sodium hypochlorite solutions of different concentrations. These starches were then reacted with urea in a dry state to yield mainly starch carbamate. The latter was isolated from the reaction products by treatment of the latter with either water or 4% aqueous NaOH solution. It was observed that regardless of the kind and molecular size of starch, treatment with water brings about starch carbamate which swells but does not dissolve completely in water. Against this was water soluble starch carbamate isolated by ethyl alcohol precipitation from NaOH solution (after neutralization). Studies of the rheological properties of the water soluble starch carbamates revealed that starch carbamates derived from rice starches are characterized by either thixotropic or pseudoplastic character depending on the molecular structure of starch. On the other hand, starch carbamates derived from maize starch exhibit pseudoplastic behaviour by virtue of their relatively lower molecular weight and higher carboxyl content. It was also found that the apparent viscosity of starch carbamates is determined by the kind of starch, the degree of oxidation and the storing time.     

Hypochlorite oxidation of field pea starch and its suitability for noodle making using an extrusion cooker

The effect of hypochlorite oxidation on the Brabendar pasting properties of field pea starch and the suitability of native and oxidized starch for noodle making by extrusion cooking were investigated. Field pea starch was oxidized with sodium hypochlorite at a level of active chlorine ranging from 0.89 to 3.28% (starch db). The degree of oxidation was determined and expressed in terms of percentage of carboxyl and carbonyl groups, which ranged from 0.02 to 0.38% and 0.06 to 0.19%, respectively. Starch recovery and peak viscosity, hot paste viscosity, cool paste viscosity, and setback of oxidized starches decreased with increasing degree of oxidation. The cooking quality attributes of noodles prepared from native field pea starches were acceptable but were negatively influenced by hypochlorite oxidation. Substitution of potato starch (40%, db) for field pea starch yielded more glossy noodles with better cooking quality. It was also observed that Brabendar pasting properties had high correlations with noodle quality characteristics.     

芭蕉芋淀粉的催化氧化

本文探讨了催化剂的种类、次氯酸钠的用量和反应时间对芭蕉芋淀粉氧化反应的影响.结果表明:氧化淀粉中的羧基随次氯酸钠的用量和反应时间的增加而增加,但粘度不断下降.有效氯为2%时,淀粉中羰基含量最高.使用催化剂A可制备羧基和羰基含量都较大的氧化淀粉,使用KI则可制备羧基少而羰基含量高的氧化淀粉.     

Preparation and Characterization of Carboxymethyl Starch (CMS) Products and Their Utilization in Textile Printing

Starch and oxidized starches of different molecular sises were carboxymethylated under identical conditions. The degree of substitution (DS) of the so obtained. CMS samples increases by decreasing the molecular sise of starch which, indeed, is a manifestation of higher extents of oxidation. The latter was effected using different sodium hypochlorite concentrations and the extent of oxidation was expressed as chlorine consumption. Pastes of these CMS samples exhibit pseudoplastic behaviour and their apparent viscosity decreases as the extent of oxidation increases, when used as thickeners in printing polyester fabric with disperse dyes, these pastes bring about prints the colour strength (K/S) of which are comparable with these for conventional thickeners, namely commercial CMS and sodium alginate. Mixing of sodium alginate with the prepared CMS samples increases the efficiency of the latter to act as the thickening agent. The highest K/S is obtained with CMS derived from starch oxidized using 1.25g active chlorine/1. Mean while, the colour fastness properties of the prints towards rubbing, washing and perspiration are nearly equal to those fabrics printed using the conventional thickeners such as sodium alginate or commercial CMS.     

Physicochemical, crystallinity, pasting and morphological properties of bean starch oxidised by different concentrations of sodium hypochlorite

The effect of bean starch oxidation at different active chlorine concentrations (0.5%, 1.0% and 1.5%) on the physicochemical, crystallinity, pasting and morphological properties of starch was investigated. The carbonyl content, carboxyl content, starch colour, swelling power, solubility, gel hardness, X-ray crystallinity, pasting properties, gelatinisation characteristics and morphology of the starches were evaluated. The bean starch oxidised with 0.5% active chlorine had the characteristic of a slightly crosslinked starch. As compared to the native and 0.5% active chlorine-oxidised starches, active chlorine at 1.0% and 1.5% increased the carbonyl content, carboxyl content and solubility of the starches. Moreover, these concentrations of active chlorine decreased the swelling power, gel hardness, relative crystallinity, breakdown, peak viscosity and setback, as compared to the native and 0.5% active chlorine-oxidised starches. The starch granules oxidised with 1.5% active chlorine had imperfections in their structure, and its surface appears to be rougher than the other granules.     

Physicochemical Properties of Oxidized Cassava Starch Prepared under Various Alkalinity Levels

The physicochemical properties of hypochlorite‐oxidized cassava starch as influenced by the alkalinity levels (pH 8 to 11) during modification process were investigated. Hypochlorite oxidation generally increased the contents of carbonyl and carboxyl groups in starch but decreased starch viscosity. The formation of carbonyl and carboxyl groups was more favorable under the milder alkaline conditions (pH 8 and 9). Oxidation conducted at higher alkalinity levels produced both functional groups at a much slower rate and to a lesser extent. Starch viscosity decreased markedly with increasing reaction time. The alkalinity levels during the modification process greatly influenced the initial viscosity of the oxidized starch paste and the viscosity stability of the paste during storage. Thermal behavior studies by differential scanning calorimetry (DSC) demonstrated that oxidation decreased both gelatinization temperature and enthalpy. The decrease in gelatinization temperature was strongly related to the carboxyl group content. The more carboxyl groups the oxidized starch contained, the lower was the gelatinization temperature. Retrogradation of amylopectin tended to increase slightly after oxidation. While the light transmittance of native starch paste drastically decreased during cold storage, the changes observed in oxidized starch pastes were less pronounced and appeared to depend on carboxyl content. The results from light transmittance studies suggested that carboxyl groups introduced into the starch molecules could effectively prevent retrogradation.     

Properties of jackfruit seed starch oxidized with different levels of sodium hypochlorite

The effect of active chlorine concentrations (1–5%) on the properties of jackfruit seed starch was investigated. Both the carbonyl and carboxyl contents of the oxidized starches generally increased with progressive increases in the active chlorine concentration. No evidences of alteration in the morphology and X-ray diffraction pattern were observed after oxidation, while the decrease in relative crystallinity was found. The swelling power of the oxidized starch tended to decrease with the active chlorine levels, particularly at a low level of active chlorine (1–3%). No significant differences in the peak temperature (Tp) and the end temperature (Te) were found between the native and the oxidized starches, while the oxidized starches had lower onset temperatures (To). Parameters, such as pasting temperature, peak viscosity, and setback, decreased with the concentration of active chlorine. In addition, lower syneresis and turbidity were found in all oxidized starches during refrigerated storage compared to the native starch.     

芭蕉芋氧化淀粉的制备与性质

采用正交法考察了淀粉悬浮液浓度、过氧化氢与催化剂用量、反应温度和反应时间对芭蕉芋过氧化氢氧化淀粉中羧基含量的影响,并比较了相同氧化剂用量下次氯酸钠、高锰酸钾、过氧化氢氧化淀粉的羧基含量和黏度。结果表明,制备芭蕉芋过氧化氢氧化淀粉的最佳反应条件为pH=7,淀粉悬浮液浓度46％,过氧化氢12％,硫酸铜0．048％,反应时间3h,反应温度50℃,在此条件下,制备的氧化淀粉羧基含量可达0．92％;次氯酸钠氧化效率高于过氧化氢和高锰酸钾;低羧基含量时次氯酸钠氧化淀粉的黏度大于过氧化氢和高锰酸钾氧化淀粉。     

Technological Evaluation of Nitrogen Containing Starch Derivatives as Sizing Agents

The structural changes brought about by introducing different nitrogen containing groups via cyanoethylation, carbamoylethylation and carbamation in the molecules of rice and maize starches and oxidized starches derived thereof and the onset of these changes on the technical properties of yarns sized with such starch products were investigated. It was found that the apparent viscosity of pastes prepared from those products depends on the nature of starch, the degree of oxidation prior to chemical modification, the nature of modification as well as the measuring conditions, i. e. the rate of shear and temperature. Cotton yarns sized using these starch derivatives were measured for yarn number, tensile strength, C.V.%, elongation at break and C.V.% in elongation. Besides, the weavability test expressed as the minimum number of cycles due to abrasion (St₁) and average number of cycles due to abrasion (St₆) were investigated. A comparison among modified starches prepared from rice starch would reveral that the highest value of St₁ is obtained with yarns sized using carbamoylethylated sample derived from unoxidized starch. With maize starch, on the other hand, the highest value of St₁ is obtained with cotton yarns sized using carbamoylethylated starch derived from starch oxidized by 1 g/l active chlorine.     

Cationized Starch Derived From Pre‐Oxidized Starch For Textile Sizing and Printing

Maize starch was subjected first to oxidation using H₂O₂ in presence and absence of ferrous sulfate as catalyst and then to cationization using 3‐chloro‐2‐hydroxypropyl trimethyl ammonium chloride. A thorough investigation of the chemical and rheological characteristics of the oxidized starch and oxidized‐cationized starch samples was made. It was found that these modified starches display characteristics, which qualify them to function as excellent sizing agent and to less extent as thickeners for printing polyester fabric with disperse dyes. The differences among the oxidized samples prepared in acidic and alkaline media in presence and absence of ferrous sulfate with respect to carboxyl and carbonyl group content were explained on the basis of the different mechanisms involved in the oxidation reaction of starch. The amenability of the different oxidized starch samples to cationization and variation in the apparent viscosity after cationization of the oxidized starches were also reported.     

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.     

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.     

Effect of deproteinization on degree of oxidation of ozonated starch

Effects of deproteinization on the degree of oxidation of ozonated starch (corn, sago, and tapioca) were investigated. Starch in dry powder form was exposed to ozone for 10 min at different ozone generation times (OGTs: 1, 3, 5, 10 min), and then native starches (NS) and deproteinized starches (DPS) were analyzed for protein content. Deproteinization caused a significant reduction in protein content for corn (∼21%) and sago (∼16%) starches relative to NS. Carbonyl and carboxyl contents increased significantly in all ozonated deproteinized starches (ODPS) with increasing OGT. Carbonyl and carboxyl contents of ODPS ranged from 0.03 to 0.13% and 0.14 to 0.28%, respectively. The carboxyl content for all ODPS was significantly higher than that of ozonated native starches (ONS). A Rapid Visco Analyser was used to analyze pasting properties of all starches. Deproteinization increased the pasting viscosities of corn and sago starches compared to their native forms. Generally, pasting viscosity of all ODPS decreased drastically as OGT increased. At the highest oxidation level (10 min OGT), all ODPS exhibited the lowest pasting viscosities compared to their ozonated native form, except for peak viscosity, breakdown viscosity, and setback viscosity for ozonated deproteinized corn starch. In conclusion, deproteinization as a pretreatment prior to starch ozonation successfully increased the degree of oxidation in the three types of starch studied. However, the extent of starch oxidation varied among the different starches, possibly due to differences in rates of degradation on amorphous and crystalline lamellae and in rates of oxidation of carbonyl and carboxyl groups.     

新型氧化剂微波干法制备氧化淀粉及其性能研究

干法制备变性淀粉已逐步在国内推广,它具有流程短,能耗低,操作简便等优点。采用微波干法工艺,研究了二氧化氯、氯酸钠两种氧化剂制备氧化淀粉(分别为氧化淀粉A和氧化淀粉B)的工艺和变性淀粉的性能。工艺研究表明,两种氧化剂均能通过微波干法制备氧化淀粉,而氧化淀粉A和氧化淀粉B的羧基含量分别为(0.068±0.002)%和(0.586±0.002)%。性能研究表明,氧化淀粉的热黏度稳定性得到了改善,氧化淀粉B的冻融稳定性较好,经2次冻融,析水率仅为23.7%;氧化淀粉A耐碱性能好,耐酸性较差,氧化淀粉B则具有较好的耐酸耐碱性;X-射线衍射结果表明淀粉的氧化反应主要发生在淀粉的无定型区,而晶体结构仍与原淀粉相同。     

Morphological,Physicochemical and Structural Characteristics of Oxidized Barley and Corn Starches

Barley starch was oxidized to different levels and the morphological, physicochemical and structural of the resultant oxidized barley starch were determined and compared with oxidized corn starch at the same oxidation level. The amylose content in oxidized starches decreased with increasing oxidation level, and the extent of decrease was similar for both starch types. No evidences of alteration in morphology and X‐ray diffraction pattern were noted after oxidation. The crystallinity of barley starch increased with increasing oxidation but corn starch displayed a reduced crystallinity at 5% NaOCl. The onset and peak gelatinization temperatures of oxidized starches as measured by differential scanning calorimetry showed a slight increase up to 3% NaOCl and then decreased at 5% NaOCl, whereas gelatinization enthalpy gradually decreased with increasing oxidation level. The melting temperature of retrograded oxidized starches increased with increasing oxidation. Both amylose and amylopectin were degraded during oxidation, but a higher degradation in both components as determined by high‐performance size‐exclusion chromatography (HPSEC) was noted for barley starch than for corn starch. Results of amylopectin chain‐length distribution showed that the proportions of A and B1 chains significantly increased while that of B2+ chains significantly decreased. These results suggest that differences in the structure of barley and corn starches affected their responses to oxidation. Barley starch seemed to be more susceptible to oxidation with more significant reduction in pasting temperature, viscosity, and molecular size than corn starch.     

氧化糯玉米淀粉的制备及性能研究

以糯玉米淀粉为原料,以次氯酸钠为氧化剂,氢氧化钠为催化剂,对氧化糯玉米淀粉的制备及性能进行了研究.考察了反应时间、反应温度、次氯酸钠用量、pH对氧化糯玉米淀粉羧基含量的影响,采用酸碱滴定法测定氧化糯玉米淀粉羧基含量.试验结果表明,随着次氯酸钠用量增加,氧化糯玉米淀粉的羧基含量也随之增大;在一定时间范围内,氧化糯玉米淀粉的羧基含量随反应时间的增加而增加;反应温度和pH对氧化糯玉米羧基含量的影响呈倒抛物线趋势,存在最大值.糯玉米淀粉经氧化后,其液透明度和黏度热稳定性提高,但其冻融稳定性和凝沉性下降.     

Transformations of Potato Starch During Oxidation with Hypochlorite

Five starch samples of different degree of oxidation were obtained with the help of sodium hypochlorite. Apart from that, commercial starch was divided into 3 fractions of differentiated size of grains and the fractions were also subjected to oxidation. The analysis of oxidized starch led to following results:

• large grains of starch undergo the oxidation process more easily than small grains, from oxidized starch hydrolysates glucuronic acid amounting to about 75% of carboxyl groups and gluconic acid to about 25% of carboxyl groups, can be separated;
• side reaction proceeding during oxidation process is hydrolytic degradation of starch molecules which is shown by the increase of reducing value and the decrease of viscosity of oxidized starch;
• in starch oxidized with hypochlorite absence of dialdehyde systems is characteristic in contrast to starch oxidized with periodate;
• in the process of oxidation with hypochlorite, starch molecules change their shape and spatial system, which is indicated by the changes of colour complexes with iodine, greater resistance to the action of amylolitic enzymes and greater capacity for forming flexible gels in the form of films.