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.     

Processing Technology Comparison of Physicochemical and Functional Properties of Cassava Starch Extracted from Fresh Root and Dry Chips

Starch was extracted from dry chips of three varieties of cassava using wet milling and dry milling methods. The physicochemical and functional properties were compared with those from fresh root. The starch obtained exhibited lower peak viscosities, breakdowns and setbacks, and higher pasting and peak temperatures than that from fresh root. Most thermal properties (onset and peak temperatures of gelatinization and retrogradation; conclusion temperatures, enthalpies and peak height indices of retrogradation; and degree of retrogradation) were found to be higher than those of fresh‐root starch. Moreover, swelling power, paste clarity and freeze‐thaw stability of the former were inferior to those of the latter. Both types of starches exhibited increased rate of syneresis with increase in freeze‐thaw cycles. Differences observed in properties of starches derived from dry chips by wet and dry millings were very minimal. No indication of major change in granule structure was noted for dry‐chip starch that would alter the properties relative to fresh root starch. Higher fiber content and annealing due to exposure to heat and moisture of the former accounted for most of the variations of properties as compared to the latter. With the advanced technology used in starch manufacturing industry today it would be possible to obtain starch from dry chips with similar quality from fresh root. This would enable the industry to overcome the cycle of glut and low season, and allow them to remain open for longer period of time in a year.     

Thermal and Pasting Properties of Microwaved Corn Starch

Corn starch with 15–40% moisture was irradiated at 0.17 or 0.5 W/g for 1 h using the sophisticated Ethos 1600 microwave apparatus that accurately controls temperature and wattage. Temperature of irradiated starch was measured during microwaving. Thermal and pasting properties were studied on dehydrated starch after microwave irradiation. Temperature increases were greatest during the first 10 min for starch at all moisture contents at both microwave power levels. Starch irradiated at 0.17 W/g had a temperature below onset gelatinization temperature (T_o) after 1 h. Higher temperatures were observed for starch with higher moisture content and microwaved at 0.5 W/g. Compared to native starch, starch with 15–40% moisture had higher T_o (measured using differential scanning calorimetry) and with 35–40% moisture had higher peak gelatinization temperature and lower enthalpy change of gelatinization. All paste viscosity parameters measured by the Rapid Visco Analyser were reduced and pasting temperature was elevated for starch irradiated at 0.5 W/g compared to native starch.     

Physicochemical,Morphological, Thermal and Pasting Properties of Starches Isolated from Rice Cultivars Grown in India

Physicochemical, morphological, thermal, and pasting properties of starches, isolated from basmati (HBC-19 and Bas-370) and non-basmati (Jaya, a coarse cultivar; P-44 and HKR-120, the medium cultivars and Sharbati, fine cultivar) rice cultivars grown in India were studied. The amylose content of starches from different cultivars ranged from 2.25 (Jaya) to 22.21 g/100 g of starch (HBC-19). Jaya, HKR-120, and P-44 cultivars showed soft gel consistency as 84, 73, and 69 mm, respectively, whereas Sharbati, Bas-370 and HBC-19 cultivars showed medium gel consistency as 54, 53, and 58 mm, respectively. Swelling power (at 95°C) indicated a significant positive correlation with amylopectin content (r = 0.828, p < 0.05) and gel consistency (r = 0.983, p < 0.01). Turbidity had a highly significant positive correlation with solubility (r = 0.919, p < 0.01) and amylose content (r = 0.945, p < 0.01). Starch form Jaya cultivar showed the presence of smallest size granules (2.4–5.7 μm) with an average size of 3.96 μm, whereas Bas-370 showed the presence of largest size granules (3.3–6.7 μm) with an average size of 5.0 μm. The transition temperatures, enthalpy of gelatinization (ΔH_gel), peak height index (PHI) and gelatinization range were determined using differential scanning calorimetry (DSC). The starch from Sharbati cultivar showed highest onset temperature (T_o), peak temperature (T_p), conclusion temperature (T_c), enthalpy of gelatinization and peak height index (PHI) of 68.8°C, 73.2°C, 79.0°C, 11.56 J/g and 2.63 respectively. Pasting temperature of rice starches varied from 68.9°C (Jaya) to 74.5°C (Sharbati). The peak viscosities observed were in the range of 2223 to 3297 cP, lowest for HBC-19 starch and highest for Jaya starch.     

Analysis of Genotypic Diversity in the Starch Physicochemical Properties of Nonwaxy Rice: Apparent Amylose Content,Pasting Viscosity and Gel Texture

A total of 499 non‐waxy rice lines including 172 landraces (the landrace set) and 327 cultivars and breeding lines (the breeding line set) were used to study the genetic diversity of starch physicochemical properties, and the differences between the landrace set and the breeding line set were compared. All the rice lines were planted in the same season and at the same location in Hainan province. Wide diversities of starch physicochemical properties were found, e.g. apparent amylose content ranged from 7.9% to 33% in normal rice and up to 39.8% in an amylose extender mutant; peak viscosity ranged from 90.1 to 305.4 RVU, hot paste viscosity from 77.5 to 248.1 RVU, and cold paste viscosity from 111.4 to 412.6 RVU; gel hardness ranged from 9.4 to 61.1 g. The breeding line set had a wider range of physicochemical properties than the landrace set with a rare exception in gel hardness. The mean values of nearly all the parameters showed significant differences between the two sets of rice except for the setback ratio. The adhesiveness and cohesiveness of landrace starches were significantly lower than those of the breeding lines whereas the other parameters of the landrace set were higher than those of the breeding line set. Analysis of correlation among these parameters indicated that most of the traits were significantly correlated. The wide range of physicochemical properties among non‐waxy rice lines allows breeders to obtain breeding lines with desirable grain quality and food processors to select unique rice materials for specialty food processing, in addition to the applications in other processing industries.     

Physiochemical,Pasting, and Thermal Properties of Starch Isolated from Different Barley Cultivars

Starches from eight different barley cultivars were isolated and evaluated for their physiochemical, thermal, and pasting properties. The amylose content varied significantly among cultivars and ranged from 21.0 to 28.3%. The majority of the starch granules were of the B-type (20 to 40 μm) in size and accounted for 50.5 to 61.6% of the total granules. The starch gel from RD-2052 showed the highest firmness (0.55 N). The pasting behavior of starch varied significantly; the PL-172 cultivar showed the highest peak viscosity (2622 cP) while it was lowest for RD-2035 (1913cP). The time to peak of pasting properties exhibited a significant (p ≤ 0.05) negative correlation with water solubility index (r =??0.74). The pasting temperature showed a significant (p ≤ 0.05) positive correlation with water binding capacity (r = 0.73) and significant negative correlation with water solubility index (r =??0.82). The highest enthalpy of gelatinization (ΔH) was exhibited by DWR-28 cultivar (4.9 J/g). Amylose content showed a significant (p ≤ 0.01) negative correlation with ΔH (r =??0.90). A significant (p ≤ 0.01) positive correlation was observed between gelatinization temperature range and water binding capacity of starch (r = 0.85).     

The Role of Reaction Parameters on the Preparation and Properties of Carboxymethyl Cassava Starch

The role of reaction variables on carboxymethylation of cassava starch was investigated using a statistically experimental design approach. The reaction was carried out in an isopropanol‐water mixture at 40°C for 3 h. The reaction parameters under investigation included water fraction in the reaction medium, the ratio of sodium hydroxide to anhydroglucose unit (AGU) and the ratio of sodium monochloroacetate (SMCA) to AGU. The dependent responses were degree of substitution (DS) of CMS and the reaction efficiency (RE) of the carboxymethylation. Carboxymethyl cassava starches with DS in the range of 0.01 to 0.86 were prepared. The result from regression analysis indicated that the most important factors in controlling the DS of CMS were sodium hydroxide and SMCA contents followed by water content. Response surface plots suggested that the optimal levels of sodium hydroxide and water content to achieve CMS with high DS were at the intermediate values. Similar effects of sodium hydroxide and water content were also observed on the RE while SMCA content had a negative effect; increasing SMCA content resulted in lower RE. The optimal conditions to achieve the highest DS and RE were found to be at a water content of 17–19% with a molar ratio of sodium hydroxide to AGU of 1.8–1.9 and a molar ratio of SMCA to AGU between 1.1–1.5. Carboxymethyl cassava starch with various DS was also prepared. The properties of CMS as affected by the degree of modification were also discussed.     

Effect of Dry Cassava Chip Storage on Yield and Functional Properties of Extracted Starch

Dry cassava chips of variety CMR35‐22‐196 and KU50 were stored at 5 and 30°C up to a period of 8 months. The yield and functional properties of the starches extracted from the chips after 2 months of storage were compared with those of starches extracted from fresh roots and freshly dried chips. Starch yield from dry chips was reduced by up to 5% after 8 months of storage. Functional properties of the starches exhibited a declining trend with increasing storage period of the chips. Peak viscosity and swelling power decreased by up to 30% and 5 g/g, respectively. Paste clarity dropped by up to 30% and syneresis of the gels increased by up to 10% after 8 months storage. A high storage temperature (30°C) was found to increase the changes in functional properties of the starches. The changes in the functional properties, however, were not so severe to negatively affect the application of the dry‐chip starches. All the properties remained within the generally recognized ranges of cassava starches. The use of dry chips for extraction of starch could thus overcome the problems of seasonal glut and closure of factories in low season.     

Screening of Starch Quality Traits in Cassava (Manihot esculenta Crantz)

Cassava (Manihot esculenta Crantz) is one of the most important sources of starch in the tropics. There is limited and contradictory information regarding cassava starch characteristics. The International Center for Tropical Agriculture (CIAT) holds in trust FAO's cassava germplasm collection. Starches from 3272 landraces (including 12 wild relatives) and 772 improved clones were extracted and analyzed over a period of several years. In most cases only one starch sample per genotype was analyzed. Average cyanogenic potential was 327 ppm but considerably higher in the landraces (340 ppm) than in improved clones (267 ppm). Average total and reducing sugars were slightly higher in improved clones (4.06 and 1.56%, respectively) than in landraces (3.68 and 1.25%, respectively). Amylose content was similar in both types of germplasm with an average of 20.7%. Average pasting temperature was 65.3°C. Maximum viscosity was 777.5 mPa s, breakdown was 298.1 mPa s, consistency was 155.8 mPa s and setback was ‐144.5 mPa s. The large sample of starches analyzed provides very robust information regarding the actual characteristics of cassava starch.     

Physicochemical and Functional Properties of Sour Starches from Different Cassava Varieties

This article reports our investigation on the effect of cassava varieties on the physicochemical and functional properties of sour starches. There were significant differences (P < 0.05) in the ash, pH, amylose, amylopectin, starch damage, total titratable acidity (TTA), sugar, and starch content but not moisture contents of various cassava sour starches. There were no significant differences (P > 0.05) in Water Absorption Capacity (WAC), swelling power, and solubility index, while significant differences were recorded in Least Gelation Concentration (LGC) and color at 5% level and granule size at P < 0.0001 for cassava sour starches. Peak viscosity values ranged from 333.17RVU (clone 4(2) 1425) to 380.75RVU (clone TME 1). There were significant differences (P < 0.05) in pasting properties except for pasting temperature and breakdown.     

Effect of Cross‐linking with Epichlorohydrin on the Properties of Cassava (Manihot esculenta Crantz) Starch

Cassava starch was cross‐linked with epichlorohydrin (EPI) at 45°C for 2 h in three different media which include water, water in the presence of a phase transfer catalyst (PTC) and N,N‐dimethylformamide (DMF). The products were characterized by determining their physicochemical, thermal and retrogradation properties. In aqueous medium, the use of a PTC, tetrabutylammonium bromide (TBAB) produced derivatives with higher degree of cross‐linking than those prepared without the use of the catalyst. The degree of cross‐linking was found to be higher using the same concentration of EPI when the reaction was carried out in DMF. At low levels of cross‐linking, the peak viscosity of the cross‐linked starches increased in comparison to that of the native starch. With increasing degree of cross‐linking, the peak viscosity showed a significant reduction. The swelling volume, solubility and light transmittance of the starch pastes were lower for the modified starches. The cross‐linked starches showed slightly reduced values for the gelatinization temperatures, T_onset, T_peak and T_end. The enthalpy of gelatinization of the modified starches increased with increase in the degree of cross‐linking. The modified starches exhibited higher water‐binding capacities (WBC) than the native starch; but with increase in the degree of cross‐linking, there was a gradual decrease in WBC. The in vitro alpha amylase digestibility of the modified starches decreased gradually with increase in the level of cross‐linking.     

Effect of Phenolic Compounds on the Pasting and Textural Properties of Wheat Starch

Pasting and textural properties of wheat starch were systematically investigated in the presence of 25 phytochemicals including phenolic acids, flavonoids, coumarins, stillbenes and tannins with a wide structural diversity. Overall, most of these phenolic compounds significantly changed functional properties of starch. Trans‐cinnamic acid increased the peak viscosity most by 37 RVU whereas catechin decreased it most by 14 RVU. All the phenolic compounds considerably increased the breakdown with the greatest effect by chlorogenic acid (135 RVU) and the least by chrysin (6 RVU). Esculetin caused the maximum increase in setback (38 RVU), and 3‐hydroxybenzoic acid caused the maximum decrease (103 RVU). All the phenolic compounds significantly reduced the peak time with the greatest effect by trans‐cinnamic acid. Chrysin and 3‐hydroxybenzoic acid most increased and decreased the hardness of starch gels stored at 23°C for 48 h by 3.9 and 24.2 g. Most of the phenolic compounds increased the adhesiveness with the greatest effect by 3‐hydroxybenzoic acid (72 g·s). pH changes of the starch suspension caused by the addition of phenolic compounds and their structural diversity affected these functional properties of wheat starch to different extents. This study may provide a basis for the use of phytochemicals in functional and starch‐based staple foods.     

Gelatinisation Characteristics of Cassava Starch Settled in the Presence of Different Chemicals

Addition of chemicals during the extraction of cassava starch for enhancing the settling rate, whiteness and compactness of the settled starch is an accepted commercial practice. The effect of addition of selected chemicals such as acids (sulphuric and hydrochloric acids), bleaching and oxidising agents (sodium metabisulphite and sodium hypochlorite) and alum during settling on the thermal and pasting properties of the cassava starch was examined. Treatment with sulphuric acid produced a noticeable increase in all DSC gelatinisation parameters, viz. onset gelatinisation temperature (T_o), temperature at peak minimum (T_p) and end temperature (T_e), with increasing concentration of acid, while only a marginal shift could be obtained even at higher concentration of hydrochloric acid. However, no major effect resulted from treatment with sodium metabisulphite, sodium hypochlorite and alum. The gelatinisation enthalpy was hardly affected by the treatments. An exception was hydrochloric acid, which brought about a perceptible decrease in enthalpy at higher concentrations indicating that starch crystallinity is influenced to a small extent by hydrochloric acid. Pasting characteristics studied using a Rapid Visco Analyser showed that sulphuric acid, even at the lowest concentration (5 mM), considerably affected the structural characteristics of cassava starch, while hydrochloric acid induced similar effect only at higher concentrations. Alum reduced the paste viscosity while the bleaching agents (sodium metabisulphite and sodium hypochlorite) were not so effective in modifying the starch viscosity characteristics.     

野葛淀粉与木薯淀粉混粉理化特性分析

以野葛淀粉和木薯淀粉为原料,将木薯淀粉分别以10%、30%、50%和70%的质量分数掺入野葛淀粉。研究了原粉基本成分、原粉和混粉的结构、凝胶特性、抗氧化活性、热特性、冻融稳定性、消化特性、冲调特性。结果表明：随着木薯淀粉比例的增多,可以根据扫描电镜中的颗粒形状明显区别原粉及混粉,混粉平均粒径(10.68～13.05μm)均比野葛淀粉(9.47μm)高。野葛淀粉与木薯淀粉分别为C型及A型晶体结构,混粉后并未改变其结构及红外光谱图。混粉的糊化起始温度随添加量增加而显著升高(P<0.05),更难糊化。混粉抗氧化能力降低、多次冻融后趋于稳定、冲调黏度增大;混粉后硬度增大,最高达到2 410.46 g,质地硬化,凝胶性能变差;混粉的抗性淀粉(质量分数0.37%～1.59%)相对野葛淀粉较低(5.65%)。木薯淀粉的掺入对混粉影响较大,有利于从淀粉的结构和理化特性等方面为鉴别野葛淀粉中是否掺有木薯淀粉提供参考。     

交联木薯琥珀酸淀粉酯高温热糊特性研究

淀粉化学变性技术是目前淀粉工业发展的方向。研究了木著淀粉经三偏磷酸钠交联和琥珀酸酐酯化变性处理后高温热糊特性的变化，指出了7个反应因素（交联时间、交联剂用量、交联pH、酯化时间、酯化荆用量、酯化pH、反应温度）对结果的影响，发现变性后的淀粉高温热糊的粘度较原淀粉提高了5～10倍。     

Thermal and Pasting Properties of Acid‐treated Rice Starches

The physicochemical properties of acid‐treated rice starches were investigated. Rice starches were treated with hydrochloric acid at different acid concentrations and hydrolysis times. The pasting properties were tested using a Rapid Visco Analyser, and gelatinization and retrogradation properties using a differential scanning calorimeter. The results showed that acid concentration had a more pronounced effect on degree of polymerization (DP) and viscosity than hydrolysis time. The onset, peak and conclusion temperatures of gelatinization were increased significantly with hydrolysis time, while the gelatinization enthalpy (ΔH_G) was decreased. In addition, there was an increase in the gelatinization temperature range with longer hydrolysis time. After storing gelatinized starches at 4°C for 7 days, the transition temperature and enthalpy (ΔH_R) to melt retrograded amylopectin did not change significantly. Additionally, the temperature and enthalpy transition for melting amylose‐lipid complex of all gelatinized and retrograded starches were in the same range.     

高静压对木薯淀粉理化特性及结构的影响

木薯原淀粉因存在不溶于冷水、易老化等诸多性质上的不足,极大地限制了其在食品、药品等领域的应 用。为了优化木薯淀粉的产品特性,通过对木薯淀粉进行高静压（200～600 MPa）改性处理,来优化其性质并拓 展其应用范围。结果显示高静压处理后木薯淀粉颗粒形貌发生明显变化,透光率、溶解度和膨润力均下降,老化值 增大,特别是在600 MPa改性处理后变化最明显,且失去偏光十字;此外,高静压处理后的木薯淀粉表观黏度低于木 薯原淀粉,剪切稀化现象更加明显。木薯原淀粉在经高静压处理后虽然晶型有一定的变化,但没有形成新的基团。     

氯化钠、蔗糖和碳酸钠对芡实淀粉糊化特性的影响

研究氯化钠、蔗糖和碳酸钠对芡实淀粉糊化特性的影响规律。采用差示扫描量热法等方法测定了不同质量分数氯化钠(1%、2%、3%、4%、5%)、蔗糖(4%、8%、12%、16%、20%)和碳酸钠(0.5%、1.0%、1.5%、2.0%、2.5%)对芡实淀粉的糊化温度、溶解度、膨胀度、冻融稳定性等糊化特性的影响。结果发现,氯化钠、蔗糖和碳酸钠均提高了芡实淀粉的糊化温度。原芡实淀粉透明度为1.3%,氯化钠的加入降低了透明度,而蔗糖和碳酸钠则提高其透明度。氯化钠、蔗糖和碳酸钠均增加了芡实淀粉糊的膨胀度和溶解度,并均降低其冻融稳定性。在凝沉性方面,三者表现不一,低含量的氯化钠(1%~3%)和碳酸钠(0.5%~1.5%)均有利于芡实淀粉糊的稳定;高含量的氯化钠(4%~5%)和碳酸钠(2.0%~2.5%)均促使淀粉糊凝沉增加,降低稳定性;而蔗糖则提高了芡实淀粉糊的凝沉稳定性。由此可见,在芡实淀粉糊化过程中,氯化钠、蔗糖和碳酸钠三者对其糊化特性的影响显著。     

小米淀粉与玉米淀粉糊性质比较研究

对小米淀粉和玉米淀粉糊性质进行较详细比较研究,包括透明度、冻融稳定性、凝沉性、膨胀力、酸解、酶解,和介质对糊粘度性质影响。结果表明,小米淀粉与玉米淀粉相比,糊的凝胶稳定性好、持水力强、膨胀力高、糊化温度高、热焓变值大、但透明度较差、冻融稳定性不佳、热稳定性差;且氯化钠及糖溶液对小米淀粉糊粘度性质影响较大。     

Characterisation of Latent Polyphenol Oxidase in Table Beet: Effect of Sodium Dodecyl Sulphate

Polyphenol oxidase (EC 1.14.18.1) from table beet leaves was extracted in both soluble and membrane-bound forms. In both cases the enzyme obtained was in its latent state. Polyphenol oxidase was kinetically characterised using 4-tert-butylcatechol as a substrate in both the latent and activated enzyme forms. The latent form was activated by sodium dodecyl sulphate (SDS) so that characterisation was carried out in the presence and absence of SDS. The kinetic parameters for both soluble and membrane-bound forms at different pH values were calculated. © 1997 SCI.