Effects of mucilage on the thermal and pasting properties of yam, taro, and sweet potato starches

This study investigates the effects of water-soluble mucilages (0, 2.5, and 5 g/100 g; w/w, dry basis) on the thermal and pasting properties of isolated starches from three root and tuber crops. The results show that yam tuber presents the greatest level of mucilage and also possess the largest amylose content of the three isolated starches. The addition of mucilage caused a remarkable increase in the temperature of gelatinization for the three tested starches due to the competition for water during starch gelatinization. Furthermore, adding mucilage increased the phase transition temperature range (Tc-To) of starches but decreased enthalpy (ΔH). However, although the pasting temperature increased with the addition of mucilage into tuber starches, it did not change that of taro starch. The peak viscosity of taro and sweet potato starches decreased significantly as their mucilages were added into each starch suspension system (p < 0.05). However, the addition of mucilage slightly increased the viscosity of yam starch. Furthermore, the addition of mucilage slightly increased the swelling power of yam and taro starches, but did not change that of sweet potato starch.     

不同芋头品种真空微波干燥品质变化的比较

分析8个不同芋头品种真空微波干燥前后营养成分的变化,比较不同芋头品种生产的芋头脆片色泽、硬度、脆度、膨化率、微观结构和感官品质等品质变化。结果表明:新鲜芋头含水量高达61.33~82.94%,奉化芋头含量最高;淀粉含量范围为15.87~30.25%,香沙芋含量最高;荔浦芋中的蔗糖最高,约为2.6 g/100 g,红香芋中的可溶性蛋白为1455 mg/100 g,明显高于其他品种。芋头片干燥后营养成分中除了蔗糖,其他含量均减少,且减少量差异显著,淀粉含量减少最多。不同品种的芋头真空微波干燥后品质差异明显,其中,荔浦芋、龙香芋、奉化芋头、槟榔芋和香沙芋亮度大、色差小,产品色泽保持良好;龙香芋和乌骨芋外形膨化且内部多孔状结构明显,硬度适中、酥脆性好;龙香芋、奉化芋头和乌骨芋的色泽、形态、口感、风味综合评分高,可接受程度明显高于其他芋头品种。     

Centrifugation and Foam Fractionation Effect on Mucilage Recovery from Dioscorea (Yam) Tuber

ABSTRACT: The yam ( Dioscorea spp., Dioscoreaceae ) is an important pharmaceutical plant that can be widely applied in the drug industry. The yam tuber is rich in starch and mucilage however, it is difficult to separate the starch from the tuber because of the viscous soluble carbohydrates-protein (glycoprotein) present in the yam. These surface-active complexes produce an extensive amount of foam. Foam fractionation is recognized as a suitable technique for recovering soluble, surface-active substances from a solution using preferential adsorption at the gas-liquid interface. The objective of this research is to compare foam fractionation and centrifugation for recovering the mucilage from yam tuber. The soluble carbohydrates and protein present in the mucilage are analyzed. The results showed that centrifugation may break down the soluble carbohydrates and protein complex, resulting in further soluble carbohydrates and protein separation in different parts of the starch paste and mucilage. With 2 consecutive centrifugations (7300 × g ), the total amounts of soluble carbohydrates and protein recovered from the Keelung yam ( D. pseudojaponica Y.) tuber were 4.8% and 33.8%, respectively. It was found that excellent soluble carbohydrates (98.8%) and protein (74.1%) yield can be recovered in the Keelung yam using foam fractionation. Foam fractionation provides an alternative method for recovering viscous mucilage from yam. This is especially suitable for starch-rich samples from the tuber.     

EMULSIFYING PROPERTIES OF ETHANOL-PRECIPITATED MUCILAGE FROM CELLULASE-HYDROLYZED GREEN ALGAE (MONOSTROMA NITIDUM)

The emulsifying properties of the ethanol‐precipitated mucilage from cellulase‐hydrolyzed Monostroma nitidum were investigated. Both emulsifying activity and emulsion stability of the mucilage increased from 51.5 and 48.0% to 69.0 and 62.0%, respectively, and oil droplets did not coalesce when the mucilage concentration was at l%(w/v). Gel permeation chromatography showed that the carbohydrate moieties of the mucilage exhibited an absence of low molecular weight fractions and a broader molecular weight range for the high molecular weight fraction than that of the cellulase hydrolysate. Also, there was a greater amount of high molecular weight protein‐containing fractions in the mucilage, while predominantly low molecular weight protein fractions were in the hydrolysate. Increasing the mucilage concentration of the solution(0–20 mg/mL) led to a reduction of surface tension to 54.9 dyne/cm, and increased the emulsifying activity and emulsion stability to 76.9 and 70.0%, respectively. The oil did not separate from the emulsion when the mucilage concentration was higher than 0.5%(w/v). When 0.2% NaCl was added to the emulsion containing 1% mucilage, the apparent viscosity decreased from 37.1 to 7.6 Pa.s (x 10^‐3). Also, the emulsifying activity and emulsion stability decreased from 69.0 and 62.0% to 50.0 and 48.0%, respectively.     

Preparation of granular cold‐water‐soluble corn starch by surface modification with poly(ethylene glycol)

The main target of this study is to synthesize one kind of granular cold‐water‐soluble (GCWS) starch by grafting poly(ethylene glycol) (PEG) segments onto the surface of native starch granules. It is found that the grafting process could introduce long PEG chains onto the granule surface, resulting in the presence of special micropits on the granule surface, as characterized by SEM. The cold water solution test verified that the resultant PEG‐grafted corn starches exhibited excellent cold‐water‐solubility. The XRD analysis and further polar optical micrograph (POM) observation indicated that the crystallites structure inside the PEG‐grafted corn starches was fully preserved, since no gelatinization process was involved. The present study provides a new train of thought that we can adjust the physiochemical properties of starch granules with proper surface modification.     

Nutrient composition of taro (Colocasia esculenta) cultivars from the Papua New Guinea Highlands

Taro samples were analysed for water, protein, fat, fructose, glucose, sucrose, maltose, starch, organic acids, dietary fibre, ash, sodium, potassium, iron, calcium, magnesium and zinc and the energy content was calculated. The composition of ‘Yaguat’ taro was determined at various intervals during growth. The most marked changes were in immature corms with a decrease in water content and an increase in starch and energy content. There were minimal changes in composition of taro from slightly immature to over-mature stages. The composition of 36 samples of mature taro from 22 cultivars grown in four districts was determined. There was a large range in proximate composition between cultivars for most nutrients; for example, water ranged from 55.8 to 74.4 g 100 g^?1, starch 20.0 to 35.1 g 100 g^?1 protein 0.5 to 2.1 g 100 g^?1, dietary fibre 1.4 to 5.4 g 100 g^?1 and energy 403 to 672 kJ 100 g^?1. However the same cultivar grown in two districts tended to have a similar composition. Mineral levels were variable between samples but the greatest variation was with zinc which varied widely between districts.     

Mucilage in linseed: effects on the intestinal viscosity and nutrient digestion in broiler chicks

A study was conducted to obtain more information on the role of mucilage in the adverse effects produced by the use of linseed in chick diets. Mucilaginous material was extracted from linseed with hot distilled water (80 °C) for 2 h; after filtration the water‐soluble extract was freeze‐dried and ground. A maize/soyabean meal basal diet with supplemental linseed mucilage extract (0, 4, 8, 12 and 16 g kg^?1) was given to chicks from 8 to 28 days of age. During the last 3 days the excreta were collected quantitatively, then the chicks were slaughtered and the jejunal and ileal contents were collected. Feeding the mucilage extract‐containing diets to birds increased markedly, from 4.35 to 18.89 mPa s, the digesta viscosity at jejunal level. The apparent faecal digestibility of crude fat and major fatty acids and the dietary AMEn value (metabolisable energy corrected to zero nitrogen retention by the body) were linear and negatively influenced by the inclusion level of mucilage extract. However, the presence of mucilage in the diet did not affect the apparent ileal digestibility of crude protein and individual amino acids. These results seem to suggest that mucilage in linseed has lower antinutritional properties than those reported for whole linseed or linseed meal when included in chick diets. © 2002 Society of Chemical Industry     

Isolation and partial characterization of Mexican taro (Colocasia esculenta L.) starch

Taro starch was isolated from Mexican variety and its morphological, physicochemical, and molecular characteristics were evaluated. Yield starch (in dry basis) was 81%, and this starch had low AM content (2.5%). Taro starch granules showed a mixture of shapes with sizes between 1 and 5 µm. Taro starch presented an A‐type XRD pattern with a crystallinity level of 38.26%. Solubility and water retention capacity did not change in the temperature range of 50–70°C and thereafter they increased as temperature increased too. Taro starch showed high peak viscosity due to its high AP content. The peak temperature of gelatinization of taro starch was 80.6°C with an enthalpy value of 10.6 J/g, with low retrogradation rate due to its low AM content. Weight‐average molar mass (Mw) and gyration radius (Rz) of taro starch were 1.21 ± 0.8 × 10⁹ g/mol and 424 ± 70 nm, respectively. Taro tuber could be an alternative for starch isolation with functional and physicochemical characteristics for food and non‐food applications.     

芋头淀粉提取工艺优化及淀粉特性研究

以NaOH为浸泡剂,探讨了料液比、pH、浸泡时间、浸泡温度对芋头淀粉提取率及色泽的影响,并对芋头淀粉特性进行了初步研究。结果显示芋头淀粉提取最佳工艺条件为:pH10.0、浸泡温度25℃、料液比1:3、浸泡时间80min。提取率可达84.82%,淀粉白度高达94.11,优于现有文献报道及市售其它常用淀粉;淀粉特性研究显示,芋头淀粉的体积平均粒度在10μm以下,d(0.5)为14.6μm,稍大于10μm;芋头淀粉具有优良的热稳定性、冷稳定性,凝胶强度和凝成特性等特性。      

Use of continuous bubble separation process for separating and recovering starch and mucilage from yam (Dioscorea pseudojaponica yamamoto)

The yam (Dioscorea pseudojaponica Yamamoto) tuber is abundant in both starch and mucilage. It is difficult to separate yam starch from its tuber because of the presence of viscous polysaccharide polymers (glycoprotein). The surface-active polysaccharide-containing complexes are capable of forming foams. The goal of this study was to develop a continuous bubble separation process for separating and recovering starch and mucilage from yam tubers in the absence of undesirable chemical additives or treatments. The results showed that the highest concentration (13.2 g/100 g) of yam slurry mucilage was obtained with a reasonably high yield of recovered starch (91.2 g/100 g) by treating the starch paste with 1 g/100 g Viscozyme^® L and Pectinex^® Ultra SP-L. In comparison with the total amount of yam fed into the system, the yield of soluble carbohydrates and protein in separated mucilage were 98.8 g/100 g and 74.1 g/100 g, respectively. The chemical composition of the separated freeze-dried mucilage was shown to be high in soluble carbohydrates (52.5 g/100 g, dry basis) and protein (40.3 g/100 g, dry basis). A very low amount of starch (0.8 g/100 g) remained in the mucilage. This method is simple, low in operational and capital costs, and especially suitable for polysaccharide–protein-containing complexes recovering from a starch-containing system.     

Preparation of spherical aggregates of taro starch granules

Taro starch spherical aggregates were prepared by including a spray drying step in a conventional pilot plant-scale starch isolation procedure. The aim of this study was to characterize these spherical aggregates. The procedure was repeated three times to verify the spherical aggregates formation, which was shown by scanning electron microscopy. Amylose was not be detected in the aggregates, and a protein content of 4.5 g/100 g was recorded. Aggregation of taro starch granules did not affect the X-ray diffraction pattern. The maximum peak viscosity of the aggregate preparation was obtained at a relatively high temperature (i.e. start of the temperature holding step). The phase transition of taro starch aggregates in excess water showed high temperatures, with low molecular reorganization during storage. During water retention capacity (WRC) and solubility tests, taro starch aggregates were stable until 70 °C. The spray drying conditions used produced spherical aggregates of taro starch that presented physicochemical and functional characteristics with potential for encapsulation of substances.     

不同品种甘薯的干燥特性及对全粉品质的影响

以9个甘薯品种为原料,研究不同品种甘薯在相同工艺条件下的干燥特性,分析甘薯品种与其全粉品质及得率的相关性。结果表明:鲜薯成分中影响熟化甘薯热风干燥速率的因素主要是可溶性糖含量,而影响颗粒全粉得率及品质的因素主要是水分、淀粉、可溶性糖、粗蛋白含量及多酚氧化酶、β-淀粉酶活性。鲜薯的水分含量及可溶性糖含量越低,淀粉含量越高,加工成颗粒全粉的产品得率越高。     

Study on the protein fractions extracted from the muscle tissue of Pinctada martensii and their hydrolysis by pancreatin

Pinctada martensii muscle proteins were separated into water‐soluble, salt‐soluble and insoluble protein fractions. The salt‐soluble protein fraction was the most abundant, comprising approximately 66.3% of the protein, followed by the water‐soluble and insoluble protein fractions in decreasing order. sodium dodecyl sulphate polyacrylamide gel electrophoresis profiles showed that 35‐ and 97‐kDa peptides represented the highest proportions of the water‐soluble and salt‐soluble protein fractions, respectively. The three protein fractions contained high levels of flavourful amino acids (Glu, Asp, Ala and Lys), with the water‐soluble protein fraction having the highest level (47.1%). The size exclusion chromatography profiles of the water‐soluble and salt‐soluble protein pancreatin hydrolysate demonstrated no significant differences in the molecular weight distributions in the >20 000, 5000–10 000 and 2000–5000 Da fractions, while those of the insoluble protein pancreatin hydrolysate were different. In conclusion, the results provided some basic information that would contribute to the utilisation of these protein fractions.     

Properties of Low‐substituted Cationic Starch Derivatives Prepared by Different Derivatisation Processes

Cationic starch ethers prepared by the chemical reaction of starch with a quaternary ammonium reagent are commercially important derivatives. Cationic potato starch derivatives were produced under pilot‐scale conditions, employing four different principles. Wet cationisation was carried out by the slurry and paste processes, in which the cationic reagent and catalyst are added to the starch. Besides being prepared by these more commonly used processes, cationic starches were also produced by dry cationisation and by adding the cationic reagent during extrusion of starch. The cationic reagent used was 2,3‐epoxypropyltrimethylammonium chloride. Derivatives with three graded degrees of substitution (DS) between 0.03 and 0.12 were prepared by each process. The physical properties of the derivatives were analysed by the following methods: polarised light microscopy, X‐ray scattering, differential scanning calorimetry (DSC), solubility and swelling behaviour, and High‐Performance Size‐Exclusion Chromatography‐Multiangle Laser Light Scattering (HPSEC‐MALLS). The degree of substitution was determined by high resolution ¹³C‐NMR spectroscopy after hydrolysis with trifluoroacetic acid. The properties of the cationic starch derivatives were highly dependent on the derivatisation method. The granular structure of the starch was not visibly affected by the slurry process. Products from the semi‐dry reaction showed some granular damage, which was particularly evident after suspension of the granules in water. In the paste and extrusion processes, the starch granules were completely destroyed. Swelling temperatures and enthalpies can be determined only for starch derivatives that still retain a granular structure. As a result, samples from the paste and extrusion reactions exhibited no swelling endotherm in DSC. The samples from the slurry process showed a shift in the swelling temperature range towards lower temperature and a decrease in swelling enthalpy both as compared to native potato starch and also with increasing DS. Similar behaviour was found for the samples from the semi‐dry process. The swelling temperature region was comparable to that of the slurry samples for the same DS but the swelling enthalpy was distinctly lower, indicating that the granular structure of the starch was altered far more by the semi‐dry than the slurry process. Swelling in excess water and solubility were affected primarily by the cationisation process, while the influence of DS was of minor importance. The extrusion products had pronounced cold‐water solubility, the semi‐dry products showed increasing cold‐water solubility with increasing DS, the paste products were highly swollen in cold water and the slurry products were insoluble in cold water. All products were soluble in hot water but the state of dissolution was different. The molar mass distributions of the samples were determined after dissolution by pressure cooking. The different derivatisation methods resulted in characteristic molar mass distributions. The average molar mass decreased in the order slurry, semi‐dry‐, paste and extrusion process.     

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.     

芋头淀粉的分离和纯化

用重结晶法可以得到纯度较高的芋头直链淀粉和支链淀粉。直、支链淀粉的蓝值分别是1 1 8和 0 2 0 ,λmax分别为 61 4nm和 5 87nm ,芋头淀粉中直链淀粉含量为 1 4 7%。高效液相色谱表明 ,芋头支链淀粉的分子质量具有较宽的分布 ;重均聚合度 ,大米支链淀粉 >芋头直链淀粉 >大米直链淀粉 >芋头支链淀粉 ;分散度 ,芋头支链淀粉 >芋头直链淀粉 >大米直链淀粉 >大米支链淀粉 ;芋头支链淀粉中 ,长支链所占比例 >短支链 ;分散度 ,长支链 >短支链。     

Effect of seed treatments on the chemical composition and properties of two amaranth species: starch and protein

The seeds of two Amaranth species were studied. The starch contents were 543 and 623 g kg^?1 while crude protein contents were 154 and 169 g kg^?1 for Amaranthus caudatus and Amaranthus cruentus seeds, respectively. The effect of several treatments, including cooking, popping and germination and flour air classification on the protein and starch properties were studied. Air classification decreased the starch content and increased the protein content, while heating increased the protein but did not affect the starch content. Germination decreased both starch and protein contents. Amylose content was increased by air classification and heating, but was not affected by germination. It was found that all treatments increased the starch swelling power and reduced the falling number. The resistant starch content was increased in the high protein flour (HPF) fraction and germinated flour compared with the raw flour, while its content decreased in the heat treated seed flours. These processes also affected the starch gelatinization temperature and peak viscosity. The thermal properties of the starch flour were not affected by air classification while gelatinization energy was decreased significantly (by 52.0 and 90.0% and by 70.0 and 95.0%) in cooked and popped A caudatus and A cruentus seed flours, respectively. The gelatinization energy was highest in germinated seeds dried at 90 °C with values of 2.67 and 3.87 J g^?1. Air classification reduced the level of all protein fractions. Thermal treatment decreased the water‐soluble fraction (albumins + globulins) and alcohol‐soluble fraction (prolamins) in both species. The levels of all fractions except the water‐soluble fraction (albumins + globulins) were reduced significantly in both species by germination, which mainly increased the amount of aspartic acid, serine and alanine, while the amounts of threonine, arginine and tyrosine decreased in both species. The polypeptide bands of the HPF in both species were unchanged compared with the raw seed flours, but more intensive coloured bands were observed. Thermal treatments eliminated major and minor bands above 35.0 KDa in both species. Copyright © 2004 Society of Chemical Industry     

A Comparison of the Molecular Properties of Sorghum Starches of Different Origins

The molecular properties of three sorghum starches and their components have been compared by methods involving iodine staining, enzymic degradation and gel chromatography. The starches from the red and chalky varieties were very similar in properties and in amylose to amylopectin ratio, but differed in their molecular weight distribution profiles. The waxy sorghum starch was fractionated by the thymol-butanol method to yield a small quantity of amylose. The three starch samples were all resistant to dissolution in boiling water but when subjected to physical damage the granules became partly soluble in cold water and almost totally soluble in boiling water.     

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。     

Composition and bioavailability of oxalates in baked taro (Colocasia esculenta var. Schott) leaves eaten with cows milk and cows milk and coconut milk

Taro leaves are an important food in the Pacific Islands but the overall oxalate composition and its nutritional effect has not been investigated. The oxalate contents of taro leaves were determined using chemical and in vitro extraction methods. Maori‐type taro leaves contained 524.2 ± 21.3 mg total oxalates 100 g^?1 fresh weight (FW) and 241.1 ± 20.9 mg soluble oxalates 100 g^?1 FW while the Japanese‐type leaves contained 525.6 ± 19.9 mg total oxalates 100 g^?1 FW and 330.4 ± 28.3 mg soluble oxalates 100 g^?1 FW. Maori‐type taro leaves contained 416.4 ± 1.5 mg gastric soluble oxalates 100 g^?1 FW and 212.4 ± 34.8 mg intestinal soluble oxalates 100 g^?1 FW while the Japanese‐type leaves contained 433.3 ± 9.7 mg gastric soluble oxalates 100 g^?1 FW and 224.2 ± 38.7 mg intestinal soluble oxalates 100 g^?1 FW). Human feeding experiments were conducted to determine the availability of the oxalates in the baked leaves following additions of cows milk and coconut milk. The consumption of a test meal of baked taro leaves resulted in a significant increase (P < 0.001) in the output of urinary oxalate in the following 6 h when compared to the output of oxalate during a reference collection. When the leaves were baked with cows milk or cows milk and coconut milk combined and consumed there was a small non‐significant reduction in urinary oxalate output which suggests that less soluble oxalate was absorbed from these mixtures.