Physicochemical Properties and Starch Digestibility of Autoclaved-Cooled Water Yam (Dioscorea alata L.) Flour

Water yam (Dioscorea alata L.) is suitable for resistant starch high flour because of its high amylose content. The purple, yellow, and white water yams were treated by autoclaving and cooling with one, two, and three cycles to obtain resistant starch. Water yam tubers were cooked in an autoclave for 15 min, and then cooled prior to drying. Autoclaving–cooling of water yams decreased protein, fat, dietary fiber, water soluble polysaccharide, dioscorin, and diosgenin but increased amylose and sugar. The treatments significantly raised resistant starch and reduced in vitro starch digestibility that depended on water yam types, and affected starch granule morphology.     

Effect of Yam (Dioscorea alata Compared to Dioscorea japonica) on Gastrointestinal Function and Antioxidant Activity in Mice

ABSTRACT:  Effects of Chinese yam ( Dioscorea alata) and Japanese yam ( Dioscorea japonica ) on gastrointestinal functions including intestinal microflora and intestinal enzymes' activities, as well as antioxidant protection against lipopolysaccharide (LPS)-induced oxidative damage, in Balb/cA mice were examined. In part I, mice were fed yam-supplemented diet for 4 or 8 wk, and killed with carbon dioxide. In part II, mice were fed yam-supplemented diet for 4 wk, and followed by intraperitoneal LPS treatment (i.p. 4 mg/kg bodyweight). The intake of Chinese yam and Japanese yam significantly changed intestinal microflora, in which the colony numbers of Bifidobacterium and Lactobacillus were increased and the colony numbers of Clostridium perfringens were decreased ( P < 0.05). The intake of both Chinese and Japanese yams also significantly elevated the activity of leucine aminopeptidase and lipase ( P < 0.05), and the activities of sucrase and maltase were increased only in 20% yam-treated groups ( P < 0.05). The preintake of yam significantly alleviated subsequent LPS-induced oxidative injury by decreasing lipid oxidation level and fibronectin production and elevating superoxide dismutase activity ( P < 0.05). Both Chinese and Japanese yams contained dietary fibers, polyphenols, and flavonoids, which may contribute to the observed gastrointestinal function and antioxidant protection. These results suggest that both Chinese yam and Japanese yam were beneficial for intestinal health and oxidation prevention.     

怀山药微波冻干过程的水分扩散特性及干燥模型

为探究怀山药干燥过程中的水分扩散特性,以怀山药为原料,使用微波真空冷冻干燥技术进行干燥,同时采用低场核磁共振的横向弛豫时间（T2）反演谱分析怀山药切片在干燥过程中内部水分的变化,并结合有效水分扩散系数、水分含量、干燥速率的变化规律对微波真空冷冻干燥过程中怀山药的内部水分扩散特性进行分析。结果表明：干燥过程中水分由自由度高向自由度低的方向迁移;不同微波功率（1.5～4.4 W）下怀山药干燥过程的有效水分扩散系数变化范围在1.129×10－9～5.439×10－9 m2/s之间,随着微波功率的增大,有效水分扩散系数升高,水分扩散迁移的速度增大,非结合水向结合水方向转化逐渐增多。采用Page、Newton等模型与实验数据进行拟合,结果表明Page拟合度较高,R2大于0.99,可以较好地对怀山药微波真空冷冻干燥过程进行预测和控制。本实验为怀山药干燥过程的水分实时监测及实现精准干燥提供了理论依据。     

Process Optimization by Response Surface Methodology and Characteristics Investigation of Corn Extrudate Fortified with Yam (Dioscorea alata L.)

Response surface methodology was used to investigate the optimum operation conditions of a single screw extruder and to analyze the effects of extrusion processing variables, including yam flour contents (10–30 %), moisture content (10–18 %), and screw speed (250–350 rpm) on characteristics of the corn–yam extrudates. Quadratic polynomial equations were also obtained by multiple regression analysis. The predicted models were adequate based on the lack-of-fit test and coefficient of determination obtained. By superimposing individual contour plots of the different responses, regions meeting the optimum conditions were also derived. The moisture content had critical effect on all responses variables. All the characteristic of the corn–yam extrudates evaluated were significantly affected by three process variables. Feed moisture content was the most significant variable with on most of characteristics. Increasing moisture content caused increase in bulk density, water absorption index and hardness, but decrease in radial expansion ratio. However, graphical optimization studies resulted in 21–23 %, 12–13 %, and 305–320 rpm of yam flour level, moisture content, and screw speed, respectively. The results suggested that corn extrudates fortified with yam produced by using the single-screw extruder are suitable for snack food development.     

UHPLC-DAD-ESI-MS/MS法分析紫山药块根和茎叶中酚类物质

本文采用微波辅助法,以80%甲醇作为溶剂提取经冻干后紫山药块根和地上茎叶中的多酚类物质,提取物经超高效液相色谱分离、电喷雾串联三重四级杆质谱正和负离子方式检测分析。根据液相保留时间、紫外吸收、相对分子质量和二级碎片离子等信息,结果表明,紫山药块根和茎叶中酚类物质主要为酚酸、花色苷及黄酮类化合物。分析得到的29种酚类化合物中,5-O-咖啡酰奎宁酸、阿魏酰奎宁酸(tR:12.289)、迷迭香酸、芦丁和槲皮素为块根和茎叶共有组分,块根中另含有芥子酸、芥子酸葡萄糖苷、丁香酸衍生物、香豆酸衍生物、阿魏酸衍生物、芥子酸二葡萄糖苷和花色苷等11种酚类物质。茎叶中除5种共有组分,还含有咖啡酸、咖啡酰奎宁酸甲酯、咖啡酰莽草酸、对香豆酰奎宁酸、香豆酰奎宁酸甲酯、山奈酚-3-O-芦丁糖苷与迷迭香酸甲酯等13种酚类化合物。     

Effect of Amylopectin Structure on the Gelatinization and Pasting Properties of Selected Yam (Dioscorea spp.) Starches

This study was aimed at elucidating the decisive structural parameters of amylopectin which govern the gelatinization or pasting behavior of yam starch dispersions, exemplified with four selected yam starches from Dioscorea alata and D. batatas with very similar amylose contents (32.2–34.6%). The results indicated that the yam amylopectins examined showed an average degree of polymerization (DP) of 3469–4474 anhydroglucose units (AGU), average chain length (CL) of 18.8–28.5 AGU, average exterior CL (ECL) of 11.8–16.4 AGU, average interior CL (ICL) of 6.0–11.1 AGU, and a noticeable proportion of extralong (> 100 AGU) and long (40–100 AGU) chains that gave the chain ratio r_(el+l)/s (the weight ratio of extralong and long chains to short chains) of 0.88–1.40. Generally, the yam amylopectin with a lower DP and NC possessed a greater CL, ECL, ICL, and r_(el+l)/s, associating with a higher blue value (BV) and maximal wavelength (λ_max) for their complexes with iodine. D. alata amylopectins exhibited a lower DP, longer chain lengths and greater r_(el+l)/s than the D. batata amylopectins. Statistically, r_(el+l)/s was decisive for the BV and λ_max; while CL and phosphate content were crucial for the gelatinization peak temperature and pasting viscosities of the yam starches examined. The role of swelling power or the volume fraction of dispersed remnants instead in governing the pasting viscosity was also mathematically explored.     

Prevention of Enzymatic Browning of Chinese Yam (Dioscorea spp.) Using Electrolyzed Oxidizing Water

In this study, the effects of electrolyzed oxidizing water (EOW) on the prevention of enzymatic browning of fresh‐cut “Jiu Jinhuang” Chinese yam were investigated. The yams were immersed in the inhibitors for 25 min at 20 °C. Compared with the tap water (TW) treatment, the chromatic attributes were significantly different after 72 h of storage (P < 0.05). The activities of polyphenol oxidase (PPO, EC 1.10.3.1), peroxidase (POD, EC 1.11.1.7), and _L‐phenylalanine ammonia lyase (PAL, EC 4.3.1.5) were inhibited when measured at 24 h. The contents of phenolic acids, including gallic and chlorogenic acid, in the group treated with the slightly acidic electrolyzed water (SAEW) were higher than those treated with TW and neutral electrolyzed water (NEW). The group treated with NEW had the highest total phenol content (P < 0.05, at 24 h), while the group treated with SAEW had the highest flavonoid content (P < 0.05) during storage. Without being treated with inhibitors, the K_m and V_max values of yam PPO were 0.0044 mol/L and 0.02627 U/min, respectively, and the K_i of samples treated with SAEW and citric acid (CA) were 15.6607 and 2.3969 μmol/L, respectively. These results indicate that EOW is beneficial as a browning inhibitor.     

Effect of Storage on the Pasting Characteristics of Yam Tubers

Yam is a popular root and tuber crop which is important as a dietary staple and potential export crop. Storage of yam tubers is an age long practice in yam growing communities of West Africa, while pasting characteristic is an important indicator of potential utilization of yam tubers. The study was carried out to investigate effect of storage of the tubers on their pasting characteristics. Six varieties each of D. alata and D. rotundata were used for the study. At harvest, the tubers were divided into two groups. The first group was stored in a conventional open-air yam barn for four months, while tubers in the second group were not stored. Pasting characteristics of both fresh and stored tubers were determined by Rapid Visco Analyser (RVA). The result showed that the effect of storage on the yam tubers were species dependent. In D. alata there was an increase in peak viscosity (231.36 to 257.56 RVU), breakdown (71.68 to 122.47 RVU), setback (42.58 to 65.99 RVU), while there was a decrease in most of the parameters except break-down and setback viscosities in D. rotundata. Generally, a decrease in peak viscosity, holding strength, final viscosity and peak time of the yam tubers during storage was observed, while the breakdown and setback viscosities of the tubers increased significantly (p < 0.05) on storage. The industrial implication of this is that starches of stored tubers may have high retrogradation tendencies but more resistance to shear-thinning and have more paste stability during processing.     

不同烹饪方式对淮山结构和糊化性质的影响

本实验采用水煮、清蒸、热炒和微波4种烹饪方式对淮山进行加工,通过对烹饪后的淮山进行质构分析、扫描电子显微镜观察以及傅里叶变换红外光谱、X射线衍射和糊化性质分析,研究烹饪方式对淮山质构、结构和糊化性质的影响.结果表明,经不同烹饪方式处理后,淮山样品硬度均显著降低(P<0.05);经微波烹饪处理后,淮山样品咀嚼性显著升高(...     

Gelling properties of extruded yam (Dioscorea alata) starch

Yam (Dioscorea alata) starch was pregelatinized in a single screw extruder. Response Surface Methodology was used to study the effect of extrusion variables: feed moisture (18, 21, 24%), extruder temperature (120, 150, 180°C) and die diameter (3, 4, 5 mm) on cold viscosity, gel-forming capacity and retrogradation of extruded starches. Cold viscosity was higher from starch samples processed at higher moisture and die diameter, at lower temperatures. Slurries of the extruded starch (8%, w/v, d.b.) formed opaque and firm gels. Higher values for gel strength were found in samples extruded at highest and lowest moistures at intermediate temperature and increasing die diameter. Gels of extruded starch had lower retrogradation values than non-extruded gelatinized starch after one and two weeks storage at refrigeration temperature. Prediction equations for the studied functional properties can be used in selecting processing conditions for specific food applications.     

Water absorption as an evaluation method of cooking quality for yam (Dioscorea alata) and cassava (Manihot esculenta crantz)

Water absorption as a new method of cooking quality (hard cooking or mealy cooking) of yam and cassava cultivars determination was studied by cooking eight (08) cultivars. 30 g of each were boiled in 500 ml of water during 20 minutes and dried at 70 °C for 15 hours and 103 °C for 3 hours in a vacuum oven. Results showed that cassava and yam have different cooking quality. Dry matter content does not influence the cooking quality of yam and cassava. Mealy cooking quality of yam absorbs less water (6.6%) during cooking but looses more soluble dry matter (9.5%) during the same process. Hard cooking quality of yam absorbs much water (23.5%), but looses less soluble dry matter (3.9%). The soluble dry matter is the main parameter to determine the quality of D. alata. It stands at 9.5% ± 2.9 for mealy cooking quality and 3.9 ± 0.73 for hard cooking quality cultivars of D. alata. Water absorbed by mealy cooking cassava (27.6%) is significantly (p < 0.05) higher compared to water absorbed of hard cooking cassava (12.4%). Water absorbed during cooking is the main parameter in determining the quality of cassava cultivars. Water absorbed stands at 27.6% ± 8.8 for mealy cooked quality and 12.4% ± 1.9, for hard cooked quality of cassava cultivars. A close relation between water absorption and cooking quality was revealed to contribute to a better selection procedure for cultivars in the frame of food security.     

山药淀粉的特性及应用研究

详细介绍了山药淀粉的制备与组成,并对其物理化学特性和加工特性,包括淀粉的颗粒形态、溶解度和膨胀度、凝胶特性等进行了较全面的综述.     

Effects of Cultivar and Drying Method on Color,Pasting and Sensory Attributes of Instant Yam (<Emphasis Type="BoldItalic">Dioscorea rotundata</Emphasis>) Flours

Effect of cultivar (Efuru and Abuja) and drying method (cabinet and foam mat) on color, pasting, and sensory properties of instant pounded yam flours was investigated. Color (L*, a*, b*) values of fresh and dried flour samples were measured, and deltachroma (∆C), color difference (∆E), and hue angle were calculated. Pasting properties of flour and sensory attributes of fresh and reconstituted flour were determined. Foam density of yam pastes decreased from 0.97 g/cm³ to between 0.362–0.538 and 0.308–507 g/cm³ for cultivars Abuja and Efuru, respectively. Foam-mat dried flour showed higher L*, ΔC, ΔE, and hue angle but lower a* and b* values. Peak viscosities of cabinet and foam-mat dried Abuja and Efuru were 217, 304, 377.42, and 316.50 RVU, respectively. Sensory attributes of reconstituted foam-mat dried Abuja and fresh pounded yam were not significantly different (p > 0.05). However, fresh pounded yam (8.5–8.9) and reconstituted foam-mat dried flour (7.4–8.5) samples were significantly different (p > 0.05) from the cabinet-dried (6.9–7.9) and commercial samples (7.2–7.8).     

Volatile components of cooked tubers of the water yam (Dioscorea alata)

Volatile constituents were isolated from yams, during cooking, by concurrent steam distillation-solvent extraction. The essence which resulted was analysed by linked gasliquid chromatography-mass spectrometry (g.l.c.-m.s.) employing capillary columns and by gas-liquid chromatography coupled with sensory evaluation of the column effluent (nasal appraisal). In addition to hydrogen sulphide and a number of high-boiling fatty acids, 29 compounds, comprising seven hydrocarbons, eight alcohols, eight aldehydes, four ketones, a furan and a disulphide, were identified for the first time in yam. A further five components were tentatively identified by g.l.c.-m.s. and by thinlayer chromatography of derivatives. 4-Phenylbutan-2-one was the major constituent of the acid-free essence.     

Genetic diversity of organoleptic properties in water yam (Dioscorea alata L)

Improving the food quality of yams (Dioscorea spp) is an ongoing challenge to yam breeders and researchers. Forty accessions of D alata were evaluated for the suitability of their tubers for the preparation of two dominant food forms (boiled and pounded) as part of an effort to identify potential parents for use in genetic improvement. Trained panellists were presented with randomised, replicated and coded samples of boiled yam tuber pieces and asked to rate them for mealiness, colour, wetness, softness and taste. The sensory attributes considered for pounded yam (dough from boiled and pounded tubers) were consistency, colour, sheen, smoothness, stickiness, elasticity and hardness. Ratings were based on hedonic scales. Cluster analysis revealed groupings of accessions into eight and nine similarity clusters for boiled yam and pounded yam respectively. The mean scores for general preference were regressed on individual attribute scores. Mealiness, colour and taste were important in the general preference for boiled yam. Consistency, colour and stickiness determined the general preference for pounded yam. Of the accessions, 67% were identified as being suitable for preparation as a boiled vegetable, while 55% were assessed to be good for pounded yam, based on the respective quality attributes evaluated. © 2003 Society of Chemical Industry     

Effect of Hydroxypropylation on the Properties of White Yam (Dioscorea rotundata) Starch

Starch isolated from white yam (Dioscorea rotundata) was subjected to hydroxypropylation under different conditions. Corresponding increases were observed between the molar substitution (MS) and the volume of propylene oxide added to the reaction mixture. After hydroxypropylation, a slight reduction in the intensity of the peak at 2θ = 19.6° was observed and the doublet peak at 23.8°, which was present in native starch, was no longer seen. Hydroxypropylation enhanced the free swelling capacity (FSC) and solubility. Setback and retrogradation of native starch declined after hydroxypropylation. Turbidity of native starch paste and syneresis were higher with storage time. The results also indicate that enzymatic digestibility improved as the MS increased, while the reverse was observed for starch paste turbidity, syneresis, setback and retrogradation. This study presents relevant information that could strategically position D. rotundata starch and its hydroxypropylated derivatives for industrial applications.     

Influence of pH and hydrocolloids addition on yam (Dioscorea alata) starch pastes stability

Yam tubers (Dioscorea alata) are a non-traditional starch source that could be used as food ingredient. The stability of yam starch pastes (6/100 g suspension) submitted to different pH conditions during gelatinization and the effect of hydrocolloids addition (guar and xanthan gums) on starch syneresis under refrigeration were analyzed. Changes in pH (3, 5, 6) or the addition of gums (0.1–0.5/100 g suspension) did not affect the starch gelatinization temperature nor the gelatinization enthalpy as determined by differential scanning calorimetry. Rheological behavior was characterized by amylograph profiles and oscillatory rheometry. Amylograms showed that yam starch pastes maintained a high viscosity under heat treatment and mechanical stirring in neutral to slightly acidic conditions. Brabender viscosity increased when gums were added; the effect of guar gum on viscosity was more marked than that of xanthan gum. During refrigerated storage exudate production was observed of pastes without gums. Xanthan gum, at a concentration of 0.5/100 g suspension, showed higher effectiveness than guar gum to reduce exudate production during refrigerated storage. The addition of hydrocolloids could allow yam starch to be used in foods requiring low temperatures.     

原生贡寮山药萃取物抗氧化成分及抗氧化活性的研究

探讨了干燥、萃取方式对原生贡寮山药(Dioscores alata)抗氧化成分以及抗氧化活性的影响。抗氧化成分分析了总多酚质量分数;体外抗氧化的测定方法包括DPPH自由基清除能力与还原力。结果表明,山药皮冷冻干燥后经过乙醇萃取所得萃取物的总多酚质量分数以及抗氧化能力最高。抗氧化能力及总多酚质量分数以冷冻干燥优于热风干燥,萃取方式以50%体积分数乙醇溶液最优,山药皮优于山药肉。HPLC分析萃取物中主要多酚成分为绿原酸。同时对体外抗氧化活性以及总多酚含量较高的原生贡寮山药的乙醇萃取物进行抑制体内细胞ROS产生测试,结果显示各个样品均可以显著降低由LPS所诱导细胞ROS的产生,抑制效果跟抗氧化能力结果一致。