Qualities and antioxidant properties of bread as affected by the incorporation of yam flour in the formulation

Yams (the tubers of Dioscorea spp.) are widely consumed but are also regarded as a medicinal food in China. Traditional Chinese herbal medicines using yams are only available on a seasonal basis, as yams quickly deteriorate during winter storage. Yam (Dioscorea purpurea, a major variety of yams in Taiwan) was freeze‐dried and ground to obtain yam flour. Bread was made by replacing up to 25% of wheat flour with yam flour. Although the loaf volume decreased with the addition of yam flour, the results showed that up to 20% of yam flour could be included in bread formulation without altering the sensory acceptance of the blended bread. The incorporation of yam flour in bread markedly increased the antioxidant capacity of the bread as tested by both DPPH free radical scavenging and total antioxidation tests. Breads containing yam flour can broaden the utilization of yams and may be regarded as possible health‐promoting foods.     

Effect of Extrusion Processing on Antioxidant Activities of Corn Extrudates Fortified with Various Chinese Yams (<Emphasis Type="Italic">Dioscorea</Emphasis> sp.)

The purpose of this experiment was to evaluate the effects of extrusion on antioxidant abilities of the extrudates of corn fortified with various (Chinese) yams. The flours from three yam varieties were used, including Dioscorea alata L. var. Tai-nung No.1 (TN1), D. alata L. var. Ta-shan (TS), and Dioscorea doryophora var. Hang-chun (HC). One commercial yam flour (TJ) was also used. Six antioxidant assays were conducted, such as 1,1-diphenyl-2-picryl-hydrazyl (DPPH) free radical scavenging effect, oxygen radical absorbance capacity (ORAC) assay, ferrous ion chelating (FIC) ability, 2,2-azino-bis-(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) free radical scavenging activity, superoxide radical scavenging (SORS) assay, and thiobarbituric acid reactive substances (TBARS) assay. The influences of extrusion on the antioxidant activities of corn were determinedly different in different assays, showing a dramatic increase of ABTS value but significant reductions of SORS and TBARS values. The effects of extrusion on antioxidant activities of corn–yam mixtures varied with yams in different assays. Overall, extrusion processing increased the TBARS inhibition ability for all yams and generally had no negative impact on DPPH, ORAC, FIC, and ABTS antioxidant abilities for most yams in corn–yam extrudates. The involvement of the addition of yam to the antioxidant activities of corn–yam extrudates during extrusion could be suggested through two different possible approaches, the effects of extrusion on the antioxidant activities of yams (susceptible, resistant, or improved), and the effects of added yams on the antioxidant activities of corn during extrusion.     

The bone‐protective effect of a Taiwanese yam (Dioscorea alata L. cv. Tainung No. 2) in ovariectomised female BALB/C mice

BACKGROUND: Yam products have been marketed for treating postmenopausal syndromes. This study investigated the effects of Dioscorea alata L. cv. Tainung No. 2 (TNG yam) on the bone density of ovariectomised (OVX) female BALB/c mice and the mechanism whereby TNG yam exerted this effect. Sham and OVX control groups were fed a control diet while remaining OVX mice were randomly allocated into experimental diets, i.e. yam (630 g TNG powder kg^?1), E2 (20 mg 17β‐oestradiol kg^?1), or genistein (2 g genistein kg^?1) diet. After 12 weeks of feeding, the uterine weight, indices of bone mass and caecal short chain fatty acids were determined. RESULTS: Neither a yam nor genistein diet restored the OVX‐induced uterine atrophy as did the E2 diet. The femoral and lumbar bone mineral density (BMD) of mice fed the yam diet was greater than those of the sham group, respectively (P < 0.05 vs OVX control), while the lumbar BMD of yam and sham groups were similar (P > 0.05 vs sham). The femoral ash and calcium content in the yam group was significantly greater than that in the OVX control group, respectively (P < 0.05 vs OVX control). The total short chain fatty acid content in the caecum, only enhanced in the yam group, was not correlated with the calcium content of either bone or the plasma calcium level. CONCLUSION: TNG yam prevented loss of BMD and improved bone calcium status without stimulating uterine hypertrophy in OVX BALB/c mice. TNG yam may be beneficial for postmenopausal women for preventing bone loss. Copyright © 2008 Society of Chemical Industry     

Interaction of aqueous extracts of two varieties of Yam tubers (Dioscorea spp) on some key enzymes linked to type 2 Diabetes in vitro

This study sought to assess the effect of processing of yam flour [from white yam (Dioscorea rotundata) and water yam (Dioscorea alata)] to paste, on the antioxidant properties and inhibition of key enzymes linked to type‐2 diabetes (α‐amylase and α‐glucosidase). The phenolic content (phenol and flavonoid), antioxidant properties, α‐amylase and α‐glucosidase inhibitory properties of the aqueous extracts of the yam products were determined. Processing into paste caused significant (P < 0.05) percentage decrease in their total phenol and flavonoid content of the yam varieties. However, significant increase (P < 0.05) in the antioxidant properties of the yam varieties was observed after processing. Furthermore, the yam extracts inhibited α‐amylase and α‐glucosidase activities in vitro in a dose‐dependent parttern (1–4 mg mL^?1), however, the pasting process caused significant (P < 0.05) decrease in the α‐amylase inhibitory and α‐glucosidase inhibitory activities. Therefore, processing the yam varieties into paste (browned) could potentially increase their antioxidant capacity as well as decreasing their α‐amylase and α‐glucosidase inhibitory properties.     

Uncooked Taiwanese yam (Dioscorea alata L. cv. Tainung No. 2) beneficially modulated the large bowel function and faecal microflora in BALB/c mice

This study investigated the effects of an uncooked Taiwanese yam, Dioscorea alata L. cv. Tainung No. 2, on faecal characteristics, faecal microflora, short‐chain fatty acid (SCFA) levels in the caecal content and faeces, and morphological and proliferation indices of the caecal and colonic crypts in BALB/c mice. Mice were randomly allocated to consume a control diet or a 25 or 50% (w/w) yam diet for 21 days. Faecal wet and dry masses increased with increasing proportions of dietary yam. Both yam diets similarly increased faecal moisture content and decreased faecal pH as compared with the control diet. The yam diets increased total bacteria and bifidobacteria counts and decreased Clostridium perfringens counts in faeces. The 50% yam diet, but not the 25% yam diet, increased total SCFA concentration in the caecal content. However, both yam diets increased total SCFA output in faeces. Both yam diets also promoted crypt depth, width and proliferation indices in the caecum; in contrast, they only promoted crypt width in the distal colon. In conclusion, the 25 and 50% yam diets increased the faecal mass and SCFA output, modulated the faecal microflora and thickened the mucosa lining of the caecum in BALB/c mice. Copyright © 2007 Society of Chemical Industry     

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.     

MICROSTRUCTURE OF BOILED YAM (DIOSCOREA SPP.) AND ITS IMPLICATION FOR ASSESSMENT OF TEXTURAL QUALITY

The effects of boiling on the microstructure of yams and their association with the textural quality of “boiled yam,” arguably the most common food product from yams, were studied using six varieties with variable cooking qualities from each of the two species, Dioscorea alata L. and D. rotundata Poir. Histological studies on raw yams showed parenchyma cells of both species to be three‐dimensional and polyhedral in shape, with starch granules loosely arranged in D. rotundata but densely packed in D. alata. Generally, there was cell separation and rounding off of cells in cooked yams of D. rotundata varieties, whereas cell separation was only partial with no rounding off in D. alata. Mealy boiled yams showed complete cell separation and the “rounding off” phenomenon, whereas the waxy ones showed partial retention of textural cell integrity. These relative changes in microstructure of yam when boiled could serve as indicators of textural quality in boiled yam.     

基于叶绿体rpoC1序列在山药分子鉴定中的应用

目的 研究基于rpoC1序列分析,建立山药物种鉴定的新方法。方法 利用DNA条形码技术对收集到的7个山药样本提取基因组DNA,以rpoC1基因引物进行PCR扩增、测序,将所得序列在NCBI数据库进行Blast比对,同时从GenBank数据库下载薯蓣属、木薯属和番薯属rpoC1序列,应用MEGA7.0软件计算种内和种间的(K2P)遗传距离,并构建邻接(NJ)系统聚类树。结果 7个山药样本rpoC1基因获得成功扩增和测序。7个山药rpoC1序列及GenBank下载9个薯蓣rpoC1序列和2个木薯番薯rpoC1序列分析显示,山药样本最大种内K2P遗传距离0.009远远小于山药与木薯番薯的种间K2P遗传距离0.104~0.118,同时也小于山药与盾叶薯蓣和穿龙薯蓣的种间K2P遗传距离0.026~0.035,构建的系统发育树显示山药与盾叶薯蓣和穿龙薯蓣、木薯和番薯单独聚为一类。结论 rpoC1序列可为食用山药物种鉴定提供新的分子鉴定方法。     

Pasting characteristics of fresh yams (Dioscorea spp.) as indicators of textural quality in a major food product – ‘pounded yam’

Low efficiency of available screening procedures constrains breeding and selection of yams (Dioscorea spp.) towards high textural quality of food products made from their tubers. This study was undertaken to determine the potential usefulness of pasting characteristics of fresh yams as rapid indicators of food textural quality in ‘pounded yam’, a staple food for millions of yam consumers, especially in West and Central Africa. Significant associations (P < 0.05) were found, through canonical correlation analysis, between pasting characteristics of fresh yams from six varieties, each, of Dioscorea rotundata and Dioscorea alata and the textural quality of pounded yam samples prepared from them. Good textural quality of pounded yam was associated with high peak viscosity, breakdown, final viscosity, holding strength and setback viscosity but with low pasting temperature in the fresh yam.     

A diet containing yam reduces the cognitive deterioration and brain lipid peroxidation in mice with senescence accelerated

The aim of this study was to evaluate the effect of a diet rich in yam tuber material [Dioscorea alata L. Var. purpurea (M.) Pouch.] on the learning and memory ability of 2‐month‐old male senescence accelerated mice (SAMP8). The mice were fed with three different diets for 12 weeks; a casein diet (control group) and either a casein diet supplemented with 10% lyophilized or with hot‐air dried yam. Results of passive and active shuttle avoidance tests showed the mice fed with the diet containing yam had significantly better learning and memory ability than the control group. The thiobarbituric acid‐reactive substances (TBARS) in the hippocampus of the group fed lyophilized yam were significantly lower than the control and also the group fed a diet containing hot‐air dried yam, whereas the spongy degeneration and the lipofuscin percentage tended to be lower but not significantly different. It was suggested that lyophilized yam was more effective than hot‐air dried yam in reducing the lipid peroxidation, brain pathological changes and the deterioration in the learning and memory ability in mice possibly because lyophilized yam contains more antioxidant compounds.