Nutritional and potential health benefits of konjac glucomannan,a promising polysaccharide of elephant foot yam,Amorphophallus konjac K. Koch: A review

Amorphophallus konjac (konjac) is one among the major vegetable (tuber) crops grown in Asian countries. In China and Japan, it has been used as food and a food additive for more than 1000 years. Over the last few decades, the purified konjac flour, commonly known as konjac glucomannan (KGM), a dietary fiber hydrocolloidal polysaccharide, has been introduced as a food additive as well as a dietary supplement in many Asian and European countries. The present article reviews the literature (up to January 2015) covering the development of various functional foods, food additives from KGM and their derivatives, Also, this review deals with global nutritional aspects and value added products of konjac corm. The bioprocessing techniques such as preparation, purification, and extraction of KGM from konjac flour and methods to improve quality of KGM are discussed.

Abbreviations: ¹³C NMR: carbon-13, nuclear magnetic resonance spectroscopy; CHD: coronary heart disease; CKF: crude konjac flour; CVD: cardiovascular disease; DA: degree of acetylation; DMSO: dimethyl sulfoxide; DOB: degree of branching; EC: European Commission; EFSA: European Food Safety Authority; EFY: elephant foot yam; FCC: Food Chemical Codex; FDA: Food and Drug Administration; GM: glucomannan; KG: konjac gel; KGM: konjac glucomannan; KGMOS: KGM octenyl succinate; KM: konjac mannan; OSA: octenyl succinic anhydride; PKF: purified konjac flour; SEM: scanning electron microscopy; USDA: United States Department of Agriculture; WHO: World Health Organization; WVP: water vapor permeability     

魔芋葡甘聚糖与瓜尔豆胶共混膜材料研究

魔芋葡甘聚糖与瓜尔豆胶共混后成膜,当魔芋胶与瓜尔豆胶共混浓度为1%,共混比例为60:40时,共混膜性能最佳。与未共混膜相比,共混膜的强度、抗水性、耐洗刷性、透明度、感官性能等各项性能显著提高。用红外光谱、X-射线和扫描电镜分析了膜的结构,阐明了结构和功能的关系,并对葡萄作了常温涂膜保鲜实验。结果表明,共混膜对果蔬有一定保鲜作用。     

Beneficial health characteristics of native and hydrolysed konjac (Amorphophallus konjac) glucomannan

The impact of ingesting glucomannans on health is not limited to colonic‐focused fermentation into short‐chain fatty acids (SCFAs), which might have some local health benefits; it also helps in treating disease states and enhancing the body's immune system, both within the gut and in/on other parts of the body. The local and systemic roles of hydrolysed glucomannans, especially konjac glucomannans, in the mouth, oesophagus, stomach, small intestine, large intestine, gut‐associated lymphoid tissue (GALT), skin and vagina, are highlighted. Therapeutic applications are discussed. © 2015 Society of Chemical Industry     

魔芋葡甘聚糖及其与大豆蛋白复合成膜的研究

对单一魔芋葡甘聚糖膜及其与大豆分离蛋白(SPI)复合膜的制备条件优化进行了研究。发现高 pH(>10)对阻隔性能不利,反应温度的提高和增塑剂的加入会分别导致膜的阻氧和阻湿性能下降,而与大豆分离蛋白的复合,则会明显地提高其阻隔特性。pH10、温度45℃、甘油含量1.5%、魔芋与大豆分离蛋白比值1∶1时制备的复合膜具有较好的阻隔性能。     

魔芋葡甘聚糖复合膜对迷你黄瓜的保鲜性研究

对魔芋葡甘聚糖及其与大豆分离蛋白、分子蒸馏单甘酯、硬脂酸复配成膜的工艺条件和对迷你黄瓜的保鲜性能进行了研究.实验确定的最佳配比及工艺条件为w(魔芋葡甘聚糖)=2.0%,w(单甘酯)=0.5%,w(硬脂酸)=0.5%,m(魔芋葡甘聚糖):m(大豆蛋白粉)=1:1,pH=9,溶胀温度为35℃.该复配膜对减少迷你黄瓜的失重率、抑制呼吸强度效果理想.     

The potential use of hydrolysed konjac glucomannan as a prebiotic

Konjac glucomannan hydrolysate was derived enzymatically from konjac flour under optimal conditions. A number of culture strains of lactobacilli and bifidobacteria were grown on De Man, Rogosa and Sharpe (MRS) media supplemented with the hydrolysate. This hydrolysate stimulated the growth of all strains examined. Colony sizes of those strains grown on konjac hydrolysate were significantly (P = 0.001) bigger than those grown on pectin or xylan hydrolysates. Bacterial growth profiles were also conducted on nutrient agar (MRS or modified MRS agar containing konjac hydrolysate) using single strains of lactobacilli or bifidobacteria (Lactobacillus acidophilus, Lactobacillus casei or Bifidobacterium adolescentis), single pathogen cultures (Escherichia coli or Listeria monocytogenes) or mixed bacterial cultures (from chicken breast extract). Although the growth of lactobacilli inhibited the growth of pathogens (single or mixed culture) the pathogens could not grow on the konjac hydrolysate as a sole carbon source. Microbial growth profiles using konjac hydrolysate or inulin in UHT milk were also investigated. The results showed that the numbers of colony forming units (cfu) obtained from milk containing the konjac hydrolysate were significantly (P = 0.01) higher than those containing inulin. It is suggested that the unique properties of konjac hydrolysate make it universally valuable as a prebiotic which can be applied to a wide range of foods, feeds and healthcare/pharmaceutical products. Copyright © 2007 Society of Chemical Industry     

浓硫酸法制备魔芋葡甘聚糖硫酸酯(KGMS)

以魔芋葡甘聚糖（KGM）为研究对象,采用浓硫酸法制备魔芋葡甘聚糖硫酸酯（KGMS）。控制浓硫酸与正丁醇总体积为10mL,并在单因素实验的基础上,选择浓硫酸与正丁醇体积比、反应时间和KGM质量为自变量,KGMS取代度为响应值,利用Box-Benhnken中心组合设计原理和响应面分析法,研究各自变量及其交互作用对取代度的影响,模拟得到回归方程的预测模型。确定最佳制备工艺为:浓硫酸与正丁醇体积比为3.22∶1、反应时间为33min、KGM质量为0.59g。在此条件下制备的KGMS的平均取代度为0.93。通过红外光谱分析表明,经过酯化后KGM在1257cm-1和814cm-1处形成新的吸收峰,为S=O和C-O-S键的特征吸收峰,说明KGM硫酸酯化成功,制备获得的产物为KGMS。      

疣柄魔芋淀粉理化及功能性质研究

为了探索一种新的淀粉资源,对疣柄魔芋淀粉的性质进行了研究。通过电子显微镜、激光粒度分析、X-衍射分析、红外光谱分析等分析手段,并以玉米淀粉和木薯淀粉进为比较,结果显示:疣柄魔芋淀粉淀粉颗粒呈多面体形,棱角较尖锐突出;其粒径小于木薯淀粉和玉米淀粉;结晶型为A-型,相对结晶度为37.4%;红外光谱吸收峰、吸收强度与木薯淀粉和玉米淀粉基本相同;凝胶强度、糊化起始温度和糊化热焓高于木薯淀粉和玉米淀粉;且其抗酶解性优于木薯淀粉和玉米淀粉。因此,疣柄魔芋淀粉是一种潜在的可被开发为抗性淀粉的新资源淀粉。     

铁棍山药粗多糖提取工艺条件研究

以水为提取剂,采用水煮醇沉法提取铁棍山药的山药多糖,以水提温度、料液比、浸提时间及乙醇体积分数4个影响因素,研究单因素对粗多糖得率的影响,L9(34)正交试验的结果表明,提取的优化工艺条件为提取温度90℃,提取时间2.5 h,乙醇体积分数75%,料液比1∶6(W∶V),粗多糖得率为6.77%,其中对山药粗多糖提取得率影响最大的因素是提取温度。     

紫山药多糖酶法提取工艺优化研究

采用正交实验优选紫山药多糖传统热水浸提法工艺参数,并在此基础上进行纤维素酶法提取紫山药多糖工艺参数研究,结果表明,传统水浸提法最佳工艺参数为温度80℃,提取时间160min,加水倍数60mL/g,粗多糖平均得率为5.65%;纤维素酶法提取最佳工艺参数为水提温度40℃、pH5、加酶量0.50%,粗多糖平均得率为8.51%,较热水浸提法提高了1.51倍。因此,纤维素酶法工艺更适用于紫山药多糖的提取。     

Physicochemical properties of konjac glucomannan extracted from konjac flour by a simple centrifugation process

Konjac flour (KF) contains main polysaccharide, konjac glucomannan (KGM) that is applied in various applications; however, extraction of KGM is complicated. A simple centrifugation process was used to extract KGM from KF and the influence of extraction temperatures on its physicochemical properties was determined. The centrifugation process was effective for the extraction of KGM and the results revealed two effective temperatures (35 °C and 75 °C). The extracted KGM was easy to grind. Ash and protein contents of the extracted KGM were clearly reduced, however the ash and protein contents of the KGM extracted at the high temperature (75 °C) were significantly lower than that extracted at the low temperature (35 °C), and thus proofs the extraction at the high temperature to be more effective. Furthermore, improved purities in both extracted glucomannan samples were attained in comparison to commercial KGM. While the yield percentages of the samples differed, no significant disparity in morphology and particle size was determined. Particles of both extracted KGM were comparable in shape and size. Moreover, the transparency of both extracted KGM solutions was higher than commercial KGM solution. These results suggested that the extraction temperature at 75 °C is effective in extraction KGM from KF.     

Effects of molecular characteristics of on konjac glucomannan glass transitions of potato amylose, amylopection and their mixtures

BACKGROUND: The purpose of this study was to explore further the functions of konjac glucomannan (KGM) in starch‐based foods. Experiments were carried out using the mixed amylose/amylopectin/KGM system as a model. High‐speed differential scanning calorimetry (hyper‐DSC) with the support of high‐performance size exclusion chromatography (HPSEC) equipped with multi‐angle laser light scattering (MALLS) and differential refractive index (RI), X‐ray diffractometry (XRD) and viscosimetry was used to investigate the effects of KGM on glass transition temperatures (T_gs) of mixtures with different amylose/amylopectin ratios. RESULTS: Hyper‐DSC results showed that the T_gs of amylose, amylopection and their mixtures decreased with increasing concentration of KGM. Based on the molecular characteristics of KGM, HPSEC‐MALLS‐RI, viscosimetry and XRD results showed that the molar masses of KGM ranged from 1.023 × 10⁶ to 1.329 × 10⁶ g mol^?1; the root mean square (RMS) radii were distributed from 110.5 to 129.6 nm, and M_w/M_n was 1.017. KGM was a linear molecule with random‐coil conformation in solution and the crystallinity was 0.00%. CONCLUSION: It is suggested that the addition of KGM has plasticizing effects on the structures of amylose and amylopectin, which can increase free volume and molecular movement of amylose and amylopectin chains, resulting in a decrease in their T_gs. Copyright © 2010 Society of Chemical Industry     

Anthocyanin-fortified konjac glucomannan/sodium alginate composite edible boba: characteristics of texture,microstructure, in vitro release behaviour and antioxidant capacity

Konjac glucomannan/sodium alginate composite edible boba (KGM/SA-boba) with good taste is very popular in China, and it is an outstanding carrier for health potential ingredients. In this work, KGM/SA-boba were fortified with 0.25, 0.50, 0.75 and 1.00% purple sweet potato anthocyanin (PSPA), then characterised by the water distribution, texture, microstructure, in vitro release property of PSPA and antioxidant capacity. LF-NMR analysis demonstrated that the free water of KGM/SA-boba could transfer to tightly bound water with the addition of PSPA that made it with better water-binding ability, higher springiness and lower hardness. And the results of SEM and rheology showed that PSPA could stabilise the microstructure of KGM/SA-boba by forming more amorphous regions and hydrogen bonds proved by the results of DSC and FT-IR. Furthermore, 50% of PSPA in PSPA-fortified KGM/SA-boba can be released at the first hour in a simulated gastrointestinal environment. And the scavenging capacity of DPPH and ABTS of the PSPA-fortified KGM/SA-boba after digestion was higher than that of PSPA alone. Generally, PSPA could improve the texture while KGM/SA-boba in turn would make PSPA more stable in the gastrointestinal digestive system.     

Effects of acid modification on physical properties of konjac glucomannan (KGM) films

Edible films prepared from partially acid-hydrolyzed konjac glucomannan (KGM) were characterised with respect to the influence of altered chain length and molecular weight distribution on water sorptive capacity (WSC), water vapour permeability (WVP), thermal, and tensile properties. Acid treatment produced films with higher WSC and WVP, and lower melting enthalpy than that of an untreated one. These effects were attributed to an increase in the number of shorter chains, which contributed to more active sites for moisture sorption but disfavoured the formation of junction zones. The elastic modulus (EM) and tensile strength (TS) increased initially with decreasing molecular weight and increasing polydispersity, and then decreased with further reduction in molecular weight. Conversely, tensile elongation (TE) exhibited the opposite trend.     

Characterisation of composite films made of konjac glucomannan (KGM), carboxymethyl cellulose (CMC) and lipid

Emulsion films prepared from konjac glucomannan (KGM), carboxymethylcellulose (CMC), with and without alkali (KOH), were characterised for selected properties such as morphological characteristics, water vapour permeability (WVP), water sorptive capacity and tensile properties. It was found that smaller lipid globules, with a homogeneous distribution, increased the apparent hydrophobicity and “tortuosity” of an emulsion film for water molecule transmission, thereby resulting in reduced WVP. This was achieved when alkaline deacetylated KGM and CMC were served as the base polymers for the emulsion, with the latter functioning as an emulsifier. Interactions between deacetylated KGM and CMC resulted in a stable emulsion.     

Effects of blanching, drying and extraction processes on the antioxidant activity of yam (Dioscorea alata)

The effects of blanching, drying and extraction processes on the antioxidant activities of one kind of Taiwanese yam peel, Darsan (Dioscorea alata), were investigated. The antioxidant measurements included total phenolic content, reducing power and α ,α‐diphenyl‐β‐pricryl‐hydrazyl (DPPH) radical‐scavenging activity. The 50% ethanolic, hot water and water extracts from the peel all had much higher antioxidant activities than those extracts from the flesh. Among three extraction methods, 50% ethanolic extraction resulted in the highest antioxidant activities in the peel, while hot water extraction was more appropriate for the flesh. Blanching by immersing the peel in 85 °C water for 30 s caused significant reductions in the antioxidant activities of all the extracts from the peel. Generally speaking, freeze‐dried peel maintained higher antioxidant activities than hot air‐dried peel.     

Effects of konjac glucomannan on physicochemical properties of myofibrillar protein and surimi gels from grass carp (Ctenopharyngodon idella)

The cryoprotective effect of konjac glucomannan (KGM) on myofibrillar protein from grass carp (Ctenopharyngodon idella) during frozen storage at −18 °C and the influence of five levels of KGM (0%, 0.5%, 1%, 1.5%, and 2%) on texture properties, water-holding capacity, and whiteness of grass carp surimi gels were investigated. KGM as a novel cryoprotectant could significantly mitigate the decrease in salt extractable protein (SEP), Ca²⁺-ATPase activity, and total sulphydryl and active sulphydryl contents of myofibrillar protein during frozen storage. KGM at the level of 1% showed the same good cryoprotective effect as a conventional cryoprotectant (10% sucrose–sorbitol, 1:1, w/w). As the levels of KGM increased, breaking force and deformation of grass carp surimi gels increased significantly. Water-holding properties of the surimi gels are improved with the increasing addition of KGM, but the whiteness decreased and the colour became darker. The optimum addition level of KGM was suggested to be 1%.     

超声对蔗糖共溶质场中大豆分离蛋白/魔芋胶共混体系流变及凝胶性质的影响

以大豆分离蛋白/魔芋胶(10.0%/0.3%)共混溶液体系为研究对象,研究了超声处理(0、10、20 min,475 W)及添加蔗糖共溶质(0%、10%、20%)对溶胶-凝胶转变过程流变性质及凝胶化速度(v_g)的影响,并分析了质构及微观结构的变化趋势。结果表明:未经超声处理时,随蔗糖共溶质浓度增加,可显著提升共混体系黏弹模量(G′)、凝胶化速率、硬度及黏附性(P0.05);未添加蔗糖条件下超声处理明显弱化了共混体系的v_g及G′,并降低了硬度及黏附性,伴随微观结构发生团块状聚集化;超声可抑制蔗糖共溶质提高共混体系凝胶强度的作用。