Food Chemistry 158 (2014) 171–176

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Food Chemistry

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A simple and feasible approach to purify konjac glucomannanfrom konjac flour – Temperature effect

http://dx.doi.org/10.1016/j.foodchem.2014.02.0930308-8146/� 2014 Elsevier Ltd. All rights reserved.

⇑ Corresponding author at: College of Food Science and Technology, HuazhongAgricultural University, China. Tel.: +86 27 63730040; fax: +86 27 87282966 (B. Li).

E-mail address: libinfood@mail.hzau.edu.cn (B. Li).

Wei Xu a,c, Sujuan Wang a, Ting Ye a, Weiping Jin a,c, Jinjin Liu a, Jieqiong Lei a, Bin Li a,c,⇑, Chao Wang ba College of Food Science and Technology, Huazhong Agricultural University, Hubei, Wuhan 430070, Chinab Research Center of Food Fermentation Engineering and Technology of Hubei, Hubei University of Technology, Wuhan 430068, Chinac Key Laboratory of Environment Correlative Dietology, Huazhong Agricultural University, Ministry of Education, China

a r t i c l e i n f o

Article history:Received 24 July 2013Received in revised form 17 February 2014Accepted 20 February 2014Available online 1 March 2014

Keywords:Konjac glucomannanExtractionRheological propertiesMorphologyKonjac flour

a b s t r a c t

A simple one-step purification process was provided to extract KGM from KF by phase separation. Theresults showed that appropriate temperature control was a key factor and the products were inodorous,colourless and of high purity at the optimal temperature 68 �C. In this purification, soluble sugar andstarch of extracted KGM were nearly clearly reduced and up to 95%, 80% (T68) of protein and ash wereremoved, respectively as compared with KF. Odour and transparency were improved 4 ranks and 30%,respectively. Besides, the gapp reached 42.30 Pa s and increased by 93.55% as compared, which could stayat a steady level for a week. Furthermore, morphology of extracted KGM displayed regular lamellar andwrinkling distribution for removed impurities. The temperature-controlled method not only enriches theknowledge of KGM purification but also has the potential to broaden the application of KGM.

� 2014 Elsevier Ltd. All rights reserved.

1. Introduction

Konjac glucomannan (KGM), one of the richest natural polysac-charide, is derived from the tubers of Amorphophallus konjac (Fang& Wu, 2004). It is the main constituent in konjac flour (KF) and hasbeen recognized as GRAS since 1994 (Khanna & Tester, 2006). As akind of non-caloric food, KGM had been applied in many kinds offood as high quality dietary fiber, thickening agent, and fat replacer(Charoenrein, Tatirat, Rengsutthi, & Thongngam, 2011; Jimenez-Colmenero, Cofrades, Herrero, Solas, & Ruiz-Capillas, 2013).Besides, KGM is also an attractive candidate for the preparationof composite materials, biodegradable film and controlled releasematrix in medicine, cosmetics and fine chemical fields (Harding,Smith, Lawson, Gahler, & Wood, 2011; Pang et al., 2012). However,commercial KF is usually light-coloured with fish-like smell andslightly harsh taste (Chua, Baldwin, Hocking, & Chan, 2010). Itspoor qualities, including low viscosity and poor transparency, usu-ally could not satisfy the demand of food and cosmetic production.Many scholars constantly purified KF before experimentation(Chen, Liu, & Zhuo, 2005; Wu et al., 2012). Therefore, it is practi-cally important to develop a convenient and economical methodto obtain KF with high purity, viscosity, and transparency.

As we know, KF is usually separated after the konjac tuberwashed, sliced, dried and ground. The content of KGM in KF usu-ally ranged from 50% to 70% (Tatirat & Charoenrein, 2011). Themain impurities trapped in KGM particles usually derived fromthe tissue space (Chua et al., 2010). Due to the well processingcharacteristics of KGM, lots of scholars focus on its applicationand only limited researchers put their energy in extractive tech-nique. Washing by water, ethanol, and benzene-ethanol solutionis often used to remove insoluble impurities (Chen et al., 2005;Zhu, Uhl, Morgan, & Wilkie, 2001). While their disadvantageand inconvenience limit their further applications (Yan, Wang, &Liu, 2006). Recently, high-energy centrifugation (1500g) methodand combining boiling water with ethanol washing were alsoexploited to isolate KGM (Jianrong, Donghua, Srzednicki,Kanlayanarat, & Borompichaichartkul, 2008; Tatirat & Charoen-rein, 2011). The results testified it was an effective and high yieldextraction approach.

Starch is the main impurity that seriously affects the purity andquality of KGM, such as reducing viscosity and increasing turbidity(Yoshimura, Takaya, & Nishinari, 1998). Additionally, starchmolecules usually interact with KGM and are difficult to be puri-fied for its low solubility in mild condition. However, gelatinizationbehaviour efficiently boosts its solubility. KGM molecules possessbetter swelling ability and become insoluble, whereas the impuri-ties could dissolve in ethanol/water system. Taking all into consid-eration, phase separation was explored to apply in KF purification.

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172 W. Xu et al. / Food Chemistry 158 (2014) 171–176

During this process, the impurities could be removed by the tem-perature effect.

To the best of our knowledge, the preparation of refined KGMby ethanol washing with temperature controlled has barely beenreported before. In this study, a simple, straightforward extractionroute in ethanol/water system was developed. The samples wereinvestigated for compositions, colour, transparency, rheologicalmeasurement and morphology to evaluate the refining effects.The results show the method is potential to purify and improvethe qualities of KF.

2. Materials and methods

2.1. Materials

KF samples were provided friendly by Hubei Yizhi Konjac Indus-try Co. Ltd. (Hubei, China). All chemicals used in this study were ofanalytical grade reagents (Sinopharm Chemical Reagent Co. Ltd.,Shanghai, China) and used without further purification.

2.2. Preparation of purified KGM via temperature controlled

KF was dissolved in 40% (v/v) ethanol solution with feed liquidratio of 1:6. While stirring, the mixture was heated at a series oftemperature (28, 38, 48, 58, 68 and 78 �C) and refluxed for 4 h.After purifying, filtering, washing with 40% ethanol solution atthe pre-temperature, the precipitates were vacuum dried at80 �C. By controlling the temperature, a series of KGM productswith different characteristic were available and coded as T28,T38, T48, T58, T68, T78, and the control sample was coded as T.

2.3. Composition of KF flour

Different kinds of KF were analyzed for the contents of mois-ture, ash, starch, protein, and residual sugar according to AOACmethods (Williams, 1984). Moisture content was measured at105 �C, ash content was performed at 500 �C, starch was measuredby acidic hydrolysis method, and protein was measured by theKjeldhal method, while the residual sugars were measured bythe DNS method. KGM and its dry basis content were measuredas our previous reported (Li & Xie, 2002; Liu, Wang, Xia, & Li, 2005).

2.4. Transparency and odor evaluation

Transparency of sample solutions were analyzed by the modi-fied method of Kobayashi using 722E visible-infrared spectrometer(Shanghai spectrum instrument Co. Ltd.). Briefly, 1.0% (w/v) KGMsolutions were prepared at 25 �C and the transparency was deter-mined at 500 nm against a distilled water blank after viscosityreaching the maximum (Kobayashi, Tsujihata, Hibi, & Tsukamoto,2002).

Because commercial KF is light-coloured with fish-like smell,osphretic evaluation was carried out by a seven-member panel.Each panel member evaluated each sample using a 0–5 point scale(0 indicates no fish-like smell; 1 imperceptible, 2 light, 3 moderate,4 great, 5 extreme).

2.5. Rheological measurements

Apparent viscosity and its variation were measured by NDJ-8SDigital display viscometer (Shanghai spectrum instrument co.Ltd.). 1.0% (w/v) KF solution was prepared with stirring for 1 h at25 �C. Apparent viscosity was determined after each 0.5 h in tripleusing NO.4 rotor at 12 r min�1. Viscosity stability was also evalu-ated by determining its variation for 1 week.

Rheological measurements were performed using an AR2000exrheometer (TA, UK) with a parallel plate (40 mm in diameter,1.0 mm). In order to avoid the destruction of the structure beingformed, a linear viscoelastic regime is needed to determine bymeasuring steady rheological viscosity. The data was collectedwith the shear rate ranging from 0–150 s�1 at 25 �C. Dynamic vis-coelastic parameters, shear storage modulus (G0) and loss modulus(G00) as functions of frequency and temperature were investigatedwith stress 0.2%. For each measurement, the sample was poureddirectly onto the lower parallel plate, which had been kept at eachmeasurement temperature without pre-shearing or oscillating. Thedynamic temperature sweep measurements were conducted from25 to 90 �C with heating and cooling rates of 2 �C min�1. While fre-quent sweep measurements were carried out ranging between0.01 and 100 rad s�1 at constant frequency (0.1 Hz) and strainamplitude (0.2%).

2.6. Morphology observation

Morphology of KF with different temperature disposed wasinvestigated using a scanning electron microscope (JSM-6390LV,Jeol, Japan). The dried samples were coated with gold–palladiumbefore observed under the microscope. The micro-appearance ofKF with the magnification of 100, 2000, 8000 could be easilyavailable.

3. Results and discussion

3.1. Composition analysis

From the application aspect, ideal KF should possess high purityproperties. KF, produced by the traditional method, generally con-tains protein and starch, which seriously affect its quality. In thisregard, we conducted the study of the component of T, T28, T38,T48, T58, T68 and T78 and the results were displayed in Table 1.The results showed that the KGM content of all refined groups in-creased companied with impurities decreased as compared with T.

Protein, soluble sugar, starch and ash could be effectively wipedout and shared the same trends during thermal process in ethanol/water system. However, it was interesting that protein and solublesugar content shared a sharp decrease as the temperature reached38 �C and then turned to be constant. That indicated protein andsoluble sugar were easily dissolved in 40% (v/v) ethanol solutionat 38 �C for 4 h. Due to the complex structure and swelling ability,starch solubility was barely affected at low temperature. However,at high temperature (48 �C), starch gelatinization occurred and itssolubility enhanced. While the major (77–83%) starch has been re-moved when the temperature is with 28–38 �C, and increasingtemperature above 48 �C could further remove the tiny amountof residual starch. This phenomenon may be cause by the interac-tion between konjac and starch. The hydrogen bond interactionwas the main interaction, besides physical package also existed.Improving temperature contributed to destroy the interaction be-tween konjac and starch. It was noticed that the gelatinizationpoint of starch in KF was lower than other kinds of starch(>60 �C). The phenomenon may be caused by various starch struc-tures and the interactions between starch and KGM. Ash, the totalamount of inorganic composition, is a crucial parameter for evalu-ating quality. In the food production, including KGM, ash is essen-tial to be kept in a controlled range, otherwise the material may beevaluated contaminated or disqualified. Increasing extraction tem-perature is hopeful to decrease ash content.

As Table 1 showed, soluble sugar and starch of extracted KGM(T68) were nearly removed and protein and ash were reduced95%, 80%, respectively as compared with KF. It was obvious that

Table 1Main composition of KGM samples (%).

Samples Protein Solublesugar

Starch Ash KGM* Transparency Odour

T 3.67 2.47 8.89 4.26 74.13 28.1 5T28 0.18 0.02 2.02 1.16 88.05 48.8 2T38 0.09 0.01 1.53 1.07 86.38 47.8 2T48 0.12 – 0.02 0.85 88.72 49.1 1T58 0.11 – 0.02 0.92 88.48 46.6 1T68 0.18 0.01 0.01 0.84 90.63 58.3 1T78 0.19 0.01 0.01 0.84 89.11 62.2 1

– No available data.* Dry basis content.

W. Xu et al. / Food Chemistry 158 (2014) 171–176 173

increasing temperature exerted an important role in shaking offthe existing 2.02% starch (T28). Therefore, temperature effect wasfavourable to improve the KGM purity and the maximum augmentreached 15%. The results were in agreement with previous study(Tatirat & Charoenrein, 2011). As the schematic demonstrated inFig. 1, the purification process could be divided into two parts.Firstly, KF swelled in the ethanol/water system and some easilydissolved impurities were removed, such as soluble sugar and par-tial proteins. Soluble sugar was clearly removed and about 95%proteins were also eliminated in swelling process. In the secondstage, heating process leads to starch gelatinization and water-sol-ubility. At the same time, 7.5% ash was further removed with thehelp of temperature. Swelling and heating process occurred atthe same and exerted a mutual interaction in the temperature con-trolled purification. The corporate effects were beneficial to purifi-cation and phase separation.

3.2. Transparency and odor evaluation

To elucidate the impacts of extraction temperature on sensoryqualities of the samples, transparency and odor evaluation ofKGM solution were determined (Table 1). The transparency ofT68 and T78 was strongly improved by about 30.20%, 34.10%,respectively as compared with the transparency of T, whereas in-creased by 10.5% and 13.4% as compared without heating (T28).The transparency improvement was contributed to eliminatingthe purities during the swelling and heating process in the etha-nol/water system, especially for starch and protein.

For commercial KF, the fishy smell limits its application in foodindustry and the representative substances are volatile compoundsproduced in the process, such as amine, phenol, alcohol, hydrocar-bon, and so on. As the odor evaluation shown, fishy smell reducedobviously after purification. The initial flour (T) had strong fishysmell, while after purified above 48 �C for 4 h refined KF (T48,T58, T68, T78) nearly exhibited no fishy smell. As compared withT28, odor evaluation was improved by two grades. The resultshad the same effect with previous studied using low concentrationethanol/water system to eliminate the odor (Jianrong et al., 2008).

Fig. 1. Schematic diagram illu

3.3. Rheological measurement

3.3.1. Apparent viscosity and stabilityFig. 2a showed the apparent viscosity (gapp) of 1.0% (w/v) KF

solution during swelling as a function of time. The gapp increasedin a typically time-dependent and heating process-dependent pat-tern. Specifically, the gapp of purified KF was much higher than thatof KF (T). Especially for T68, the gapp was 42.30 Pa s and increasedby 93.55% as compared. The increase of gapp was resulted from theKGM purification (Table 1). After dissolved for 2 h, the gapp reachedthe maximum and then decreased gradually with the storage time.However, the gapp of T decreased significantly afterwards, whilethe purified KGM (T28, T38, T48, T58, T68 and T78) possessed bet-ter viscosity stability. It also verified temperature effect was help-ful to improve viscosity as compared with un-disposed samples(T28), especially for T68 and T78.

Instability of KGM hydrosol is a common shortage and limits itsfurther application. Viscosity of KGM solution normally declined infurther 2 h. In order to investigate the effect of thermal control pro-cess on the viscosity stability, storage time was taken as a functionof gapp for further study and the results were shown in Fig. 2b. Ascan be seen, the gapp of non-disposed KF exhibited a decreasingtrend as time extended. However, the viscosity of purified KFexhibited a maximum value rapidly and then kept at a steady levelfor a week, which indicated that the viscosity stability of refined KFin aqueous solution was greatly improved. Besides, higher temper-ature disposed groups obtained a better stability than that of roomtemperature treated sample (T28). It might attribute to the furtherreducing of impurities, which plays an important role in promotingcrystal formation and boosting assembly and flocculation for KGMmolecule.

3.3.2. Steady flow propertiesThe viscosity and stress as functions of the shear rate were con-

ducted in the range of 0.01–300 rad s�1 for all samples. A typicalnon-Newtonian pseudoplastic behaviour was exhibited for allsamples. From Fig. 2c, it was observed that all samples showed re-marked shear thinning phenomena and the viscosities of disposedKF increased with different increscent as compared with the non-disposed sample. T48 and T68 were observed to exhibit the highestviscosity and thixotropic behaviour, followed by T38 and T78. Theroom temperature disposed sample (T28) possessed a lower vis-cosity. The reason could be divided into two parts. Firstly, due tothe purity affection, increasing purity was beneficial to improvethe viscosity. The other may be the temperature affection. Thehigher temperature in the ethanol/water system, the hydrophobicinteraction between KGM molecule and solution could much morestrengthen and had greater influences on characteristics of KGM,including viscosity. This shear-thinning behaviour of refined KFsolution could be explained by breaking of an entangled polysac-charide molecule network during shearing, as represented by theprevious report (Bhandari, Singhal, & Kale, 2002). Briefly, in a rangeof low shear rate (0.016 rad s�1), viscosity stays nearly unchanged

strating KF purification.

Fig. 2. Apparent viscosity and steady flow curves of 1.0% KGM samples solution. The apparent viscosity measured for each 0.5 h (a) and every day (b) were conducted at 25 �C.The viscosity (c) and stress (d) as functions of the shear rate were conducted in the range of 0.01–300 s�1 at 25 �C.

Fig. 3. K and n value of 1.0% KGM samples solution K is the consistency index. n isthe flow behaviour index.

174 W. Xu et al. / Food Chemistry 158 (2014) 171–176

with rate increasing. While at higher shear rate, the rate of disen-tangle of KGM molecule became greater than the rate of re-entan-glement and the effect could be amplified with increasing shearrate. As a result, the intermolecular resistance to flow reducedand a lower apparent viscosity appeared.

The shear stress charged with increasing shear rate also demon-strated the extent of molecular assembling and winding of dis-posed flour were much higher than that of the original one (T).As Fig. 2d shown, it required a much higher shear stress for thepurified KGM at the same shear rate. It was interesting that T48and T68 shared the same trend and both the shear stress had apeak at about 1 s�1, and then exhibited an increasing trend as be-fore. It may be caused by structure-zone formed between molecu-lar. The Power Law s = KDn (Chao et al., 2012; Herranz, Borderias,Solas, & Tovar, 2012) was widely used to evaluate the equality ofKGM and the parameters K and n were displayed in Fig. 3 Indexn is a measure of the pseudoplastic flow and K is a measure ofthe liquid viscosity. It is believed that KGM process better qualitywhen n is small and K becomes large. So it was clear that all dis-posed samples had greatly improved in the liquid properties. Tak-ing both n and K into consideration, T48 and T68 had moreexcellent qualities. As compared with the sample of room temper-ature disposed (T28), n and K of T68 possessed a decline of 0.11 andan increase of 7.84%, respectively.

3.3.3. Dynamic viscoelastic propertiesFig. 4a showed frequency dependence of 1.0% (w/v) KGM solu-

tion with different temperature disposing at 25 �C. All KGM sam-ples solution exhibited a typical concentrated solution bondingphenomenon (Chao et al., 2012). The G00 value was larger than thatof G0 and they both increased with frequency increasing at lowerfrequencies, performing the dominant liquid characteristic, mean-while the behaviour approached to that of solid-like materials athigher frequencies. The obvious change was that G0 turn larger

than G00 and they both displayed frequency independent. Thiswas attributed to the effect of entanglement network betweenKGM molecules as mentioned above. Briefly, there was adequatetime to entangle during the oscillation course at the low frequen-cies, while at higher frequencies, the oscillate rate exceeded thetime range of molecular entanglements benefiting to form a tem-porary network structure. The properties of KGM were similar withmany other polysaccharide, such as gellan, starch (Kim & Yoo,2011), gellan and blended KGM (Mei et al., 2012). The shift of thecrossover of G0 and G00 to a lower value conformed that different ex-tract temperature exerted a significant impact on the temporarynet work structure of KGM. As Fig. 4a showed, the crossover valueof T68 was 1.0 rad s�1 and the T was 5.0 rad s�1. The reducingparameter indicated an enhancement among the structures ofKGM chains.

Fig. 4. Frequency (a) and temperature (b) dependence of G0 (j) and G00 ( ) for 1.0% KGM solution at 25 �C.

Fig. 5. Scanning electron photographs of samples (a) KF, (b) T68, the magnification was 100�, 2000�, 8000� and the scale bar was 100, 10, 2 lm, respectively.

W. Xu et al. / Food Chemistry 158 (2014) 171–176 175

In previous study, both G0 and G00 of KGM dropped with temper-ature raising due to weakening interactions between water andpolymers, such as hydrogen bonding (Du, Li, Chen, & Li, 2012).However, both modulus of T had an inflexion at 65 �C. That proba-bly caused by the gelatinization behaviour of starch contained inKGM. T28, T48, and T68 were inclined to achieve crossover at85 �C. As Fig. 4b showed, the available G0 and G00 of the disposedsample (T28, T48, T68) were higher than the value of T, which indi-cated that total modulus was enhanced and the net-structure ofKGM formed easily after thermal control process. Additionally,for further purification, both modulus (G0 and G00) obviously in-creased with raising temperature as compared with T28.

3.4. Morphology analysis

The SEM images were obtained to characterize the microstruc-ture of the refined KF (T68) and KF and the results were presentedin Fig. 5. It was obvious that raw KF particle was round and pro-cessed coarse surface without obvious wrinkle. Morphology of KFshowed good agreement with the results of Tatirat (Tatirat & Cha-roenrein, 2011). Additionally, the surface was in a cluttering state

with particles at high magnification (8000�) (Fig. 5a). Whereasthe surface of refined KF became smooth with much fewer parti-cles. Local magnification showed the appearance of KGM particlesdisplayed regular lamellar and wrinkling distribution (Fig. 5b). Thecluttering particles may be the impurities trapped in the surface ofKGM, including starch, protein and soluble sugar. With the help ofethanol aqueous solution and thermal effect, the impurities at-tached to surface could be removed.

4. Conclusions

Based on the magnified solubility differences, phase separationwas used to purify KF by ethanol solution washing with controlledtemperature effect. KGM with 90% purity, nearly no fishy smell,high transparency and high viscosity could be easily obtained byadjusting the extraction temperature. Refined KF produced at68 �C tended to possess viscosity of 42.30 Pa s within severalweeks. SEM results also verified the purification from the appear-ance of KGM particles. It is obvious that controlling the disposaltemperature is a simple method to purify KGM from KF, which

176 W. Xu et al. / Food Chemistry 158 (2014) 171–176

has potential to purify KF and promote its applications in foodfields.

Acknowledgements

This work was financially supported by the National NaturalScience Foundation of China (Grant No. 31371841). The authorsgreatly thank colleagues of Key Laboratory of Environment Correl-ative Dietology of Huazhong Agricultural University for offeringmany conveniences.

References

Bhandari, P. N., Singhal, R., & Kale, D. (2002). Effect of succinylation on therheological profile of starch pastes. Carbohydrate Polymers, 47(4), 365–371.

Chao, W., Mei, X., Wen-ping, L., Pei, Q., Yuan-yuan, G., & Dong-sheng, L. (2012).Study on rheological behavior of konjac glucomannan. Physics Procedia, 33,25–30.

Charoenrein, S., Tatirat, O., Rengsutthi, K., & Thongngam, M. (2011). Effect of konjacglucomannan on syneresis, textural properties and the microstructure of frozenrice starch gels. Carbohydrate Polymers, 83(1), 291–296.

Chen, L. G., Liu, Z. L., & Zhuo, R. X. (2005). Synthesis and properties of degradablehydrogels of konjac glucomannan grafted acrylic acid for colon-specific drugdelivery. Polymer, 46(16), 6274–6281.

Chua, M., Baldwin, T. C., Hocking, T. J., & Chan, K. (2010). Traditional uses andpotential health benefits of Amorphophallus konjac K. Koch ex NEBr. Journal ofEthnopharmacology, 128(2), 268–278.

Du, X., Li, J., Chen, J., & Li, B. (2012). Effect of degree of deacetylation onphysicochemical and gelation properties of konjac glucomannan. Food ResearchInternational, 46(1), 270–278.

Fang, W., & Wu, P. (2004). Variations of konjac glucomannan (KGM) fromAmorphophallus konjac and its refined powder in China. Food Hydrocolloids,18(1), 167–170.

Harding, S. E., Smith, I. H., Lawson, C. J., Gahler, R. J., & Wood, S. (2011). Studies onmacromolecular interactions in ternary mixtures of konjac glucomannan,xanthan gum and sodium alginate. Carbohydrate Polymers, 83(2), 329–338.

Herranz, B., Borderias, A. J., Solas, M. T., & Tovar, C. A. (2012). Influence ofmeasurement temperature on the rheological and microstructural properties ofglucomannan gels with different thermal histories. Food Research International,48, 885–892.

Jianrong, Z., Donghua, Z., Srzednicki, G., Kanlayanarat, S., & Borompichaichartkul, C.(2008). A simplified method of purifying konjac glucomannan. In Asia PacificSymposium on Assuring Quality and Safety of Agri-Foods 837 (pp. 345–350).

Jimenez-Colmenero, F., Cofrades, S., Herrero, A., Solas, M., & Ruiz-Capillas, C. (2013).Konjac gel for use as potential fat analogue for healthier meat productdevelopment: Effect of chilled and frozen storage. Food Hydrocolloids, 30(1),351–357.

Khanna, S., & Tester, R. F. (2006). Influence of purified konjac glucomannan on thegelatinisation and retrogradation properties of maize and potato starches. FoodHydrocolloids, 20(5), 567–576.

Kim, W., & Yoo, B. (2011). Rheological and thermal effects of galactomannanaddition to acorn starch paste. LWT – Food Science and Technology, 44(3),759–764.

Kobayashi, S., Tsujihata, S., Hibi, N., & Tsukamoto, Y. (2002). Preparation andrheological characterization of carboxymethyl konjac glucomannan. FoodHydrocolloids, 16(4), 289–294.

Li, B., & Xie, B. (2002). Study on the gelatin mechanism of konjac glucomannans.Scientia Agricultura Sinica, 35(11), 1411–1415.

Liu, T., Wang, Y., Xia, J., & Li, B. (2005). Influence of purification method on thestructure and properties of konjac gluconannan. Chemistry & Industry of ForestProducts, 3, 019.

Mei, T., Xu, X., Li, B., Li, J., Cui, B., Zhou, B., et al. (2012). Synergistic interaction ofkonjac glucomannan and gellan gum investigated by rheology and textureanalysis. Journal of Applied Polymer Science, 125(2), 1363–1370.

Pang, L., Zhang, C., Liu, D. H., Zhong, C. L., Luo, X. G., & Lin, X. Y. (2012). Mesoscalesimulation of drug molecules distribution in the matrix of konjac glucomannan(KGM) at varying drug concentrations. Key Engineering Materials, 501, 202–207.

Tatirat, O., & Charoenrein, S. (2011). Physicochemical properties of konjacglucomannan extracted from konjac flour by a simple centrifugation process.LWT – Food Science and Technology, 44(10), 2059–2063.

Williams, S. (1984). Official methods of analysis of the Association of Official AnalyticalChemists. (Vol. ed. 14).

Wu, C., Wen, C., Wang, X., Fan, L., Deng, R., & Pang, J. (2012). Structuralcharacterization and properties of konjac glucomannan/curdlan blend films.Carbohydrate Polymers, 89(2), 497–503.

Yan, H., Wang, Z., & Liu, H. (2006). Three kinds of methods in using phosphoric acidfor purifying konjac glucan-mannan [J]. Hubei Agricultural Sciences, 3, 043.

Yoshimura, M., Takaya, T., & Nishinari, K. (1998). Rheological studies on mixtures ofcorn starch and konjac-glucomannan. Carbohydrate Polymers, 35(1), 71–79.

Zhu, J., Uhl, F. M., Morgan, A. B., & Wilkie, C. A. (2001). Studies on the mechanism bywhich the formation of nanocomposites enhances thermal stability. Chemistryof Materials, 13(12), 4649–4654.

http://refhub.elsevier.com/S0308-8146(14)00278-7/h0010http://refhub.elsevier.com/S0308-8146(14)00278-7/h0010http://refhub.elsevier.com/S0308-8146(14)00278-7/h0015http://refhub.elsevier.com/S0308-8146(14)00278-7/h0015http://refhub.elsevier.com/S0308-8146(14)00278-7/h0015http://refhub.elsevier.com/S0308-8146(14)00278-7/h0020http://refhub.elsevier.com/S0308-8146(14)00278-7/h0020http://refhub.elsevier.com/S0308-8146(14)00278-7/h0020http://refhub.elsevier.com/S0308-8146(14)00278-7/h0025http://refhub.elsevier.com/S0308-8146(14)00278-7/h0025http://refhub.elsevier.com/S0308-8146(14)00278-7/h0025http://refhub.elsevier.com/S0308-8146(14)00278-7/h0030http://refhub.elsevier.com/S0308-8146(14)00278-7/h0030http://refhub.elsevier.com/S0308-8146(14)00278-7/h0030http://refhub.elsevier.com/S0308-8146(14)00278-7/h0035http://refhub.elsevier.com/S0308-8146(14)00278-7/h0035http://refhub.elsevier.com/S0308-8146(14)00278-7/h0035http://refhub.elsevier.com/S0308-8146(14)00278-7/h0040http://refhub.elsevier.com/S0308-8146(14)00278-7/h0040http://refhub.elsevier.com/S0308-8146(14)00278-7/h0040http://refhub.elsevier.com/S0308-8146(14)00278-7/h0045http://refhub.elsevier.com/S0308-8146(14)00278-7/h0045http://refhub.elsevier.com/S0308-8146(14)00278-7/h0045http://refhub.elsevier.com/S0308-8146(14)00278-7/h0050http://refhub.elsevier.com/S0308-8146(14)00278-7/h0050http://refhub.elsevier.com/S0308-8146(14)00278-7/h0050http://refhub.elsevier.com/S0308-8146(14)00278-7/h0050http://refhub.elsevier.com/S0308-8146(14)00278-7/h0060http://refhub.elsevier.com/S0308-8146(14)00278-7/h0060http://refhub.elsevier.com/S0308-8146(14)00278-7/h0060http://refhub.elsevier.com/S0308-8146(14)00278-7/h0060http://refhub.elsevier.com/S0308-8146(14)00278-7/h0065http://refhub.elsevier.com/S0308-8146(14)00278-7/h0065http://refhub.elsevier.com/S0308-8146(14)00278-7/h0065http://refhub.elsevier.com/S0308-8146(14)00278-7/h0070http://refhub.elsevier.com/S0308-8146(14)00278-7/h0070http://refhub.elsevier.com/S0308-8146(14)00278-7/h0070http://refhub.elsevier.com/S0308-8146(14)00278-7/h0075http://refhub.elsevier.com/S0308-8146(14)00278-7/h0075http://refhub.elsevier.com/S0308-8146(14)00278-7/h0075http://refhub.elsevier.com/S0308-8146(14)00278-7/h0080http://refhub.elsevier.com/S0308-8146(14)00278-7/h0080http://refhub.elsevier.com/S0308-8146(14)00278-7/h0090http://refhub.elsevier.com/S0308-8146(14)00278-7/h0090http://refhub.elsevier.com/S0308-8146(14)00278-7/h0090http://refhub.elsevier.com/S0308-8146(14)00278-7/h0095http://refhub.elsevier.com/S0308-8146(14)00278-7/h0095http://refhub.elsevier.com/S0308-8146(14)00278-7/h0095http://refhub.elsevier.com/S0308-8146(14)00278-7/h0100http://refhub.elsevier.com/S0308-8146(14)00278-7/h0100http://refhub.elsevier.com/S0308-8146(14)00278-7/h0100http://refhub.elsevier.com/S0308-8146(14)00278-7/h0105http://refhub.elsevier.com/S0308-8146(14)00278-7/h0105http://refhub.elsevier.com/S0308-8146(14)00278-7/h0105http://refhub.elsevier.com/S0308-8146(14)00278-7/h0120http://refhub.elsevier.com/S0308-8146(14)00278-7/h0120http://refhub.elsevier.com/S0308-8146(14)00278-7/h0120http://refhub.elsevier.com/S0308-8146(14)00278-7/h0125http://refhub.elsevier.com/S0308-8146(14)00278-7/h0125http://refhub.elsevier.com/S0308-8146(14)00278-7/h0130http://refhub.elsevier.com/S0308-8146(14)00278-7/h0130http://refhub.elsevier.com/S0308-8146(14)00278-7/h0135http://refhub.elsevier.com/S0308-8146(14)00278-7/h0135http://refhub.elsevier.com/S0308-8146(14)00278-7/h0135

A simple and feasible approach to purify konjac glucomannan from konjac flour – Temperature effect1 Introduction2 Materials and methods2.1 Materials2.2 Preparation of purified KGM via temperature controlled2.3 Composition of KF flour2.4 Transparency and odor evaluation2.5 Rheological measurements2.6 Morphology observation

3 Results and discussion3.1 Composition analysis3.2 Transparency and odor evaluation3.3 Rheological measurement3.3.1 Apparent viscosity and stability3.3.2 Steady flow properties3.3.3 Dynamic viscoelastic properties

3.4 Morphology analysis

4 ConclusionsAcknowledgementsReferences