Industrial Crops and Products 16 (2002) 11–21

Edible canna (Canna edulis) as a complementary starchsource to cassava for the starch industry

Kuakoon Piyachomkwan a, Sunee Chotineeranat a, Chukiet Kijkhunasatian a,Ratchata Tonwitowat b, Siripatr Prammanee c, Christopher G. Oates d,

Klanarong Sriroth e,*a Cassa�a and Starch Technology Research Unit, National Center for Genetic Engineering and Biotechnology (BIOTEC),

Bangkok, Thailandb Plant Science Di�ision, Rajamangala Institute of Technology, Pathumtani, Thailand

c Faculty of Liberal Arts and Science, Kasetsart Un�iersity, Bangkok, Thailandd Agro Food Resources (Thailand) Co., Ltd., Bangkok, Thailand

e Department of Biotechnology, Faculty of Agro-Industry, Kasetsart Uni�ersity, Jatujak, Bangkok 10900, Thailand

Accepted 19 December 2001

Abstract

Edible canna (Canna edulis Ker) as an alternative starch source was evaluated on the basis of genetic characteristics,agronomic traits and starch properties. Four canna varieties indigenous to Thailand were examined includingThai-green, Japanese-green, Thai-purple and Chinese-purple and compared with cassava (Manihot esculenta Crantz).Using the Random Amplified Polymorphic DNA (RAPD) technique employing ten 10-base primers, four primersimplied that at least three types of canna including Thai-green, Japanese-green and Thai/Chinese-purple existed andcorresponded to plant characteristics as identified by flower, stem, leaf and rhizome colors. Despite geneticdiversification, starch properties were not variable. All four varieties produced 30.4–38.4 tonne/ha of rhizomes withstarch content about 13% (wet basis). Starch yields of canna (4.1–4.9 tonnes/ha) were comparatively lower thancassava (6.5 tonnes/ha). The starches were characterized by giant granules (10–80 �m), and compared with cassavastarch pastes had a higher peak viscosity (930–1060 BU for canna starches and 815 BU for cassava starch), occurringat a higher temperature. Pastes of canna starch were more stable and when cooled, viscosity increased to 1800 BU.Gelatinized pastes of canna starches also rapidly formed good gels on cooling. It is evident that edible canna providesstarches with very attractive properties and totally different from cassava and is the greatest promise for the new basestarch to be employed complementarily with cassava starch. © 2002 Published by Elsevier Science B.V.

Keywords: Canna; Cassava; Variety; Starch

www.elsevier.com/locate/indcrop

1. Introduction

Starches have a wide range of food and non-food applications. The inherent functional diver-

* Corresponding author. Tel.: +662-9405634; fax: +662-9405634.

E-mail address: aapkrs@ku.ac.th (K. Sriroth).

0926-6690/02/$ - see front matter © 2002 Published by Elsevier Science B.V.

PII: S0 926 -6690 (02 )00003 -1

K. Piyachomkwan et al. / Industrial Crops and Products 16 (2002) 11–2112

sity of materials extracted from different biologi-cal sources adds to the range of applications.However, commercial starch sources are limitedto a few crops, which are further restricted withingeographic regions to one or two crops. Impor-tant starch sources are cereals such as corn (Zeamays L.) and wheat (Triticum spp.) in NorthAmerica; rice (Oryza sati�a L.) in Asia; roots andtubers such as potato (Solanum spp.) in Europeand cassava (Manihot esculenta Crantz) in Asia,Latin America and Africa. The portfolio of com-mercial sources does not represent the entire spec-trum of potential starch functionality. Novelsources include roots and tubers such as ahipa(Pachyrhizus ahipa), arracacha (Arracacia xanth-orrhiza), yam (Dioscorea spp.), arrowroot(Maranta arundinacea), yacon (Smallanthussonchifolius), sweet potato (Ipomoea batatas) andedible canna (Canna edulis Ker). Opportunitiesfor improving the potential value, and in turnproduction, of these crops are possible if theirutilization can be expanded, such as a source ofindustrial raw material of starch production.Studies supporting utilization should consider im-proving production, and for down-stream pro-cesses characterizing this raw material in terms ofstarch properties. Expanding utility of these cropsis dependent on expanding or developing theirutilization in either fresh or primary processedforms.

Edible canna (C. edulis Ker), one of the Andeanroot and tuber crops known as Achira is a nativecrop of South America (Hermann and Heller,1997). This crop is distributed across many re-gions of the world, and is known by a variety oflocal names such as ‘Chisgua’ in Columbia, ‘Ca-pacho’ in Venezuela, ‘Imbirg’ in Brazil, ‘Tous lesmois’ in West Indies, ‘Queensland arrowroot’ inAustralia, ‘Zembu’ in Philippines, ‘Lotus tuber’ inTaiwan and ‘Sagu’ in Thailand (Tonwitowat,1994). This plant has high starch rhizomes thatare traditionally used as a staple food for nativepeople. This crop is typically cultivated in sub-tropical highland, at an altitude of 1000–2500 m,mainly in China and Vietnam, with the variablerhizome production (150 000–258 4000 tonnes ofrhizomes per year). Interest in canna in parts ofAsia suggests potential for this crop as a raw

material supply to industry especially after a suc-cessful field trial of canna in low land plantation(Tonwitowat, 1994). The rhizomes can be pro-cessed into starch, which is used for making trans-parent noodles being regarded as higher qualitythan mungbean. Preliminary studies of cannastarch suggest some interesting properties, such aspaste properties. Two types of edible cannanamely the ‘green’ and ‘purple’ types are docu-mented (Kay, 1973; Tawornmas, 1987). However,there are at least four types of edible canna,including Thai-green, Japanese-green, Thai-purpleand Chinese-purple, found locally in Asia (Ton-witowat, 1994).

In this study, genetic characteristics, agronomictraits and starch properties of these four cannavarieties were investigated and compared withcassava, the most important commercial root cropin Asia and Latin America, to evaluate the useful-ness of canna starch as a complementary productto cassava starch. Well-characterized properties ofthese four canna varieties will be also advanta-geous for plant breeders, farmers, starch proces-sors and users to develop this crop industrially.

2. Materials and methods

2.1. Field study

Four canna varieties, Thai-green, Japanese-green, Thai-purple and Chinese-purple were fieldplanted at Department of Agronomy, Rajaman-gala Institute (Pathumthani campus) in July 1999.A Randomized Complete Block Design (RCBD)of four replicates was employed and planting areaextended over 24 m2 (planting space of 1×1 m,four rows). Three month old sprouts germinatedfrom underground rhizomes were used as plantingmaterials. After 8 months, the rhizomes were har-vested for starch extraction and leaves were col-lected and kept at −70 °C prior to use forgenetic analysis. Agronomic characteristics andrhizome yield of plants were also recorded. Cas-sava variety Kasetsart 50 (KU50), the most popu-lar variety grown by farmers, was also planted ina similar way and the roots were harvested at 8months for starch extraction.

K. Piyachomkwan et al. / Industrial Crops and Products 16 (2002) 11–21 13

2.2. Genetic analysis

Genomic DNA was extracted from leaf tissuesfrozen in liquid nitrogen following a modifiedmethod of Dellarporta and Wood (1983) withRNase treatment, including phenol–chloroformextraction. The concentration and purity of DNAsamples were analyzed spectrophotometrically(Pharmacia Biotech) and DNA purity was furtherconfirmed by 0.7% agarose gel electrophoresiswith ethidium bromide staining. Genetic mappingof extracted DNA was accomplished by RandomAmplified Polymorphic DNA (RAPD) technique.Ten primers containing ten base pairs were usedto amplify the genomic DNAs. Six of them werethe universal random primers obtained fromPharmacia Biotech (Sweden), including primer 1(5�-GGTGCGGGAA-3�), primer 2 (5�-GTTTCG-CTCC-3�), primer 3 (5�-GTAGACCCGT-3�), pri-mer 4 (5�-AAAAGCCCGT-3�), primer 5 (5�-GTT-TCGCTCC-3�), primer 6 (-5�CCCGTCAGCA-3�).Two primers including primer 7 (5�-TGGT-CACTGA-3�) and primer 8 (-5�TGGACACTGA-3�) were used following the method of William etal. (1990). The last two primers were Operon no.06 (primer 9; 5�-AAGGCGGCAG-3�) and Operonno. 18 (primer 10; 5�-TGCCCAGCCT-3�). In 25�l of reaction mixture; there were 1×PCR buffer(3 mM MgCl2, 30 mM KCl, 10 mM Tris–HCl,pH 8.0), 0.4 mM each of dNTPs (Promega), 25pmol of the primer and 0.6 u Taq DNA poly-merase (Promega) and 20 ng of genome DNA.The thermal program was 45 cycles of 95 °C for1 min, 36 °C for 1 min and 72 °C for 2 min(Gene Amp PCR System 2400, Perkin–Elmer).DNA amplified products were analyzed on 2%agarose (SeaKem® LE Agarose) in TBE buffer(0.89 M Tris–base pH 8.3 containing 0.89 mMboric acid and 24 mM EDTA) at 90 V in 5.0 h.The gel was stained with ethidium bromide (0.5�g/ml) for 30 min.

2.3. Rhizome and starch properties

Physical and chemical properties of harvestedrhizomes were investigated for protein, fat, fiberand ash contents according to the AOAC meth-ods (AOAC, 1990). Starch was extracted by

grinding peeled rhizomes with water and filteringthrough a 88 �m sieve. Starch slurry was thencollected and settled. After starch sedimentation,water was decanted and starch cake was rewashedtwice before drying at 50 °C. Starch purity wasdetermined by a polarimetric method (AOAC,1995). Properties of dried starch were character-ized and compared with cassava starch extractedin the same manner from 8 month old roots ofKasetsart 50 (KU50).

2.3.1. Granule morphology and sizeStarch granules were viewed under normal and

polarized light microscope (Meiji Techno., Japan)at 4× magnification. Images were taken with aMeiji CK 3800 (Meiji Techno., Japan) color videocamera and the granule sizes were then analyzedby image analysis software (Image Pro Plus 3.0,Media Cybernatic, LP, USA).

2.3.2. WhitenessStarch whiteness was estimated using a KETT

Digital Whiteness Meter Model C-100 (KETTElectric Laboratory, Germany) with a blue filter(� 440 nm) as a calibration plate.

2.3.3. Paste clarityStarch suspension (1% w/v) was gelatinized in a

boiling bath for 30 min. The clarity of paste, aftercooling, at room temperature for 60 min wasmeasured as the percentage light transmittance(%T) at 650 nm, using water as a blank, accord-ing to the method of Craig et al. (1989).

2.3.4. Swelling and solubilitySwelling and solubility determinations were car-

ried out at 55, 65, 75 and 85 °C by the procedureof Schoch (1964).

2.3.5. Paste propertiesPasting profiles of starch slurries were investi-

gated by a Visco Amylograph (Barbender, Ger-many) using 30.00 g (dry basis) starch suspendedin 470 ml distilled water (6.00%starch). The starchsuspension was heated from 50 to 95 °C within 40min and the holding time at 95 °C was 30 min.After which, starch paste was cooled down to50 °C at the same rate and this temperature was

K. Piyachomkwan et al. / Industrial Crops and Products 16 (2002) 11–2114

Fig. 1. DNA polymorphisms of four canna varities from RAPD using (a) primer 1 (5�-GGTGCGGGAA-3�) (b) primer 7(5�-TGGTCACTGA-3�) (c) primer 9 (5�-AAGGCGGCAG-3�) and (d) primer 10 (5�-TGCCCAGCCT-3�). Lane 1: Thai-green, Lane2: Japanese-green, Lane 3: Thai-purple, Lane 4: Chinese-purple and Lane M: marker 100 bp DNA ladder of 1500, 1200, 1000, 900,800, 700, 600, 517, 500, 400, 300, 200 and 100 bp.

Fig. 2. Rhizomes of edible canna (C. edulis) of different varieties: (a) Thai-green (b) Japanese-green (c) Thai-purple and (d)Chinese-purple.

K. Piyachomkwan et al. / Industrial Crops and Products 16 (2002) 11–21 15

Table 1Phenotypes and agronomic traits of four edible canna (C. edulis) varieties

VarietyCharacteristics

Japanese-green Thai-purpleThai-green Chinese-purple

GreenStem color BronzeGreen BronzeGreenLeaf color Green/purpleGreen Green/purple248 243235 243Plant height (cm)

50% Inflorescence (days after planting) 7986 80 93Red RedOrange RedFlower color8 8Harvest time (months) 8849 4340 33Number of shoots per plant at harvest50 48Number of rhizomes per plant at harvest 4446Yellow Yellow/purpleYellow Yellow/purpleRhizome color38.4 33.7Rhizome yield at harvest (tonnes/ha) 30.433.525.8 22.922.2 21.9Total plant yield at harvest (tonnes/ha)0.62 0.64 0.58Harvest index 0.6412.74 13.2313.52 13.63Starch content of harvest rhizomes (% wet basis)

4.53Starch yield (tonnes/ha) 4.89 4.46 4.14

Table 2Chemical composition of edible canna rhizomes of different varieties and cassava roots

Sample Content (% dry basis)

FatProtein Fiber Ash

0.25�0.01Thai-green canna 3.00�0.113.26�0.12 5.56�0.011.63�0.22Japanese-green canna 2.90�0.062.89�0.04 5.26�0.010.29�0.09 3.18�0.242.39�0.03 5.70�0.08Thai-purple canna

Chinese-purple canna 3.16�0.36 0.34�0.06 2.99�0.00 5.11�0.060.22�0.03 1.31�0.061.15�0.04 1.91�0.01Cassava

held for 30 min. The viscosity of starch paste,including peak viscosity (P), final viscosity at95 °C (H), viscosity at 50 °C (C) and gelatiniza-tion temperature was recorded. The breakdown(P–H), setback (C–P) and consistency (C–H)were also reported.

2.3.6. Enzyme susceptibilityEnzyme susceptibility of starch was measured

by using �-amylase and amyloglucosidase (NovoNordisk Co., Bagsvaerd, Denmark), similar to themethod of Wang et al. (1995). The 10 ml reactionmixture contained a 2.0% starch suspension in 0.1M sodium acetate buffer (pH 5.0) and 40 ppmCa2+ and the enzyme solution containing 3 KNU

of �-amylase (Termamyl® 120L from Bacilluslicheniformis with 120 Kilo Novo �-amylase Unit(KNU)/g; 1 KNU is the amount of enzyme thathydrolyzes 5.26 g of starch per h under the fol-lowing standard conditions, i.e. at 37 °C, pH 5.6for 7–20 min) and 6 AGU of amyloglucosidase(AMG 300L from Aspergillus niger with 300Amyloglucosidase Unit (AGU)/ml; 1 AGU is theamount of enzyme which hydrolyzes 1 �molemaltose per min under the following standardconditions, i.e. at 25 °C, pH 4.3 for 30 min).After incubating at 37 °C for 48 h, the content ofreducing sugar was analyzed using the Somogyi–Nelson method (Somogyi, 1952) and total sugarsby the method of Dubois et al. (1956).

K. Piyachomkwan et al. / Industrial Crops and Products 16 (2002) 11–2116

2.3.7. Acid susceptibilityStarch samples (1% w/v) were suspended in

aqueous sulfuric solution (1.35 N H2SO4) andincubated at 37 °C with intermittent shaking. After24 and 72 h, samples were collected and centrifugedat 10 000 rpm 5 min. The supernatant was analyzedfor total sugar contents by the phenol–sulfuricmethod (Dubois et al., 1956).

2.3.8. Starch gel textureTo prepare gels, starches (9.2% w/w) were

cooked in the Rapid Visco Analyzer according toSriroth et al. (1998). The paste was covered with aparafilm sheet and allowed to cool and set at the

Table 3Whiteness and paste clarity of canna starches of differentvarieties and cassava starch

Sample Whiteness Paste clarity(%transmittanceat 650 nm)

91.5�0.07Thai-green canna 43.55�0.3549.70�0.4290.6�0.00Japanese-green canna

89.9�0.00Thai-purple canna 43.15�0.07Chinese-purple canna 51.30�1.1390.8�0.07

38.00�0.2893.4�0.07Cassava

Fig. 4. Swelling power and % solubility of canna starches ofdifferent varieties and cassava starch.

Fig. 3. Granular appearance of canna starches under a (a)normal light and (b) polarized light microscope at 40× mag-nification.

room temperature. The set gel was then stored at4 °C for 15 h and equilibrated at the room temper-ature for 4 h before texture analysis using a TextureAnalyzer (LLOYD TA 500, IntroEnterprise Co.LTD, USA; Collado and Corke, 1999). The gel of

K. Piyachomkwan et al. / Industrial Crops and Products 16 (2002) 11–21 17

Tab

le4

Pas

tevi

scos

ity

prop

erti

esby

aB

rabe

nder

Vis

coA

myl

ogra

phof

cann

ast

arch

esob

tain

edfr

omdi

ffer

ent

vari

etie

san

dca

ssav

ast

arch

(6%

w/w

)

Gel

atin

izat

ion-

Con

sist

ency

Pea

kvi

scos

ity

Bre

akdo

wn

Fin

alvi

scos

ity

atSe

tbac

kSa

mpl

eV

isco

sity

at50

°C(P

,B

U)

95°C

(H,

BU

)(C

–P,

BU

)te

mpe

ratu

re(°

C)

(P–H

,B

U)

(C,

BU

)(C

–H,

BU

)

Tha

i-gr

een

cann

a68

.910

5898

916

6169

603

672

Japa

nese

-gre

enca

nna

69.1

1044

1011

1801

3375

779

069

.493

292

1T

hai-

purp

leca

nna

1567

1163

564

668

.810

4710

0016

68C

hine

se-p

urpl

eca

nna

4762

166

863

.481

524

746

1C

assa

va56

8−

354

214

K. Piyachomkwan et al. / Industrial Crops and Products 16 (2002) 11–2118

20 mm in height was compressed by 40% of theoriginal height at a speed of 20 mm/min using acylindrical probe with a diameter of 50 mm. Theanalysis was performed into two cycles. The peakheight at 30% compression of the first cycle wastermed as hardness. Cohesiveness is the ratio ofthe area of work during the second compressionto the first compression. Springiness is the ratio ofthe compressed time of the second cycle to thefirst cycle. Gumminess is the product of hardnessand cohesiveness.

3. Results and discussion

3.1. Genetic characteristics

Genetic diversity of four canna varieties includ-ing Thai-green, Japanese-green, Thai-purple andChinese-purple were probed by the RAPD tech-nique using ten 10-base primers. Except primer 4,nine sets of primers were able to generate DNApolymorphism patterns in all canna varieties.DNA patterns which were amplified by primer 2,

Fig. 5. Paste viscosity profiles of canna starches of different varieties and cassava starch when determined by a Brabender ViscoAmylograph using 30.00 g (dry basis) starch in 470 ml distilled water.

Table 5Texture Profile Analysis (TPA) of canna and cassava starch gels

Hardness (N) Cohesiveness Springiness (mm) Gumminess (N)

13.96�1.5434.98�2.95 0.40�0.03 7.44�0.13Thai-green canna18.58�0.987.67�0.280.46�0.05Japanese-green canna 40.98�2.6413.88�1.5138.20�2.74 0.36�0.02 7.69�0.08Thai-purple canna

0.44�0.0430.44�1.25 13.29�0.72Chinese-purple canna 7.76�0.19n.a.n.a.n.a.n.a.Cassava

n.a.=not applicable.

K. Piyachomkwan et al. / Industrial Crops and Products 16 (2002) 11–21 19

Table 6Acida and enzymeb susceptibility of canna starches of different varieties and cassava starch

Acid susceptibility (%) Enzyme susceptibility (%)

at 72 hAt 24 h

91.5�0.07 36.56�3.73Thai-green canna 43.55�0.3590.6�0.0049.70�0.42 31.32�3.51Japanese-green canna89.9�0.00Thai-purple canna 44.55�4.3743.15�0.0790.8�0.0751.30�1.13 39.42�5.22Chinese-purple canna

38.00�0.28Cassava 93.4�0.07 54.56�5.72

a By 1.35 N sulfuric acid at 24 and 72 h.b By 3 KNU �-amylase (Termamyl® 120L from B. licheniformis with 120 Kilo Novo �-amylase Unit (KNU)/g; 1 KNU is the

amount of enzyme that hydrolyzes 5.26g of starch/hr under the following standard conditions, i.e. at 37 °C, pH 5.6 for 7–20 min)and 6 AGU glucoamylase (AMG 300L from A. niger with 300 Amyloglucosidase Unit (AGU)/ml; 1 AGU is the amount of enzymewhich hydrolyzes 1 �mole maltose per minute under the following standard conditions, i.e. at 25 °C, pH 4.3 for 30 min).

3 and 8 exhibited genetic similarity in all fourvarieties. When using primer 5 and 6, there wereslightly different genetic patterns among the fourvarieties. Genetic differences between Thai-greenand Japanese-green were observed by the amplifica-tion with primer 1, 7, 9 and 10, they were differentfrom the other two varieties (Thai-purple andChinese-purple) (Fig. 1). Only two varieties ofcanna are reported in the literature which are the‘green’ and ‘purple’ types. However, this studysuggests that at least three types of canna existincluding Thai-green, Japanese-green and Thai/Chinese-purple.

3.2. Phenotypes and agronomic traits

Similarly, on the basis of plant characteristics,three types of canna could be categorized includingThai-green, Japanese-green and Thai/Chinese-pur-ple. The first two could be readily differentiatedfrom the last by color of stems, leaves and rhi-zomes. They were in green for the former andgreen/purple for the latter (Fig. 2). Thai- andJapanese-green types were distinguished by flowercolor. Other phenotypes and agronomic traits ofthese four varieties were similar as summarized inTable 1. Rhizome yields for the four canna varietiesvaried from 30.4 to 38.4 tonnes/ha with theJapanese-green type providing the highest yield(Table 1) and slightly greater than typical rootyields of cassava (25 tonnes/ha). However, averagecanna yields reported in this study are lower than

those achieved in field trials in the highlands ofEcuador of 56 tonnes/ha (Hermann et al., 1996).Harvest index, the ratio of the rhizome to totalplant weight (�0.62) and starch content of har-vested rhizomes (�13% wet basis) of the fourvarieties corresponded to a previous study; harvestindex of 0.56 and rhizome starch content of 14%wet basis (Hermann et al., 1996). In this trial, starchyields of four canna varieties were 4.14 to 4.89tonnes/ha, which is lower than that attained in fieldtrials in Ecuador (7.8 tonnes/ha; Hermann et al.,1996). Starch yields of canna were also lower thanthose of cassava (6.5 tonnes/ha).

3.3. Rhizome and starch properties

Potential use of canna for industrial purposeswas evaluated by characterizing rhizome and starchproperties. Similar to other root and tuber crops,canna rhizomes are high in starch content withsmall amounts of other impurities (protein �2.39–3.26, fat �0.25–1.63, fiber �2.90–3.18 and ash�5.11–5.70% dry basis; Table 2). Canna rhizomescontain a higher ash content than cassava roots(Table 2). Canna starch can be readily extractedfrom the rhizomes by simple techniques includinggrinding, sedimentation and drying which are effec-tive enough to produce pure canna starch (starch�94.0–96.6, protein �0.05–0.20, fat �0.01–0.15, fiber �0.40–0.90 and ash �0.70–0.90% drybasis). All varieties of canna starch had roundedand oval-shaped granules with wide size distribu-

K. Piyachomkwan et al. / Industrial Crops and Products 16 (2002) 11–2120

tion ranging from 5 to 100 �m (Fig. 3). Granularsizes were similar to potato starch, the large gran-ules (�70%) were 30–70 �m and much largerthan cassava starch (granule size ranging from 5to 30 �m with the average size of 12–15 �m).

In general, genetic factors did not seem tocontribute to the variation in starch functionalproperties. All four canna varieties providedstarch with high whiteness (89.9–91.5), close tocassava starch (93.4) (Table 3). When gelatinized,the cooked starch paste was very clear and clearerthan cassava starch (Table 3). Independent ofvariety, all canna starches exhibited lower swellingpower than cassava starch at all temperaturestested, while starch solubility was lower only atlow temperatures (Fig. 4). Among four varieties,Thai-green canna yielded starch with the highestswelling power and solubility, which were evidentat high temperatures. Significant changes inswelling power of all four canna starches occurredat higher temperatures (�65 °C) compared withcassava starch (�55 °C), as ascertained byBrabender Visco amylograph (Table 4). Gela-tinization of the four canna starches began athigher temperatures than cassava starch (starchgelatinization temperatures were 69 and 63 °C,respectively). Paste profiles of all four cannastarches were similar, Japanese-green canna gavethe highest cold paste viscosity (Fig. 5). All wereconsiderably different to cassava starches. Viscos-ity after holding at 95 °C for canna paste (finalviscosity at 95 °C, H, was 921–1011 BU) de-creased slightly from the maximum viscosity(peak viscosity, P, was 932–1058 BU) indicatingvery good paste stability (breakdown, P–H was11–69 BU). After cooling to 50 °C, paste viscos-ity of all four canna markedly increased (Viscosityat 50 °C, C, was 1567–1801 BU), resulting inhigh setback (603–757 BU). In contrast, cassavastarch provided hot paste with low stability(breakdown, P–H was 568 BU), after cooling,paste viscosity also increased, yet it was still lowerthan the peak viscosity (815 BU). Consequently,setback of cassava starch was negative (−354BU). The results are comparable to previous re-ports (Perez et al., 1997, 1998). Gels formed fromthe gelatinized canna starches had superior tex-tural properties than cassava starch (Table 5).

Granule susceptibility of canna starches to acidand enzymatic hydrolysis was also evaluated incomparison with cassava starch. The initial acidhydrolysis of canna starches was more rapid thancassava starch but all were degraded to about thesame extent after prolonged hydrolysis (Table 6).Starch granules were more susceptible to acidthan enzymatic hydrolysis. Degree of enzymatichydrolysis of canna starches was slightly lowerthan that of cassava starch. Among four cannavarieties, Thai-purple canna had the highest de-gree of enzymatic hydrolysis (Table 6).

It is conclusive that edible canna providesstarches with distinct paste and gel characteristicsand totally different from cassava. The starchesare potential candidates for industrial utilizationas a new base starch. Interesting is to use cannastarch as a complementary starch to cassavastarch, allowing the production of tailor-madecomposite starches with improved and desiredproperties.

Acknowledgements

This work was partially supported by the Min-istry of Industry, Thailand.

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