Journal ofScience and Technology 54 (3) (2016) 347-355
DOl 10,5625/0866-708X/54/3/7,01
O X I D I Z E D M A I Z E S T A R C H : C H A R A C T E R I Z A T I O N A N D I T S E F F E C T O N T H E B I O D E G R A D A B L E F I L M S I. C H A R A C T E R I Z A T I O N O F MAIZE S T A R C H O X I D I Z E D BY
SODIUM H Y P O C H L O R I T E
Dao Phi Hung*, Truong Thi Nara, Mac Van Phuc, Nguyen Anh Hiep, Trinh Van Thanh, Nguyen Thien Vuong
Insuiule for Tropical Technology. Vielnam Academy ofScience und Technology IS Hoang Quoc Viel. Cau Clay Ha Noi Viel Nam
Email: dphiinulaiii lyjw v»
Receipted: 21" September 2015: Accepted^ 19 February 2016 ABSTRACT
struetl?: : r r p V l i c o T m L t p ' : ; e „ ' " V- T ' / '""' ^''°""= 8"°°S ^'-=h. - fte obtained results s h T t h a ^ t o n T g e e ^ e r t ; " ; ! ™ ' " ""t " ? '"™^''^^'=^- '"'
gelatinization temperatute b e t w r „ ' L ' ' ^ : t t s , t c r a n d t l d , r e I , " a r c h T ' ' ' " ° ' '"''''"'' "^
Keyiuords sodium hypochlorite, maize starch, oxidation, starch oxidized.
1. INTRODUCTION
Starch is a kind of low-costly renewable and biodegradable nolvmer . nv. u m academic research and industiy fot the past few decades H„i*^ ' * • " " "PP''""' hmited by their low themtal stability, suscepdbility to exit me oH r r " " ™ '"""'"' ""«' rettogradation rate etc. Chemical modification JIcZ^l Z T T ' ' " < ^ ^'''''''"'' (unclionahties ofstatch and makes It appropriate for vanous L 1^ '^^''^^ly '"iprove the of chemical modification, involve the mtrolctioro c a i "l d t r b " ?l"''''°" " " * " "
by means of subsequent depolymerization of the starch S e H , K = ' '^"""°™' '^''^P^' mdustries, pattieularly in applications whete fi m fomtation a d d ="" " """='" " " " " """^
Such starches have established to be whiter in color ^ ^ ^ 1 . 1 * . ' ' °° P ^ P ' " ' " '" ' ' « " - ' i - r J ... cipj^iitaiiuiis wnere n m tomiatinn anH ^^i,., Suchstarches have established to be Whiter in c o l o . a n d ' ^ v r r o l t r e t r g S ' a n L ' n
Oxidized stareh is .„H„.„ ^ ^^^^,^^ amount'of oxidizi a.ents 71 Hydroxyl groups, pnmanly at C-2, C-3, and C-6
„ . , , , . """""= resmcted retroeradalion 11 - 71 Oxidized starch is produced by reacting starch with a snecifl / undet controlled temperature and pH [2 - 7] Hvdroxvl „„,,!!! „,f"""""' "^"'"I'z'nE agents
^M
Dao Phi Hung. Tmono Thi Nam. Mac Van Phuc. Nguyen Anh Hiep. T V. Thanh, N Thien Vuon^
positions, are transformed to carbonyl and/or carboxyl groups by oxidation [8 9]. Therefore, the number of these carboxyl and carbonyl groups of oxidized starch indicates the level of oxidation, Several oxidants have been applied to prepare oxidized starch mcluding hydrogen peroxide, air oxygen ozone, bromine, chromic acid, peimanganate, nitrogen dioxide and hypochlonte. Tlie oxidant hypochlorite is the most common method for the production of oxidized starches in an industnal scale [ 1 0 - 12],
Starch modified by oxidizing agent presents changes m its molecular structure resulting in a raw material with different charactenstics. The concentration of sodium hypochlonte employed for the oxidation of starch depends on the desired degree of modification. Garrido oxidized cassava starches with NaCIO at three different concentrations (0.8, 2.0 and 5.0 %). The results showed that oxidized starches also exhibit higher susceptibihty to syneresis, as assessed by the release of liquid during freezing and thawing. Apparent viscosity analysis showed a decrease in peak viscosity of the oxidized starches. X-ray diffractograms showed that the oxidation influenced the extent of cassava starch relative crystallinity found to lie between 34.4 % (native) and 39.9 % (2.0 % active chlorine) [10].
The objective of this work was to modify maize starch with relatively cheap sodium hypochlorite (0.5, I 0 and 2 0 %) and evaluate selected characterization of the modified starches oxidation with desire lo extent maize starch applications to a wider range.
2. EXPERIMENTAL
Native maize starch was obtained from ASEA-VNPICO-FOODS Ltd. Company, Thanh Liet, Thanh Tri, Ha Noi, Vietnam.
Sodium hypochlonte containing approximately 80 % active chlorine (w/w) was obtained from China. Accuracy active chlorine was determined by chemical titration according to method Garrido etal used [10]. The sodium hypochlorite was properly diluted and a quote of 10 mL was transferred to an Erienmeyer, added of 30 mL of potassium iodide (10 %, w/v) and 30 mL of acetic acid 1:2 (v/v). This solution was titrated with 0.1 M sodium thiosulphate to a light yellow color, when five drops ofa 0.5 % (w/v) starch solution were added an the titration followed until the solution became coloriess. Active chlorine content was calculated by using the equation:
Active chlorine = (V x fc x 0.3722)/(Vs x d) =< 10 x 0.953,
where V is 0.1 M thiosulphate solution volume (mL); fc is correction factor of the 0.1 M thiosulphate solution; Vs and d are volume of the sample in mL and density of the sample in g/L, respectively.
All other chemicals used in the study were of analytical grade.
2.2. Preparation of oxidized starch
Hypochlorite-oxidized maize starch was prepared as previously described (Fonseca et al„
[12]) with some modifications A maize starch sample (200 g dry basis {d b.)) was suspended in 500 mL of distilled water in a glass reactor of I L, heated at 40 "C and subjected to a sodium hypochlonte treatmem The pH of the starch slurry was adjusted to 7.0 with 0.5 mo! equi/L NaOH and 0.5 mol equi/L HCl After addition of 100 ml buffer solution NajHPO, + NaHiPOj (pH - 7), the sodium hypochlorite was added in the starch slurry. After the reaction (300 min),
Oxidized maize starch: charactenzation and Its effect on the biodegradable films
I.acuum'''in1,.T'?i,""" " " " " ' • " " * = ' ' ~ ' " "•"' '1"^"''=<' ''•'«" ™'' '*"'='' »' to °C in the (O.5T0 lnd2 ^ i J o V s r c T " * " ' " " ""'""'' ' " ' " * ™ " ' " " "^""""^ concenttations 2,3, Carbonyl and carboxyl contents
Fonseca eta ? n TT".'"'^ determined according to the titnmctric method adapted by flLk The susien - f""" '^ ° ' " " ' " " ' « ' ' ° ""> " ^ " " ' ^ " " c " " ^ ' ^ i- » 500-mL adTusted o a „ Z i r f ? 7 ' ' " I " ^ ' ' '" " *""""« " " " " " * '"' ^° ™»' -ol^-i <° 40 X. and thenldH HI ^t " " ' * "^' ™ ' ^'^^"- " ^ 1 . A bydroxylammc reagem (15 mL) was t t a p H ^ u ' e of 3 2 w?h r H ' ^ H ' T O " " ' ' " ™ " ' = ' ' "^ '^P'^'^ ' " " " " S the reaction mixture hydroxvtotme re» '"^""^'"•ze'i »1 -nol equi/L HCl. A blank detenmnation with only the pronarTdbv first H^ was perfomted in the same manner. The hydroxylamine reagent was S r l e L " * -fin I'v'ol ' ° " ^ * » ^ " ' ™ - hydrochlonde m IOO t i of 0.5 md equi^
eoiS^=n;wa^°c:icuLtXequa™n"" '''"'''' '° ""' "^ ™ * "'""^ ™ " - ^"^ ™*""y' CO(g/100g)= (VA-_^s)jam)^8)<JI00_
IA/
Ts L f v ; c u u ^ 1 l t S ' t Z u r : ? 5 o ' m ; ° " ' ' H ' ' " ' ° """ """ ^ '"^«"="= ^«™ The ! C with 400 mL of d i s i L waret The s« f 7 ™ f"'"^ *'"'"='' ^"'' ^'"''' ""1 ^^hed beaker, and * e ^ t r w r ^ ^ I s t d t l o f m L T i t L ^ l - ^ e r t l T a t r T t t ' T ^ ="" "^
heated in a boiling water bath with continuous t i n g for Ts t^n m "^ T '
?^=rrp?:r r?/s=- o t i i S r F F -
perfonned with umnodified starch The carboxyl content was cTuttedby",utt,'Ii " "
COOH (g/IOOg) = - ' - ^J'W i M j i a045x-100
w where- Vs is the volume of NaOH required for the samnle tml 1 vt, - o,
.0 test the blank (mL). M is the moLtv of NaOHTequt/LTand W s th™ ™ 1°™"™ ""'^
basis) (g). • Icqui/Lj and W is the sample weight (dty 2.4, Viscosity of starch paste
The viscosity of starch paste samples were detennined iis,„„ , ci ,-
ISO Viscosity Cup No 4, Elcometer, England, accorZg ,0 ASTM S ^ s ^ f / P ' " ' " " ' = ' " '''' expressed m seconds (s) flow time Statch samples wete ptenltd foH ? . " ' " ' " ^ ™'' a 12], the starch weighed direcdy and distilled w a r L s added •" * " " "t- "
of 1:20 (w:w, Then the sample heated ,0 95 T in 3.5 J l X l t t s x Z t s Z ^hh
Dao Phi Hung, Tmong Thi Nam. Mac Van Phuc. Nauyen Anh Hiep. T V. Thanh. N. Thien Vuom
mechanical stirring on whole process. After that, the sample was put in cup and detennined the time flow. Measuremenis were perfonned three times and average the values were reported.
2.5. Scanning electron microscopy (SEiM)
Morphological properties of native maize starch and oxidized maize starch were studied by using Scanning Electronic Microscope S4800 (Japan) at Institute of Matenals Science, VAST Subsequently, all of the samples were coated with gold and examined using a scanning electron microscopy under an acceleration voltage of 15 kV at a magnification of 5000x.
%
2.6. Thermal analysis % The gelatinization characteristics of starches were detennined using a differential scammM
calorimeter (DSC) which mean Labsys Evo (France) at Institute of Matenals Science, VASM Starch samples (approximately 2.5 mg, dry basis) were weighed directly in an aluminum pa^
and distilled water was added to obtain a starch-water rafio of 1:3 (w:w) The sample pans we^
then heated in presenceof air from30 to 150 "C at a rate of 10 "C/min. .;j' 3. RESULTS AND DISCUSSIONS
3.1. Carbonvl and carboxyl contents
Carbonyl, carboxyl contents and oxidation degree of oxidized maize starches at various hypochlorite concentrations were illustrated in Table I. Oxidadon with sodium hypochlorite grew up all of the carbonyl and carboxyl content of maize starches The carboxyl content sS9t higher mcrease than the content of carbonyl. The oxidized maize starch with the highest acti^' chlorine concentration (2 g/IOO g) showed a higher carboxyl and carbonyl content as compareS to other oxidized maize starches (Table I). The presence of carbonyl and carboxyl groups fi oxidized starches is due to oxidation of the hydroxyl groups of maize starch molecules to carbonyl groups and then the carboxyl groups.
Table 1. Carbonyl and carboxyl contents of the oxidized maize starches. ''^- Active chlorine
(j^/IOOgsiarch) Native
0.5 1 2
Carbonyl conlent (g/IOO g)
0 238 0-294 0 336 0 378
Carboxyl content (g/!00g)
0.036 0 086 0.194
Sum (CO + COOH)
0.33 0.422 0 572 Several authors studied the oxidation of cassava and common bean starches with different concenttations of sodium h>T)ochlonte and leportcd that there was a gradual increase in the catbonyl and caiboxyl contents with the increasing concentration of active chlorine [7, 8, 10, 13]
while other studied showed the significant differences of carboxyl content with various concenttation of active chlorine [12], Because the level of carbonyl and carboxyl depends on
Oxidized maize starch: characterization and Its effecl on the biodegradable fi
vanous factois such as: the source of starch, type and concennation of oxidants pH and leaction temperamre. "^ ' 3.2, Starch granules morphology
The scanmng elecnron micrographs of the native and oxidized maize starches are presented
(a)
(d)
Figure I Scanning electron micrographs of maize slatch In) and oxidized starches ofO 5 % (b|
I %(c)and2%(d)nclivedilonneconlem ' The SEM data show that native maize statch granules had i r r „ „ , i „ . j ,.
Surface of unmodified maize starch granules was s S h w,.hou o b t b t * " " ' fttr the maize starch modified by 0 51- chlonnClOO g s t r c h s ' hdv7„u h e " " ; ' r ° ™ ™ "
observed Slightly roughened surface due to e x o - e o L s i o n w^s 1 1 ° f , b " f t ' " i"'',!;
with highet ehlonne active concenttation When s.udvmg e f ct ^ he " ™,' " "
concenttauon on the physicochemical properties of cassaia sta ch .he , hypochlonte observed rougher granules and the presence of fissurl in n v ' , r T ° ' ' ° ™ ' ' * ' " ' ' ' ' ° F c Ul assures in oxidized cassava starch [13]
Dao Phi Hung Tnjong Thi Nam. Mac Van Phuc. Nguyen Anh Hiep, T. V Thanh. N Thien Vuot^
However, there was no changes in the granule morphology of potato starches modified with hypochlorite at < 2 % active ehlonne levels [12].
3,3. Viscosity
Viscosity of starch paste expressed via flow time (second) of native starch and oxidation starch are shown on Figure 2.
Active chlorine content {%)
Figure 2. Flow time (second) of native starch and oxidation suirch.
Overall, the flow time of starch paste dirough flow cup reduced when starch was oxidized at higher level of oxidant. There was no different flow time (second) between native starch anil starch oxidized by lowest oxidant content, 0.5 % (the flow time of both samples were 48 s) For starch oxidized by oxidant content doubled, leveling off I %, the flow time of oxidation starch paste reached 44 s. If the oxidant contmuously increased, at 2 %, viscosity of oxidation starch paste reduced to 38 s. Hence, if the oxidant incieased, the carboxyl and carbonyl groups content grew up but the viscosity of starch paste reduced. It means that the oxidation process not only transfetred hydroxyl group to carbonyl and carboxyl groups but also, more or less, occurred polymer chain scission to create the various molecular compounds widi different weights.
3.4, Gelatinization
The gelatinization process is characterized by an endothemi obtained by a differential the t e m i ' t " " T V i ^ ' ; ^'"' """"'"'"'' °f K ^ P ^ ^ ^ e at the onset of gelatinization (TJ, tejemperature al peak (T,) and the temperature at the end of gelatinization (TJ ate shown in aelatili'zali™'f"'' T ' ' " " " i * " " ' * • " * " • " concentrations of active chlorine had active c ^ r '""T^'T^ T ' " '° ""'"^ '•=••*! ''°"''^='- ""^ '"'''>'^''' ^'^^h with I g/IOO g stachesoxidi, H T l " ' ^ " gelatinization temperature compared to native starch and to starches oxidized with the other levels of active chlorine (0.5 and 2.0 g/IOO g).
ehlonne'wei!.'',"""" V ™ P ? ' " ' ' ' ^'^'^ °f ""= ^'""^hes oxidized with 0.5 % and 2.0 % active (T b"e 2) M I V si?^ T * ' ' " * ™ *<"" *"= '^""'^"'^i™ temperature of the native starch I able 2). Many studies have repotted the influence of oxidation on the gelattnizatton properties
Oxidized maize starch: characterization and Its effect an the biodegradable fi
of starch, but the results are inconclusive and vary due to starch onein and modification conditions [2, 3, 5, 12].
Tabte 2. Gelannization characteristics of the nanve and hypochlorite-oxidized maize starches.
Acnve ehlonne (g/IOO g starch) Nanve
Transition tempeiatuies ("C)'
75.30 74,35
81.14
T,-T„
11 30 10.04 1085 Nole. T.,. T, and T, are lhe Imiperalures al llie ousel midpolm and end of gelalimcalmii. i-especlively
Sangseethong et al [7] found a teduction in the gelatinization tempetatures (To Tp and Tc) of cassava oxtdizcd starches when compared to native starch, they suggested that th negabv y wat r a n r S t e T T T T ' '"""' """""' " " " ' ^ ' " " " ^ """""'" - " - a d i l y ' a d s o r b water and facilitate hydration, thus weakening statch granules and resuhing in gelatinization at
:cZn'x:.z:\ r'7'°'°°"r"°" f^^-'^=^= 'h^^^y^-iccharacten:,;:"„
gelatinization can be largely associated with the weakening of the mtennolecular bonds responsible forthe c o s t a l structuie of amylopecin, due to the i ; c o t p o r a t i o n T e a ^ x y ™
h w T h f s u r f r c e d ? ' ' r • " " ' " f """"''' " " " " S " ^ ' ^ ' ' = - - ' -O'i.ficat.on'thrma";
Show, on the suriace, disturbances such as ftactures and pores which also facilitate the penetiation of water ,n the granules. Moreover, the oxidation'of hypochlonte on mai s a h could create particle products with different molecular weights V a r i a t i o r m The ' h e m a l be tl e ratio of amylose/amylopectin, the residual lipids and protein, the molecular strttcture of amylopectin, moiphology and the distnbution of statch gia'nules, the products of " x l b o n
4, CONCLUSIO.N
cha.^r:?::;a::st^Mo^mr:^;L:;ii^°""' *-=" ^"^-"^ "-=
intensity of oxidation of the m a i z l i t a i c h e s ' b m : e : u S T h e ' t o " : t ; ° „ " r s r : ; ; ; : i u T t l '
.emp„atuies between the native statch and staiches oxiSized w"'h d i r e " r c o n t n ? r a n ' : T v :
o t s r n J f r T r a X " ' " """" "" '''""' ' ° " '^"™"' ^ ' " " ™ ' "•" °f ^ • • « « ' " A=ade,ny
Dao Phi Hung. Tmong Thi Nam. Mac Van Phuc. Nguyen Anh Hiep. T V. Thanh. N. Thien Vuonf
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Srolt°5;(MT3,°439r3*'°™'-°"''^'' '"'" ''''''• "*^ - '°°' ^-"- ""
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rhrc6„,2m5;'7i4*a °" "°''^='^^"'""'- ^^^ - ^-^ ^-»- ^^
'^' H o Z " ^ C h n t ? " ^ ' ^'^^f ^ ' " '^''°'' "^S-yen Q"ang Huy, Nguyen Kim Hung, Thai loZi'ofn ?^1T °' '"P""" ''"'='' °'<'*^='' '>y ^•"'i"™ hypochlonte, Vietnam Journal ot Chemistry-47 (2009) 393-396.
Oxidized maize starch- charactenzation end its effect an the biodegradable films
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I. TiNH CHAT CUA TINH BOT NGO OXI HOA BANG NATRI HYPOCLORIT Eiao Phi Hiing', Tmong Thi Nam, Mac Van Phiic. Nguyen Anh Hicp,
Tnnh Van Thanh, Nguyen Thien Vuong
Vien Ky ihudl nhiel den. Vien Han ldm Klma hoc vi Cdng nghi Viel Nam.
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Anh huong eua ham lucmg nam clont, voi ii le 0.5. I. 2 gam do hoat hoa'lOO gam tinh bot den can trac va tmh chat h6a li cua tinh hot ngo oxy h6a da duoc nghien ciiu. Kk qua thu dttoc MmTu™„ c h s " "V^}!"' "S6 tang khi tang hSm luong nam hypoclont, dac biet, khi tang ham luong chat oxy hoa, ham lugng nhom cacboxyl tang nhanh hmt so vtri ham luong nhora cacbonyl. Anh SEM cho thay hinh thai hoc bi mat hat tinh hot ng6 oxy hoa gh6 gh5 ban so v6
XV hd Tuv • k" ,"™ T ^ ' 'T ""^ •"=• " '' ""•*" ™ 0 ' 8« '^' W m l cua tmh bo. „g6 oxy hoa Tuy vay. ket qua phan tich DSC cho thay kh6ng co su thay dot nhita vl nhiet do M hoa cua Unh bot ngo oxy hoa so veil tmh hot ban diu.
Tiitluia- nam hypoclont. tmh bot ngd. oxy hda. tinh boi oxy hoa
