PREPARATION AND PROPERTIES OF OXIDIZED STARCH WITH HIGH DEGREE OF OXIDATION

Anny Yanuriati

M. Iqbal Prawira

Yu-Rong Zang, Xiu-Li Wang, Guo-Ming Zhao, Yu-Zhong Wang

Carbohydrate Polimers; 87 (2012) :2554-2562.

Pati telah banyak digunakan pada indutrsi karnea biaya murah, biodegradability dan renewability

Dalam pemanfaatan pati, sering dilakukan modifikasi untuk meningkatkan sifat pati

Salah satu yg sering digunakan pada indsutri adalah modifikasi kimia yaitu Oksidasi

Oksidasi pati memiliki sifat pembentukan film yg bagus . Sehingga sering dimanfaatkan industri tekstile(Kuakpetoon & Wang, 2001)

Gugus hidroksil pad atom C2, C3, C6 dirubah menjadi gugus karboksil dan/atau gugus karbonil.

Pendahuluan

Pendahuluan Pada skala indutri memakai hypoclorite bekerja pada

kondisi larutan alkaline Sodium, calcium hypoclorite, permanganate, persulfate

dan periodate Side effect oxidation : mengahasilkan jumlah besar

limbah inorganic seperti produk chlorinate Oksidasi dengan hidrogen periodate hi cost,

decompossed reaction product would pollute the environment

Salah satu oksidasi menggunakan : hidrogen peroksida low cost, green water decomposition, mudah diperoleh dan metal katalis yang murah untuk mempercepat reaksi

Preparasi pati oksidasi dengan hidrogen peroksida dengan DO tinggi membutuhkan waktu reaksi yang lama yaitu 72 jam {DO : 51,2% dengan ratio 2:1(oksidan : pati) pada suhu 35 0C}

o Mengetahui peran Cu (II) sebagai katalist pada modifikasi pati dengan oksidasio Mengetahui pengaruh kondisi reaksi terhadap pati asli, jumlah oksidasi, suhu, jumlah katalist, dan waktu reaksi terhadap derajat DO (degree oxidation)o Perilkau termal transtition, thermal stability, XRD, dan transmitance dari pati teroksidasi

The Objective

Material Corn starch, pea starch, and sweet potatoes

starch dengan mositure 11-13% Hydrogen peroxide (H2O2, 30%) and CuSO4.5H2O

(analytical grade 95%)

Material and Methods

10 g Pati100 ml Air distilasi

Pati slurry

Pendinginan hingga suhu 60 0C

Pemanasan dan pengadukan T : 80 0C; t: 30 menit

CuSO4 Solution

H2O2 , setelah 30 menit

Pati Oksidasi

Prosedur oksidasi pati (Wang et al., 2007; Zhang et al., 2009; dan Zhang et al., 2009) dengan modifikasi.

Pati Oksidasi

Etanol berlebih

penggilingan

Bubuk pati Oksidasi

Pemisahan dgan sentrifuge

precipitated

Pengeringan T : 50 0C, t : 24 jam

Pengeringan T : 80 0C, t : 24 jam

Derajat oksidasi : jumlah dari total gugus karboksil dan gugus karbonil per 100 unit glukosa

Prinsip analisis gugus karboksil dan karbonil berdasarkan dua metode berbeda yaitu :

Kandungan gugus karboksil ditentukan dengan titrasi pada larutan sample denganlarutan standart NaOH

Penentuan gugus karbonil dengan mereaksikannya gugus karbonil dengan reagent Hydroxylamine dan kemudian dititrasi ulang dengan larutan HCL

o DOS = DOT - DOB

Penentuan derajat Oksidasi

CNaOH dan CHCl = konsentrasi larutan NaOH dan CHCl

VNaOH dan VHCl = Volume larutan NaOH dan CHCl

m = berat pati oksidasi (db)DOS = DO sampleDOB = DO blanko (nature starch)

RESULT AND DISCUSSION

1. EFFECT OF DIFFERENT STARCH ORIGINS ON THE DEGREE OF OXIDATION (A)

-Corn Starch has the highest DO. Up to 45%, while DO of pea and sweet potato starch is 21,1% and 34%, respectively

-Corn starch has lower amylose but higher amylopectin -Gelatined amylopectin branches chain increase the space distant more facile for H2O2 to enter and oxidize OH

2. EFFECT OF MOLAR CONTENT OF CATALYST ON THE DEGREE OF OXIDATION (B)

-CuSO4 -> an effective catalyst for the oxidative system -> helf form *OH -> oxidize OH to carbonyl and/or carboxyl groups

-0,02% Cu2+ proper dosage (increase DO 5,9 % to 33,5%; a white product)->DO 5X higher than no catalyst

-more higher DO increased slightly (0,1%, 5,9->40,5%; 0,5%->48,7) -> undesirable colour

-excessive catalyst->nosufficient oxidant to be catalyzedCu2+ can be retained by carboxyl groups of oxidized starch undesirable colour

3. EFFECT OF REACTION TEMPERATURE ON THE DEGREE OF OXIDATION (C)

-Reaction T 15->55oC DO increases 25,4% to 53,8%; 55-60oC DO drops to 48,3%-T increase enhances H2O2 activity and swelling of starch gels, but >55oC H2O2 decomposes to O2 and H2O DO drops

4. EFFECT OF REACTION TIME ON THE DEGREE OXIDATION (D)

5. THE EFFECT OF THE CONTENT OF OXIDATION ON REACTION

-0,5-1,5 MolarH2O2/glucose of starch 19,5%-40,5% (optimal); 1,5%-10%40,5%-56,3%

- >1,5% catalyst unsufficient to react with H2O2 to form *OH lower reaction efficiency and decomposes

6. EFFECT OF DEGREE OF OXIDATION ON THE INTRINSIC VISCOSITY OF OXIDIZED STARCH

-oxidation of starch by H2O2 --> (OH carbonyl and carboxyl + starch depolimerization):

* at beginning faster reduction rate of viscosity & depolimerization; later slower

* when catalyst content >0,1 molar, reaction time at > 60 min, or oxidant at >1,5 molar increased H2O2

oxidized OH at C2 and/or C3 to carbonyl and carboxyl weakend the bond at C1 opening monomeric ring depolimerase starch chain via β-elimination reduction rate of viscosity * >>>>>>>>> H2O 2 mainly oxidized OH at C1 of anhydroglucose reduction rate of viscosity more modest

7. INFRARED SPECTROSCOPY

-OH3426.7

-CH2

2927.7

-C=O1735.6

Native

40,5%

56,3%

-Native starch were successfully oxidized by H2O2 OH changed to carbonyl and/or carboxyl groups

8. THERMAL STABILITY OF OXIDIZED STARCH

-Reduction in thermal stability < 210oC with increase of the DOindicates the ozidized starch can be thermally process into products -Oxidation->depolymerization->BM increase->DO increase

9. THERMAL TRANSITION BEHAVIOUR OF OXIDIZED STARCH

-No glass transition in oxidized starch from 20 to 200oC not thermoplastic, although DO increased from 5,9 to 56,3% -So many intra-intermolecular H bonds in starch which restrain the movement of molecules no glass transition in the oxidized starch

10. X-RAY DIFFRACTION OF OXIDIZED STARCH

Native crystallize

Gelatined

40,5%

56,3% = amorph

-The oxidized starch with low and high DO has different impact on the type and degree crystallization

11. TRANSMITTANCE OF OXIDIZED STARCH SUSPENSION

-oxidized starch more prone to gelatinize starch paste more transparant

-Molecular weight of oxidized starch dropped with increase of DO and its crystallized is destroyed easier to be gelatined , harder to be retrograde

-Stronger electrostatic repulsion between starch molecules when DO increase is caused by negarive charges of carboxyl groups easier transmittance light through the solution

CONCLUSIONS

CuSO4 was an effective catalyst for the oxidation of starch by hydrogen peroxide

Molecular weight, thermal stability of oxidized starch was decreased during the oxidation process

oxidized starch (upto 56,5%) did not have a glass transition temperature

Crystal structures were destroyed by the oxidation

The light transmittance increased greatly as the degree oxidation increased along with the heating temperature

Oxidized starch had potential application in the food industry, paper, textile, laundry finishing, plastics etc.

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