Prepare the indigestible dextrin from rice starch by pyrolysis with different catalysts and characterise their product

The effect of gamma-ray radiation combined with acid catalyst on pyrolysis to create resistance dextrin from rice starch .... Change in indigestible fraction of irradiated rice starch M1

MINISTRY OF EDUCATION AND TRAINING

NHA TRANG UNIVERSITY

MAI VU HOANG GIANG

PREPARE THE INDIGESTIBLE DEXTRIN FROM RICE STARCH BY PYROLYSIS WITH DIFFERENT CATALYSTS

AND CHARACTERISE THEIR PRODUCT

MASTER THESIS

KHANH HOA - 2020

MINISTRY OF EDUCATION AND TRAINING

NHA TRANG UNIVERSITY

Ơ

MAI VU HOANG GIANG

PREPARE THE INDIGESTIBLE DEXTRIN FROM RICE STARCH BY PYROLYSIS WITH DIFFERENT CATALYSTS

AND CHARACTERISE THEIR PRODUCT

MASTER THESIS

Decision on establing the commitee:

Suppervisor:

Assoc.Prof.Dr Nguyen Duy Lam

Chairman:

Dr Khong Trung Thang

Faculty of Graduate Studies:

KHANH HOA - 2020

UNDERTAKING

I undertake that the thesis entitled ―Prepare the indigestible dextrin from rice

starch by pyrolysis with different catalysts and characterise their product‖ is my own

work The work has not been presented elsewhere for assessment until the time this thesis is submitted

Ha Noi, Date 1 month 7 year 2020

Author

Mai Vu Hoang Giang

ACKNOWLEDGMENT

I would like to express my deepest appreciation to the teachers in the Food Technology Faculty of Nha Trang University (NTU) for helping and offering the best conditions for me to complete the thesis

My special thanks go to Assoc Prof Dr Nguyen Duy Lam for the continuous support of my master study and research, for his patience, motivation, enthusiasm, and immense knowledge His guidance helped me in all the time of research and writing of this thesis

I would like to express my sincere gratitude to many researchers and staff of the Center of Food Quality and Safety Research (CEFORES) under the Vietnam Institute

of Agricultural Engineering and Post-harvest Technology (VIAEP) for supporting and facilitating me during the time of researching and doing the thesis

Last but not the least, I would like to thank my parents and to my brothers and sister for supporting me spiritually throughout writing this thesis

TABLE OF CONTENT

UNDERTAKING iii

ACKNOWLEDGMENT iv

TABLE OF CONTENT v

LIST OF ABBREVIATIONS ix

LIST OF TABLES x

LIST OF FIGURES xi

ABSTRACT xiv

CHAPTER 1 INTRODUCTION 1

1.1 Introduction 1

1.2 Research objectives 3

1.2.1 Main objective 3

1.2.2 Specific objectives 3

CHAPTER 2 OVERVIEW OF RESEARCH ISSUES 4

2.1 Introduction of resistant dextrin 4

2.1.1 Starch, rice starch and modified starch 4

2.1.2 Resistant starch 6

2.1.3 Resistant dextrin 7

2.1.4 Biological activity, health significance and food additive 8

2.1.5 Resistant dextrin/maltodextrin market 10

2.2 Starch pyrolysis to create pyrodextrin with acid catalyst 10

2.2.1 Steps of starch pyrolysis with acid catalyst 10

2.2.2 Pyrolysis reactions and the formation of indigestible fraction 12

2.3 Starch pyrolysis to create pyrodextrin with gamma radiation as catalyst 14

2.3.1 The effect of gamma irradiation on starch 14

2.3.2 The effect of irradiation treatment on the content of resistant starch 15

2.4 Starch pyrolysis to create pyrodextrin with other catalysts 16

2.5 Characteristics of resistant pyrodextrin and typical analytical techniques 17

2.5.1 Characteristics of resistant dextrin 17

2.5.2 Typical analytical methods 18

CHAPTER 3 MATERIALS AND METHODS OF RESEARCH 20

3.1 Research subjects 20

3.2 Chemicals 20

3.2.1 Kit sets 20

3.2.2 Acids used as catalysts 20

3.2.3 Other analytical chemicals 20

3.3 Equipment and tools 21

3.4 Experiment design 21

3.4.1 Experiment 1 Effects of different acid on pyrolysis 21

3.4.2 Experiment 2 Effect of concentration of HCl on pyrolysis 22

3.4.3 Experiment 3 Effect of pyrolysis temperature 22

3.4.4 Experiment 4 Effect of pyrolysis time 22

3.4.5 Experiment 5 Effects of gamma radiation in different doses 23

3.4.6 Experiment 6 Effect of gamma radiation in different dose rates 23

3.4.7 Experiment 7 Effect of gamma irradiation combined with non-acidic catalysist pyrolysis 23

3.4.8 Experiment 8 Effect of gamma irradiation combined with HCl catalysist pyrolysis 24

3.4.9 Experiment 9 Effect of the rate of activated carbon added 24

3.4.10 Experiment 10 Effect of pyrolysis time with activated carbon catalyst 24 3.4.11 Experiment 11 Verification of pyrolysis at pilot scale and final product charactification 24

3.5 Analytical methods 25

3.5.1 Indigestible Fraction (IDF) 25

3.5.2 Total Dieatary Fiber (TDF) 25

3.5.3 Color difference 25

3.5.4 Water absorption 26

3.5.5 Solubility 26

3.5.6 pH of starch and dextrin 27

3.5.7 Protein and crude fat content 27

3.5.8 Investigation with scanning electron microscope (SEM) 27

3.5.9 Investigation by X-ray diffraction measurement (XRD) 28

3.5.10 Fourier transform infrared spectrometry (FTIR) 28

3.5.11 Differential scanning calorimetry (DSC/DTA) 28

3.5.12 Rapid viscosity analysis (RVA) 28

CHAPTER 4 RESULTS AND DISCUSSION 30

4.1 Acid catalytic effect on pyrolysis to create resistant dextrin from rice starch 30

4.1.1 Effect of some acid as catalyst on products of pyrolysis 30

4.1.2 Effect of concentration of HCl as catalyst on products of pyrolysis 33

4.1.3 Effect of pyrolysis temperature on products of reaction 35

4.1.4 Effect of pyrolysis time on products of reaction 37

4.2 Effects of gamma-ray radiation on rice starch 40

4.2.1 Effect of gamma-ray radiation on the indigestible fraction 40

4.2.2 Effect of radiation dose rate on the indigestible fraction 42

4.2.3 Effects of gamma-ray radiation on physicochemical properties 43

4.2.4 Effects of gamma-ray radiation on molercular structure 48

4.3 The gamma-ray radiation as catalysits for pyrolysis to create indigestible dextrin from rice starch 53

4.3.1 Change in the indigestible fraction 53

4.3.2 Change in the whiteness of dextrin 54

4.3.3 Change in the solubility and pH of dextrin 55

4.3.4 Change in molercular structue 56

4.4 The effect of gamma-ray radiation combined with acid catalyst on pyrolysis to create resistance dextrin from rice starch 60

4.4.1 Pyrolysis having the same duration 60

4.4.2 Pyrolysis having whiteness 65% 61

4.4.3 Pyrolysis at different temperatures to the same 65% whiteness 63

4.4.4 Change in molercular structure 64

4.5 The effects of gamma-ray radiation, acid and activated carbon on pyrolysis create

pyrodextrin from rice starch 66

4.5.1 The effect of activated carbon with different rate added 66

4.5.2 Effect of activated carbon with different pyrolysis duration 69

4.6 Technological flowchart and its verification at pilot scale 72

4.6.1 Process flowchart and process description 72

4.6.2 Quality parameters of final product 76

CHAPTER 5 CONCLUSION AND RECOMMENDATION 78

5.1 Conclusion 78

5.2 Recommendation 78

REFRENCES 79 APPENDIX 1: Some other analytical methods I APPENDIX 2: Results of data processing on Minitab VII APPENDIX 3: Pictures of some laboratory equipment and tools XXVIII APPENDIX 4: Pictures of some experiments and products XXXI APPENDIX 5 Spectrums of XRD, FTIR, DSC/TGA, SEM, RVA XXXIV

LIST OF ABBREVIATIONS

AACC : American Association for Clinical Chemistry

AOAC : Association of Official Analytical Chemists

DE : Dextrose Equivalent

DF : Dietary Fiber

DP : Degree of Polymerization

DP : Degrees of polymerization

DTA : Differentail thermal analysis

EPR : Electron paramagnetic resonance

FAO : Food and Agriculture Organization of the United Nations FDA : Food and Drug Administration

GMP : Good Manufacturing Practices

GPC : Gel permeation chromatography

GRAS : Generally Recognized as Safe

IDF : Indigestible Dextrin Fraction

TGA : Thermogravimetric analysis

WHO : World Health Organization

LIST OF TABLES

Table 4.1 Effect of acid concentration on quality of resistant dextrin products 34

Table 4.2 Change in RVA viscosity characteristics of irradiated starch 47

Table 4.3 The weight reduction of specific samples 51

Table 4.4 The quality of final product 76

Table 4.5 The weight reduction of specific samples 76

LIST OF FIGURES

Figure 1 1 Chemical structure of starch 4

Figure 4.1 Effect of different acids as catalyst in pyrolysis to produce resistant dextrin from rice starch M1 (170C, 120 min) 30

Figure 4.2 Change in whiteness of dextrin pyrolyzed with acetic, citric, hydrochloric or lactic acid as catalyst for 120 minutes 31

Figure 4.3 Effect of acetic, citric or lactic acids as catalyst in pyrolysis to produce resistance dextrin at 170°C for 300 minutes 32

Figure 4.4 Effect of pH due to acid addition as catalyst on color of resistant dextrin product 34

Figure 4.5 Effect of pyrolysis temperature on quality of resistant dextrin from rice starch M1 35

Figure 4.6 Effect of pyrolysis temperature on quality of resistant dextrin from rice starch M2 36

Figure 4.7 Effect of pyrolysis temperature on pyrodextrin color from rice starch M1 37 Figure 4.8 Effect of pyrolysis time on quality of resistance dextrin from rice starch M1 38

Figure 4.9 Effect of pyrolysis time on quality of resistance dextrin from rice starch M2 38

Figure 4.10 Effect of pyrolysis time on the whiteness of rice starch M1 and M2 with HCl acid catalyst 39

Figure 4.11 Change in indigestible fraction of starch M1 at different irradiation dose 40

Figure 4.12 Change in indigestible fraction of starch M1 at different irradiation dose 41

Figure 4.13 Change in indigestible fraction of irradiated rice starch M1 at different irradiation dose rates 42

Figure 4.14 Change in amylose content of rice starch M1 at different irradiation dose 43

Figure 4.15 Change in E of starch M1 at different irradiation dose 44

Figure 4.16 Change in solubility of starch M1 at different irradiation dose 45

Figure 4.17 Change in pH of starch M1 at different irradiation dose 46

Figure 4.18 RVA pasting profiles of native (0kGy) and irradiated starch 48

Figure 4.19 Results of XRD diffraction of starch M1 at different irradiation doses without catalyst 49

Figure 4.20 FTIR of starch M1 at different irradiation doses without catalyst 50

Figure 4.21 TG results of starch M1 at different irradiation doses 51

Figure 4.22 SEM pictures of starch at different irradiation doses without catalyst 52

Figure 4.23 DSC results of starch at different doses without catalyst 52

Figure 4.24 Changes in content of indigestible fraction of pyrodextrin from irradiated rice starch M1 at different dose rates, without acid catalysis 54

Figure 4.25 Change in whiteness of pyrodextrin from rice starch M1 irradiated at different dose rates, without acid catalyzed 55

Figure 4.26 Change in the solubility of pyrodextrin from irradiated rice starch M1 at different irradiation dose rates, not acid catalytic 56

Figure 4.27 Results of XRD diffraction of starch M1 at different irradiation doses for pyrolysis 56

Figure 4.28 FTIR of starch M1 at different irradiation doses with pyrolysis 57

Figure 4.29 TG results of starch M1 at different irradiation doses with pyrolysis 58

Figure 4.30 SEM pictures of starch M1 at different irradiation doses with pyrolysis 59 Figure 4.31 DSC results of starch M1 at different irradiation doses with acid catalyst for pyrolysis 60

Figure 4.32 Indigestible fraction of pyrolysis starch M1 (170C, 350 minutes) with catalytic irradiation 61

Figure 4.33 Effect of irradiation and pyrolysis on indigestible fraction of pyrodextrin at the same time 62

Figure 4.34 Effect of irradiation and pyrolysis on indigestible fraction of pyrodextrin with the same 65% whiteness at different temperatures 63

Figure 4.35 Results of XRD diffraction of starch M1 at different irradiation dose combined acid HCl for pyrolysis 64

Figure 4.36 FTIR of starch at different irradiation doses with acid catalyst for pyrolysis 64

Figure 4.37 TG results of starch at different irradiation doses with acid catalyst for pyrolysis 65

Figure 4.38 SEM pictures of starch at different irradiation doses with acid catalyst for pyrolysis 66 Figure 4.39 Change in whiteness and E of pyrodextrin by pyrolysis 10 kGy irradiation combined with actived carbon catalyst 67 Figure 4.40 Change in color of pyrodextrin solution by pyrolysis 10 kGy irradiation combined with actived carbon catalyst 68 Figure 4.41 Change in visual color of pyrodextrin solution by pyrolysis 10 kGy irradiation combined with actived carbon catalyst 68 Figure 4.42 Change in indigestible fraction of pyrodextrin by pyrolysis 10 kGy irradiation combined with actived carbon catalyst 69 Figure 4.43 Change in indigestible fraction and whiteness of pyrodextrin by pyrolysis

10 kGy irradiation combined with actived carbon catalyst at different times 70 Figure 4.44 Change in color of pyrodextrin by pyrolysis 10 kGy irradiation combined with actived carbon catalyst at different times 71 Figure 4.45 Change in color of pyrodextrin solution by pyrolysis 10 kGy irradiation combined with actived carbon catalyst at different times 71 Figure 4.46 Illustration of the location of the starch tanks in the irradiation chamber 73 Figure 4.47 Schematic diagram of the production process of indigestible rich pyrodextrin from irradiated rice starch 75 Figure 4.48 Weight reduction of starch samples during different processing conditions 76

ABSTRACT

The aim of this thesis is to study the effect of catalysts on the pyrolysis of rice starch to produce resistant (indigestible) dextrin, and also determine pyrolysis condition such as time, temperature of pyrolysis, color change and some other factors

to build the process of producing resistant dextrin from rice starch

Four acids of acetic, citric, lactic and hydrochloric have been tested as acidic catalyst for pyrolysis reaction The results have shown that only acid clohydric has a high catalytic efficiency, as shown in the results of producing resistant dextrin products with the highest content of indigestible fraction and solubility, while need processing time for pyrolysis short and lowest mixing ratio with acid When using hydrochloric acid as a catalyst, that is necessary to add this acid to the starch so that it has a pH of 2.3 - pH 2.5, regardless of the original pH of starch

In the pyrolysis process, with the same pH, the higher pyrolysis temperature and the longer pyrolysis time, the rice starch will be changed stronger However, when the whiteness drops below 55%, the color is deep-brown and has a burnt smell Under experimental conditions, depending on the starch purity, the appropriate treatment temperature is 170-180°C and the appropriate treatment time is about 120 minutes High dose gamma irradiation has effect of increasing the indigestible fraction very clearly This increase is of practical significance because at doses 5-10 kGy has shown very significantly Rice starch IR50404 has content of indigestible fraction (IDF) 23.39%, irradiation of 10 kGy increased to 27.86% (increased by nearly 20%), dose of 30 kGy increased to 30.02% (increased by nearly 30%) The amylose content

of rice starch IR50404 was significantly reduced when irradiated in the 5-50 kGy dose range High dose irradiation increases the color difference (ΔE) of rice starch, and there exists a clear relationship between increased ΔE and increased indigestible fraction The whiteness difference irradiated starch from the non-irradiated starch cannot be detected with the naked eye nor with the whiteness meter Kett C-300, even

at a dose of 50 kGy, is displayed when measuring ΔE The indigestible fraction and solubility increase when the dose of irradiation increases However, the solubility was low even at high doses, indicating that the low molecular components are not much Irradiation in the 5-50 kGy dose range reduced the pH of starch Irradiation reduces

the RVA viscosity in accordance with the result of increase or decrease in amylose, solubility, and pH The effect of 10 kGy dose is clear and significant, occurring with irradiation of 1, 2 and 3 kGy/h doses rate for starch and acid-catalyzed pyrodextrin products from the irradiated starch

Activated carbon has been added to the pyrolysis process as a catalyst used to color the product.When adding activated carbon at different proportions, there is quite

de-a lde-arge difference in both the content of indigestible frde-action de-as well de-as in color When the concentration of additional activated carbon increases from 1-5%, the color of the starch solution after filtration becomes lighter a lot However, the content of IDF tended to decrease When pyrolysis with different times, it can be seen, the longer the pyrolysis time, the more the content of IDF, but reduces the ability of the activated carbon to decolorize Pyrolysis at 170ºC with 2% activated carbon until 38% whiteness found that the indigestible fraction was less than to that of acid catalytic irradiated starch, but much better dextrin color reduction

The results of research on molecular structure and properties show that RVA viscosity varies greatly with irradiated dose However, irradiation does not change the structure of amylose or amylopectin starch molecules even at doses up to 50 kGy This

is shown when examining RMD spectrum (X-ray diffraction), infrared spectrum (FTIR), nuclear magnetic resonance (NMR) Scanning electron microscopy (SEM) image analysis also did not detect the morphological change of starch particles due to irradiation The spectral change of the above structural analyzes shows only the difference due to heat treatment and the combination of HCl acid catalytic heat treatment From the results stated, a technological process for the preparation of pyrodextrin powder as feedstock for the production of resistant maltodextrin from rice starch has been proposed The process has been tested at a pilot scale of 8 kg/batch, achieving consistent product quality results in independent pyrolysis runs, and achieving quality comparable to laboratory pyrolysis

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CHAPTER 1 INTRODUCTION 1.1 Introduction

Currently in Vietnam, many rural localities still popularly plant some low-quality rice varieties because these varieties have high yield, disease resistance and easy adaptation to poor farming and care conditions Low quality rice has a large yield but low quality, which significantly affects the ability to export, price and reputation of Vietnamese rice A processing solution to diversify products from rice in general and low-quality rice in particular is a very potential output direction However, due to the lack of deep processing technology, there are not many products with high added value Currently, rice-processed products mainly meet Vietnamese traditional culinary habits without high-end products Obviously, new technology is needed to make a breakthrough in processing new products of high value from rice

The new products from starch in Vietnam most successful so far are "modified starches" created by modified starch structure by chemical methods and enzyme However, most such modified starches are made from starch of cassava, corn, potatoes, and wheat without using rice starch Most importantly, due to chemical denaturation that changes the structure, especially due to curing, grafting, or oxidation, they are not allowed to be used as food in the true sense of the word, but only as additives, i.e is only a certain percentage of the food

Processing rice into resistant starch has many benefits for health and food processing Beneficial for health because when eaten, they are not hydrolyzed by the enzyme amylase, so they are not absorbed through the small intestine, significantly reducing energy supply to the body, not increasing blood sugar This is very suitable for the health of the group of people with diabetes, obesity, blood fat, heart disease, weight loss diets Resistant starch is yet another (new generation) dietary fiber that has

health benefits for everyone because of its properties superior to existing fibers (Ye al,

2015) On the other hand, this fiber is acid stable, heat resistant, and is not altered as

an additive in food processing or by digestive enzymes in the body when consumed In addition, this fiber has a suitable color and odor, does not change the texture and taste

of food when mixing and does not need to change the recipe (Park et al, 2011).

Dextrin pyrolysis is the most common denaturation of starch, in which thermal or acid catalytic hydrolysis converts the starch into oligosachcharides with a much smaller molecular weight During this process, there is a breakdown of the glycozide bonds and a rupture of the intermolecular and intermolecular bonds, making dextrin easily soluble in water Simultaneously with the new arrangement, created many other links make products become resistant dextrin digest for enzyme of human digestion So, dextrin produced by the pyrolysis method is called resistant dextrin The structure of the resistant dextrin has straight and branched lines, in which the glucose units are bound by α-1,2; α-1,3; β-1,2; β-1,3 and β-1,4 bonds next to the common α-1,4 and α-1,6 bonds Acid-catalytic dextrinisation is an ionization process in which pyrolysis follows a free radical mechanism That is, starch pyrolysis will create free radicals whose concentration depends on the starch roasting temperature and time.Heat-generated dextrin is also known as the resistant pyrodextrin or the resistant dextrin From a technological standpoint, there are four main steps in pyrodextrin production: pretreatment, pre-drying, pyrolysis and quenching In the above steps, the most important step to decide the final product is pyrolysis During pyrolysis or dextrinization, the parameters determining the quality of dextrin products are pH, humidity, temperature and time We will use different catalysts and conditions in the pyrolysis process In this study, we choose acids, gamma rays and activated carbon as catalysts for pyrolysis

Hydrochloric acid is most commonly used in research as well as in actual industrial production of maltodextrin Belonging to inorganic acids, phosphoric acid is also used in limited use There are not many catalytic studies on weak organic acids and incomplete results on efficacy and lack of comparison Even when using hydrochloric acid as a catalyst, there is little information from previous studies on the effect of this acid mixing ratio on starch In most cases, a ratio of 0.1% is used without mentioning the base of use Irradiation can also cut the circuits of starch in the same way that acids do That is the basis for this topic to apply irradiation or in combination with the acid catalyst involved in the fecal irradiation process as a catalyst to improve the process efficiency as well as the value of the product Some technologists around the world have introduced using activated carbon as catalyst for glucose pyrolysis The effectiveness of the activated carbon catalyst is so obvious for glucose syrup that the

proposed process is used industrially However, the use of activated carbon for starch pyrolysis has not been announced

From the above reasons, we performed the topic ―Prepare the indigestible dextrin

from rice starch by pyrolysis with different catalysts and characterise their products”

1.2 Research objectives

1.2.1 Main objective

Evaluate the effects of several types of catalysts in the pyrolysis reaction to produce pyro dextrin from rice starch and determine the changes in the product's characteristics, properties, and structure

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CHAPTER 2 OVERVIEW OF RESEARCH ISSUES

2.1 Introduction of resistant dextrin

2.1.1 Starch, rice starch and modified starch

2.1.1.1 Starch

Starch is a major agricultural product that is consumed and/or used on a daily basis nearly the whole world over Starch is composed of the 2 glucohomo-polysaccharides amylose and amylopectin Amylopectin has straight chain α-(1-4)-linked sections as well as α-(1-6)-glycosidic linkages, which results in a highly branched structure, whereas amylose is a predominantly α-(1-4)-linked straight-chain glucan Starch is found in high proceedings in various cereal grains, pulses, tubers, as well as some roots in the form of discrete particles referred to as starch gran- ules Starches from different botanical sources vary in their functionality depending on the amounts of amylose and amylopectin, their respective degrees of polymerization (DP), crystallinity, and mineral content, especially phosphorus Amylopectin ranges in molecular weight from 1x107 to 1x109 Daltons, with the peripheral A- and B1-chains

on the amylopectin molecule having respective DP of 12 to 16 and 20 to 24 glucose units Primary branches (B2-, B3-, and B4-chains) have a DP of 42 to 48, 69 to 75,

and 101 to 119, respectively, and are attached to a sole C-chain (Tester et al., 2004) In

contrast, amylose has a lower molecular weight, ranging in size from 1x105 to 1x106 Daltons, with chains having up to 700 glucose units, but containing few (<1%) alpha-(1-6)-linked branch chains

Figure 1 1 Chemical structure of starch

Crystalline powder degraded (hydrolysed) by enzyme α-amylase, glucoamylase and sucrase-isomaltase in the small intestine glucose free form it is absorbed However, not all carbohydrates in the diet are digested and absorbed The digestibility of starch depends on the enzyme how to reach the circuit glucose in food supply or somehow make them the process of linking together Therefore, starch sources are classified into three categories: fast digestion (FDS), slow digestion (SDS) and resistant (RS) Starch is the main source of food for mankind, but also has great applications in many industries, including the food industry

2.1.1.2 Rice starch

Rice starch is a natural polymeric carbohydrate and the main component of rice In its native form it is an insoluble white powder consisting of both amylose and amylopectin The difference between rice starch and flour is that most of the native proteins and lipids in the flour have been removed The protein content of milled rice

in a germplasm collection reportedly ranged from 4.5% to 15.9% Lipids exist in rice

at much lower content Therefore, isolation of starch from rice mainly involves techniques to remove proteins The majority of rice protein is alkaline soluble, and so alkaline steeping method is commonly used in industry and research to produce rice starch with good recovery, low residual protein content, and low damaged starch

content The goal for the protein content of isolated rice starch is generally 0.5% or less

Besides proteins, other minor constituents including lipids, phosphorus, and trace elements, are commonly found in the isolated rice starch Non-waxy rice contains 0.3%-0.4% bound lipids, while waxy rice starch contains less of this fraction (0.03%) The formation of an amylose-lipid complex (sometimes referred to as starch-lipid or

phospholipids) was reported by Morrison et al (1993) in intact starch using a

solid-state nuclear magnetic resonance technique The composition of total starch lipids

in nonwaxy rice starch has an average of 32% free fatty acids and 68% lysophospholipids (LPLs) including lysophosphatidyl choline (LPC) and lysophos-phatidylethanolamine (LPE)

Phosphorus plays an extremely important role in starch functional properties, such as, paste clarity, viscosity consistency, and paste stability Phosphorus in starch is

mainly present in two forms: phospholipids and phosphate monoesters In nonwaxy rice starch, phosphorus is mainly in the form of phospholipids, in waxy rice,

phosphorus is present as starch phosphate monoesters

2.1.1.3 Modified starch

To create modified starch, there are 3 groups of methods that are applied: physical, chemical and enzyme-hydrolysis methods Chemically modified starch is widely used in many industries, including the food industry, while the modified physical and hydrolyzed starch is mainly used in the food processing industry products Chemically modified starches to be divided into two types of starch and starch cutting replacements

Starch modified by the enzyme: Application enzyme to handle starch essentially

2 groups was resolution purposes and modified starch Enzyme resolution reduces the molecular weight form of starch or sugars oligosaccharide, also modified only mitigate

or increase the molecular weight Starch hydrolysis by enzyme very popular and offers Vietnam than hydrolysis chemistry (such as alkali or dilute acid), products created are simple sugars (glucose, maltose, fructose, HFCS), syrup with DE (dextrose equivalent)

> 20 and maltodextrin have DE <20

Starch modified by physical methods: Belongs to the physical modification method, mainly the moist heat method, in addition to the microwave heat method, irradiation, and high-pressure treatment (HHP) Gelatinization occurs when heat treatment occurs depending on the temperature and type of starch Currently, to produce resistant starch , mainly using moist heat method because of its efficiency and economy

2.1.2 Resistant starch

Resistant starch and resistant starch products are not digested when passing the small intestine Resistant starch is not hydrolyzed to D-glucose in the small intestine within 120 minutes of ingestion but fermented in the colon Many studies have shown that starch sidelines digestible molecules containing α-linear-glucan 1,4-D is transformed from amylose degeneration (retrograded) and the molecular weight is relatively low (1,2x105 Da ) (Ratnayake & Jackson, 2007) Currently, inert starch is

classified into 5 groups as follows:

Group RS1: Starch is synthesized in the endosperm of the grain, and the starch particles are surrounded by protein base and cell wall material These physical structures limit the ability of starch to digest and reduce blood glucose response The cell wall and protein base materials create a physical barrier that interferes with enzyme access and hydrolysis of starch Examples of foods containing group 1 resistant starch include whole grain or coarse ground bread and pasta made from extruded hard wheat

Group RS2: Unprocessed high-amylose potato starch, green banana, ginkgo biloba with polymorphic structure B or C are starch that is highly resistant to

hydrolysis of an enzyme Group 2 inert starch group (RS2) (Jiang & Jane,

2013) However, after cooking, most of the starches, such as baked potatoes and

cooked bananas, become easily digestible, causing starch gelatinization and disappearance of the B and C crystals

Group RS3: Is a resistant starch group formed by the retrogradation of starch, ie when the starch is cooked and cooled RS3 is assessed to be very resistant to temperature and curing agents

Group RS4: A group of resistant starch obtained from chemical transformation This resistant starch is very diverse in structure and is not found in nature RS4 starch

is a group of chemically modified starches including those that are ethers, esterified or chemically cured to reduce the digestibility of starch The soluble form of polysaccharide is resistant maltodextrin also called resistant starch

Group RS5: When starch interacts with fat, amylose and amylopectin long

branched chains form single helix combinations with fatty acids and alcohols (Hasjim

et al., 2013) When linear starch circuits are in helical structure with fatty acids in the

spiral groove, the binding and separation of starch by amylase is prevented

2.1.3 Resistant dextrin

Resistant dextrin in foreign countries usually produced from corn starch, potato and wheat using high temperatures and low humidity (dry roasting process or pyrolysis) As with conventional dextrin, these resistance products are heterogeneous mixtures of D-glucose polymers with molecular weights ranging from 3500 to 6000 depending on quality After that, the dextrin is purified and concentrated to varying

degrees by standard methods in the powdered sugar industry to produce different grades of product quality Finally, they are spray dried This final dextrin product has a relatively low viscosity, high water solubility and contains between 40% and 60% of food fiber The structure of the resistant dextrin has straight and branched lines, in

which the glucose units are bound together by α - 1,2, α - 1,3, β -1,2, β -1,3 and β -1,4,

next to the common links α - 1,4 and α - 1,6 These and other similar products have

been used in many foods, and as dietary fiber or bulking agents

Compared with conventional dextrin, the difference in resistant dextrin is that resistant dextrin contains beta bonds To make the difference outside digestibility also differ in technology: resistance dextrin is using pyrolysis or glucosyltransferil

chemicals by enzymes are α -glucosyltransferase in liquid

2.1.4 Biological activity, health significance and food additive

High fiber intake has been clinically proven health benefits, especially for diabetes, weight loss, and other digestive health problems National Cancer Institute researchers recently reported that increased fiber intake is also linked to a reduced risk

of death from cardiovascular, infectious, and respiratory diseases There are two types

of dietary fiber: insoluble in water and soluble in water The water-soluble types can

be divided into viscous and non-viscous fibers Insoluble and viscous fibers, although beneficial for health, can negatively affect food sensory properties Soluble and non-viscous fibers, besides having a positive effect on gut health, are virtually undetectable

in fortified foods Even to a significant extent, they do not affect food product flavor or viscosity The International Food Standards Commission (DF) defines food fiber (DF)

as "A carbohydrate polymer with 10 or more monomer units, not hydrolyzed by

endogenous enzymes in the human small intestine" This definition includes resistant

starch Thus, DF is the type of carbohydrates that are eaten, but not digested in the small intestine, but to the large intestine where intestinal bacteria can be broken down

(fermented) to form easily absorbed substances (Filliz et al.,2013)

To be accepted as a supplement to a food product, the DF must satisfy many requirements that it must first be a food ingredient Then there are many properties and effects for the food system DF can provide many functional properties at once when they are incorporated into the food system Therefore, the addition of fiber contributes

to the alteration and improvement of the structure, sensory properties, and shelf life of foods due to its water-binding capacity, gel-forming ability, fat imitation, anti-

adhesion, anti-pilling, improving structure (Balto et al, 2016) FAO and WHO

recommends a daily intake of fiber totaling 38 grams for men and 25 grams for women However, in the US, it is only about 40%, in Europe and Japan, about 50-60% In Vietnam, there are no survey data, but modern life with a new trend of eating, certainly does not meet the recommended amount of fiber

In recent years, awareness of the importance of DF consumption for health benefits has increased dramatically globally The biggest reason is that there is sufficient scientific evidence on the relationship between fiber deficiency and many chronic diseases such as cardiovascular disease, certain cancers, diabetes, and obesity Furthermore, a lack of fiber can lead to several diseases and disorders of the digestive system To the growing prevalence of these diseases and disorders, food technologists have added "functional fibers", namely resistant carbohydrates, of which resistant

maltodextrin is ingested food series (Anderson J.W et al, 2009)

Resistant maltodextrin (RMD) is resistant starch (belonging to the RS4 group) These resistant starches have been studied and proven to function as dietary fibers They can control body weight by: 1- Reducing the number of calories consumed; 2- Increased feelings of fullness; 3- Increased fat oxidation; 4- Reduce fat reserves RMD can control blood sugar, as shown in: 1- Reduced blood sugar response in healthy people and diabetics; 2- Insulin sensitivity increases in healthy people, type II diabetics as well as people with insulin resistance; 3- The health of blood sugar of the next generation is increased when the pregnant mother uses the resistant maltodextrin; 4- Improves group I insulin secretion RMD can help with the maintenance of a healthy colon and digestive system through several mechanisms, such as ―prebiotic fiber‖ and preservative compounds RMD is slowly fermented in the colon, producing less acid and gas than most other conventional fibers, thus avoiding the side effects of

high intake of substances fiber (Maria et al.,2016)

Resistant maltodextrin (RMD) is compatible with almost any product and is multifunctional so it can be used in a multitude of applications It is the perfect application for processors as well as consumers It can be incorporated into all types of beverages, processed foods, dairy products, frozen milk desserts, confectionery, and

dietary supplements of any kind In addition to being a fiber supplement as mentioned above, RMD has many valuable characteristics, functions, and sensory properties and

is superior to other fiber or additives, providing many benefits useful in food and

beverage processing (Blazek & Gilbert, 2010)

2.1.5 Resistant dextrin/maltodextrin market

While some manufacturers of conventional dextrin are abundant, the number of companies and firms manufacturing and trading in resistant dextrin is significantly lower and has been around for about 10 years The product with the trade name Fibersol® by Matsutani Chemical Industry Co., Ltd (Japan) has been introduced to the world market since 1990 Twenty years later, the British Tate & Lyle Company launched the PROMITOR® Soluble Corn Fiber, company Roquette Freres (France) introduces the Nutrias® product All three of these products are essentially resistant maltodextrin In China have Biology Baolingbao company engaged in research and development, production, and marketing of functional sugar and food ingredients in China and internationally, including digestion resistant maltodextrin Very recently (2015) Fibrixa products manufactured by Hayashibara Co Ltd under Nagase Group Japan were also recognized by the FDA (USA) as a GRAS safe product and released

to the market However, Fibrixa is an iso maltodextrin Resistant maltodextrin products are supplied by companies around the world, and their factories are constantly under construction For example, in 2014, Tate & Lyle built a large factory

in China that was its third-largest after two factories in the Netherlands, USA In China, there are also several companies producing and trading resistant maltodextrin and dextrin made by China

2.2 Starch pyrolysis to create pyrodextrin with acid catalyst

2.2.1 Steps of starch pyrolysis with acid catalyst

The process begins with the starch treated with acid, the most common being hydrochloric acid Then dry again to achieve very low humidity, usually only 4-5% The dextrination process is the roasting (pyrolysis treatment) process The resulting products are called dextrin or more precisely pyrodextrin Depending on the reaction conditions (e.g acid concentration, humidity, temperature, and curing

time), different products are available There are four main steps in the pyrodextrin process: pretreatment, pre-drying, pyrolysis, and cooling

2.2.1.1 Pretreatment

Starch pretreatment is the process necessary to achieve the goal of reducing the

pH of starch during processing A very low pH is required during the production of golden dextrin, usually achieved by spraying starch with a dilute solution of inorganic acids (such as hydrochloric acid) in a horizontal or vertical mixer Gaseous hydro-chloric acid may also be used especially when treating gelatinized starch British gum

is manufactured without additives or using only salts such as trisodium phosphate, ammonium bicarbonate to maintain a neutral or alkaline pH After spraying or mixing additives, the incubation time can be about 30 minutes with white dextrin, up to 18

hours with British gum, but for yellow dextrin usually a few hours (Terpstra K.R., et

al.,2010) The uniform distribution of the additive (acid) in the starch is very important

to avoid a phenomenon in the subsequent heating step

2.2.1.2 Pre-drying

The drying step that reduces the water content can accelerate the hydrolysis of starch polymers at heating, especially at acid pH Hence, this step is crucial for the production of yellow dextrin However, this is less important for the production of white dextrin, where hydrolysis is the main reaction involved and for British gums where pyrolysis occurs at higher pH The pre-drying process can be combined with the pyrolysis step, if the starch is heated slowly and stirred continuously

2.2.1.3 Starch pyrolysis (pyrodextrinization)

The pyrolysis can be performed in a vertical or horizontal mixer heated directly

or with a steam or oil Stirring during the process is important for a homogeneous product due to even heat distribution Acidity, temperature, speed of temperature rises and the incubation period is variable number of important stages of this pyrolysis For example, white dextrin is usually produced between 95°C and 120°C, yellow dextrin between 150°C and 180°C and British gum between 170°C and 195°C The change

of the variables of this will lead to create many kinds of pyrodextrin (Ohkuma K et al,

2001) In general, the increase in acidity causes pyrodextrin to have a lower viscosity

while a higher temperature causes pyrodextrin to have a higher degree of branching

2.2.2 Pyrolysis reactions and the formation of indigestible fraction

The chemical changes that occur during dextrination are not fully understood However, three types of chemical reactions are thought to be involved: hydrolysis, transglucosidation, and polymerization The importance of each reaction will depend on the type of pyrodextrin produced

2.2.2.1 Hydrolysis

This first step in the pyrolysis of dextrin is characterized by hydrolysis of

the α (14) glycozite bonds during pre-drying and the first stage of pyrolysis Due to the hydrolysis of starch polymers, the viscosity of the product decreases and the reduction degree increases Hydrolysis reaction seems to be the main reaction occurring during white dextrin production

2.2.2.2 Transglucositization process

A related second reaction is that the transglucositisation process begins when the water content of starch is low Therefore, this reaction dominates the production of yellow dextrin and British gum In summary, starch chains are broken down at (14) bonds and react with hydroxyl groups of different chains to produce branching points Theoretically, this chain rearrangement could produce glucoside bonds (12), (13), (14), and (16), existing either in the α or β-anomers

However, Theander & Westerlund (Theander & Westerlund, 1987) has

reported statement in the presence of O-α-glucopyranosyl-maltosan (14) Anhydro-β-D- glucopyranose after pyrodextrin hydrolyzate of potato starch and wheat by enzymes (Termamyl and amyloglucosidase) These authors suggest that 1,6-anhydro-β-D-glucose (or levoglucosan) was present as the terminal unit in these pyrodextrins

1,6-Recently, a number of authors have studied the cycloheptaamylose pyrolysis as a model for starch The pyrolysis is carried out at extremely high temperatures (usually 250-1000ºC) and at different pressures (for example in a vacuum) Under these conditions, starch produces a wide variety of volatile and non-volatile compounds However, low temperature pyrolysis can provide information about the reactions that occur during high-temperature metabolism Indeed, Lowary & Richards found that 1,6-anhydro-β-D-glucose was the main product (38 - 50%) from the vacuum pyrolysis of cyclohepta amylose using different temperatures (280, 300 and 320C) The authors proposed a reaction mechanism involving the short-lived glucosyl cation: 1- Heterogeneous dissociation of the glucoside bond produces a seven-member open-chain oligosaccharide with a glucosyl cation at a head, 2- Glucosyl cation stabilized through an internal attacks molecule O6 on cationic Cl, creating a oligosaccharide with anhydro-glucose at the bottom and 3-Glucose anhydro released by segment follows glucoside there is also another glucose cation

Lowary & Richards (Lowery& Richard, 1991) also proposed a similar

mechanism that might work for high temperature pyrodextrin In this case, the division divorce of starch chains also creates a cation glucosyl at one end, but the stability of cationic glucosyl This can happen by transglucosit chemistry (attack associated molecules) rather wise g must be due to an endolecular attack The addition of the glucosyl cation to the hydroxyl groups of the nearby starch chains leads to branching points Furthermore, it seems that pyrolysis at a lower than normal temperature (171ºC) and atmospheric pressure (a more pyrodextrin-like condition) favor metabolic reactions via intermolecular addition

2.2.2.3 Re-polymerization

There is some evidence that the slight increase in viscosity and decrease the removal of pyrodextrin occur during production of the yellow dextrin, especially if a long lag time is used This has been explained by the re-polymerization

of glucose or oligosaccharides into larger molecules that is taking place The high temperature and acidity required to produce yellow dextrins can provide a suitable condition for glucose to polymerize

2.3 Starch pyrolysis to create pyrodextrin with gamma radiation as catalyst 2.3.1 The effect of gamma irradiation on starch

Recently, author Zhu of the University of Auckland, New Zealand gave a review titled ―Impact of γ-irradiation on structure, physicochemical properties, and

applications of starch ‖ published in the journal "Food Hydrocolloids" (Zhu,

2016) According to this article, irradiation produces free radicals in starch, which

interact with the water and starch components to alter the molecular structure and starch particles At the molecular level, irradiation reduces the size of both amylose and amylopectin, while increasing the ratio of unit chains to DP 6-12 At the starch particle level, grain morphology was unaffected at low doses, while higher doses brought visible damage to particles The polymorph type of starch is hardly affected, while the degree of crystallization tends to decrease with irradiation Gamma-ray increase water solubility and amylose leaching, and reduce starch granular swell This leads to a decrease in viscosity during the liquefaction process Irradiation can either increase or decrease the temperature and the enthalpy change of the gelatinization process is measured with DSC The enzyme sensitivity to gamma irradiated starch can also be increased or decreased

Gamma irradiation in combination with other types of agents gives a wide range

of properties, increasing the efficiency of reactions for certain chemical variations In the combination types, mainly with chemicals such as acids, peroxide, but very little is known about the association with physical agents such as heat treatment Irradiated starches have been used to produce a wide variety of products including nanoparticles, thermoplastics, and sizing agents for the textile industry

Though there is a lot of data on the effects of gamma irradiation in the different conditions of the composition, physicochemical properties, and morphology of the starch from plant sources diverse fields should be a better deal to improve gamma irradiation usage for starch applications should focus on: 1- Important test parameters: starch moisture, dose and irradiation dose rate; 2- The structural aspects of starch relevant to irradiation still need to be better explored as the molecular basis for starch change and enzyme sensitivity; 3- Use of higher dose starch irradiation (e.g >100 kGy)

to explore potential industrial applications; 4- Chemical, physical, and enzymatic

treatments need to be combined with irradiation with different treatment sequences to give a wider range of properties and to improve reaction efficiency

The topic of choosing a dose range of 5-50 kGy is with an idea aimed at mainly application in the food industry These high and very high doses are meaningful only non-food applications

2.3.2 The effect of irradiation treatment on the content of resistant starch

Gamma irradiation is a physical method used to change starch properties, with the advantages of not significantly increasing product temperature, requiring minimal,

fast sample preparation and not dependent on catalysts (Gani et al, 2014) Gamma

irradiation is usually performed on a Co-60 gamma-ray source device with a dose rate

of 0.4 to 10 kGy/h The given irradiation dose given for starch samples can be as high

as 100 kGy, however currently in Canada and the European Union, food irradiation processes are limited to 10 kGy and in the US (2013) it was 30 kGy for ordinary

(1-2004) Starch with beta bonds is undigested A third reason is the formation of curing

between gluco-polymer chains with DP > 25 increased because the number of these vessels is increased by amylopectin fracture The final reason is the increased

crystallinity (type V) due to the formation of amylo-lipid complexes (Shu et al.,

2013) International studies show that the outstanding advantage of irradiation

technology to create food fiber over other technologies (chemistry, enzymes, and physics) is that it reduces production time, does not leave residues matter

The benefits of using irradiation to increase resistant starch over other methods are, first of all, very fast, as compared to hydroxypropylation, 40 hours, or cyclic

autoclave/degeneration, 24 to 216 hours (Dundar & Gocmen, 2013) A fast irradiation treatment rate is achieved when using large dose rates, e.g up to 10 kGy/h (Yoon et al.,

2010) In addition, the use of irradiation has the added benefit of leaving no harmful

residues in starch, compared to many chemical methods Rice starch with high (8%),

medium (3.8%), and low (2%) content of endogenous inert starch was irradiated to 5 kGy The sample with high resistance starch (8%) had the highest increase at 2 kGy, while the other 2 samples with the highest remaining inert starch levels at 4 kGy Dose rate irradiation lower will generate less than the decomposition of amylose, the formation of carboxyl, breakage amylopectin, is the process of increasing

crystallinity and function of resistant starch (Chung & Liu 2009) When comparing

dose rates 0.40; 0.67; and 2 kGy/h, the dose rate of 0.40 kGy/h with the highest resistant starch was 24.7%, while at higher dose rates only 23.0% and 22.2% respectively The effect of irradiation for cross-linked corn starch STMP/STPP also

e u reachable study Natural samples had the highest resistant starch after irradiation of

40 kGy at a dose of 10 kGy/h of 30.4%, while samples using 5% or 10% STMP/STPP had the highest at 10 and 20 kGy, sequence 57.2% and 67.3%

So, irradiated rice starch or other starches can increase the content of indigestible fraction The essence of the process is not clear because of even resistant starches what

it is, how the star formation not also reachable know However, there are many different types of resistant starch reachable created by the different mechanisms by the effects of irradiation The effect of resistant starch formation depends on irradiation dose, dose rate, starch moisture, and on the nature of each starch and impurities in it

So far, no results have been published on the combined effects of gamma irradiation with pyrolysis to produce pyrodextrose Irradiation not only creates some resistant starch, but also as a circuit breaker and catalyst to replace acids in pyrolysis

2.4 Starch pyrolysis to create pyrodextrin with other catalysts

Recently Hamaguchi has an article ―Production of Water-soluble Indigestible

Polysaccharides Using Activated Carbon‖ (Hamaguchi et al.,2014) According to this

paper, a new process for the efficient production of water-soluble resistant polysaccharides is developed by heating glucose at 180°C in the presence of activated carbon In addition to being a catalytic aid for polycondensation, activated carbon offers additional benefits for easy separation from reagents and coloring of products According to the results of this paper, very different results were found when comparing different catalysts in the pyrolysis of a glucose solution with the same reaction conditions and time Indigestible fraction of the sample does not use catalysts

is only 55.4% of the sample had used 2% activated carbon (w/w) is 85.8%, and the sample using catalytic acid HCl 0.2% (w/w) is 80.5% However, the color of the solution using acid catalysis is very dark the solution that uses activated carbon catalyst to lighter

Before refining, the indigestible content over 80% of the reaction mixture After hydrolysis was catalyzed by α-amylase and glucoamylase, and fractionated by ion exchange chromatography, the total fiber content reached 99.7% This indigestible fraction, called the resistant glucan, is minimally impaired by the upper digestive enzymes, similar to the digestibility of polydextrose Structural analysis by methylation and NMR showed that the resistant glucan formed a highly branched structure containing α- and β-1,2-; 1,3-; 1,4-; and 1,6- On an industrial scale, glucan antibodies were obtained from glucose syrup (DE 86) by heating with activated charcoal, hydrolyzed with enzyme, purified, separated segments and drying spray

In addition, in the world as well as in Vietnam, there are currently not many studies on the impact of activated carbon on the pyrolysis process The researches mainly focus on the ability to decolorize by activated carbon in the hydrolysis process There are no documents to compare the catalytic ability of activated carbon when added right from the pyrolysis process Therefore, we would like to be able to thoroughly understand the impact of activated carbon on pyrolysis as well as the effect

of this catalyst on the process of creating resistant dextrin

2.5 Characteristics of resistant pyrodextrin and typical analytical techniques 2.5.1 Characteristics of resistant dextrin

Changes in molecular size, the ability of branching and glucosidic bonding determine pyrodextrin's main functional properties First, a reduction in the molecular size results in a decrease in the viscosity of the modified starch, so pyrodextrin can

be synthesized at a higher water concentration than its natural starch counterpart

Second, the increase in the degree of branching affects the stability of the solution; making pyrodextrin soluble in cold water and eliminating the tendency to

upgrade, as reported in the work of Bernadine Brimhall (1944) using commercial

pyrodextrin prepared in the absence of an acid catalyst (British chewing gum) Finally, the formation of non-starch bonds may impair the in vitro digestibility of

pyroconverted starch (Laurentin et al., 2003) Therefore, pyrodextrin is soluble in cold

water, develops low or no viscosity in solution, and is partially resistant to digestion The chemical changes that pyrodextrin undergoes also cause them to become a free-flowing, colored powder (from white or light brown to dark brown), with low moisture (typically 1-4%), with no change in color There was a marked change in grain morphology and a relatively low reduction capacity (although higher when compared to natural starch)

2.5.2 Typical analytical methods

deconvolution of overlapping peaks is needed in some complexity process (Yao et al.,

2008) DTG is useful for starch degradation analysis, for instance, to distinguish

overlapping mass loss events, to identify shapes and maxima of mass loss processes, and to help identify minor mass loss steps Furthermore, dynamic TG has frequently been used to study the thermal degradation kinetics of polysaccharides because it gives reliable information on the activation energy, the exponential factor, and the overall reaction order

2.5.2.2 TGA-FTIR and TGA-MS

The TGA provides a quantitative measurement of mass lost from the sample, but

it does not provide information on the nature of the products that are lost from the sample These chemicals during thermal decomposition are very important for studying the mechanisms of decomposition processing Coupling a gas analyzer or detector (such as MS and FTIR) to a TGA allows evolved gases to be analyzed and

identified giving this additional valuable information, which is important for polymer characterization, such as detection of moisture or solvent loss from a sample, study of thermal stability process and reactions mechanism Evolved gas analysis (EGA)

(Darribere, 2010) is a method used to study the gas evolved from a heated sample that

undergoes decomposition or desorption

2.5.2.3 Gel permeation chromatography

Gel permeation chromatography (GPC, also termed size exclusion graphy, SEC) is a common technique for determining size and MW distribution of starch However, characterizing the molecular size distribution of starch polymers by

chromato-GPC is still a sizeable job Many reviews (Gaborieau & Castignolles, 2011) have

questioned the currently available size separation technology to obtain size distribution applicable for the elucidation of the macromolecular structure of starch, especially high branched starch such as waxy starch

2.5.2.4 Electron paramagnetic resonance

Electron paramagnetic resonance (EPR) or electron spin resonance spectroscopy (ESR) is a technique for studying chemical species that have one or more unpaired electrons, such as organic and inorganic free radicals or inorganic complexes possessing a transition metal ion Radicals in starch were generated during thermal

processing, such as conventional heating (Krupska et al., 2012), microwaves (Dyrek et

al., 2007), extrusion, and irradiation EPR is a useful technique, is a tool for studying

radical processes induced by heating of starch in the temperature range 150–250C

========

CHAPTER 3 MATERIALS AND METHODS OF RESEARCH 3.1 Research subjects

- Rice starch TB1 (M1): is the starch produced from rice IR50404 supplied by Hoa Phat Company Starch has carbohydrate, protein and pH content of 82.3%, respectively 5.2% and pH 4.16 In irradiation experiments, rice IR50404 again was purified to have protein content of less than 1% and lipid less than 0,5%

- Rice starch TB2 (M2): Provided by the Company in Ho Chi Minh City, has carbohydrate, protein and pH content of 86.2%, 2.4% and pH 3.86 respectively

- Rice starch TB3 (M3): TB1 starch is refined in the laboratory, with carbohydrate, protein and pH 85.7%, 2.8% and pH 7.63 respectively

- Actived carbon, symbol MD-1 provided by Minh Duong Food Joint Stock Company Main parameters: fine powder, black color, iodine index: 900-1000 mg/g, pH: 8 ’ 9

3.2.3 Other analytical chemicals

- Enzymes (amylase, amyloglucosidase, protein: (Novozymes A/S, Denmark)

- NaOH (≥96%)

- Chemical analysis of protein, lipid, amylose, inert starch,….

3.3 Equipment and tools

- Whiteness meter: Kett C-300 (Japan)

- Croma meter (CR-400 Konica Minota colorimeter)

- Spectrophotometer (Thermo Scientific, England)

- Analytical balance (Precisa,

- Technical scales (Ohaus, Wisstherland)

- pH meter (portable and portable)

- Dryer (JSOF, Memmert, Germany)

- Oven of all kinds (Dryer JSOF-100, Memmert)

- Mixer (small and big)

- Vortex shaker(VX100)

- Magnetic stirrer (IKEA, Germany)

- Centrifuge EBA21(Hettich, Germany)

- Thermometers (100, 200C)

- Vacuum rotary evaporator (Heidolph, Germany);

- Mixing - drying - roasting equipment, pilot scale (Vietnam) (5-8 kg / batch)

- Another necessary laboratory equipment

3.4 Experiment design

3.4.1 Experiment about the effects of different acid on pyrolysis

The purpose of the experiment is to choose the safe acid to serve as the most suitable catalyst for pyrolysis, shown mainly by creating dextrin products with high levels of indigestible fraction, short time, low color difference Prepare 4 solutions of acetic acid (CH3COOH), citric (C6H8O7), hydrochloric (HCl), lactic (CH3CH(OH)COOH) Mix 100 g of rice starch with 10 ml of different acid solutions have the same concentration of 0.33 M by the mixing machine Put samples in sealed plastic containers and incubate overnight Take 20 g of each sample into Petri dish

dried to expel moisture at 105°C for 60 minutes and then pyrolysis (cover) at 170ºC for 120 minutes Then take the sample out and cool quickly at room temperature, the sample is sealed in a sealed bag and stored for analysis Each recipe prepared 3 independent samples (repeated 3 times) for 12 Petri dishes

3.4.2 Experiment about the effect of concentration of HCl on pyrolysis

The aim of the experiment is to select an appropriate concentration of acid clohydric to act as a catalyst for the pyrolysis process Prepare hydrochloric acid HCl

at concentration 1.00; 1.5; and 1.75% and mixing with dry starch to produce starch samples with pH 2.1; 2.3; 2.5; and 2.7 After mixing, incubate the sample for 10-15 hours in a sealed plastic container at room temperature Take 20 g each sample to the Petri dish to dry, open the lid to remove moisture at 105 ºC for 60 minutes and then pyrolysis at 170°C until the starch color reaches 60-62%, repeat 3 times Analytical criteria: whiteness, IDF

3.4.3 Experiment about the effect of pyrolysis temperature

The aim of the experiment 3 is to determine the effect of temperature, there by pick out about the temperature best suited to perform pyrolysis resistant dextrin has the best quality Use starch M1 (TB1) and M2 (TB2) as ingredients Dry at 105ºC to 4-5% moisture Use 100 g of this starch to mix well with 1% acid and incubate overnight Get 20 g each formula to the petri dish, drying moist pursue without lid for

60 minutes and then heat treatment division has uncovered in 120 minutes at the temperature difference: 140, 150, 160, 170, and 180C Then take the sample to cool quickly at room temperature, the sample is bagged, preserved and analyzed the analytical criteria including whiteness, IDF content, solubility The experiment was repeated 3 times

3.4.4 Experiment about the effect of pyrolysis time

The aim of the experiment is to be selected out of about the optimum time for the pyrolysis process to produce resistant dextrin The procedure is similar to experiment

3 Using 100 g of starch with 4% moisture, mixing with 10 ml of 1% HCl acid solution Incubate the sample overnight in a plastic container, then take 20 g of each recipe into a Petri dish, and dry to remove moisture and open the lid at 105 C for 60 minutes Cover and pyrolysis at 170ºC according to 4 different formulas of pyrolysis

time of 60, 90, 120 and 150 minutes Then take the sample out to cool at room temperature, the sample is bagged and stored in a vacuum desiccator Analytical parameters include dextrin whiteness, IDF content, solubility The experiment was repeated 3 times

3.4.5 Experiment about the effects of gamma radiation in different doses

Starch M1 (re-purified with protein < 1%, lipid < 0,3%) moisture content 5%, take about 400 g, filled in a plastic container (rectangular box, 750

ml, size: 17 x 10 x 5 cm ) Each irradiation doses has 3 boxes Irradiation with absorbed dose: 5, 10, 20, 30, 40 and 50 kGy at dose rate 5 kGy/h Irradiation was at the Hanoi Irradiation Center, Cobalt-60 gamma radiation source with an activity of

100 kCi The difference between the theoretical dose and the actual dose measured with the ECB dosimeter (ethanol chlorobenzene) is approximately <10% The evaluation of the effect of irradiation dose on starch was with various criteria related

to pyrodextrin purpose The criteria include: the indigestible fraction IDF, the change of starch whiteness (Kett C-300 powder whiteness tester ) and color deviation

ΔE (CR-400 Konica Minota colorimeter), water solubility at 25C and 70C and pH

3.4.6 Experiment about the effect of gamma radiation in different dose rates

The aim of the experiment is to determine the appropriate irradiation dose rate to obtain pyrodextrin with the highest indigestible fraction The irradiation procedure was similar to the above mentioned, but with dose of 10 kGy and at 3 different dose rates

of 1 kGy/h, 2 kGy/h and 3 kGy/h The criteria to evaluation include: the indigestible fraction IDF and some other measurements

3.4.7 Experiment about the effect of gamma irradiation combined with acidic catalysist pyrolysis

non-After irradiation as described in experiment 5, the irradiated starch was placed in Petri dishes of the same size (Φ12 cm) Pyrolysis was carried out at 170°C for 300 min Each recipe has 4 plates The manner in which the samples are placed in the oven should ensure an even distribution of heat After drying, the samples are rapidly cooled

by placing in the refrigerator's cooler Evaluate the effect of irradiation by the following criteria: Color change (whiteness tester Kett C-300, croma imeter CR-400 Konica Minota), water solubility at 30oC, content of IDF

3.4.8 Experiment about the effect of gamma irradiation combined with HCl catalyst pyrolysis

Purified rice starch 5% moisture irradiated with gamma doses 0, 10 and 30 kGy

is used Add HCl acid solution of concentration 0.25; 0.5; 0.75; and 1.0 into the starch

at a ratio of 1: 10 (v/w) Mix well and incubate for 5 hours Dry to 4-5% moisture and then pyrolysis at 150 - 170°C Evaluation criteria include: pH before pyrolysis (composted acid), roasting time to a brightness of 60%, whiteness, color difference

ΔE, the indigestible fraction

3.4.9 Experiment about the effect of the rate of activated carbon added

Use 10 kGy irradiated starch with a moisture content of 5% Add activated carbon in the ratio of: 0, 1, 2, 3, 4, 5, each with 5 Petri dishes (30 dishes) Use 0.5% HCl solution to mix samples at the rate of 0,05% by weight of powder Incubate for 5

h and then roast at 170ºC until whiteness of the formula without charcoal reaches 65% whiteness The experiment was repeated 3 times Measurements to evaluate quality changes were similar to previous experiments

3.4.10 Experiment about the effect of pyrolysis time with activated carbon catalyst

From experiment about the effect of rate of actived carbon, choose an appropriate ratio of activated carbon to experiment on the effect of pyrolysis time on pyrodextrin product Using 5% moisture irradiated starch, add activated carbon (5 plates each formula) Use 0.5% HCl solution to mix samples at the rate of 0.05% by weight of powder Incubate for 5 hours then roast at 170ºC and remove at 3 different times The experiment was repeated 3 times The experiment was repeated 3 times Measurements

to evaluate quality changes were similar to previous experiments

3.4.11 Experimetn about verification of pyrolysis at pilot scale and final product charactification

The purpose of the experiment was to compare the quality of the digestible pyrodextrin product in 3 pilot batches (8 kg / batch) and compare with the quality of the product at a small laboratory scale Refined M1 starch is used in the laboratory pyrolysis treatment and pilot scale With a pilot scale, using 8 kg of starch and processing on roasting equipment designed and manufactured by KC.05.20 / 06-20 with the same steps as small scale All starch samples at the two scales had the same

acidification (pH 2.5), treatment temperature of 160oC Processing times are recorded until the color reaches 60-65% whiteness

3.5 Analytical methods

3.5.1 Indigestible Fraction (IDF)

The IDF content was measured using the method of Englyst & Hudson (1996) with some suitable improvements Accordingly, 1 gram of pyrodextrin sample was accurately weighed, 50 ml of 0.08M phosphate buffer (pH 6.0) was added, followed

by 0.1 ml of the heat resistant enzyme α-amylase (Termamyl 120L, Novo) Laboratories, Inc., USA) and react at 95°C for 30 minutes Cool to room temperature and adjust the pH of the solution to pH 7,5 ± 0,1 with a 0.275 M NaOH solution (use about 10 ml) Add 0.5 mL of protease solution and allow to react at 60°C for 30 minutes The reaction mixture was cooled and pH adjusted to 4.5 Cool the solution and adjust to pH 4,5 ± 0,2 using 0.325 M HCl (approx 10 ml) Add 0.3 ml of the enzyme amyloglycosidase and allow to react at 60°C for 30 minutes Heat to 90°C for

15 minutes to terminate the reaction The resulting mixture will be filtered and diluted

to 100 m with distilled water and the resulting glucose content will be determined by pyranose-oxidase using K-GLUC kit (GOPOD Format) (Novozymes, Denmark) The indigestible fraction (IDF) is calculated from the following formula:

IDF (%) = 100 - Glucose content (%) x 0.9

3.5.2 Total Dieatary Fiber (TDF)

TDF content of pyrodextrin or starch was determined according to AOAC 2001.03 method (AOAC, 2005) with some improvements in sugar determination by HPLC Accordingly, K-MASUG kit (Novozymes, Denmark) is used to determine total sugar DP1 and DP2 (3 types of sugar maltose, sucrose and glucose)

3.5.3 Color difference

The color difference is analyzed based on Hunter , using a photoelectric colorimeter (CR-300 Minota, Tokyo, Japan) This system classifies colors by three

attributes: L (white = 100, black = 0); a (red = positive, blue =negative ); and b (yellow

= positive, blue = negative) Color difference (ΔE) were measured using the color of