Influences of formulations, processing conditions and storage on gaba content and quality of germinated brown rice milk

1 HO CHI MINH CITY UNIVERSITY OF TECHNOLOGY AND EDUCATION FACULTY FOR HIGH QUALITY TRAINING GRADUATION PROJECT Thesis code [2022-18116002] INFLUENCES OF FORMULATIONS, PROCESSING CONDI

MINISTRY OF EDUCATION AND TRAINING

HO CHI MINH CITY UNIVERSITY OF TECHNOLOGY AND EDUCATION

FACULTY FOR HIGH QUALITY TRAINING

GRADUATION THESIS FOOD TECHNOLOGY

1

HO CHI MINH CITY UNIVERSITY OF TECHNOLOGY AND EDUCATION

FACULTY FOR HIGH QUALITY TRAINING

GRADUATION PROJECT

Thesis code [2022-18116002]

INFLUENCES OF FORMULATIONS, PROCESSING CONDITIONS AND STORAGE ON GABA CONTENT AND QUALITY OF GERMINATED BROWN RICE MILK

NGÔ GIA BẢO

Student ID: 18116002

Major: FOOD TECHNOLOGY

Advisor: HOÀNG VĂN CHUYỂN, PhD

Ho Chi Minh City, August 2022

HO CHI MINH CITY UNIVERSITY OF TECHNOLOGY AND EDUCATION

FACULTY FOR HIGH QUALITY TRAINING

GRADUATION PROJECT

Thesis code [2022-18116002]

INFLUENCES OF FORMULATIONS, PROCESSING CONDITIONS AND STORAGE ON GABA CONTENT AND QUALITY OF GERMINATED BROWN RICE MILK

NGÔ GIA BẢO

Student ID: 18116002

Major: FOOD TECHNOLOGY

Advisor: HOÀNG VĂN CHUYỂN, PhD

Ho Chi Minh City, August 2022

3

THE SOCIALIST REPUBLIC OF VIETNAM

Independence – Freedom– Happiness

-

GRADUATION THESIS ASSIGNMENT

Student name: Ngo Gia Bao Student ID: 18116002

Student name: Student ID: _

Major: Food Technology Class: 18116CLA

Supervisor: Dr Hoang Van Chuyen Email: chuyenhv@hcmute.edu.vn

Date of assignment: 14/02/2022 Date of submission: 09/08/2022

1 Thesis title: Influences of formulations, processing conditions and storage on GABA content and quality of germinated brown rice milk

2 Thesis assignment:

Design process of germinated brown rice milk

Determine the effects of soaking time and rice to water ratio to the GABA content of germinated brown rice milk, determine the effects of time and temperature of thermalizing process to the GABA content of germinated brown rice milk, determine the effects of thickeners at different concentrations to the GABA content of germinated brown rice milk, determine the viscosity and stability of germinated brown rice milk by use of different thickeners at different concentrations, determine the preservation parameters for germinated brown rice milk

The content and requirements of the graduation thesis have been approved by the Chair of the Food

Technology program

CHAIR OF THE PROGRAM

(Sign with full name)

Ho Chi Minh City, August 9, 2022

SUPERVISOR

(Sign with full name)

1

ACKNOWLEDGEMENT

In order to complete my thesis, a lot of work and time was put in There have been many challenges

for me during this study But thanks to my lecturers, my beloveds and others around that have help

me and motivate me to move on and coming through

For that, I want to sincerely thank to all the lecturers in charge of the

Department of Food Technology, Faculty of Chemical and Food Technology, and Ho Chi Minh

City University of Technology and Education for having valuable knowledge and give me the best

conditions in equipment as well as facilities for me to complete this thesis

I want to give a sincerely thank mine supervisor, PhD Hoang Van Chuyen, who has always been

enthusiastically guiding and sharing all teaching knowledge and experience for me to accomplish

this graduation thesis Sincerely, I would like to thank Ms Ho Thi Thu Trang of the Department

of Food Technology for facilitating and helping me able to use the measuring tools and equipment

that are available at the laboratory of the Faculty of Chemical and Food Technology

Nevertheless, I would like to send our sincere thanks to our schoolmates, for supporting in the

experiment of the thesis and always be there to support me I sincerely thank!

DECLARATION

Except where there is obvious recognition and reference to the work of others, where by declare that all content and material presented and involved in this thesis is my work

We also certify that the contents referenced in the thesis have been adequately and accurately cited

in accordance with regulations

9th August 2022 Signature

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Table of Contents

ACKNOWLEDGEMENT 1

DECLARATION 2

ABSTRACT 7

Chapter 1: Introduction 8

1.1 Research rationale 8

1.2 Objective of the thesis 8

1.2.1 General objective 8

1.2.2 Specific objectives 8

1.3 Meaning of the thesis 9

Chapter 2: Literature review 10

2.1 Overview about germinated brown rice 10

2.2 Overview about germinated brown rice milk 11

2.2.1 Introduction about germinated brown rice milk 11

2.2.2 Introduction about GABA 12

2.2.3 Factors affect the stability of GABA in a product 13

2.2.4 Nutritional value of germinated brown rice milk 13

2.2.5 Health benefits of rice milk 14

2.2.6 Overview of thickening agents used in processing of GBRM 14

2.2.6.1 Xanthan gum 15

2.2.6.2 Pectin 15

2.2.6.3 Guar gum 17

2.3 Researches about GBRM in Vietnam 19

2.4 International Researches about GBRM in foreign 19

Chapter 3: Materials and methods 20

3.1 Materials 20

3.2 Methods 20

3.2.1 Experimental design 20

3.2.1.2 Determination of water – rice ratio for preparation 22

3.2.1.3 Storage study of GBRM 22

3.2.2 Analytical methods 22

3.2.2.1 Method for determination of GABA content using UV-VIS spectrophotometry 22

3.2.2.2 Determination of viscosity of GBRM with the addition of different thickeners 23

3.2.2.3 Determination of stability of GBRM 23

3.2.2.4 Determination of emulsion particle size of GBRM 24

3.2.2.5 Sensory evaluation of GBRM 24

3.2.2.6 pH determination 24

3.2.2.7 Determination of bacterial count 24

3.3 Statistical analysis 24

Chapter 4: Result and discussion 25

4.1 Determination of the suitable soaking time and ratio of rice for achieving GABA 25

4.2 Sensory evaluation of the GBRM 26

4.3 Effects of heating time and temperature on the GABA content of the germinated rice milk (µg/ml) 28

4.4 Influence of different thickener formulations on the stability of the rice milk 29

4.5 Determination of the suitable use of thickeners and their effects on the GABA content of GBRM 33

4.6 Determination of the preservation parameters of GBRM 34

Chapter 5: Conclusion and recommendations 37

5.1 Conclusion 37

5.2 Recommendations 37

REFERENCES 38

APPENDICES 45

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List of Figures

Figure 2 1:Germinated brown rice and germinated brown rice milk 11

Figure 2 2:The structure of Gamma-amino butyric acid 12

Figure 2 3:Synthesis pathway of GABA in rice 12

Figure 2 4:The chemical structure of xanthan gum 15

Figure 2 5:Structure of pectin 16

Figure 2 6:Structure of Guar Gum 18

Figure 3 1: Diagram of experimental design 20

Figure 4 1: GABA content (µg/ml) by soaking time and ratio of rice to water 25

Figure 4 2:Sensory evaluation of GBRM 27

Figure 4 3:GABA of GBRM at different thermalize temperature and time (µg/ml) 28

Figure 4 4:Stability (%) of GBRM between the use of hydrocolloids 29

Figure 4 5:Seperate time of GBRM between hydrocolloids (h) 30

Figure 4 6:Viscosity (mPa) of GBRM between different use hydrocolloids and concentrations 31

Figure 4 7:GABA (µg/ml) content between hydrocolloids and formulation 33

List of Tables

Table 2 1:Comparison of nutritional values of brown rice and white rice 10

Table 3 1:Ratio of rice – water for soaking of GBR 22

Table 3 2: Ratio of rice to water and time for soaking of GBR 22

Table 4 1:Proximate composition of germinated brown rice milk product 26

Table 4 2: The GABA loss of GBRM preserved at different temperature for 7 days (µg/ml) 34

Table 4 3: Microbial count of GBRM preserved at different temperature for 7 days (CFU/ml) 35

Table 4 4: pH value of GBRM preserved at different temperature for 7 days 36

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ABSTRACT

In the recent years, germinated brown rice has been recognized as a nutritious product for consumption for specific people Rice milk is known to be most convenient and sufficient way to consume germinated brown rice Thus researching the formulation, processing conditions and storage conditions effects on the GABA content of this product is necessary In this study, all the mentioned criteria have been experimented through the GABA content achieved by soaking time and ratio of rice to water, effects of thermalization temperature and duration on the GABA content

of the GBRM, effect of different formulation by using different thickeners at different concentrations to the GABA content and stability of the GBRM product, effects of storage parameter on the GABA content As the result, the soaking ratio of rice to water 1:10 at 8 hours of soaking produce the most favorable GABA content 304.70±19.47 µg/ml comparing to other ratio and time for soaking for the purpose of this research The thermalizing temperature under 90C regardless of time are suitable for retaining the GABA content during processing In the use of thickening agents, the mixture of Guar gum and Pectin retain the most GABA content 421.65±11.79 µg/ml when added to the rice milk while mixture Guar gum and Xanthan gum create

a more stabilized product with the stability approximately 100% after 7 days of storage Storage condition of the GBRM result in the best quality of storage is when stored at 5C

Chapter 1: Introduction

1.1 Research rationale

Ever since introduced, germinated brown rice is known for its many beneficial to the human health,

as the rice contain more nutritional value than regular brown rice, mainly vitamins, antioxidants, sugars, especially the amount of gamma-amino butyric acid (GABA)[1] This substance is an amino acid which act as a neurotransmitter in the human brain GABA has been proven to have calming effect, development in the children brain, healing and curing effect in overactive children and autism[2] Nowadays, more and more product using the germinated brown rice to produce other product which are easier for consumption Germinated brown rice milk is the most ideal way for consumption, the process for suitable yield of GABA However, the loss of this substance is found to be loss by different influences during process and preserving[3] Heat is known to be the main cause for the loss of GABA during processing Research conducted by[4] show that GABA

is sensitive to heat, the greater the heat, the greater the loss in GABA There are also concerns that the rice – water ratio for extraction and the extraction time can also affect the retrieved GABA content as well as other nutrients post extraction GABA also known to have chemical interaction with other chemical component within the rice itself, but these interactions mostly occur due to the catalyst components such as enzymes or lipid oxidation[5]

Thus for retaining the GABA content, determination of the appropriate conditions for processing, suitable formulation and preservation of the produced germinated brown rice milk is necessary In this study, effects of parameter including soaking time and ratio of rice, preserving temperature and different formulations of thickening agents (xanthan gum, guar gum, pectin) of the product were investigated

1.2 Objective of the thesis

- Determine the preserving method and food safety parameters of the GBRM

- Determine the suitable formulation of food additives (xanthan gum, guar gum, pectin) and their effects on the GABA content and quality of the germinated brown rice milk

- Evaluate the sensory criteria of the germinated brown rice milk

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1.3 Meaning of the thesis

This thesis results an be used as a reference for developing the production procedures of

germinated brown rice milk and further studies on the processing of related food products

Chapter 2: Literature review

2.1 Overview about germinated brown rice

Rice (Oryza sativa L) is the most important cereals product and is the major staple food for most

parts of the world[6] There has been a trend in the current modification of this product by germinating its to achieve more nutritional values, mainly the Gamma-aminobutyric acid content Germinated brown rice (GRB) is the unpolished rice that has been germinated for gaining more nutrition The germinated brown rice has a better texture and flavor, most importantly is that the Gamma-aminobutyric Acid (GABA) is increased[7] Germinated brown rice is used in many different cuisines such as Japanese and Korean The nutritional content of the Germinated brown rice appears to be higher than its normal white counterpart

The nutritional value of brown rice is compared with milled white rice and rice bran is described

in the Table 2.1

Table 2 1:Comparison of nutritional values of brown rice, milled and rice bran[8]

anti-2.2 Overview about germinated brown rice milk

2.2.1 Introduction about germinated brown rice milk

Rice milk is a cereal product belong to a group known as bran milk, this group of products is a suitable substitution for customer suffer from lactose intolerant The bran milk product is plant-based, non-dairy beverage achieved by mixing milled bran with water[10] The bran milk field is full of products such as soybean milk, peanut milk, etc For GRB milk, the rice milled after a time

of soaking in water, more water is added to the create a slurry before they can be filtered to remove any large particles The GRB milk is then treated with amylase enzymes for breaking down the starch content partially and create a suspension[11]

Figure 2 1:Germinated brown rice and germinated brown rice milk

Bran milk products are often meet with a common problem where the precipitate within the milk will separate after an amount of time of storage[12] This happened because the bran milk is an emulsion between water and milled rice particles, these particles are not uniform and are depended

on the milling property of the device used for milling Through a time of storage, the milled rice particles will separate to the lower of the milk solution, thus lowering the stability of the product

and sensory properties The solution for this is to introduce the rice milk solution to stabilizers such as xanthan gum, guar gum, pectin[13]

2.2.2 Introduction about GABA

Figure 2 2:The structure of Gamma-amino butyric acid

Gamma – amino butyric acid (GABA) is a health beneficial substance contained in the germinated rice and naturally found in other plants It is an inhibitory neurotransmitter which helps in creating better sleep and calming mood Many researches has point out that the addition of GABA to the human brain help reduce stress,anxiety[14] GABA is considered to be the most important nutrient within the GBR since it bring beneficial effects to the nervous system and is achieved by synthesize within the brown rice during germination

During the germination process within the rice bran, glutamate decarboxylase enzyme (GAD) which is naturally present in the cytosol catalyzes the irreversible alpha-decarboxylation of l-glutamic acid (Glu) to produce gamma-aminobutyric acid (GABA) and carbon dioxide[9]

Figure 2 3:Synthesis pathway of GABA in rice

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There has been many methods for increasing the value of GABA content within GBR These are base on improving yield of the germination process By controlling the time, temperature[15], biological modification[16],gaseous treatment[17] These methods are proven to have significant enhancement to the GABA yield post-germination

The primary inhibitory neurotransmitter in the CNS, gamma-aminobutyric acid (GABA), functions through ligand-gated ion channel The essential mode of action for AEDs is the potentiation of GABA inhibitory transmission Additionally, there is proof that GABA functions

as a trophic component in children's brain growth For children at age from 5-10, consuming product containing GABA helps them develop better as well as increase the quality of sleep In special cases, GABA rice milk is used as a substituent for over-active kids

2.2.3 Factors affect the stability of GABA in a product

a Heat

GABA is an amino acid, therefore it can be heavily affected by heat during processing For most amino acid, the heat enduring capability is about 120C While GABA can be degraded when a product is heat treated at 121C, lower heat treatment temperature can lead to a decrease in GABA content Many researches on investigating the effect of heat to the GABA content within the product have shown that when treated at 80-90C, a decrease in GABA content loss was found[18]

b Chemical composition

GBR is a type of grain which contain mainly starch During the process of germination, most enzyme are active to take part in the process for germination including α-amylase Starch is broken down into simple sugars which are able to interact with the amino acid during the process of heat treatment These two components take part in a non-enzymatic browning which is the Maillard reaction[19] Thus a reducing trend in the GABA content can be predicted

c Natural loss

GABA has been observed to be lost naturally during preservation Different methods of preserving

by controlling the time, temperature and condition of preserving GABA contained product has been proven to have effects on the loss of GABA naturally[20]

2.2.4 Nutritional value of germinated brown rice milk

a Starch

Starch is the main component of rice grain and it is also the main nutrient for consumption Starch

is a chain of glucose monomers which are linked through the 1,4 glycosidic bonds The structure

of starch is divided into two structures, the linear chain which is amylose and the branched form

is amylopectin Starch when consumed will be broken down by α-amylase enzyme into small linear malto-oligosaccharide This will in term be hydrolyzed by other enzymes α-glucosidases

and maltase-glucoamylase, sucrase-isomaltase into glucose for the absorption to transform these into energy for human[21]

Starch is main nutrient component within the rice milk product as well as the main structural component The white turbidity which gives the characteristic of white color to rice milk is mainly starch To maintain the homogenous phase of the rice milk, these starch particles must be homogenized to create a homogenous texture and create a higher sensory quality for the rice milk product[22]

b GABA

GABA in GBRM is achieved through the germination process of the brown rice Consuming GABA into the human body have health beneficial effects such as stress reducing and enhance the quality of sleep[23]

c Vitamins

Brown rice contain mainly vitamins B1, B3, B6 and other health beneficial vitamins[24] These vitamins mainly play a role in the immune system and cell repair

2.2.5 Health benefits of rice milk

Rice milk and other plant-based milk is known to be a sufficient milk substitution product for different groups of consumers People endured with lactose intolerant can use rice milk as their main source of milk Lactose intolerant is a digestion disease where the mucosa within the smaller intestine unable to absorb lactose when milk is consumed[25] By consuming lactose without knowing the consumer having this disease, within minutes could cause vomit, nausea, diarrhea which is disturbing and unpleasant[26] This is mainly caused by a lack of activity and presence

of a specific lactase enzyme in the human intestine known as β-D-Galactosidase (E.C 3.2.1.23)[27], [28] Milk protein allergy consumers can also use bran milk instead of normal animal-based milk Milk is a rich source of proteins but casein and whey protein are known to have cause allergy in human, thus consuming milk could cause allergic reaction to the human body[29], [30]

Moreover, the use of rice milk can also be applied to different lifestyle of human Rice milk contain mainly nutrients that are required for an active daily life By consuming rice milk regularly, nutrients are offered to the body in a faster duration of consumption than having a small diet[31], [32] This is suitable for people with a crowded work clock Vegetarian can also use rice milk because of their lifestyle choice not to consume any animal-based product Consumption of rice milk is suitable for this lifestyle because being a plant-based product and containing mainly starch and other vitamins, rice milk can provide any nutrients and benefits to the vegetarian as needed[33]

2.2.6 Overview of thickening agents used in processing of GBRM

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2.2.6.1 Xanthan gum

Xanthan gum is classified as a food hydrocolloid that is mainly used for improving the stability of

a food product It is a polysaccharide gum that is derived from X anthomonas campestris through

a fermentation process which use simple sugars and is recovered by using isopropyl alcohol Xanthan gum is mainly used as an additive in beverage product especially bran milk as it provides the thicker characteristic by increasing the viscosity of the product as well as act as an emulsifying

Using 1% of xanthan gum can has a significant increase in the viscosity, commercialized product mainly used from 0.05% to 1%, although higher intake of xanthan gum is harmless for human health as it can be digested in the human intestine but can cause could cause bulking for beverage product[35]

Figure 2 4:The chemical structure of xanthan gum

The structure of xanthan gum comprise of a β-(1-4)-d-glucose backbone with trisaccharide side chains which consisting of mannose, glucuronic acid, and mannose Pentasaccharide chains are formed by attaching two molecules of glucose, two molecules of mannose and one glucuronic acid The glucose backbone hence is protected from any form of attack such as enzyme, alkalis,etc

By dissolving xanthan gum into the solution, the side chains act as a wrap to cover up the glucose backbone, the negatively charged carboxylates from glucuronic acid at the trisaccharide sidechains allow it to form highly viscous fluids at appropriate pH

2.2.6.2 Pectin

Almost all plants contain pectin, a high-molecular-weight carbohydrate polymer that contributes

to the construction of plant cells The name "pectin" refers to a range of polymers that varies in terms of their molecular weight, chemical make-up, and the neutral sugars content Additionally, different plant species produce pectin with various functional characteristics The word "pectin" is derived from the Greek word "pektos," which means "stiff and unyielding," and refers to pectin's capacity to create gels[36]

Pectin is used as an emulsifier in beverages and soft drinks, and high-ester pectin may be used as

a mouth-feel improver This use has been widely developed for juice drinks with a reduced juice content or sugar-free soft drinks[37]

Pectin can be produced from many fruits, or other plant tissues such as beetroots, but most commercial pectins are derived from citrus peels by precipitating the pectin from solution with alcohol Pectin is a reversible colloid It may be dissolved in water, precipitated, dried, then redissolved without alteration of its physical properties

Pectin substances are polysaccharides, straight chains, composed of linkages between chains of galacturonic acid molecules C6 H10O7, linked together by 1,4-glucoside bonds In which some acid radicals contain methoxyl group (-OCH3) The length of the polygalacturonic acid chain can vary from a few units to hundreds of polygalacturonic acid units[36]

D-Structure of one unit of the pectin chain:

Figure 2 5:Structure of pectin

The molecular weight of pectin isolated from different fruit sources varies within a wide range according to the number of galacturonic acid molecules and generally ranges from 10,000 to 100,000 Among glucid compounds, in terms of molecular length, pectin is higher than starch but lower than cellulose For example, from apples and plums, pectin has a molecular weight of 25,000

- 35,000, while pectin from oranges has a molecular weight of up to 50,000

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The pectin molecule consists of 3 types of components, namely Homogalacturonan, Rhamnogalacturonan-I and Rhamnogalactorunan-II These three types of compounds are called pectin polysaccharides, and they can be covalently linked to form a network of pectin distributed throughout the middle lamina and primary cell wall

Pectin belongs to the group of coagulants Pectin is considered to be one of the safest and most accepted food additives, and this is evidenced by the "unknown" allowable ADI level issued by the JECFA (Joint Food Expert Committee), SCF (Scientific Committee for Food) in the European Union and GRAS (Generally Regarded)

Based on the degree of methylesterification and by functional group, pectin is classified into 3 main types; HMP, LMP, LMAP

The ability to form gels depends mainly on two factors: length of the pectin chain and the degree

of methoxylation; Length of pectin chain If the pectin molecule is too short, it will not form a gel even at high doses If the pectin molecule is too long, the gel formed has a hardened structure

2.2.6.3 Guar gum

Guar gum is an additive in the group of additives to support product structure, widely used in food, especially in confectionery and beverage technology

Guar gum is obtained from the seeds of the plant Cyamopsis tetragonoloba (Cluster Bean) This

plant is grown mainly in India, Pakistan and Texas, America Guar flour has a moisture content of 10-15%, contains 5-6% protein, 2.5% fiber and 0.5-0.8% crude ash Its main components are the β-D-mannopyranosyl and D-galactopyranosyl units Guar gum has a high viscosity and this viscosity also depends on the shape of the gum.[34]

The molecular structure of guar gum comprises linear polysaccharidic chains of (1 → mannopyranosyl residues and branching occurs with α-d-galactopyranosyl residues interconnected via the (1 → 6) linkages

4)-β-d-Figure 2 6:Structure of Guar Gum

Guar gum has good emulsifying properties, especially suitable for oil-in-water emulsion systems, and is widely used in emulsion flavor stabilizers It also has good film forming properties, used as

a thin film to help preserve the flavor of foods and prevent oxidation

Guar gum has typical physical properties of a natural emulsifier Guar Gum is a white to yellowish white powder and is almost odorless It is soluble in hot and cold water, disperses a highly viscous colloid when diffuse into cold water but insoluble in organic solvents Has strong hydrogen bonds Guar gum is non-ionic and maintains a consistently high viscosity in different pH When hydrated

in water, the time required for complete hydration is low to achieve maximum viscosity

The most important feature of guar is its ability to be dispersed in water and hydrate or swell rapidly and almost completely in soil water to form a viscous colloidal dispersion The viscosity achieved is time and temperature dependent concentration, pH, agitation rate and actual size of the powdered gum used, the presence of salts and other solids Above 80ºC the viscosity is slightly reduced The guar powders are better, rise faster than the raw gum powders Gum guar has the ability to thicken, emulsify, contribute to swelling, as a stabilizer to maintain the uniformity of food products[38]

Guar gum is more soluble than locust bean gum and is a better stabilizer, as it has more galactose branches Unlike locust bean gum, it does not gel itself However, either borax or calcium can cross-link guar gum making it gel In water Guar gum is a gelling agent, unaffected by ionic strength or pH, but will degrade at particular pHs at temperature (e.g pH 3 at 50 °C) Guar gum remains stable in the pH 5-7 range Strong acids cause hydrolysis and loss of viscosity, and high concentrations of alkalis also tend to reduce viscosity Guar gum is insoluble in most organic solvents Guar gum has a strong ability to absorb water and can bind to adjacent molecules,

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resulting in a solution's viscosity Guar gum combined with xanthan gum results in a gel

formation[39]

2.3 Researches about GBRM in Vietnam

In Vietnam, ever since the introduction of GBR to the food science community in Vietnam, many

researches on this type of rice have been conducted by researchers These research focus mainly

on the manufacturing capacity for producing the GBR and GBRM in Vietnam Currently in the

marketing state of Vietnam, there are many germinated brown rice milk products(C Thị et al.,

2013; T Thị et al., 2017; Tú et al., 2016)

2.4 International Researches about GBRM in foreign

Many researches have been focusing on improving the germination process by investigating

different factors that could affect the GABA yield rate[43]–[45] Dhakal et al used Lc Lactis

subsp lactis PU1 to produce a higher yield of GABA 1031 ± 9 mg/kg in chickpea sourdoughs

[43] In 2022, Munarko et al., show that different types of Indonesian germination can produce a

different GABA content post germination [45] These reseach show that the GABA content can

greatly affected by the germination method and parameters Thus to obtain the suitable GABA

content for this study, choosing a qualified manufacturer of germinated brown rice milk is

necessary

In Japan and Korea, rice milk is a common product for everyone, brown rice milk is produced as

a health beneficial substitute to regular rice milk[46], [47] Now GBRM is the new trend on the

industrial flow, researches on the regulation of heat and pH on the GABA content has been

conducted[20] but none research about the use of other food additives can affect the GABA is to

be found

In conclusion, germinated brown rice milk is a valuable product for many consumers, as not only

providing the nutritional value like other plant-based milk product but it also introducing the

GABA to the consumer This substance is known to help people with different health issues mainly

psychologically The need for retaining the GABA content within the germinated brown rice milk

is required as this substance is known to be affected in a negative way by different parameters of

heat, chemical composition, formulation of rice milk and preservation thus making a loss during

process This is necessary as the loss of GABA can cause a loss to the product value as well as

decrease in the intentional benefits of consumption of Germinated brown rice milk

Chapter 3: Materials and methods

3.1 Materials

The GBR used is Vibigaba GBR which is obtained at Gao Mam Vibigaba retailer in District 10,

Ho Chi Minh City Xanthan gum, Guar gum, Pectin, Acid boric, Phenol, Sodium hypochlorite, Borax and other laboratory equipment is purchased from Hoa Chat Bach Khoa chemical store in District 10, Ho Chi Minh City Enzyme amylase is purchased from Angel Biotic Inc retailer in District 1, Ho Chi Minh City All chemicals are analytical grade

3.2 Methods

3.2.1 Experimental design

The process for producing the germinated brown rice is shown in the figure 3.1

Figure 3 1: Diagram of experimental design

of the hardened layer Soaking the rice at warm temperatures cause the grain to be gelatinized to attain the desired physical, chemical, viscosity, rheological, nutritional properties for the rice milk product

In 2015, Kale et al., 2015 stated that soaking rice at 40C is proven to have least effects on the chemical composition of the product, where as soaking at higher temperatures can lead to decrease

in starch and vitamins Thus choosing 40C water is effective for the soaking process

b Milling

Milling the rice by using a milling device (Oku San No miller Series 1000) The rice is wet milled for ease of process since it is swollen and has a softer texture than the unsoaked rice The softer the rice, the higher yield of milling can be achieved The type of miller used affect the rice particle size, as the speed for milling and sharpness of the blade can reduce these particle size The size of these After milling is done, the unprocessed GBR milk is achieved

c Filtrating

The rice milk after milling is full of large particle and coarse which are not uniform to the rice milk product can cause separation and undesirable sensory texture To remove this, the GBRM is filtrated through cloth bag

3.2.1.1 Determination of soaking time for preparation

Soaking is an important step during the production of GBRM, as the unprocessed GBR has a hardened structure which is unsuitable for achieving the highest milling efficiency Soaking the rice in warm water at different time for soaking is surveyed to determine the most efficient time