Effect of Acidified Sodium Chlorite against microbial contamination and maintain the quality of mung bean (Khóa luận tốt nghiệp)

Effect of Acidified Sodium Chlorite against microbial contamination and maintain the quality of mung bean (Khóa luận tốt nghiệp)Effect of Acidified Sodium Chlorite against microbial contamination and maintain the quality of mung bean (Khóa luận tốt nghiệp)Effect of Acidified Sodium Chlorite against microbial contamination and maintain the quality of mung bean (Khóa luận tốt nghiệp)Effect of Acidified Sodium Chlorite against microbial contamination and maintain the quality of mung bean (Khóa luận tốt nghiệp)Effect of Acidified Sodium Chlorite against microbial contamination and maintain the quality of mung bean (Khóa luận tốt nghiệp)Effect of Acidified Sodium Chlorite against microbial contamination and maintain the quality of mung bean (Khóa luận tốt nghiệp)Effect of Acidified Sodium Chlorite against microbial contamination and maintain the quality of mung bean (Khóa luận tốt nghiệp)Effect of Acidified Sodium Chlorite against microbial contamination and maintain the quality of mung bean (Khóa luận tốt nghiệp)

THAI NGUYEN UNIVERSITY

UNIVERSITY OF AGRICULTURE AND FORESTRY

PHAM THI CHUYEN

Effect of Acidified Sodium Chlorite Against Microbial Contamination and Maintain The Quality of Mung Bean Sprout

BACHELOR THESIS

Study Mode : Full-time Major : Post-Harvest Technology Faculty :Biotechnology and Food Technology Batch :2013 – 2017

Thai Nguyen, 12/06/2017

THAI NGUYEN UNIVERSITY

UNIVERSITY OF AGRICULTURE AND FORESTRY

PHAM THI CHUYEN

Effect of Acidified Sodium Chlorite Against Microbial

BACHELOR THESIS

Study Mode : Full-time

Major : Post-Harvest Technology

Faculty : Biotechnology and Food Technology

Supervisors : Assoc Prof Dr Pongphen Jitareerat

Ms Trinh Thi Chung

Thai Nguyen, 12/06/2017

Thai Nguyen University of Agriculture and Forestry

Major Post-Harvest Technology

Student name Pham Thi Chuyen

Student ID DTN1353140010

Thesis title Effect of Acidified Sodium Chlorite against microbial

contamination and maintain the quality of mung bean sprout

Supervisors

Assoc Prof Dr Pongphen Jitareerat

Ms Trinh Thi Chung Abstract:

The use of suitable sanitizers can increase the quality and reduce the risk of foodborne illnesses of mung bean sprout The objective of this research was to study

the effects of acidified sodium chlorite (ASC which was prepared from mixture of

0.1g/l sodium chlorite and 5% citric acid, pH 2.3) to control microbial contamination

and maintain the quality of mung bean sprout The optimal concentation (0.1, 0.25,

0.5 and 1.0 g/l) and dipping time (1, 5, 10, and 15 min) of ASC solution for

controlling browning of sprouts was investigated The result revealed that 0.1 g/l

ASC for 1 min was the best concentration and dipping time for controlling

browning This concentration and dipping time was selected to study its effects on

microbial decontamination and maintaining the quality of mung bean sprout in

compared with non-treated sprout, water washed sprout, and common sanitizing

agent (100 ppm sodium chlorite) treated sprout All samples were then stored at

10°C for 5 days The sprout treated with 0.1 g/l ASC for 1 min resulted in a

significant reduction of bialtotal bacteria, and coliform in comparing with the other

treatments ASC treatment also maintained the quality of sprout by inhibiting the

browning as indicated by browning score and the changes of color (high L* value

and low a* value) Furthermore the treatment with ASC could delay weight loss but

did not show any significant negative effect on texture and total soluble solids

content Sensory evaluation showed that ASC treated sprout had higher score of

color, odor, and over all acceptance than non-treated sprout Therefore, this result

indicated that 0.1 g/l ASC for 1 min has the potential to minimize microbial growth

and maintaining quality of mung bean sprouts

Key words browning, coliform, food born pathogens, sanitizing agent,

sprout Number of pages 43 pages

Date of Submission 12/06/2017

ACKNOLEDGMENT

This thesis was completed by support and assistance of a number of people whom I would like to personally thank First and foremost, I would like to express my gratitude to the both my supervisor, Assoc Prof Dr Pongphen Jitareerat of the School

of Bioresources and Technology, King Mongkut’s University of Technology Thonburi (KMUTT), Thailand and Master Trinh Thi Chung from the Biotechnology and Food Department of Thai Nguyen University of Agriculture and Forestry (TUAF), Vietnam Whose expertise, understanding, patience and provide valuable advice, support and guidance during the my study

A special thanks also to my lab teacher, Dr Kanlaya Sripong, for sharing her knowledge, inspiring ideas and discussions, both academic and non-academic Thanks for helping me all the time when I was doing my internship Thanks you for always being supportive and for taking care of me whenever I needed help

I would like to thank every people on Post-harvest Technology Department and special thank to all members Postharvest Pathology Laboratory at King Mongkut’s University of Technology Thonburi for helping me fit in and feel welcome from the moment and for the unlimited patience to explain me every doubts which I had during

my intership

I would also like to all of my teacher in Faculty of Biotechnology and Food Technology for teaching me how to become a good student, helping me how to get knowledge and how to become a useful person

And I wish to express my great gratitude to my friends whose support given throughout the 6 months when I stayed at Thailand

Finally, I would like to thanks my family, especially to my parents for their unconditional love, overflowing support and words of encouragement Words a truly not enough to express how thankful I am to you

TABLE OF CONTENTS

PART I INTRODUCTION 1

1.1 Researcher rationale 1

1.2 Objectives 5

1.2.1 To determine the optimal concentration of ASC on browning inhibition of mung bean sprouts 5

1.2.2 To determine the effect of ASC dipping times on browning inhibition

of mung bean sprouts 5

1.2.3 To study the effect of ASC on the microbial contamination and quality

of mung bean sprouts 5

1.3 Scope of study 5

1.3.1 To study effect of ASC concentration on browning inhibition of mung bean sprouts 5

1.3.2 To study effect of dipping time of ASC on browning inhibition of mung bean sprouts 6

1.3.3 To study the effect of ASC on the microbial contamination and quality

of mung bean sprouts 6

PART II MATERIALS AND METHODS 7

2.1 Materials 7

2.2 Methods 7

2.2.1 Experiment 1: To determine the optimal concentration of acidified sodium chlorite (ASC) on browning inhibition on of mung bean sprouts 7

2.2.2 Experiment 2: To determine the effect of acidified sodium chlorite (ASC) dipping times on browning inhibition of mung bean sprouts 7

2.2.3 Experiment 3: To study the effect of acidified sodium chlorite (ASC) on the microbial contamination and quality of mung bean sprouts 8

2.3 Parameters measurement 9

2.3.1 Browning score 9

2.3.2 Color (L*, a*) 9

2.3.3 Weight loss 9

2.3.4 Texture analysis 9

2.3.5 Total soluble solids 10

.2.3.6 Sensory evaluation 10

2.3.7 Microbial count 10

2.4 Statistical analysis 11

PART III RESULTS AND DISCUSSION 12

3.1 To determine the optimal concentration of ASC on browning inhibition

of mung bean sprouts 12

3.2 Effect of ASC dipping times on browning inhibition of mung bean sprouts 13

3.3 To study the effect of ASC on the microbial contamination and quality

of mung bean sprouts 15

3.3.1 Browning score 15

3.2.2 Color change (L* and a* values) 16

3.2.4 Weight loss 17

3.2.5 Texture (shear force) 18

3.2.5 Total soluble solids (TSS) 19

3.2.6 Sensory evaluation 20

3.2.7 Total aerobe bacteria population 23

3.2.8 Coliform population 24

DISCUSSION 26

PART IV CONCLUSION AND SUGGESTION 30

4.1 Conclusion 30

4.2 Suggestion 30

LIST OF TABLES AND FIGURES

Table 1 Effect of concentration and dipping times of ASC on browning inhibition of mung bean sprouts

Table 2 Effect of H2O, SH, ASC dip treatment on weight loss of mung bean sprouts during storage at 10oC for 5 days

Table 3 Effect of H2O, SH, ASC dip treatment on texture of mung bean sprouts during storage at 10oC for 5 days

Table 4 Effect of H2O, SH, ASC dip treatment on brightness value of mung bean sprouts during storage at 10oC for 5 days

Table 5 Effect of H2O, SH, ASC dip treatment on a* value of mung bean sprouts during storage at 10oC for 5 days

Table 6 Effect of H2O, SH, ASC dip treatment on browning score of mung bean sprouts during storage at 10oC for 5 days

Table 7 Effect of H2O, SH, ASC dip treatment on color acceptance of mung bean sprouts during storage at 10oC for 5 days

Table 8 Effect of H2O, SH, ASC dip treatment on smell acceptance of mung bean sprouts during storage at 10oC for 5 days

Table 9 Effect of H2O, SH, ASC dip treatment on overall acceptance of mung bean sprouts during storage at 10oC for 5 days

Table 10 Effect of H2O, SH, ASC dip treatment on total soluble solids of mung bean sprouts during storage at 10oC for 5 days

Table 11 Effect of H2O, SH, ASC dip treatment on total bacteria population of mung bean sprouts during storage at 10oC for 6 days

Table 12 Effect of H2O, SH, ASC dip treatment on total coliform population of mung bean sprouts during storage at 10oC for 6 days

Figure 3.1 Effect ASC concentration to appearance of sprouts

Figure 3.2 Effect ASC concentration on browning inhibition of sprouts

Figure 3.3 Effect of ASC dipping times to appearance of sprouts

Figure 3.4 Effect ASC dipping times on browning inhibition of sprouts

Figure 3.5 Effect of H2O, SH, ASC dip treatment on browning score of sprouts

Figure 3.6 Effect of H2O, SH, ASC dip treatment on L* value of sprouts

Figure 3.7 Effect of H2O, SH, ASC dip treatment on a* value of sprouts

Figure 3.8 Effect of H2O, SH, ASC dip treatment on weight loss of sprouts

Figure 3.9 Effect of H2O, SH, ASC dip treatment on texture of sprouts

Figure 3.10 Effect of H2O, SH, ASC dip treatment on total soluble solids of sprouts

Figure 3.11 Effect of H2O, SH, ASC dip treatment on color acceptance of sprouts

Figure 3.12 Effect of H2O, SH, ASC dip treatment on smell acceptance of sprouts Figure 3.13 Effect of H2O, SH, ASC dip treatment on overall of sprouts

Figure 3.14 Effect of H2O, SH, ASC dip treatment on total aerobe bacteria of sprouts

Figure 3.15 Changes in mung bean sprouts total bacterial population

Figure 3.16 Effect of H2O, SH, ASC dip treatment on total coliform of sprouts

Figure 3.17 Changes in mung bean sprouts total coliform population

PCA Plate Count Agar

EMB Eosin Methylene Blue Agar

FDA Food and Drug Administration

CDC Centers for Disease Control

CFU/g Colony forming units per gram

CFU/g-1 Colony forming unit

o C Degree celsius

min Minute

C.V Coefficient of Variation

PART I INTRODUCTION 1.1 Researcher rationale

In the world, the increased consumption of seed sprouts in the past decades which could be due to sprouts was an inexpensive product and good source of dietary proteins, carbohydrates, minerals, and vitamins According to Oregon Public Health Division et al (2005) reported that the most popular consumption of sprouts such as alfalfa, mung bean, red clover, radish, broccoli and wheatgrass sprouts In 2015, this institution also showed that in sprout types, mung bean sprouts were the most commonly consumed and it contained the high nutrient composition This result indicated by Dahiya et al (2014) that mung bean sprouts contained 617 ppm iron, 247 ppm zinc, 13557 ppm calcium and an approximately 19.5-31.3% of protein ingredient (Masood et al., 2014) In addition, the presence of approximately 20-24% protein and 50-60% carbohydrate was also founded by Tang et al (2014) Besides, mung bean sprouts contained other composition such as ascorbic acid, vitamin C, phosphorus, potassium, sodium and other compounds which have possible health benefits, and it was considered as potential benefits product for cancer prevention and suppression

(Muñoz et al, 2006)

Mung bean sprouts were allocated to many countries in the world include the United States (Robertson et al., 2002; Bari et al., 2004) but the most popular in Pakistan, Philippines, China, Korea, Japan, India and Bangladesh (Ali Siddiqui et al.,

2001; Hur and Kor, 2002 and Gabriel et al., 2007) With the increase in consumer

demand for the sprouts product can be causes the increase of foodborne illnesses involved to bean sprouts because sprouts were regularly eaten raw (in salad and in sandwiches) or slightly cooked as well as stir fry in oriental-type meals (Rajkowski and Thayer, 2001; Robertson et al., 2005) Moreover, the production areas of all producers were also found to be inappropriate for safe sprout production The study by Van Beneden et al (1999) and Proctor et al (2001) reported that the happening of foodborne illness by consumption of raw sprouts as the critical risk factor

According to statistics by FDA (Food and Drug Administration) and CDC (Centers for Disease Control and Prevention) in recent years, caused high foodborne illness outbreaks which were indicated as between 1996 and 2010 at United States

where it occurred 34 foodborne illness outbreaks led to 123 hospitalizations and one death due to sprouts consumption (Johanson, 2012) A reported by FDA (2004) when conducted investigation from 1996 to 2003 showed that caused to 25 foodborne illness outbreaks related sprouts CDC (2016) also investigated on raw sprouts between 2009 and 2016 and reported that there were 11 foodborne illness outbreaks This pathogens

outbreaks popularly caused by Salmonella, E coli and Listeria monocytogenes (CDC,

2016)

General, the increase of microbial amounts due to the inclusion of favorable feature which needs to pathogens growth such as nutrients, pH, time, temperature, oxygen and moisture A study by Phue et al., (2014) found that mung bean sprouts contained on average 9 log CFU/g total aerobic microorganisms and also contained approximately 1.7х 107 CFU/g yeasts and molds when it was not treated (Tournas, 2005) Warriner et al (2003) showed that when mung bean sprouts were inoculated by

E coli and Salmonella montevideo, the pathogens became internalized Moreover, in the sprouts also existed other microbial such as Aeromonas hydrophila, Bacillus cereus, and Staphylococcus aureus (Beuchat, 1995; Thompson and Powell, 2000)

Deering et al (2012) also suggested that a conductive environment was created surrounds of the pathogens which allowed the growth of microbial populations inside boundaries of the plant

However, the shelf life of the fresh-cut product (sprouts) is not only decided by the microbial quality which caused product pathogens but also determined by physiological quality A study by Brecht (1995) showed that after processing, Fresh-cut vegetables (sprouts) still viable and their action could be compared with an observed in plant tissues which were wounded or were exposed to pressure conditions This behaviour consists of the increase in respiration rate and ethylene production Beside, also occurred the wound-healing processes oxidative browning reaction and lipid oxidation or water loss was increased

A study evaluated by Yon (2012) indicated that the color was an important sensory property with the role in determining product quality In his study also mentioned the major postharvest problems resulting in decreased in the commercial value of fruits and vegetables Browning of fruits and vegetables caused by polyphenol

oxidase (PPO) which was created due to the oxidation of phenolic compounds to

o-quinones, subsequently polymerize to form dark-color pigments (Jos-lyn and Ponting, 1951; Mayer and Harel, 1979) In addition, Ilker et al (1977) and Mateos et al (1993) also showed that browning was one of the main causes of quality loss during the postharvest storage of head lettuce and the processing of minimal lettuce The studies

by He et al (2008), Lu et al (2007) found that the disorder of primary physiology which caused the reduction of sensory quality and shelf life of fresh-cut apples Therefore, in order to understand the biochemical basis of browning and find treatments to inhibit these color changes, the research expansion should be more concerned (Hyodo et al., 1978; Ke and Saltveit, 1986d Siriphanich and Kader, 1985; Fujita et al., 1991; Chazarra et al., 1996)

Along with the enzymatic browning control, the control of microbial populations also was an important element to maintain quality and prolong the shelf life of fresh-cut products, this confirmation was reported by Luo et al (2011) Recently, several agents which were used to prevent browning and reduced microbial growth on mung bean sprouts also as fresh-cut products were found There were many reports investigated the effect of antimicrobial treatments on sprouts included physical, chemical and biological treatments such as chlorine (Bang et al., 2011), ozone (Singla

et al., 2011), electrolyzed water (Zhang et al., 2011), heat (Jaquette et al., 1996), chilling (Tian et al., 2012), irradiation (Saroj et al., 2007), supercritical carbon dioxide (Jung et al., 2009), antagonistic microorganisms (Liao, 2008), antimicrobial metabolites (Nandiwada et al., 2004) and bacteriophages (Ye et al., 2010) Several agents were used to inhibit browning of fresh-cut product such as ascorbic acid, calcium lactate, chlorine dioxide, cysteine, phytoncide, citric acid, calcium chloride, sodium metabisulphite, L-cysteine and acetic acid (Martin-Diana et al., 2005; Gómez-López, 2008; Chen et al., 2010; Kim et al., 2014; Manolopoulou and Varzakas, 2013; Ibrahim et al., 2004) In addition, McEvily et al (1992) also indicated that based on the working mechanisms of browning, can be divided into six groups which were able

to anti-browning included: reducing agents, acidulants, chelating agents, complexing agents, enzyme treatments and enzyme inhibitors However, there are the limited information about antibrowning treatment on mung bean sprouts Therefore, in order

to maintained quality of sprouts as well as fresh-cut products in postharvest technology, the use a suitably sanitized solution as an urgent need for inhibited browning and microbial growth

Acidified sodium chlorite (ASC) which is combined by mixing a sodium chlorite (NaClO2) solution and organic acid, it also is was sanitizing agent recently accepted by FDA for a dip or spray application for food items, including fresh and fresh-cut fruits and vegetables ASC was indicated by an affection to pathogens

control such as the presence of Escherichia coli O157: H7, L monocytogenes, Salmonella Poona, etc on fresh-cut carrots and cilantro (Allende et al., 2009;

Gonzalez et al., 2004; Ruiz-Cruz et al., 2006) Office of the Federal Register, U.S Government Printing Office (1999) also reported that ASC was used in poultry, red meat, comminuted meat products, and fruit and vegetable products to decreased bacterial contamination

According to a study in ASC solution by Madduri (2007) reported that when this solution was combined, metastable chlorous acid is formed in an equilibrium reaction Chlorous acid is a precursor to a series of strong oxidants (chlorate, chlorite, chlorine dioxide) which able to kill bacteria, fungi, viruses, and algae As a product was produced from acidified sodium chlorite (ASC), Chlorine dioxide showed is a disinfectant equal to or more effective than chlorine (Lillard, 1979), and it was also found the oxidation capability in prevention bacteria, bacterial spores and virus (Foegedineg et al., 1986; Lukasik et al., 2003) Several investigations mentioned the effectiveness of aqueous chlorine dioxide to inhibit bacterial growth on the surface of lettuce, cabbage, cucumber, and green pepper (Reina et al., 1995; Zhang and Farber, 1996; Han et al., 2001) In addition, Anon-ymous (1999) also proved that chlorine dioxide was a strong oxidizing agent with oxidizing capability is about 2.5 times higher than hypochlorous acid These studies further demonstrated the effectiveness of ASC in against microbial growth

Moreover, ASC was also demonstrated is a potential browning inhibitor of the fresh-cut industry Luo et al (2011) hypothesized that at low pH concentration (~2.5), ASC may be able to control the browning reaction of fresh-cut apples The study by institutes such as CFIA (2001), FSANZ (2003), EFSA (2006), and FDA (2011) also

reported that the use of ASC at < 1,200 ppm sodium chlorite (SC) with pH levels from 2.3 to 2.9 has been demonstrated for the decontamination of food products (fish, poultry, processed fruits and vegetables, and red meat) Sodium chlorite (SC) is a major ingredient of ASC which was studied on their mechanism of browning inhibition SC acts as the inhibitor of polyphenol oxidase activity (He and Luo, 2007;

Lu et al., 2006; Lu et al., 2007) In addition, citric acid also widely used commercial as

an anti-browning agent, and is known to have inhibitory activity on polyphenol oxidase in minimally processed fruits and vegetables ((Pizzocaro et al., 1993; Rocha et al., 1998) Therefore, the combination of SC (sodium chlorite) and CA (citric acid) for surface washing of products was extensively researched in fresh-cut produce The microbial decontaminated efficacy of ASC was often reported with different level, because the reduction of microbial populations was affected by experimental conditions such as inoculation process and washing methods (Singh et al., 2002) In addition, there have been limited reports dealing with the washing effectiveness of ASC on microbial control including aerobic plate counts, coliforms, as well as the browning control of fresh-cut root vegetables in general and sprouts products in particular

Therefore, the objective of this study was to evaluate the effects of ASC treatment on a reduction of microbial growth and maintenance of the quality of mung bean sprouts

The mung bean sprout was treated with ASC solution at 0.1-1.0 g/l for 1 min before stored at 10°C The browning score was assessed 7 days

1.3.2 To study effect of dipping time of ASC on browning inhibition of mung bean sprouts

The mung bean sprout was treated with 0.1 g/l ASC solution for 1, 5, 10, and 15 min before stored at 10°C The browning score was assessed 7 days

1.3.3 To study the effect of ASC on the microbial contamination and quality of mung bean sprouts

The mung bean sprout was treated with 0.1 g/l ASC solution for 1 min before stored at 10°C The quality of treated sprouts such as browning score, changes of color, weight loss, texture, total soluble solids content, and sensory test were determined during storage for 5 days, the microbial population such as total bacteria, and Coliform were determined during storage for 6 days

PART II MATERIALS AND METHODS 2.1 Materials

Mung beans sprouts are produced in the laboratory of the postharvest technology, King Mongkut’s University of Technology Thonburi Sprouts were handled basic and were selected to obtain damage-free and uniform size and color to

prepared for experiments

Treatment 1 = Dipped with tap water at room temperature for 1 minute (Control 1) Treatment 2 = Dipped with 0.1 g/l SH (Sodium hypochlorite) for 1 minute (Control 2)

Treatment 3 = Dipped with 0.1 g/l ASC for 1 minute

Treatment 4 = Dipped with 0.25 g/l ASC for 1 minute

Treatment 5 = Dipped with 0.5 g/l ASC for 1 minute

Treatment 6 = Dipped with 1 g/l ASC for 1 minute

After treating, the exceed solution or water was removed by handle spinner Twenty grams of sprouts from each treatment was placed on the foam tray and covered with PVC film The samples were then kept at 10°C for 7 days to evaluate the browning score Each treatment had replicates (trays) Browning score of sprout was evaluated on day 0, 1, 2, 3, 4, and 7 acccording to the method of Junkwon et al (2015) The area of surface browning of the sprouts was scored from the percentage of browning intensity of 0 to 3 when 0 = <10%, 1 = 11-25%, 2 = 26-50%, and 3 >50%

2.2.2 Experiment 2: To determine the effect of acidified sodium chlorite (ASC) dipping times on browning inhibition of mung bean sprouts

Mung bean sprouts prepared as described on above The sprouts were dipped in 0.1 g/l ASC solution for 1, 5, 10, and 15 min Mung bean sprout treated with 100 ppm

sodium hypochlorite (SH) or tap water were used as the controls All treatments were shown as follows:

Treatment 1 = Dipped with tap water at room temperature for 1 minute

(control 1)

Treatment 2 = Dipped with 0.1 g/l SH (Sodium hypochlorite) for 1 minute

(Control 2) Treatment 3 = Dipped with 0.1g/l SH for 1 minute

Treatment 4 = Dipped with 0.1 g/l ASC for 1 minute

Treatment 5 = Dipped with 0.1 g/l ASC for 5 minutes

Treatment 6 = Dipped with 0.1 g/l ASC for 10 minutes

Treatment 7 = Dipped with 0.1 g/l ASC for 15 minutes

After treating, the exceed solution or water was removed by handle spinner Twenty grams of sprout from each treatment was placed on the foam tray and covered with PVC film The samples were then kept at 10°C for 7 days to evaluate the browning score Each treatment had 3 replicates trays) Browning score of sprout was evaluated on day 0, 1, 2, 3, 4, and 7 according to the method of Junkwon et al (2015) The area of surface browning of the sprouts was scored from the percentage of browning intensity of 0 to 3 when 0 = <10%, 1 = 11-25%, 2 = 26-50%, and 3 >50% of browning intensity

2.2.3 Experiment 3: To study the effect of acidified sodium chlorite (ASC) on the microbial contamination and quality of mung bean sprouts

Mung bean sprouts prepared as described on above The sprouts were dipped in 0.1 g/l ASC solution for 1 min Mung bean sprout treated with 0.1 g/L (or 100 ppm) sodium hypochlorite (SH) or tap water were used as the controls All treatments were shown as follows:

Treatment 1 = Non-dipped sample (Negative control 1)

Treatment 2 = Dipped with tap water at room temperature for 1 min

(Negative control 2) Treatment 3 = Dipped with 0.1g/l SH (sodium hypochlorite) for 1 minute

(Positive control) Treatment 4 = Dipped with 0.1 g/l ASC for 1 minute

After treating, the exceed solution or water was removed by handle spinner Thirty grams of sprout from each treatment was placed on the polypropylene (PP) tray and covered with PVC film The samples were then kept at 10°C for 6 days Each treatment consisted with 3 replicates (trays) The quality of sprout (browning score, changes of color, weight loss, texture, total soluble solids content, and sensory test) were determined 5 days during storage whereas the microbial growth (total bacteria,

E.coli, and Coliform) were determined 6 days interval

2.3 Parameters measurement

2.3.1 Browning score

Browning score of sprout was evaluated according to the method of Junkwon et

al (2015) The area of surface browning of the sprouts was scored from the percentage

of browning intensity of 0 to 3 where; 0 = <10%, 1 = 11-25%, 2 = 26-50%, and 3

>50% of browning intensity

2.3.2 Color (L*, a*)

Color changes of mung bean sprouts were determined using colorimeter (CR

400, Minolta, Japan) The value of a* and L* from each replication (sprouts) was measured The L* value shows lightness or darkness of the sprouts, while a* value shows the green to red color as it moves from negative and positive value Three replicates were used per treatments Results were reported as average of individual values as L* (lightness) or a*

2.3.3 Weight loss

Weights of mung bean sprouts were determined using electronic weighing balance every day until the end of the experiment Weight was recorded in 3 replications for each treatment, and weight loss was determined as a percentage of initial weight at the start of the experiment The calculation was done using the

2.00 and 10.00 mm/s, respectively In this study, the shear forces were determined on the stem part of the mung bean sprout by cutting through with a shear blade at the middle part of sprouts Four replicates with 3 sprouts each were analyzed and data was reported as Newton (N)

2.3.5 Total soluble solids

Total soluble solids (TSS) contents were measured by hand digital refractometer (Brix 0-32%, Atago, PAL-1, Japan) The mung bean sprouts was crushed with mortar and pestle The supernatant of sprouts was obtained by squeezing out using clean pieces of cloth The supernatants from each sample were used to measure total soluble solids The data was reported as °Brix

.2.3.6 Sensory evaluation

The sensory evaluation of sprout was conducted using ta least 5 untrained panelists The sensory test was conducted following techniques at the Quartermaster and the University of Chicago The questionnaire was designed to collect information

on color acceptance, odor (smell) acceptance and overall acceptance of the product A 9-points hedonic scale was used in collecting key information from the give sprout samples and was indicated as following:

9 = Like extremely 4 = Dislike slightly

8 = Like very much 3 = Dislike moderately

7 = Like moderately 2 = Dislike very much

6 = Like slightly 1 = Dislike extremely

5 = Neither like or dislike

2.3.7 Microbial count

A 25 g of mung bean sprouts was randomly taken from each replication and transferred to 225 ml of sterile peptone water soluble The sample was placed in the stomacher and shook for 60 seconds The suspension from each sample was diluted and used to determine the population of microbial Serial dilution of this solution (0.1 ml) was performed in the triplicate standard method using Plate Count Agar (PCA) plates to determine the total aerobe bacteria, Eosin Methylene Blue (EMB) agar plates

to determine the Escherichia coli (E coli) and coliform enumeration The amounts of

colonies were counted after 24 hr for PCA medium and 48hr for EMB medium after incubating at 37°C Microbial counts were expressed as log CFU/g fresh weight

2.4 Statistical analysis

Three replicates per treatment were used in the experiments All data points represent the mean ± SD of the three replications Analysis of variance (ANOVA) followed by Duncan’s Multiple Range Test with a significance level of, P<0.05, and correlation test was performed on data using the statistic software SAS (SAS Institute, 1989)

PART III RESULTS AND DISCUSSION 3.1 To determine the optimal concentration of ASC on browning inhibition of

mung bean sprouts

The browning symptom and browning score in mung bean sprouts treated with ASC at different concentrations for 1 min are shown in Figure 3.1 and Figure 3.2 in

compared with sodium hypochlorite (SH) treatment and tap water treatment (control)

Sprout treated with 0.1 and 0.5 g/l ASC showed significant lower browning score than

the control since 1th until 4th day of storage (p<0.05) Among of treatments, the samples

were treated with 0.1 g/l ASC for 1 minute discovered the lowest browning score

value However, on day 7, no significant difference was showed between all

treatments, and the sprouts were treated by 100 ppm SH for 1 minute indicated the

highest score value compared to other treatment

Day 0 Day 1 Day 2 Day 3 Day 4 Day 7

Figure 3.1 The appearance of mung bean sprout after treating with acidified sodium

chlorite (ASC) at 0, 0.1, 0.25, 0.5, and 1.0 g/l for 1 min compared to sprout treated

tap water and sodium hypochlorite (SH) All samples were stored at 10°C for 7 days

0 1 2 3 4 7 0

as the controls

3.2 Effect of ASC dipping times on browning inhibition of mung bean sprouts

Figure 3.3 and 3.4 show the appearance and browning score of mung bean sprout respectively The effect of ASC dipping time on browning inhibition of mung bean sprout was observed during storage at 10°C for 7 days The brown color gradually presented towards from the initially day to the end of storage period No significant difference in browning was observed between all treatments in during of storage But it seemed to observe that the sprout samples treated with 0.1 g/l ASC for 1 and 15 min had the lowest value of the browning score Furthermore, the highest browning score was discovered in 100 ppm SH treated sprout This result indicated that SH treatment does not have antibrowning activity

*

Day 0 Day 1 Day 2 Day 3 Day 4 Day 7

Figure 3.3 The appearance of mung bean sprout after treating with 0.1 g/l acidified sodium chlorite (ASC) for 1, 5, 10 and 15 min compared with sprout treated with tap water (control) and sodium hypochlorite (SH) All samples were stored at 10°C

Figure 3.4 Effect of different dipped time of 0.1 g/l ASC solution on browning

inhibition of mung bean sprouts during storage at 10°C for 7 days The sprout

treated with tap water and sodium hypochlorite (SH) were served as the controls

3.3 To study the effect of ASC on the microbial contamination and quality of mung bean sprouts

3.3.1 Browning score

Browning of mung bean sprouts treated with tap water, 0.1 g/l SH, and 0.1 g/l ASC for 1 minute was observed during 5 days of storage Figure 3.5 showed that no significant difference of browning score was found between all treatments throughout

of the storage But it seemed that the samples treated by 0.1 g/l ASC for 1 minute had the lowest browning score during of storage while the samples were treated with tap water had a highest browning score especially on day 5 Therefore, this result indicated that treatments with ASC or SH could not inhibit the browning symptom in mung bean sprouts

SH 100 ppm, 1 minASC 0.1 g/l, 1 min

SH 100 ppm, 1 minASC 0.1 g/l, 1 min

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