Effect of Ocimum gratissimum in fresh tomato preservation

ABSTRACT

 The ability of leaf powder and leaf extract of Ocimum gratissimum plant to preserve tomatoes (Solanum lycopersicum) from early spoilage was investigated in  this study. Mixed cultures of tomatoes purchased from a  retail outlet in Ogun, Southwestern Nigeria, were treated with  the powder  and  some  with  the  leaf  extract  of  Ocimum  gratissimum  plant  and  observed  for preservation or spoilage for 30 days. The plant powder gave positive preservation results when compared to the plant leaf extract. The mean preservation rate of the leaf powder in 30 days gave 48.77% as against 32.51% of the leaf extract. Fresh tomatoes were also infected with Citrobacter freundii and Pseudomonas fluorescens previously isolated from spoilt tomatoes and then treated with plant leaf powder and the other replicates with 15% w/v plant leaf extract and observed for preservation  or  spoilage.    The  results  obtained  did  not  show  any  significant  difference  in preservation  between  the  infected  and  non-infected  tomatoes  when  treated  with  Ocimum gratissimum  plant  parts.  The  study  therefore  shows  that  Ocimum  gratissimum  leaf  which  is reported to have antimicrobial properties can be used as a preservative for enhancing the shelf life of fresh tomatoes.

TABLE OF CONENTS TITLE PAGE………………………………………………………………………………………i CERTIFICATION………………………………………………………………………………...ii

DEDICATION………………………………………………………………………………...….iii ACKNOWLEDGEMENT………………………………………………………………………..iv

TABLE OF CONTENTS………………………………………………………………………….v

LIST OF TABLES………………………………………………………………………………..xi

LIST OF   FIGURES…………………………………………………………………………….xii

ABSTRACT…………………………………………………………………………………….xiii

CHAPTER ONE…………………………………………………………………………………..1

1.0  INTRODUCTION…………………………………………………………………………..1

1.1   AIMS AND OBJECTIVES………………………………………………………….............3   

CHAPTER TWO………………………………………………………………………………….4 

2.0  LITERATURE REVIEW……………………………………………………………….…..4

2.1   TOMATO TAXONOMY………………………………………………………………..….4

2.2   BRIEF   HISTORY OF TOMATO CULTIVATION……………………………………..  .4     

2.3   RECIPES OF TOMATO………………………………………………………….………...5 

vi  2.4   NUTRITIONAL VALUES IN TOMATO…………………………………………………..5

2.4.1 HEALTH BENEFITS OF TOMATOES……………………………………………………7 

2.5    TOMATO PRODUCTION AND POST-HARVEST SPOILAGE IN NIGERIA………….7 

2.5.1    DISEASES AFFECTING TOMATO………………………………………………….….9

2.5.1.1    BACTERIAL DISEASES……………………………………………………………....9

2.5.1.1.1 BACTERIAL SPOT…………………………………………………………………...10

2.5.1.1.2 BACTERIAL CANKER……………………………………………………………….10

2.5.1.1.3 BACTERIAL SPECK………………………………………………………………….10

2.5.1.2     FUNGAL DISEASES…………………………………………………………………10

2.5.1.2.1 SOUR ROT…………………………………………………………………………….11

2.5.1.2.2 RHIZOPUS ROT………………………………………………………………………11

2.5.1.2.3 BUCKEYE ROT……………………………………………………………………….11

2.5.1.3      VIRUSES……………………………………………………………………………..12

2.5.1.3.1 TOMATO SPOTTED WILT VIRUS (TSWV)………………………………………..12

2.5.1.3.2 TOMATO YELLOW LEAF CURL VIRUS (TYLCV)……………………………….12

2.5.1.4     ROOT KNOT NEMATODE………………………………………………………….12

2.5.1.5 PHYSIOLOGICAL DISORDERS………………………………………………………13 

vii  2.6    TOMATO QUALITY DETERIORATION…..…………………………………………...13

2.6.1 PHYSIOLOGICAL DETERIORATION………………………………………………….13

2.6.2 PHYSIOLOGICAL DISORDER………………………………………………………….13

2.6.3 MECHANICAL DETERIORATION……………………………………………………..14 

2.6.4 MICROBIOLOGICAL DETERIORATION………………………………………………14 

2.7     TOMATO PRESERVATION…………………………………………………………….15 

2.7.1 CHLORINATED WATER………………………………………………………………...15

2.7.2 OZONAATED WATER…………………………………………………………………...15

2.7.3 LOW TEMPERATURE…………………………………………………………………...16

2.7.4 HEAT TREATMENT (HT)………………………………………………………………..16

2.7.5 UV-C RADIATION………………………………………………………………………..16

2.7.6 EDIBLE COATINGS……………………………………………………………………...17

2.7.7 PLANT MATERIALS………………………………………………………….………….17

CHAPTER THREE……………………………………………………………………………...18

3.0      MATERIALS AND METHODS………………………………………………………..18

3.1        MATERIALS……………………………………………………………………………18

3.1.1     MEDIA………………………………………………………………………………….18 

viii  3.1.2     EQUIPMENT…………………………………………………………………………...18

3.1.3     REAGENTS……………………………………………………………………………..18

3.1.4      MATERIALS…………………………………………………………………………...18

3.2          METHODS…………………...………………………………………………………..19

3.2.1       STERILIZATION OF MATERIALS………………………………………………….19

3.2.2       MEDIA   PREPARATION…………………………………………………………….19

3.2.3        Ocimum gratissimum PLANT MATERIAL………………………………………….19 

3.2.4       ISOLATION OF BACTERIAL ORGANISM …………………………………….….20

3.2.5      SUB- CULTURING OF BACTERIAL ISOLATES………………………………..….20

3.2.6     CHARACTERIZATION AND IDENTIFICATION OF BACTERIAL ISOLATES…..20

3.2.6.1      GRAM STAINING…………………………………………………………….……..21

3.2.6..2     CATALASE   TEST………………………………………………………………….21

3.2.6.3      OXIDASE TEST……………………………………………………………………..22

3.2.6.4       INDOLE TEST………………………………………………………………………22

3.2.6.5      METHYL RED (MR) AND VOGES PROSKAUER (VP) TEST …………………..22

3.2.6.6      CITRATE UTILIZATION TEST ……………………………………………………22

3.3           PREPARATION OF HOT AQUEOUS PLANT MATERIAL……………………….23 

ix  3.4           SELECTION OF TOMATOES………………………………………………………23

3.5           TREATMENT AND STORAGE OF TOMATOES USING THE LEAF POWDER OF Ocimum gratissimum………………………………………………………………………………………24

3.5.1        EXPERIMENTAL INFECTION OF TOMATOES…………………………………..24

3.6           TREATMENT AND STORAGE OF TOMATOES USING HOT AQUEOUS EXTRACT OF Ocimum gratissimum…………………………………………………………………..25

3.6.1        EXPERIMENTAL INFECTION OF TOMATOES …………………………………25

3.7            DATA COLLECTION ………………………………………………………………26

3.7.1         PRESERVATION RATE ……………………………………………………………26

3.7.2         FIRMNESS DECREASE…………………………………………………………….26 

3.7.3         ORGANOLEPTIC PROPERTIES …………………………………………………..26

CHAPTER FOUR……………………………………………………………………………….28 

4.0 RESULT……………………….…………………………………………………………….28

4.1 ISOLATION OF BACTERIA……………………………………………………………….28

4.2 IDENTIFICATION AND CHARACTERIZATION OF BACTERIA ISOLATED………..28 4.3 PRESERVATION RATE……………………………………………………………………31 

4.3.1 TREATMENT OF FRESH TOMATOES WITH Ocimum gratissimum LEAF POWDER  ……………………………………………………………………………………………………31       

x  4.3.2 TREATMENT OF FRESH TOMATOES WITH Ocimum gratissimum LEAF EXTRACT……………………………………………………………………………………….31   

  4.4 FIRMNESS DECREASE……………………………………………………………………31

4.5 ORGANOLEPTIC PROPERTIES…………………………………………………………..32

CHAPTER FIVE………………………………………………………………………………...41

5.0 DISCUSSION………………………………………………………………………………..41

5.1 CONCLUSION………………………………………………………………………………43 REFERENCES…………………………………………………………………………………..44

APPENDIX…..……………………………………………………………………………….….51          

xi  LIST OF TABLES: TABLE  1:  Major  nutrients  derived  from  consuming  a  123g  of  ripened tomatoes…………………………………………………………………………………….……..6 TABLE 2:  Summary of treatment of fresh non- inoculated and inoculated tomatoes with plant (Ocimum gratissimum) material ……………………………………………………………..… 27 TABLE 3: Biochemical characteristics of bacteria isolated from spoilt tomatoes. ……………..29        TABLE  4:  Preservation  rate  (%)  of  fresh  tomatoes  coated  with  Ocimum  gratissimum  leaf powder…………………………………………………………………………………………...33 TABLE 5: Preservation rate (%) of fresh tomatoes dipped in 15% w/v Ocimum gratissimum leaf extract………………………………………………………………………………………...…. 35 TABLE 6:  Firmness decrease calculation  for tomatoes treated with  Ocimum  gratissimum  leaf powder………………………………………………………………………………………..…..38 TABLE 7:  Firmness  decrease calculation  for tomatoes treated  with  Ocimum  gratissimum  leaf extract…………………………………………………………………………………………….39                                                                                                                                                           

LIST OF FIGURES

FIGURE 1:A pie- chart showing the frequency of Bacterial isolates……………………………30

FIGURE 2: The preservation rate of tomatoes stored in Ocimum gratissimum leaf powder for 30 days………………………………………………………………………………………………34

FIGURE 3: The preservation rate of tomatoes stored in 15% Ocimum gratissimum leaf extract for 30 days…………………………………………………………………………………………………..36

FIGURE  4:  Comparison  between  the  mean  preservation  rate  of  Ocimum  gratissimum  leaf powder and 15% w/v leaf extract………………………………………………………………...37

FIGURE  5:  Comparison  between  the  decreases  in  firmness  of  tomatoes  stored  in  Ocimum gratissimum leaf extract and leaf powder………………………………………………………..40          

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