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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