ABSTRACT

The effects of some processing methods on the malonaldehyde (MDA) content of some selected legumes and cereals were investigated. The unprocessed legumes had varying concentrations of MDA ranging from 1.23 ± 0.29pglg in cowpea — L25 (Vigna unguiculata) to 6.63 ± 0.l4pg/g in breadfruit (Treculia africana). The unprocessed cereals had MDA concentrations ranging from 0.72 ± 0.l5pg/g in maize — Obubra Local (Zea mays) to 2.96± 0.l4pg/g in maize — Suwan ISR-Y (Zeamays). Green malting significantly (p<0.05) increased the MDA content of all the legumes studied ranging from 17.59 ± 7.26% in soybean - TGX 1448E (Glycine max) to 160.30 ± 85.27% in cowpea -L25. In finished malt (kilned green malt), the MDA content also significantly (p<0.05) increased. The increase ranged from 29.30 ± 2.76% in breadfruit to 291.43 ± 68.97% in cowpea- L25. In the cereals, green malting significantly (p<0.05) increased the MDA. This ranged from 13.87 ± 0.06% in maize-Suwan lSR-Y to 195.80 ± 100.99% in millet — Pearl (Pennissetumtyphoides). In finished malt, the MDA also significantly (p<0.05) increased. This ranged from 77.21 ± 32.87% in wheat (Triticum vulgare) to 421.01 ± 67.66% in maize-Obubra Local. Roasting significantly (p<0.05) increased the MDA level in the legumes. This ranged from 8.79 ± 4.29% in cowpea — Ife Brown (Vigna unguiculata) to 140.20 ± 56.84% in cowpea — L25. Roasting also significantly

 

(p<0.05) increased the MDA in cereals ranging from 7.17 ± 10.14% in maize-

Suwan lSR-Y to 104.41 ± 42.45% in maize — Obubra Local. Steeping and roasting

 

significantly (p<O.05) decreased the MDA in the legumes ranging from 33.02 ±

14.14% in beniseed (Sesamum indicum) to 63.11 ± 32.39% in cowpea — L25.

Steeping and roasting also significantly (p<0.05) decreased the MDA in the cereals

ranging from 25.00 ± 35.36% in millet-Pearl to 65.27 ± 11.21% in maize-Suwan

ISR-Y. Fermentation significantly (p<0.05) reduced the MDA of the cereals. After

three (3) days of fermentation, the MDA content was reduced. This ranged from

71.33 ± 0.00% in sorghum — lCSV 400 (Sorghum vulgare) to 96.73 ± 4.62% in

maize-Suwan lSR-Y. These findings show that processing affects the MDA

concentrations of both legumes and cereals. The legumes and cereals also

contained varying concentrations of tannic acid, cyanogenic glycosides, saponins,

oxalates and phytate.

 TABLE OF CONTENTS

TITLE PAGE - - - - - - -

CERTIFICATION - - - ii

DEDICATION - - -

DECLARATION - - - - - - - iv

ACKNOWLEDGEMENT - - - v

TABLE OF CONTENTS - - - Vi

LIST OF TABLES - - - - - ix

LIST OF FIGURES - - - - - - x

ABSTRACT - - - - - xi

CHAPTER 1: INTRODUCTION

1.1 BACKGROUND TO THE PROBLEM- - - - - - 1

1.2 OBJECTIVE OF THE STUDY - - - 2

1.3 SIGNIFICANCEOFThESTUDY- - - 2

1.4 SCOPEOFTHESTUDY-- - - - - - 2

1.5 RESEARCH QUESTIONS - - 2

CHAPTER 2: LITERATURE REVIEW

2.1 LIPIDS IN FOODS - 3

2.2 LIPID PEROXIDATION - - - 4

2.2.1 History of Lipid Peroxidation - - - - 4

2.2.2 Mechanism of Lipid Peroxidation - - - - - - 6

2.3 FOOD PROCESSING AND PRESERVATION - - - 7

2.3.1 What is Food Processing? - - - - - - 8

2.3.1.1 Canning- - - - - - - - - 8

2.3.1.2 Freezing- - - - - - - 9

2.3.1.3 Drying and Dehydration- - - - - 9

2.3.1.4 Freeze drying- - - - - - - 10

2.3.1.5 Fermentation- - - - - - - 10

2.3.1.6 Irradiation- - - - - - - - - 10

2.3.1.7 Food Additives- - - - - 11

2.3.1.8 Miscellaneous Methods - - - - - - - 11

2.3.2 Why we Process Food - - - - - - 11

2.3.2.1 Food Safety- - - - - - 11

2.3.2.2 Preservation- - - - - - - - - 12

2.3.2.3 Nutrition- - - - - - - 12

2.3.2.4 Convenience- - - - - 12

2.3.2.5 Variety- - - - - - - - 12

2.3.2.6 Affordability-- - - - - - - - 12

2.4 THE BIOLOGY AND CHEMICAL COMPOSITION OF CEREALS AND

LEGUMES- - - 13

2.4.1 Cereals - - 13

2.4.2 Legumes - 14

2.5 CHEMISTRY OF MALONALDEHYDE - - - 15

2.6 PHYTOCHEMICALS - - - - - - 17

2.6.1 How Phytochemicals Work- - - - 17

2.6.1.1 Antioxidant- - - - - - - - 17

2.6.1.2 HormonalAction- - - - - 17

2.6.1.3 Stimulation of Enzymes- - - - - - 17

2.6.1.4 Interference with DNA Replication- - - - 17

2.6.1.5 Antibacterial Effect- - - - - - - 18

CHAPTER 3: MATERIALS AND METHODS

3.1 PLANT MATERIALS - - - 19

3.2 DETERMINATION OF MDA CONTENT - - 19

3.3 MALTING - - - - 19

3.4 ROASTING - - - 20

3.5 STEEPING AND ROASTING - 20

3.6 FERMENTATION - - - - 20

3.7 DETERMINATION OF TANNIC ACID - - - 20

3.8 DETERMINATION OF CYANOGENIC GLYCOSIDES - 21

3.9 DETERMINATION OF SAPONINS - - - - 22

3.10 DETERMINATION OF OXALATE - - 22

3.11 DETERMINATION OF PHYTATE - - 23

3.12 STATISTICAL ANALYSIS - - - - - 24

CHAPTER 4: RESULTS AND DISCUSSION

4.1 RESULTS - - - - - - 25

4.1.1 Malonaldehyde of Unprocessed Legumes and Cereals 25

4.1.2 Effect of Malting on MDA of Legumes and CereaIs- - 26

4.1.3 Effect of Roasting on MDA of Legumes and Cereals. - - 29

4.1.4 Effect of Steeping and Roasting on MDA of Legumes and Cereals 32

4.1.5 Effect of Fermentation on MDA of cereals - - 34

4.1.6 Phytochemical and Antinutritional Content of Legumes and

Cereals - - - - - — 36

4.2 DISCUSSION - - - - - - - 38

4.2.1 Malonaldehyde of Unprocessed Legumes and Cereals 38

4.2.2 Effect of Malting on MDA of Legumes and Cereals - - 38

4.2.3 Effect of Roasting on MDA of legumes and cereals - - 38

4.2.4 Effect of Steeping and Roasting on MDA of Legumes and Cereals 38

4.2.5 Effect of Fermentation on MDA of Cereals. - - - 39

4.2.6 Phytochemical Content of Legumes and Cereals - - 39

CHAPTER 5: CONCLUSION AND RECOMMENDATION - 40

REFERENCES

APPENDICES