CHARACTERISATION OF MICROWAVED AND OVEN DRIED AERIAL YAM (Dioscorea bulbifera) STARCH

ABSTRACT

Native Starch was extracted from Aerial yam (Dioscorea bulbifera). The starch extracted was

dried using oven (at 300C for 24 hours) and microwaved for (30, 45, 60 seconds). Starch obtained

using different drying methods and conditions were analysed for their physicochemical, functional

properties and pasting characteristics. Results obtained showed that amylose, amylopectin, colour,

pH, bulk density, swelling power, least gelation capacity, oil absorption capacity, water absorption

capacity ranged from 26.87% to 32.77%, 66.89% to 73.12%, 40.35 to 53.65, 5.67 to 5.68, 0.568

3

to 0.704 g/cm , 7.26 to 8.43%, 9 to 15%, 112.89 to 121.98%, 164.39 to 306. 46% respectively.

The pasting properties ranged from 48.9 to 80.70C for pasting temperature, 10.9 to 20.50 minutes for pasting time, 493 to 545 BU for peak viscosity, 355 to 823 BU for final viscosity, 315 to 341 BU for breakdown viscosity, 178 to 217 BU for setback viscosity. The effect of different drying methods and conditions on the physico-chemical properties of the starch showed that oven dried starch has a relatively low bulk density compared to microwaved starch, and this implies that oven dried starch is better in terms of storability and transportation while higher bulk density of the microwaved starch showed that it will be a greater ease of dispersibility and reduction in paste thickness. The higher swelling power of the oven dried starch is a very important criteria for a good quality starch and water intake of the starch. The oven dried starch had better gelation capacity, because the lower the gel, the better the sample, and this is for starch granules to rise when incorporating into food products. The oven dried starch had higher water absorption capacity than the microwaved starch, in which it is suitable to entrap large amount of water during processing. The oven dried starch had higher advantages than microwaved dried aerial yam starch.

TABLE OF CONTENTS

LIST OF TABLES viii
LIST OF FIGURES ix
LIST OF PLATES x
ABSTRACT xi

CHAPTER 1 1

1.0 INTRODUCTION 1

CHAPTER 2 3

2.0 LITERATURE REVIEW 3

2.1 Roots and Tuber Crops 3

2.2` History of Aerial Yam (Dioscorea bulbifera) 5 2.2.1 Botanical Description 5

2.3 Nutritional Composition of Aerial Yam (Dioscorea bulbifera) 6

2.4 Microwave Drying 9

Advantages of Microwave Drying 10
Disadvantages of Microwave Drying 11
Health Effects of Microwave on the Body 11

2.5 Starch 11

2.6 Pasting Properties

2.7 Physicochemical Properties of Starch

 2.7.1 pH 16

2.7.2 Bulk Density 16

2.8 Functional Properties of Starch 17

Water Absorption Capacity 17
Oil Absorption Capacity 17
Least Gelation Capacity 17
Swelling Power 17

CHAPTER 3

3.0 MATERIALS AND METHODS 19

3.1 Materials 19

3.2 Methods 19

3.2.1 Extraction of Aerial Yam Starch 19

3.2.2 Yield Capacity 19

3.3 Physicochemical Properties 21

Determination of Amylose in Starch 21
Determination of Amylopectin in Starch 21

Pasting Properties Colour

Bulk Density

pH

Functional Properties

Swelling Power (SP)

Least Gelation Capacity
Water Absorption Capacity
Oil Absorption Capacity

3.5 Statistical Analysis 24


CHAPTER 4 25

RESULTS AND DISCUSSION 25
Physicochemical Properties of Aerial Yam Starch 25
Functional Properties of Aerial Yam Starch 31

CHAPTER 5
CONCLUSION AND RECOMMENDATION 33

5.1 Conclusion

5.2 Recommendation

REFERENCES
APPENDIX