NUTRIENT COMPOSITION, MINERALS AND ANTI-NUTRIENTS PROPERTIES OF FRESH, STEAMED AND BAKED TOFU COAGULATED WITH GRAPE JUICE

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Department of Nutrition and Dietetics

ABSTRACT

The nutrient composition, minerals and anti-nutrient properties of fresh, steamed and baked tofu coagulated with grape juice was studied. The proximate composition, mineral content, anti-nutrient properties and sensory attributes of the fresh, steamed and baked tofu samples were determined using standard laboratory procedures. The data obtained were statistically analyzed using Statistical Product of Service Solution (SPSS) version 23.0. The proximate composition of the tofu showed there was decrease in moisture content of the fresh tofu from 64.83% to 21.79% on baking. Baking also helped to increase the protein of fresh tofu from 16.46% to 18.65%. Fat increased from 2.73% in fresh tofu to 3.45% on steaming. Baking increased the fibre, ash, carbohydrate and energy value of the fresh tofu from 0.32% to 1.21%, 1.18% to 2.29%, 14.45% to 52.68% and 148.19 Kcal/100g to 315.79 Kcal/100g, respectively. The mineral contents of the tofu showed that baking decreased the calcium (110.49 mg/100g to 108.93 mg/100g), magnesium (122.14 mg/100g to 120.48 mg/100g), potassium (58.58 mg/100g to 56.85 mg/100g) and sodium (4.21 mg/110g to 3.40 mg/100g) contents of fresh tofu whereas steaming increased the iron content of fresh tofu from 3.86 mg/100g to 4.03 mg/100g. The antinutrients of the fresh tofu showed that the tannin (1.56 mg/100g), saponin (0.86 mg/100g), phytate (0.95 mg/100g) and oxalate (0.35 mg/100g) contents decreased to 0.64 mg/100g, 0.43 mg/100g, 0.72 mg/100g and 0.72 mg/100g, respectively on baking. Fascinatingly, the anti-nutrients of all the tofu samples were below the lethal dose for humans. The outcome of the sensory evaluation showed that beside the texture of deep-fried chicken (Control) that was liked moderately, its colour, taste, flavour and general acceptability were liked very much compared to the other tofu samples. Tofu can serve as a healthy and nutrient-dense snack or mid-day meal alternative.

TABLE OF CONTENTS

TITLE PAGE i

CERTIFICATION ii

DEDICATION iii

ACKNOWLEDGEMENTS iv

TABLE OF CONTENTS v

LIST OF TABLES viii

LIST OF FIGURES ix

ABSTRACT x

CHAPTER 1

INTRODUCTION1

11 Background of the study 3

12 Statement of problems 4

12 Objectives of the study 5

13 Significance of the study 6

CHAPTER 2

LITERATURE REVIEW6

21 Tofu 6

22 Coagulants 7

221Salt coagulants7

222Enzyme coagulant9223Acid coagulant9

2231 Grape juice as an acid coagulant10

23Soybean 11

231Nutritional value of soybean seeds12

232Health benefits of soybean seeds13

233Anti-nutrients of soybean seeds 14

234Food uses of soybean seeds 16

24Steaming technique 17

25Baking technique 18

CHAPTER 3

MATERIALS AND METHODS20

31 Study design 20

32 Materials 20

33 Methods 20

331 Extraction of grape juice 20

332Processing of fresh, steamed and baked tofu samples20

333Proximate analysis24

3231Determination of moisture content24

3232 Determination of ash content 25

3233 Determination of fat content 25

3234 Determination of fibre25

3235 Determination of protein263 236 Determination of carbohydrate content 26

3237 Determination of energy value26

324Mineral analysis273241 Determination of calcium and magnesium273242 Determination of sodium28

3243 Determination of iron 29

3244 Determination of potassium29325Anti-nutrient analysis 30

3251 Determination of phytate30

3252 Determination of tannin30

3253 Determination of saponin31

3254 Determination of oxalate 32

326 Sensory evaluation33

327Statistical analysis34

CHAPTER 4

RESULTS AND DISCUSSIONS35

41Proximate composition of fresh, steamed and baked tofu35

42Mineral contents of fresh, steamed and baked tofu 41

43Anti-nutrient properties of fresh, steamed and baked tofu 46

44Sensory properties of fresh, steamed and baked tofu50

CHAPTER 5

CONCLUSION AND RECOMMENDATIONS55

51 Conclusion 55

52 Recommendations 55

References 57

APPENDIX 69

LIST OF TABLES

Table 41: Proximate composition and energy value of fresh,

steamed and baked tofu 36

Table 42:Mineral content of fresh, steamed and baked tofu42

Table 43:Anti-nutrients content of fresh, steamed and baked tofu 47

Table 44: Sensory properties of fresh, steamed and baked tofu

and fried chicken used as the control 51

LIST OF FIGURES

Figure 31: Flow chart for extraction of grape juice 22

Figure 32: Flow chart for tofu production 23