Investigating carotenoid loss after drying and storage of

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7.2.7.! Statistical analysis ........................................................................................................... 155! 7.3.! RESULTS AND DISCUSSION ............................................................................................... 155! 7.3.1.! Measurement of pH value ................................................................................................ 155! 7.3.2.! Degradation of !-carotene in liquid medium .................................................................. 156! 7.3.3.! Enhancement of β-carotene oxidation using a free radical generator ............................ 160! 7.3.4.! EDTA assay ..................................................................................................................... 161! 7.3.5.! Effect of storage on peroxidase activity........................................................................... 162! 7.3.6.! Effect of water activity (aw) on the peroxidase activity .................................................... 163! 7.4.! CONCLUSION ........................................................................................................................ 164! CHAPTER 8.! CAROTENOID DEGRADATION AND FORMATION OF VOLATILE COMPOUNDS IN DRIED SWEET POTATO CHIPS STORED UNDER CONTROLLED CONDITIONS OF TEMPERATURE, HUMIDITY AND OXYGEN ................................................ 165! 8.1! INTRODUCTION.................................................................................................................... 165! 8.2! MATERIALS & METHODS ................................................................................................... 166! 8.2.1! Raw materials .................................................................................................................. 166! 8.2.2! Storage conditions ........................................................................................................... 166! 8.2.3! Experimental design ........................................................................................................ 170! 8.2.4! Carotenoid analyses ........................................................................................................ 171! 8.2.5! Volatile compounds analysis ........................................................................................... 171! 8.2.6! Statistical analysis and kinetics modelling ...................................................................... 171! 8.3! RESULTS & DISCUSSION .................................................................................................... 173! 8.3.1! Sampling .......................................................................................................................... 173! 8.3.2! Assessment of the storage system .................................................................................... 174! 8.3.3! Carotenoid degradation kinetics ..................................................................................... 175! 8.3.4! Influence of water activity and oxygen on carotenoid degradation ................................. 181! 8.3.5! Relationship between norisoprenoid formation and carotenoid degradation ................. 187! 8.4! CONCLUSION ........................................................................................................................ 193! CHAPTER 9.! GENERAL DISCUSSION AND FUTURE WORK ............................................... 195! 9.1! OBJECTIVES AND ACHIEVEMENTS ................................................................................. 195! 9.2! QUANTIFYING CAROTENOID LOSSES DURING DRYING ............................................ 196! 9.2.1! Levels of carotenoid loss during drying .......................................................................... 196! 9.2.2! Comparison of dryers ...................................................................................................... 197! 9.2.3! Potential for dried products ............................................................................................ 198! 9.3! QUANTIFYING CAROTENOID LOSSES DURING STORAGE ......................................... 198! 9.3.1! Actual levels of carotenoid loss and their prediction ...................................................... 199! 9.3.2! The issue of carotenoid loss in storage............................................................................ 199! 9.3.3! How to reduce these losses .............................................................................................. 199! 9.4! QUANTIFYING INFLUENCE OF PROCESS VARIABLES ON CAROTENOID LOSS ..... 199! 9.4.1! Chipping influence .......................................................................................................... 199! 9.4.2! Varietal influence ............................................................................................................ 201! 9.4.3! Influence of pre-treatment ............................................................................................... 202! 9.5! UNDERSTANDING INFLUENCE OF PHYSICO-CHEMICAL AND BIOCHEMICAL FACTORS ON CAROTENOID LOSS ................................................................................................. 202! 9.5.1! Light ................................................................................................................................ 202! 9.5.2! Temperature .................................................................................................................... 204! 9.5.3! Water activity .................................................................................................................. 205! 9.5.4! Oxygen ............................................................................................................................. 206! 9.5.5! Enzymatic oxidation ........................................................................................................ 206! 9.6! CONCLUSION AND FUTURE WORK ................................................................................. 207! REFERENCES…………… .................................................................................................................... 211 APPENDICES………….. ........................................................................................................................ 239 X
1.1 BACKGROUND 1.1.1 Introduction CHAPTER 1. LITERATURE REVIEW 1 1. Literature review Vitamin A deficiency is a major public health issue in developing countries; with children and pregnant/lactating women the most vulnerable (FAO/WHO 2002). Sub- Saharan Africa is one of the most affected areas with 33 million pre-school children who are deficient, which accounts for a third of the world cases (West 2002). There are different strategies to tackle vitamin A deficiency. Traditional interventions consist of administration of vitamin A capsules. Although a single dose can be given every six months or every year, these medical interventions are costly (Nestel et al. 2006). Food fortification is another approach used to reduce vitamin A deficiency that works by adding vitamin A to food commodities (e.g. sugar). An alternative approach is biofortification, which consists of breeding staple crops to increase their content of vitamins and/or minerals. Compared to the two other strategies, biofortification is considered a more sustainable approach because it has the potential to provide vitamins or minerals throughout the year with a one-off intervention and in the longer term at lower cost (Kósambo et al. 1998). For the same level of impact on public health, the cost of biofortification is estimated to be half that of vitamin A supplementation (Nestel et al. 2006). Moreover, rural and low-income communities, which have been shown to be more at risk, can be reached by this approach and it also creates opportunities for income generation from production and marketing of these crops. Sweet potato is a very important crop that is widely consumed in sub-Saharan Africa and Uganda one of the major producers (Woolfe 1992). In sub-Saharan Africa the majority of sweet potato that is consumed is white-fleshed and has low levels of provitamin A (β- carotene) (Ameny and Wilson 1997). There are efforts through the Vitamin A Partnership for Africa (VITAA) Initiative and also through a Bill and Melinda Gates
Page 1 and 2: Investigating carotenoid loss after
Page 3 and 4: DECLARATION I certify that this wor
Page 5 and 6: ACKNOWLEDGEMENTS I am deeply gratef
Page 7 and 8: CONTENTS CHAPTER 1.! LITERATURE REV
Page 9: 4.3.2! Effect of trial and sweet po
Page 13 and 14: 3 1. Literature review It is estima
Page 15 and 16: 5 1. Literature review food corresp
Page 17 and 18: - the leaves that make energy and s
Page 19 and 20: 9 1. Literature review Uganda and M
Page 21 and 22: 11 1. Literature review communicati
Page 23 and 24: 13 1. Literature review soya grains
Page 25 and 26: 15 1. Literature review Drying is a
Page 27 and 28: 17 1. Literature review Modelling o
Page 29 and 30: 19 1. Literature review Other types
Page 31 and 32: 21 1. Literature review The perform
Page 33 and 34: 23 1. Literature review degradation
Page 35 and 36: 25 1. Literature review carotene an
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Page 39 and 40: 29 1. Literature review red (>800 n
Page 41 and 42: 31 1. Literature review Figure 1-17
Page 43 and 44: 33 1. Literature review induced by
Page 45 and 46: 35 1. Literature review Enzymatic c
Page 47 and 48: 37 1. Literature review Volatile pr
Page 49 and 50: 39 1. Literature review Carotenoid
Page 51 and 52: Table 1-5: Effect of type of proces
Page 53 and 54: Comparison of losses in drying proc
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Page 57 and 58: 47 1. Literature review Different p
Page 59 and 60: Oxygen 49 1. Literature review Oxyg
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51 1. Literature review the storage
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2.2.2 Root samples 53 2. Assessment
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2.2.5 Water activity 55 2. Assessme
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57 2. Assessment of Methods below t
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59 2. Assessment of Methods !-carot
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61 2. Assessment of Methods indicat
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63 2. Assessment of Methods were we
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65 2. Assessment of Methods Table 2
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67 2. Assessment of Methods Intra-l
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69 2. Assessment of Methods Signifi
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71 2. Assessment of Methods Table 2
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Content (µg/g) Content (µg/g) Con
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75 2. Assessment of Methods way-ANO
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77 2. Assessment of Methods puree.
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Percentage loss "a" redness 45% 40%
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CHAPTER 3. 81 3. Preliminary study
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83 3. Preliminary study Figure 3-1:
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85 3. Preliminary study Air velocit
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3.2.10 Statistical analyses 87 3. P
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89 3. Preliminary study because it
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Sample area (cm2) 91 3. Preliminary
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Figure 3-9: UV-Visible spectrum of
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95 3. Preliminary study Mulokozi an
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97 3. Preliminary study One hundred
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99 4. Ugandan field study respectiv
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Transmittance (%) 101 4. Ugandan fi
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4.2.5 Total carotenoids extraction
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105 4. Ugandan field study The dryi
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107 4. Ugandan field study individu
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109 4. Ugandan field study values a
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111 4. Ugandan field study caroteno
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113 4. Ugandan field study observed
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115 4. Ugandan field study OFSP chi
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117 5. Mozambican field study carot
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119 5. Mozambican field study kg (p
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121 5. Mozambican field study Table
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Tot. carotenoid content (!g/g) Tot.
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127 5. Mozambican field study 5.3.6
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a b c c 129 5. Mozambican field stu
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131 5. Mozambican field study Table
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133 5. Mozambican field study #-car
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CHAPTER 6. 137 6. Effect of pre-tre
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139 6. Effect of pre-treatment out
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141 6. Effect of pre-treatment afte
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143 6. Effect of pre-treatment leve
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145 6. Effect of pre-treatment Citr
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147 6. Effect of pre-treatment trea
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149 6. Effect of pre-treatment inte
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CHAPTER 7. 151 7. Involvement of en
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7.2.2. pH measurement 153 7. Involv
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155 7. Involvement of enzymes glyce
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157 7. Involvement of enzymes Table
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159 7. Involvement of enzymes carot
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161 7. Involvement of enzymes carot
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163 7. Involvement of enzymes Perox
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CHAPTER 8. 165 8. Study under contr
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Kilner jar (with metal lever catch
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Figure 8-2: Storage system for wate
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8.2.4 Carotenoid analyses 171 8. St
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8.3 RESULTS & DISCUSSION 8.3.1 Samp
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175 8. Study under controlled condi
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k (day-1) k (day-1) 0.10 0.08 0.06
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CHAPTER 9. GENERAL DISCUSSION AND F
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197 9. Discussion carotene loss aft
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199 9. Discussion total carotenoids
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9.4.2 Varietal influence 201 9. Dis
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203 9. Discussion 2008). The side e
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205 9. Discussion Absence of cis-is
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207 9. Discussion (Chapter 7). Howe
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209 9. Discussion of these cultivar
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References 211 References Aguayo, V
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213 References Bechoff, A., Dhuique
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215 References Chen, H.E., Peng, H.
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DIAS (2006) Semi-Annual and Annual
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219 References Tropical Agriculture
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221 References has a positive effec
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223 References Kamiya N. and Nagamu
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Lee, S.B. and Kim, K.J. (1995) Effe
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227 References Mills, R.C. and Hart
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Nestel, P., Bouis, H.E., Meenakshi,
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231 References Preston, C.M. and Ba
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Simon, P.W. (1997) Plant pigments f
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235 References Tran, T.H., Nguyen,
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237 References Walter, W.M., Purcel
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! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! A
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Arrhenius model: = ∞ − Ea RT ek
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242 Appendix 1 B/Calculation of Arr
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Temperature is integrated for each
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2) Integration of temperature in Ug
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Appendix 2b: Dryers cost in Lualua,
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250 Appendix 2 Technical informatio
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252 Appendix 2 Technical informatio
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Open air flat and sloped dryers 254
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Appendix 3: Total carotenoids metho
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4. Partition - Pour 40 ml of Petrol
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