Investigating carotenoid loss after drying and storage of

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2.4 OPTIMISATION OF EXTRACTION AND REPEATABILITY OF CAROTENOID ANALYSIS …………………………………………………………………………………………… 64 2.4.1! Optimisation of extraction on dried sweet potato .............................................................. 64! 2.4.2! Reproducibility of the analysis .......................................................................................... 66! 2.4.3! Comparison of Dhuique-Mayer and Rodriguez-Kimura’s methods .................................. 67! 2.5! COMPARISON OF INSTRUMENTS ....................................................................................... 67! 2.5.1! Correlation between spectrophotometric and HPLC methods .......................................... 67! 2.5.2! Estimation of total carotenoid content by colorimetric reading ........................................ 69! 2.6! EFFECT OF STORAGE ON ISOMERISATION AND DEGRADATION OF CAROTENOIDS………. ....................................................................................................................... 70! 2.6.1! Effect of freezer storage on total carotenoid content ........................................................ 70! 2.6.2! Effect of elevated temperature storage on β-carotene cis-isomerisation .......................... 71! 2.7! PREPARATION FOR FIELD WORK ...................................................................................... 74! 2.7.1! Influence of choice of roots or fresh chips as initial point to determine carotenoid losses…………………………………………………………………………………………………………….74! 2.7.2! Influence of density of OFSP fresh chips on carotenoid losses ........................................ 75! 2.7.3! Influence of freeze-drying .................................................................................................. 76! 2.7.4! Influence of screening plastic coverage on sweet potato flour exposed to artificial sun light ……………………………………………………………………………………………………………..77! 2.8! CONCLUSIONS ........................................................................................................................ 79 CHAPTER 3.! EFFECT OF HOT AIR, SOLAR AND SUN-DRYING TREATMENTS ON CAROTENOID RETENTION IN ORANGE-FLESHED SWEET POTATO .................................... 81! 3.1! INTRODUCTION...................................................................................................................... 81 ! 3.2! MATERIALS AND METHODS ............................................................................................... 81! 3.2.1! Raw material ..................................................................................................................... 81! 3.2.2! Sample preparation for drying .......................................................................................... 82! 3.2.3! Drying of chips .................................................................................................................. 82! 3.2.4! Cross flow dryer ................................................................................................................ 82! 3.2.5! Greenhouse solar dryer and open air-sun-drying ............................................................. 83! 3.2.6! Dimensions of chip and slice samples ............................................................................... 85! 3.2.7! Moisture and water activity determination ........................................................................ 85! 3.2.8! Sample preparation for carotenoid analysis ..................................................................... 86! 3.2.9! Carotenoid analysis ........................................................................................................... 86! 3.2.10! Statistical analyses ............................................................................................................ 87! 3.3! RESULTS AND DISCUSSION ................................................................................................. 87! 3.3.1! Quality of flour .................................................................................................................. 88! 3.3.2! Influence of drying treatment on provitamin retention ...................................................... 88! 3.3.3! Influence of either chipping or slicing on carotenoid content ........................................... 89! 3.3.4! Identification of provitamin A carotenoids ........................................................................ 92! 3.3.5! Quantification of provitamin A carotenoids ...................................................................... 94! 3.3.6! Vitamin A activity .............................................................................................................. 95! 3.4! CONCLUSION .......................................................................................................................... 97! CHAPTER 4.! EFFECT OF DRYING AND STORAGE ON THE DEGRADATION OF CAROTENOIDS IN ORANGE-FLESHED SWEET POTATO IN RESEARCH STATION TRIALS IN UGANDA ...................................................................................................................................... 98! 4.1! INTRODUCTION...................................................................................................................... 98! 4.2! MATERIALS AND METHODS ............................................................................................... 99! 4.2.1! Sweet potato root samples ................................................................................................. 99! 4.2.2! Handling and processing prior to drying ........................................................................ 100! 4.2.3! Drying of sweet potato chips ........................................................................................... 100! 4.2.4! Storage of dried chips for four months ............................................................................ 102! 4.2.5! Total carotenoids extraction and analysis ....................................................................... 103! 4.2.6! Dry matter determination ................................................................................................ 104! 4.2.7! Statistical analyses .......................................................................................................... 104! 4.3! RESULTS AND DISCUSSION ............................................................................................... 104! 4.3.1! Carotenoid losses in solar and sun drying treatments .................................................... 104! VIII
4.3.2! Effect of trial and sweet potato cultivar .......................................................................... 107! 4.3.3! Effect of storage on provitamin A retention .................................................................... 111! 4.3.4! Effect of sweet potato cultivar on provitamin A retention in storage .............................. 112! 4.3.5! Estimation of vitamin A activity in OFSP chips .............................................................. 113! 4.4! CONCLUSION ........................................................................................................................ 114! CHAPTER 5.! UNDERSTANDING ON-FARM CAROTENOID LOSSES AFTER DRYING AND STORAGE OF ORANGE-FLESHED SWEET POTATO IN MOZAMBIQUE ..................... 116! 5.1.! INTRODUCTION.................................................................................................................... 116! 5.2.! MATERIALS AND METHODS ............................................................................................. 117! 5.2.1.! Sweet potato root samples ............................................................................................... 117! 5.2.2.! Dryers .............................................................................................................................. 118! 5.2.3.! Drying .............................................................................................................................. 119! 5.2.4.! Collection of dried sweet potato chips for analysis ......................................................... 119! 5.2.5.! Carotenoid analysis ......................................................................................................... 119! 5.2.6.! HPLC analysis ................................................................................................................. 119! 5.2.7.! Dry matter determination and colour measurement ........................................................ 120! 5.2.8.! SPME/GC/MS analysis .................................................................................................... 120! 5.2.9.! Statistical analyses and calculation of carotenoid degradation rates ............................. 120! 5.3.! RESULTS AND DISCUSSION ............................................................................................... 120! 5.3.1.! Effect of dryer type on carotenoid retention in OFSP chips ............................................ 120! 5.3.2.! Effect of variety of sweet potato on carotenoid retention in drying................................. 123! 5.3.3.! Effect of chipping on carotenoid retention in drying ....................................................... 123! 5.3.4.! Effect of chipping on carotenoid retention in storage ..................................................... 124! 5.3.5.! Effect of variety on carotenoid retention during storage................................................. 126! 5.3.6.! Correlation between spectrophotometer values, HPLC results and colour of samples .. 127! 5.3.7.! Identification of individual carotenoids before and after storage ................................... 128! 5.3.8.! Kinetics of carotenoid degradation during storage ......................................................... 130! 5.3.9.! Volatile formation in dried sweet potato during storage ................................................. 133! 5.4.! CONCLUSION ........................................................................................................................ 135 CHAPTER 6.! EFFECT OF PRE-TREATMENTS ON CAROTENOID LOSSES IN DRYING AND STORAGE OF ORANGE-FLESHED SWEET POTATO ........................................................ 137! 6.1! INTRODUCTION.................................................................................................................... 137! 6.2! MATERIALS AND METHODS ............................................................................................. 138! 6.2.1! Sweet potato root samples ............................................................................................... 138! 6.2.2! Pre-treatments ................................................................................................................. 139! 6.2.3! Drying .............................................................................................................................. 140! 6.2.4! Storage ............................................................................................................................ 140! 6.2.5! Carotenoid analysis ......................................................................................................... 141! 6.2.6! Statistical analysis ........................................................................................................... 141! 6.3! RESULTS ................................................................................................................................ 141! 6.3.1! Effect of pre-treatments on drying ................................................................................... 141! 6.3.2! Effect of pre-treatment on storage ................................................................................... 145! 6.4! DISCUSSION .......................................................................................................................... 147! 6.5! CONCLUSION ........................................................................................................................ 150 CHAPTER 7.! INVOLVEMENT OF ENZYMES IN CAROTENOID DEGRADATION DURING STORAGE OF ORANGE-FLESHED SWEET POTATO ................................................. 151! 7.1.! INTRODUCTION.................................................................................................................... 151! 7.2.! MATERIALS AND METHODS ............................................................................................. 152! 7.2.1.! Sweet potato root samples ............................................................................................... 152! 7.2.2.! pH measurement .............................................................................................................. 153! 7.2.3.! Enzyme assay on !-carotene............................................................................................ 153! 7.2.4.! Enzymatic extraction ....................................................................................................... 154! 7.2.5.! Measurement of peroxidase activity ................................................................................ 154! 7.2.6.! Measurement of lipoxygenase activity ............................................................................. 155! IX
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: CONTENTS CHAPTER 1.! LITERATURE REV
Page 11 and 12: 1.1 BACKGROUND 1.1.1 Introduction C
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
Page 37 and 38: 27 1. Literature review (Rees, NRI,
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
Page 55 and 56: 45 1. Literature review observed we
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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Page 197 and 198:
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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
Page 233 and 234:
223 References Kamiya N. and Nagamu
Page 235 and 236:
Lee, S.B. and Kim, K.J. (1995) Effe
Page 237 and 238:
227 References Mills, R.C. and Hart
Page 239 and 240:
Nestel, P., Bouis, H.E., Meenakshi,
Page 241 and 242:
231 References Preston, C.M. and Ba
Page 243 and 244:
Simon, P.W. (1997) Plant pigments f
Page 245 and 246:
235 References Tran, T.H., Nguyen,
Page 247 and 248:
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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