Investigating carotenoid loss after drying and storage of

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!
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