Tuesday theme 2 1035 1050 room 11 nganga

1. RETENTION OF ZINC, IRON AND VITAMIN A IN
HIGHLAND SWEET POTATO (ipomoea batatas) VARIETIES
AFTER DIFFERENT COOKING METHODS IN KENYA.
John N. Ndung’u, Joyce Maling’a, Laura Karanja, Samuel Ngure, Ann
Gichangi and David K. Lelgut
Kenya Agricultural and Livestock Research Organization, Food Crop
Research Institutee
Egerton University

2. Outline of presentation
 Title
 Introduction
 Justification
 Objective
 Results
 Discussions
 Conclusions and Recommendations
 Acknowledgements

3. Introduction
 Sweet Potato (ipomoea batatas) is the 7th most important staple
in the world.
 Adaptable to a broad range of agro-ecological conditions
including highlands
 In Kenya productivity at farmers fields at 5-7 tons/ha
compared to 30-50 tons/ha under experimental conditions
 Sweet potatoes play an import role in Kenya:
 Food and nutrition security
 Important source of pro vitamin A, protein (leaves),
minerals (Fe, Zn, ) and dietary fiber.
 Income generation

4. ….Introduction
 However, processing of sweet potato tubers through different cooking
methods:
 Leads to nutritional leakage of important nutrients
 Aggravation of already existing malnutrition problem
 Globally, more than 3 billion people suffer from:
 Micronutrient malnutrition (‘hidden hunger’) especially lack of iron,
zinc and Vitamin A.
 Individuals largely dependent on plant-based diets like sweet
potato are at major risk.
 Consequences to human health, felicity, livelihoods and national
development due to malnutrition are staggering.
 Kenya among 22 countries in Africa where malnutrition remains a
serious public health problem.

5. Solution Challenge
1 Micronutrient supplements for children (Fe&zinc) Malnutrition
2 The Doha development agenda Trade
3 Micronutrient fortification (iron and salt
iodization)
Malnutrition
4 Expanded immunization coverage for children Diseases
5 Biofortification Malnutrition
6 Deworming, other nutrition programs in school Malnutrition
7 Lowering the price of schooling Education
8 Increase and improve girl’s schooling Women
9 Community-based nutrition promotion Malnutrition
10 Provide support for women’s reproductive role Women
Reference: http://www.copenhagenconsensus.com

6. Justification
 Therefore we require focused attention on understanding:
 The effects of cooking methods in the nutritional leakage
of sweet potato varieties.
 This is an important parameter in selecting cultivars for
consumption with highly retained nutritional contents.

7. Objective
To Determine the effect of cooking methods to nutrition
loss in the sweet potato varieties grown in the highlands
areas of Kenya

8. Materials and Methods
 Plant Materials
 Five highland sweet potato varieties used i.e (Kenspot 001, Kenspot
002, Kenspot 003, Kenspot 004 and Kenspot 005)
 1check: SPK 004
 Experimental design and treatments:
 Randomized complete block design (RCBD) rep three times.
 Recommended practices followed to sustain plant growth and filling
of tubers.

9. ……..Materials and Methods
Experimental site
Trial was done
at KALRO,
Njoro for one
season
Njoro – Site Kenya
Njoro
e
- 2- 3
– 5-
- 1-, 0-
- 1-3
4-
Trial site Alt.
masl
Soil type Annual
Rainfal (mm)
Mean maximum
Temperature (0C)
Mean minimum
Temperature (0C)
Njoro (NPBRC) 2300 Fluvisols 1200 28 16.8

10. ……..Materials and Methods
 Tubers harvested seven months after
planting:
 Three healthy tubers (150 g) selected
per variety and washed in distilled
Water
 Each peeled and split into four
longitudinal sections with a stainless
steel knife.
 Samples first submitted to two different
cooking methods:
 The first portion was pot boiled in
distilled water (1:2 w/v) for 20
minutes
 The second portion was subjected to
pressure cooking in distilled water
(1:1 w/v) for 12 minutes.

11. ……..Materials and Methods
 Third Sample separately
milled using
 Chromium ball mill
(Retsch mill model, MM
400)
 Micro nutrients
determined by atomic
absorption spect. (AAS)
following Okalebo
protocol, 2002.
 Protein analysis following
AACC, 1983.

12. ……..Materials and Methods
 Fourth raw sample used for
analysis of beta carotene
 Column Chromatography
following (Williamson
protocal,1999).
 Data subjected to:
 Analysis of variance (ANOVA)
using statistical analysis
system(SAS) version 8.02 (SAS,
2000).
 Differences between means
ranked by Fisher’s least
significant difference(LSD) test

13. Results
 The analysis of variance showed varieties were significantly (p≤0.05)
different in mean values for Iron, Zinc, β-carotene and Protein
 For the mineral contents, a linear regression equation y = 0.00238x with
R2 = 0.9991 was observed eg zinc
Calibration curve for mineral analysis (Fe, Zn,
Mg and Ca)
y = 0.0238x
R2
= 0.9991
0.0000
0.0500
0.1000
0.1500
0.2000
0.2500
0.00 2.00 4.00 6.00 8.00 10.00 12.00
Concentration (ppm)
Absorbance

14. ……Results
Nutritional Profile of Raw Sweet potato
Varieties
 Averagely, Kenspot 4 had
highest readings in all
parameters
 For Iron, only Kespot 3,
Kenspot 4 and Kenspot 5
had above breeding target
(BT)of 20 ppm
 For Zinc all 6 varieties had
BT of 30ppm and above
 Protein levels between
average of 5 to 16 percent
 β-carotene Kenspot 3,4,5 and
SPK 004 above BT of 15
mg/kg

15. ……Results
Nutritional Profile of Boiled Sweet potato
Varieties
 Kenspot 4 had highest
readings in all parameters
 For Iron, only Kenspot 4
had above BT of 20 ppm
 For Zinc only Kespot 1
and SPK 004 had BT
below 30ppm
 Protein levels between
average of 5 to 16 percent
 β-carotene Kenspot 3,4 and
5 had BT above 15
mg/kg……same var. as
raw

16. ……Results
Nutritional Profile of Pressure Cooked Sweet
potato Varieties
 Kenspot 4 had highest
readings in all parameters
 For Iron, none had above
BT of 20 ppm
 For Zinc only Kespot 1 and
SPK 004 had BT below
30ppm….same var. as
boiling
 Protein levels between
average of 5 to 16 percent
 β-carotene Kenspot 3,4 and
5 had BT above 15
mg/kg….same var as before

17. ……Results
Nutritional Profile of Combined Cooking Methods

18. ……Results
Nutritional Loss of Cooking Methods on
Sweet potato Varieties
 Pressure cooking
showed pronounced
nutrient loss in:
 Iron (6.59 % for SPK004
to 24.57 % for Kenspot
4)
 Zinc( 5.11 % for Kenspot
3 to 15.63 for SPK004)
 β-carotene ( 14.29 % for
Kenspot 5 to 45.71 % for
Kenspot 2)
 Protein (7.37 % for
Kenspot 5 to 22.96% for
SPK004).

19. Discussion
 Differences in nutrition content in raw varieties attributed to:
 Allelic variation at chromosomal locus of different varieties:
 That promotes senescence and remobilization of
nitrogen, iron and zinc from senescing leaves to roots.
 Planting season and soils
 Differences in nutrition content in cooked samples attributed:
 Additionally to cooking methods used.

20. ……Discussion
 Pot boiling produced a significant reduction in the amount of
Zn,Fe and protein as agreed also by (Bell, (1983) and Chavez
et al (2000)
 Khwairakpam et al (2012) and others also found that beta
carotene in sweet potato tubers was reduced by pot boiling.
 Pressure cooking had a deleterious decrease of nutrition
contents in tubers as compared to pot cooking method:
 Because of increased heat and pressure which highly broke
plant cells increasing nutrients loss

21. Conclusion and Recommendations
 Observed values for Fe, Zn, β-carotene and protein suggest:
 The potential for improving the nutritive health of the population.
 Contribute greatly to sustaining national development efforts.
 Some cultivars can therefore be used as parents for nutritional breeding
 Pressure cooking had a more pronounced reducing effect on the
nutritional composition in tubers.
 Promote Nutritious Sensitive Processing methods
 The study recommends Kenspot 4 variety the best among the rest:
 In terms of the nutrients content as raw and after both cooking
methods.
 Way Forward:
 More studies different seasons, sites and cooking methods

22. ACKNOWLEGEMENTS

23. Thank you…