corn quality changes in hermetic storage in sub-saharan africa (ssa)
DESCRIPTION
Corn quality changes in hermetic storage in Sub-Saharan Africa (SSA) . Nda-Agyima K. Addae-Mensah , MSc . PhD Student Klein Ileleji , PhD. Assoc. Professor & Extension Engineer. Presentation Outline. Introduction Materials and Methods Objectives Results Summary & conclusions. - PowerPoint PPT PresentationTRANSCRIPT
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Corn quality changes in hermetic storage in Sub-Saharan Africa (SSA)
Nda-Agyima K. Addae-Mensah, MSc.PhD Student
Klein Ileleji, PhD.Assoc. Professor & Extension Engineer
Presentation Outline
Introduction Materials and Methods Objectives Results Summary & conclusions
Introduction
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Inadequate drying!
Problems in storage!
Introduction
High humidity and limited sunshine hours
Safe moisture content levels,13% mc or below are not really reached .
Corn harvested at high mc levels (~30% mc) is typically dried to between 16% to 20% mc levels using open air solar drying (Weinberg, 2008)
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Corn de-husked right after harvest
Introduction
PICS bag storage technology – successful and flourishing with cowpea storage (Murdock, 2012) and (Baributsa et. al. 2010)
Cowpea, usually stored at very low moistures since its mostly grown in arid areas in the tropics
However, little is known as to how well PICS bags will do for other grains stored at intermediate moisture levels
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Storage bag types
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Mycotoxins Mycotoxin production is a significant issue for
SSF in SSA.
Mycotoxins have been shown to have adverse effects on human health
Suppress the immune system Cause chronic damage to liver and kidney Cause damage to the digestive and nervous
system Interferes with the reproductive system Liver cancer caused by aflatoxins (naturally
occurring mycotoxins) contributed to 70% of cancer related deaths in Africa (Farombi.,2006)
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Research goals
To systematically evaluate the effect of initial corn moisture content on oxygen depletion rate, mold growth and grain quality over time in hermetic conditions
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Methods and Materials Storage tests
400 g of corn were placed in 1L glass bottles.
20 glass bottles in total were used for the preliminary study.
10 bottles were non-insulated 10 bottles were temperature
insulated The stored bottles in a controlled
chamber at 25C
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Methods – Measurement Variableso CO2 and O2 levels
o pH (Acidity)
o Moisture content
o Water Activity
o Temperature
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Methods : Quality tests
Microbiological tests
Fat Acidity tests
Germination tests
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Objectives
This study determined the changes in quality of hermetically stored corn above safe
threshold levels (14% & 22% moisture content) after 7 and 14 days of storage.
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Results (Exploratory Analysis)Tests were conducted before and after Storage Analysis - Paired Sample t-tests at alpha levels of 0.05
probability levels using Microsoft Excel Grain Quality testso Fat Acidityo Percent corn kernels Infectedo Mycotoxin (not reported)
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Results: Moisture content testsResults for moisture content at 7 & 14 days at 25C, for
non-insulated bottles
0
5
10
15
20
25
14.1 14.1
22.1 22.1
13.58 13.83
21.15 20.6
Before MC level (%) After MC level (%) 7 days 14 days 7 days 14 days
Moi
stur
e co
nten
t (%
)
Results for moisture content at 7 & 14 days at 25C, for temperature-insulated bottles
0
5
10
15
20
25
14.1 14.1
22.1 22.1
13.6 13.79
21.05 20.59
Before MC level (%) After MC level (%) 7 days 14 days 7 days 14 days
Moi
stur
e co
nten
t (%
)
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Results: Fat Acidity/ pH tests
0
20
40
60
80
100
120
140
160
180
200
Fat Acidity values of corn stored for 7 and 14 days - Non-insulated bottles at 25C
Fat Acidity (Before) 22%mc Fat Acidity (After)
Fat A
cidi
ty v
alue
4.8 4.8 4.8 4.8
6.43 6.176.71
5.98
pH levels of corn stored for 7 and 14 days – Non-insulated bottles at 25°C
pH level (Before) 22%mc pH level (After)
7 days, 14%mc 14 days, 14%mc 7 days, 22%mc 14 days, 22%mc7 days, 14%mc 14 days, 14%mc 7 days, 22%mc 14 days, 22%mc
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Results: Fat Acidity/ pH tests
14 days, 22%mc 14 days, 22%mc
92.14
138.8
Fat Acidity values of corn stored for 14 days- Temperature - insulated bottles at 25°C
Fat Acidity (Before) 22%mc Fat Acidity (After)
4.8
6.52
pH levels of corn stored for 14 days- Temperature - insulated bottles at
25C
pH level (Before) pH level (After)
Results: Microbiological tests
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Non-insulated bottles (Final)
Before (Initial) Moisture level (%) 7 days 14 days
24.8% 14% 15.2% 19.2%
22% 20.8% 42.4%
Percent number of corn kernels infected after 7 and 14 days of storage for non-insulated bottles
Temperature insulated bottles (Final)Before (Initial) Moisture level (%) 7 days 14 days
24.8% 14% 21.6% 16.8%22% 32% 40.4%
Percent number of corn kernels infected after 7 and 14 days of storage for temperature insulated bottles
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Carbon dioxide and oxygen measurements Non-insulated bottles
CO2 levels 0 days 7 days 14 days
22%mc 0% 24.87% 28.75%
14%mc 0% 0.38% 0.71%
O2 levels 0 days 7 days 14 days
22%mc 20.89% 1.93% 1.66%
14%mc 20.93% 20.43% 20.16%
NB: Temperature insulated bottles were not used for these tests
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Summary and Conclusions There were no significant changes in the number of infected
kernels at 22% mc and 14% mc.
There was an increase in the percent of infected kernels from
the start of storage to 7 and 14 days, respectively.
Some lessons were learned in correcting and refining our
methods for bench-scale studies
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Summary and Conclusions
Fat acidity levels increased with increase in storage
time and moisture content
There will be heating of grain due to mold growth
Learned from mistakes made in this study and will
refine methods for long-term study of quality
changes in hermetic stored corn at 14 to 22%
moisture.
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Acknowledgements We would like to thank Prof. Larry Murdock for
helping with the Mocon device used for carbon dioxide and oxygen measurements.