Technological Aspects of Preparing Porridges
Made from Local Crops in Mozambique
Irene Stuart Torrié De Carvalho
Department of Food Technology,
Engineering and Nutrition
Faculty of Engineering
Lund University
Sweden
Doctoral Thesis
2014
Technological Aspects of Preparing Porridges
Made from Local Crops in Mozambique
Irene Stuart Torrié De Carvalho
2014
Department of Food Technology, Engineering and Nutrition
Faculty of Engineering, LTH
Lund University, Sweden
Academic thesis which, by due permission of the Faculty of Engineering at
Lund University, will be publicly defended on Friday 28th November 2014 at
10:15 a.m. in Lecture Hall B, Center for Chemistry and Chemical Engineering,
Getingevägen 60, Lund, for the degree of Doctor of Philosophy in Engineering.
Faculty opponent: Associate professor Ulla Kidmose, Department of Food
Science, Aarhus University, Denmark.
Organization
Document name
LUND UNIVERSITY
Department of Food Technology, Engineering and
Nutrition, Faculty of Engineering
P.O.Box 124, SE-221 00 Lund, Sweden
DOCTORAL DISSERTATION
Author: Irene Stuart Torrié De Carvalho
Sponsoring organization: Swedish International
Development Cooperation Agency (SIDA)
Date of issue: November 28th 2014
Title and subtitle: Technological Aspects of Preparing Porridges Made from Local Crops in Mozambique
Abstract
Child malnutrition is one of the major health problems in many developing countries and involves
many sectors such as health, agriculture and research. Malnutrition in infants usually develops
during the introduction of complementary foods, due to a deficit of nutrients, low energy density
and the poor bioavailability of vitamins and minerals leading, in turn, to an increase in the risk of
disease and infant mortality. These complementary foods are usually prepared from starchy plants,
the flour being heated with water causing swelling, resulting in a viscous porridge that is not
suitable for consumption by small children. To circumvent this problem, it is common practice to
dilute the porridge with water, which further reduces its nutritional value. Meat is often
unaffordable for most of the population in the developing countries, while starchy crops are readily
available. The aim of this study was, therefore, to investigate the use of locally available crops to
produce complementary porridges with a palatable consistency, while maintaining the nutritional
quality and energy density.
Flours were produced from various crops: orange-fleshed sweet potato, cowpea, maize, sorghum
and soybean. Three methods of measuring the swelling were investigated (centrifugation, gravity
sedimentation and least gelation concentration), and the consistency of the porridges made from
each flour was measured with the back-extrusion method. It was not possible to predict the
consistency of the porridges based on the results of the swelling measurements, but it was possible
to estimate the flour concentration that would give porridge with an acceptable consistency
preferably using the gravity sedimentation method.
Based on the results obtained for the consistency and assuming that the volume fraction
contributions from different flours were additive, all possible two-flour combinations were
investigated, all mixes gave a porridge with low consistency or in the predicted range.
Fresh orange-fleshed sweet potato and cassava flour were used to develop a new product similar to
garri, by roasting. The retention of β-carotene, the consistency, energy density and the consumer
acceptance were evaluated. The higher retention of β-carotene (above 80%), overall preference
(above 60%) and a significant reduction in viscosity made this product a promising source of
precursor of vitamin A, while having a high energy density.
Linear programming was used in an attempt to formulate a nutritious and affordable
complementary food for children aged 1-8 years, using locally available crops. It was not possible
to formulate a food with an acceptable nutritional value and consistency, using locally available
crops that would be affordable for most rural residents of Mozambique. However, if the cost of
supplemental micronutrients such as zinc and calcium can be reduced, the cost of this food could be
reduced by more than 70%.
Key words: Child malnutrition, consistency, complementary porridge, developing countries, energy
density, carotenoids
Classification system and/or index terms (if any)
Supplementary bibliographical information
Language English
ISSN and key title
ISBN 978-91-7422-375-0
Recipient’s notes
Number of pages 144
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Signature
Date
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Technological Aspects of Preparing Porridges
Made from Local Crops in Mozambique
Irene Stuart Torrié De Carvalho
2014
Universidade Eduardo Mondlane
Technological Aspects of Preparing Porridges Made from
Local Crops in Mozambique
Doctoral Thesis
Department of Food Technology, Engineering and Nutrition
Faculty of Engineering
P. O. Box 124, SE-221 00 Lund
Lund University, Sweden
ISBN
Copyright © Irene De Carvalho*
*Full name Irene Stuart Torrié De Carvalho
Printed in Sweden by Media-Tryck, Lund University
Lund 2014
Cover photo: Rale made from white cassava, fresh orange-fleshed sweet potato
and porridge made from G-OFSP. By Irene De Carvalho
Abstract
Child malnutrition is one of the major health problems in many developing
countries and involves many sectors such as health, agriculture and research.
Malnutrition in infants usually develops during the introduction of
complementary foods, due to a deficit of nutrients, low energy density and the
poor bioavailability of vitamins and minerals leading, in turn, to an increase in
the risk of disease and infant mortality. These complementary foods are usually
prepared from starchy plants, the flour being heated with water causing
swelling, resulting in a viscous porridge that is not suitable for consumption by
small children. To circumvent this problem, it is common practice to dilute the
porridge with water, which further reduces its nutritional value. Meat is often
unaffordable for most of the population in the developing countries, while
starchy crops are readily available. The aim of this study was, therefore, to
investigate the use of locally available crops to produce complementary
porridges with a palatable consistency, while maintaining the nutritional quality
and energy density.
Flours were produced from various crops: orange-fleshed sweet potato, cowpea,
maize, sorghum and soybean. Three methods of measuring the swelling were
investigated (centrifugation, gravity sedimentation and least gelation
concentration), and the consistency of the porridges made from each flour was
measured with the back-extrusion method. It was not possible to predict the
consistency of the porridges based on the results of the swelling measurements,
but it was possible to estimate the flour concentration that would give porridge
with an acceptable consistency preferably using the gravity sedimentation
method. Based on the results obtained for the consistency and assuming that the
volume fraction contributions from different flours were additive, all possible
two-flour combinations were investigated, all mixes gave a porridge with low
consistency or in the predicted range.
Fresh orange-fleshed sweet potato and cassava flour were used to develop a new
product similar to garri, by roasting. The retention of β-carotene, the
consistency, energy density and the consumer acceptance were evaluated. The
higher retention of β-carotene (88%), overall preference (above 60%) and a
significant reduction in viscosity made this product a promising source of
precursor of vitamin A, while having a high energy density.
Linear programming was used in an attempt to formulate a nutritious and
affordable complementary food for children aged 1-8 years, using locally
available crops. It was not possible to formulate a food with an acceptable
nutritional value and consistency, using locally available crops that would be
affordable for most rural residents of Mozambique. However, if the cost of
supplemental micronutrients such as zinc and calcium can be reduced, the cost
of this food could be reduced by more than 70%.
Keywords: Child malnutrition, consistency,
developing countries, energy density, carotenoids.
complementary
porridge,
Popular scientific summary
Malnutrition is one of the problems affecting many developing countries,
sometimes leading to disease and death. Complementary foods, especially infant
porridges prepared by families in rural areas, are based on plants (cereals, roots
and tubers). These porridges are mainly composed of starch, and when mixed
with hot water the starch gelatinizes and swells, resulting in a thick porridge that
cannot be eaten by small children. It is therefore common to dilute these thick
porridges making it necessary for the child to consume large quantities.
However, dilution reduces the energy density and the nutritional value of the
porridge. Several complementary foods have been developed by research groups
and the food industry, and greater attention is being paid to locally available
crops in order to retain local traditions and to minimize the cost of the final
product. However, little information is available on the consistency of these
foods.
Porridges were prepared from flour made from local crops, and their consistency
was predicted using the consistency of commercial instantaneous porridges as
references. Using the model for consistency obtained from porridges prepared
from individual flours, the consistency of porridges prepared from mixtures of
two flours was predicted. A new product (G-OFSP) was then developed by
roasting a mixture of two well-known locally grown crops, namely white
cassava and orange-fleshed sweet potato. This new product has similar
characteristics to a product known locally as rale, called garri in West Africa.
The acceptability and consistency of the new product by the rural population
were investigated. As this new kind of garri contains components that are easily
degraded by heat, in particular carotenoids, the retention of carotenoids during
the roasting process was investigated. Finally, a model was developed to help in
the formulation of palatable foods with high nutritional value based on local
crops using linear programming, in which the consistency was one of the
governing factors.
It was found to be possible to estimate the amount of flour resulting in a
porridge with an acceptable consistency. Using the consistency of porridges
prepared from individual flours, porridges based on a mixture of two flours were
formulated. In some cases, it was possible to predict the consistency of these
porridges. However, for all mixtures containing germinated maize and some
mixtures containing cowpea, the experimental results were below the
predictions. This reduction in consistency in the mixtures including germinated
maize may be to the proteolytic and amylolytic activities of germinated maize,
which may have degraded the starch in the other flour used in the mixture. For
some mixtures including cowpea flour the reduction in the consistency may
have been due to the difference in particle size of the two flours. Smaller
particles are accommodated in the interstices between larger particles preventing
their swelling, and leading to a reduction in consistency.
The G-OFSP was ranked highest in the overall acceptance test, being preferred
by more than 60% of the panellists. The energy density was almost twice that of
the garri made from cassava using the amount of flour that gave porridge with
an acceptable consistency. This new product may offer a means of improving
the energy density and nutrients intake.
It is known that the level of β-carotene is reduced by degradation during heat
treatment in the presence of oxygen. A high retention of β-carotene was
observed in G-OFSP (about 88%) made from roasted orange-fleshed sweet
potato and white cassava. This can be compared with 43% found in yellow
cassava garri. It was therefore concluded that the β-carotene was less degraded
in the process used to make G-OFSP. The lower levels of β-carotene in yellow
cassava garri may be due to fermentation, as well as the temperature and time
used in the roasting process. It is thus possible to provide about 51% of the safe
daily-recommended intake level of vitamin A to children of preschool age, using
G-OFSP.
Based on the values of porridge consistency obtained experimentally, linear
programming was used in an attempt to formulate nutritious and affordable food
for children aged 1-8 years using locally available crops. However, it was not
possible to formulate a food with acceptable nutritional value and consistency,
which would be affordable by most of the rural Mozambican population. If
micronutrients such as zinc and calcium were available at affordable prices, the
cost of this food could be reduced by more than 70% and linear programming
could be used to formulate foods that fulfil both nutritional and sensory
requirements.
Resumo de divulgação científica
A desnutrição é um dos problemas que afecta muitos países em
desenvolvimento, por vezes conduz a doenças e morte. Os alimentos
complementares, especialmente papas infantis, preparados pelas famílias em
áreas rurais são a base de plantas (cereais, raízes e tubérculos). Essas papas são
na sua maioria compostas por amido, e o amido quando misturado a água quente
gelatiniza e ”incha”, resultando numa papa espessa, que não pode ser consumida
por crianças de menor idade. Tem sido prática a diluição (adicionando mais
água) dessas papas espessas para que a criança consiga ingeri-las em maior
quantidade. Porém, a diluição reduz a densidade energética e o valor nutricional
das papas. Nessa perspectiva, vários alimentos complementares têm sido
desenvolvidos por grupos de pesquisadores e indústrias, com enfoque para as
culturas disponíveis localmente de forma a manter as tradições locais e
minimizar os custos do produto final. No entanto, pouca informação sobre a
consistência desses alimentos tem sido divulgada.
Neste trabalho, as papas foram preparadas a partir de farinhas feitas de culturas
locais, e as consistências foram preditas usando a consistência de papas
instantâneas comerciais como referência. Com base no modelo de consistência
obtido a partir de papas preparadas por farinhas individuais foi possível predizer
a consistência de papas preparadas a partir de mistura de duas farinhas.
Um novo produto (G-OFSP) foi desenvolvido a partir de torrefacção de mistura
de duas culturas bem conhecidas localmente, nomeadamente a mandioca branca
e a batata-doce de polpa alaranjada. Este novo produto tem características
similares a de um produto conhecido localmente por rale, chamado garri na
África Ocidental. A aceitabilidade do novo produto e a sua consistência foram
testadas pela população rural. Como este novo tipo de garri contém
componentes que são facilmente degradados pelo aquecimento, em particular os
carotenóides, a retenção dos mesmos (carotenóides) durante o processo de
torrefação foi pesquisado.
Finalmente, foi desenvolvido um modelo para ajudar na formulação de
alimentos palatáveis a base de culturas locais com valor nutricional aceitáveis,
usando o programa linear, em que a consistência foi um dos factores limitantes
(ou de restrição).
Como resultados, verificou-se ser possível estimar a quantidade de farinha que
pode resultar numa papa com consistência aceitável. Usando a consistência de
papas preparadas a partir de farinhas individuais, foram formuladas papas com
base em mistura de duas farinhas. Em alguns casos, foi possível predizer a
consistência dessas papas. Todavia, para todas as misturas que contêm a farinha
de milho germinado e algumas misturas contendo a de feijão nhemba, os
resultados experimentais foram inferiores ao predito. Esta redução na
consistência em misturas que incluem a farinha de milho germinado pode ser
pelas actividades proteolíticas e amilolíticas do milho germinado, as quais
podem ter degradado o amido da outra farinha usada na mistura. Para algumas
misturas que incluem a farinha de feijão nhemba, a redução da consistência pode
ter sido pela diferença no tamanho das partículas das duas farinhas. As
partículas com menor tamanho podem ter-se acomodado nos interstícios entre as
partículas maiores, impedindo o seu inchamento e conduzindo a uma redução na
consistência.
O G-OFSP foi o mais cotado no teste de aceitabilidade geral, preferido por mais
de 60% dos painelistas. A densidade energética do G-OFSP foi praticamente o
dobro, da do garri feito só com mandioca branca, usando a quantidade de
farinha suficiente para obter uma consistência aceitável. Este novo produto
pode significar uma melhoria na densidade energética e na ingestão de
nutrientes.
Tendo em conta que o nível de β-caroteno é reduzido pela degradação durante o
tratamento térmico e a presença de oxigénio, foi observado um elevado nível de
retenção de β-caroteno (cerca de 88%) no G-OFSP feito a partir da torrefacção
da mistura de batata-doce de polpa alaranjada e farinha de mandioca branca.
Este nível de retenção pode ser comparado com 43% obtido no garri feito de
mandioca amarela. Portanto, com estes resultados pode-se concluir que o βcaroteno foi menos degradado no processo usado para produzir G-OFSP. O
baixo nível de retenção de β-caroteno no garri produzido pela mandioca amarela
pode ser pela fermentação assim como a temperatura e o tempo utilizados no
processo de torrefacção. Portanto, pode ser possível fornecer cerca de 51% do
nível seguro de ingestão de vitamina A recomendado diariamente, a crianças
com idade pré-escolar, usando G-OFSP.
Com base nos valores da consistência das papas obtidas experimentalmente, a
programação linear foi usada para tentar formular alimentos nutritivos e
acessíveis para crianças entre 1-8 anos de idade, usando culturas disponíveis
localmente. Contudo, não foi possível formular um alimento com valor
nutricional e consistência aceitáveis, que fosse acessível ao orçamento de
grande parte da população rural de Moçambique. Caso os micronutrientes como
o zinco e o cálcio forem disponibilizados a preços acessíveis, o custo deste
alimento pode ser reduzido em mais de 70% e a programação linear pode ser
usada para formular alimentos que satisfaçam os requisitos nutricionais e
sensoriais.
List of Publications
This thesis is based on the following papers, which will be referred to in the text
by their Roman numerals. The papers are appended at the end of the thesis.
I.
De Carvalho, I. S. T., Granfeldt, Y., Eliasson, A. C., Dejmek, P.
(2013). Predictability of the consistency of porridges using
different methods to measure flour swelling. Starch/Stärke 65:1-9.
II.
De Carvalho, I. S. T., Granfeldt, Y., Eliasson, A. C., Dejmek, P.
(2013). Predictability of the consistency of porridges using
mixtures of different flours. Food and Nutrition Sciences 4:933-939.
III.
De Carvalho, I. S. T., Tivana, L. D., Granfeldt, Y., Dejmek, P. (2014).
Improved energy and sensory properties of instant porridge made
from a roasted mixture of grated orange-fleshed sweet potatoes
and flour made from shredded sun-dried cassava. Food and
Nutrition Sciences 5:1428-1438.
IV.
De Carvalho, I. S. T., Bechoff, A., Tivana, L. D., Dejmek, P.,
Håkansson, A. Granfeldt, Y., (2014). Higher retention of provitamin
A in garri made from white cassava and orange-fleshed sweet
potato than garri from yellow cassava. Submitted.
V.
De Carvalho, I. S. T., Granfeldt, Y., Dejmek, P., Håkansson, A.
(2014).
From diets to foods – Using linear programming to formulate a
nutritious minimum-cost porridge for children aged 1-8 years.
Submitted.
Related publications not included in this thesis
Fernando, A., Carvalho, I., Oliveira, J. F., Mendes, B. (2009). Obtenção de
farinha mista, para alimentação de crianças com deficiência nutricional, a
partir de banana e milho. In: SPQ e CITAA (eds) Actas do 9° Encontro de
Química de Alimentos, Qualidade e Sustentabilidade: uma abordagem integrada,
29 de Abril-2 de Maio 2009, Universidade dos Açores, Angra do Heroísmo,
Açores. Sociedade Portuguesa de Química e Centro de Investigação e
Tecnologia Agrária dos Açores, CD-Rom, 6 p. (ISBN: 978-989-20-1532-3).
De Carvalho, I. S. T., Tivana, L. (2012). Effect of agglomeration-roasting
process and the addition of cowpea and OFSP (orange fleshed sweet
potatoes) on the viscosity of porridge made from sun-dried cassava flour.
Oral presentation at the 16th Triennial Symposium of the International Society
for Tropical Root Crops. Theme: The roots (and Tubers) of Development and
Climate Change, 23th to 28th September 2012. Book of Abstracts/Conference
Programme (page 155), Federal University of Agriculture, Abeokuta, Ogun
State, Nigeria.
The author’s contribution to the papers
I.
The author designed the experiment together with the co-authors. The
author carried out the fieldwork and data collection, and performed the
experimental work. The author evaluated the results together with the
co-authors. The author wrote the first draft of the manuscript, which
was finalized with contributions from the co-authors.
II.
The author designed the experiment based on discussions with the coauthors. The author performed the experimental work and evaluated
the results together with the co-authors. The author wrote the first draft
of the manuscript, which was finalized with contributions from the coauthors.
III.
The author designed the experiment, carried out the fieldwork and data
collection, and performed part of the experimental work together with
L. D. Tivana. The author evaluated the results together with the coauthors and wrote the first draft of the manuscript, which was finalized
with contributions from the co-authors.
IV.
The author designed the experiment based on discussions with L. D.
Tivana, and performed part of the experimental work. A. Bechoff
performed the HPLC analysis. The author evaluated the results and
wrote the first draft of the manuscript, which was finalized with
contributions from the co-authors.
V.
The author participated in the design of the study together with P.
Dejmek and A. Håkansson. The author carried out the fieldwork and
data collection. A. Håkansson performed the linear constraint
programming using Matlab. The author evaluated the results together
with A. Håkansson and wrote the first draft of the manuscript. The
manuscript was finalized with contributions from the co-authors.
Abbreviations and symbols
OFSP
Orange-fleshed sweet potato
G-OFSP
Garri made from a roasted mixture of fresh grated OFSP
and white shredded sun-dried cassava flour
HPLC
High Performance Liquid Chromatography
LGC
Least Gelation Concentration
Ci
Initial flour concentration
Ci,acceptable
Concentration of flour giving an acceptable consistency