ABSTRACT
Extrusion cooking was used to formulate rice and pigeon pea
blend with the aim of providing high energy, protein enriched and affordable
foods for malnourished children. Three (3) factors (screw speed, feed moisture
content and feed blend composition) affecting the extrusion cooking process
were subjected to Central composite design (CCD) and functional properties were
used to optimize production variables. Furthermore, the expansion index of 9.56
± 0.15, bulk density of 0.05 ± 0.01 g/ml and water absorption index of 5.55 ±
0.07 at screw speed of 200 rpm, feed moisture content of 30 % and feed blend
composition of 20% (run 12) were obtained. Regression model and response
surface plots were developed and tested via coefficient of determination (R2
and adjusted R2), analysis of variance, lack of fit and residual
plots. The developed quadratic model showed significant (p < 0.05) effect of
the process variables on the functional properties of instant porridges from
rice-pigeon pea flour blend. Similarly, the coefficient of determination (R2)
was found to be 0.96, 0.93, and 0.88, for expansion index, bulk density and
water absorption index of the extrudates. Furthermore, lack of fit for the
quadratic models were not significant (p > 0.05), which suggested that the
model equations were adequate in describing the functional properties of the
rice-pigeon pea extrudates. In order to optimize the quadratic models, four
formulations were prepared and subjected to nutritional and sensory properties
where formulation 3 showed higher protein (22.10 ± 0.01 g/100g), limiting amino
acids, (lysine and methionine) of 3.44 ± 0.04 g/100g and 1.44 ± 0.02 g/100g,
calcium (3.41 ± 0.07 mg/100g), iron (12.64 ± 0.03 mg/100g), zinc (9.33 ± 0.02
g/100g) contents and general acceptability (6.68 ± 0.06). In conclusion,
convenient complementary food was developed from rice-pigeon pea flour blend
through extrusion which improved the nutritional and sensory properties of the
products.
CHAPTER ONE
1.0 INTRODUCTION
1.1 Background of the study
Food processing technology via locally available raw
materials and innovative processing technologies that maintain high nutrient
compositions and consumer acceptability have been extensively studied (Singh et
al., 2000; Anuonye, 2012; Filli et al., 2013). Cereals and legumes are the
principal sources of energy and protein for significant population in
developing countries including Nigeria (Muller and Krawinkel, 2005). The
production of cereal-legume based products to supply additional protein and
minerals has increased significantly over the years (Muller and Krawinkel,
2005). Extrusion cooking technology has played a central role in enhancing food
security for development of different types of products such as breakfast
cereals, flakes, quick cooking paste, instantised legume powders and breakfast
gruels (Chaiyakul and Winger, 2009). This technology requires a high
temperature short time (HTST) cooking process which provide an alternative for
improving traditional food processing (Guy, 2001a). It also has the ability to
produce a shelf-stable food of reduced microbial load, minimal anti-nutrient
content and low moisture content. (Filli et al., 2011). Products with these
characteristics are suitable for countries like Nigeria where infrastructure is
limited and inadequate (Filli et al., 2011).
Extrusion method is one of the contemporary food processing
technologies applied to foods in order to mitigate the problems associated with
processing of traditional cereal based-products in terms of functional
properties, physical state and shelf-life (Guy, 2001a). It offers many
advantages over spray-drying and roller-drying technologies in terms of
preparation of ready-to-eat foods of desired shape, size, texture and
sensory characteristics at very low processing cost (Guy, 2001a; Sumathi et
al., 2007).
Rice (Oryza sativa) is an important food crop in the world
and the number of consumers depend on it as their staple food (Juliano, 2016),
which could be linked to its attractive color, bland taste, hypoallergenicity
and ease of digestion (Guy, 2001). It has been reported that an average
Nigerian, consumes 21 kg of rice per year (WARDA, 2004). In most developing
countries, rice accounts for daily supply of 27% of energy, 20% of protein and
3% of fat (Kennedy and Burlingame, 2003). Similarly, extruded products from
rice are currently less available compared to those from maize and wheat
(Danbaba et al., 2015). Guha and Ali (1998) reported that the free glutinous
rice is suitable material for production of the extruded products such as
ready-to-eat snacks and breakfast cereal with low bulk density, high expansion
and low shear stress.
Pigeon pea (Cajanus cajan) is an indigenous crop and one of
the major leguminous crops cultivated in many countries of the tropics and
subtropics (Troedson et al., 1990). It is known as Waken Kurawa in Hausa, Fio
fio in igbo and Otilli in yoruba (Anuonye et al., 2012). Similarly, it is
considered as number four after groundnut, cowpea and Bambara nut and highly
cherished for its protein content (17 - 30%) which makes it indispensable along
with cereals in human diet (Troedson et al.,1990). The plant has also been
listed as one of the under-utilized legumes with broad potentials and its seed
could serve as an ideal supplement to traditional african cereal and
tuber-based diets which are generally protein deficient (Badifu, 1992; Onu and
Okongwu, 2006; Eneche, 2009). Therefore, blending of rice and pigeon pea will produce adequate meals of balanced nutrient
compositions for both infant and adult usage.
1.2 Statement of Problem
In Africa, poverty, poor agricultural practices, low
productivity and inadequate processing are the major causes of food shortage
(Danbaba et al., 2015). Based on this, significant populations survive
predominantly on staple food crops such as rice, maize, sorghum, millet,
cassava, with little or no animal products to meet the protein need for normal
growth and development (Danbaba et al., 2015). These problems are further
aggravated by the menace of epidemic diseases that increased the number of
vulnerable populations, which resulted in wide spread of maternal and infant
malnutrition in most of the countries (Danbaba et al., 2015). Despite Africa’s
vast natural resources and a considerable progress in economic growth; hunger
and malnutrition have remained endemic amongst the African population, and it
is estimated that 200 million Africans are chronically malnourished (WFP, 2011;
Mohammed, 2017).
Similarly, several strategies have been adopted to reduce
maternal and infant malnutrition including diversification, fortification and
complementation of foods with indispensable amino acid sources, supplementation
with good quality protein and the utilization of locally grown crops for the
production of high protein, shelf stable and affordable recipes for addressing
the deepening global nutrition challenges in developing countries (Iwe, 2001).
The production of cereal-legume based products provides an
ideal source of dietary protein for human populations; such products include
nutritionally enhanced biscuits, breads, cakes, porridges and extruded snacks
(Filli et al., 2011). Nutritionally, rice and rice-based products are deficient
in lysine, an essential amino acid, that can easily be improved by blending
rice with food materials rich in lysine.
In addition, researches on utilization, development and
commercialization of pigeon pea and its associated products are limited in
Nigeria when compared with other legumes such as cowpea (Akande, 2007).
However, several researches have been reported on the use of extrusion cooking
for cereals and legumes singly (Bredie et al., 1998; Iwe, 2001; Pelembe et al.,
2002; Ding et al., 2006), and no available report in the literature to the best
of our knowledge on the development of rice-pigeon pea blend using this
technology.
Hence, extrusion technology could contribute in this
direction through the production of foods containing cereals and legumes, which
are highly acceptable, and meet consumer’s specifications. Furthermore,
extrusion processes could help in producing quality products with improvement
in nutritive value, colour, flavor and bioactive substances as well as
reduction in production cost (Tabo et al., 1995).
1.4 Aim and Objectives
The aim of this research is to optimize and characterize
instant porridge developed from rice-pigeon pea flour blend using extrusion
cooking method.
i. To determine the optimum process conditions for production of
instant porridge from rice- pigeon pea flour blend using statistical
optimization technique.
ii. To evaluate the characterization on proximate, amino acid and
mineral compositions of the developed instant porridge from rice-pigeon pea
flour blend.
iii. To carry out sensory evaluation of the developed instant
porridge from rice- pigeon pea flour blend.
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