This study evaluated "the
effects of processing methods on the physico-chemical properties of sweet
potato and sorghum flour". Sweet potato (Ipomoea
batatas) is an important food crop in the tropical and sub-tropical
countries and belongs to the family convolvulaceae.
Sweet potatoes are rich in dietary fiber, minerals, vitamins, and anti oxidants
such as phenolic acids,
anthocyannins,-carotenetocopherol.Theproximatecompositionand ofβ sweet potato
was determined and these include moisture, lipids, ash, protein, carbohydrates
and fiber. In carrying out the analysis practically, methods used vary
according to the food material. The anti oxidants were also determined
alongside with phenol oxidase, pasting properties, minerals and sugar contents.
Sorghum is a tropical plant belonging to the family of poaceae. More than 35% of sorghum is
grown for human consumption. The analyses carried out in sweet potatoes are
same with sorghum with the exclusion of phenol oxidase.
TWO: LITERATURE REVIEW
ORIGIN AND DISTRIBUTION OF SWEET POTATO
2.1.1. DESCRIPTION OF SWEET
2.1.2. USES OF SWEET POTATO
2.1.3. NUTRITIONAL VALUE OF SWEET
NUTRIENT COMPOSITION OF SWEET POTATO
188.8.131.52. POLYPHENOLS COMPOSITION
ANTI-MUTAGENICITY AND ANTI-
ANTI-NUTRIENTS IN SWEET POTATO
ENZYME COMPOSITION OF SWEET POTATO
ORIGIN AND DISTRIBUTION OF SORGHUM PLANT
DISTRIBUTION OF SORGHUM PLANT
USES OF SORGHUM
ENZYME COMPOSITION OF SORGHUM
NUTRITIONAL COMPOSITION OF SORGHUM
ANTI-NUTRIENTS IN SORGHUM
THREE: MATERIALS AND METHODS
3.2.1. PROCESSING OF SWEET
3.2.2. PROCESSING OF SORGHUM
SWEET POTATO AND SORGHUM ANALYSIS
3.3.1. PROXIMATE ANALYSIS
184.108.40.206. DETERMINATION OF FAT
OF ASH CONTENT
DETERMINATION OF CRUDE FIBRE
220.127.116.11. DETERMINATION OF MOISTURE CONTENT
18.104.22.168. DETERMINATION OF PROTEIN
22.214.171.124. DETERMINATION OF
ANTI-NUTRIENTS AND PHYTOCHEMICALS
DETERMINATION OF TANNINS
DETERMINATION OF HYDROCYANIC ACID
DETERMINATION OF ANTHOCYANNINS
DETERMINATION OF PHYTATE/PHYTIC ACID
DETERMINATION OF MINERAL CONTENT
DETERMINATION OF PASTING PROPERTIES
DETERMINATION OF PHENOL OXIDASE
DETERMINATION OF REDUCING SUGARS; FRUCTOSE, GLUCOSE AND SUCROSE
CHAPTER FOUR: RESULTS AND
4.1. TABLE 1: PROXIMATE COMPOSITION OF THE SAMPLES AND
TABLE 2: MINERAL COMPOSITION OF SAMPLES AND DISCUSSION
TABLE 3: PHYTOCHEMICAL COMPOSITION OF THE SAMPLES AND DISCUSSION
TABLE 4: PHYSICO-CHEMICAL PROPERTIES OF SAMPLES AND DISCUSSION
4.4. TABLE 5: SUGAR COMPOSITION OF THE
SAMPLES AND DISCUSSION
Sweet potato (Ipomoea
batatas) is an important food crop in the tropical and sub tropical
countries and belongs to the family convolvulaceae.
It is cultivated in more than 100 countries. ( Woolfe, 1992). Nigeria is the
third largest producer in the world with china leading, followed by Uganda.
Sweet potato ranks seventh among the world food crops, third in value of
production and fifth in caloric contribution to human diet (Bouwkamp, 1985).
Sweet potatoes are rich in dietary fibre, minerals, vitamins and anti oxidants
such as phenolic acids, anthocyanins, tocopherol and ß- carotene. Besides
acting as anti oxidants, carotenoids and phenolic compounds also provide sweet
potatoes with their distinctive flesh colours ( cream, deep yellow, orange and
purple). Sweet potato blends with rice, cowpea and plantain in nigerian diets.
It is also becoming popular as a substitute to yam and garri. It can be reconstituted
into fofoo or blended with other carbohydrate flour sources such as wheat ( Triticum aestivum) and cassava ( Manihot esculenta) for baking bread,
biscuits and other confectioneries (Woolfe, 1992).
The leaves are rich in protein and
the orange flesh varieties contain high beta carotene and are very important in
combating vitamin A deficiency especially in children.
Sorghum (sorghum bicolor (S. bicolor) is a
tropical plant belonging to the family of poaceae, is
one of the most important crops in Africa, Asia and Latin America. More than
35% of sorghum is grown directly for human consumption. The rest is used
primarily for animal feed, alcohol production and industrial products ( FAO,
1995). The current annual production of 60 million tons is increasing due to
the introduction of improved varieties and breeding conditions. Several
improved sorghum varieties adapted to semi-arid tropic environments are
released every year by sorghum breeders. Selection of varieties meeting
specific local food and industrial requirements from this great biodiversity is
of high importance for food security. In developing countries in general and
particularly in West Africa demand for sorghum is increasing. This is due to
not only the growing population but also to the countries policy to enhance its
processing and industrial utilization.
More than 7000 sorghum varieties have been
identified, therefore there is a need of their further characterization to the
molecular level with respect to food quality. The acquisition of good quality
grain is fundamental to produce acceptable food products from sorghum. Sorghum
while playing a crucial role in food security in Africa, it is also a source of
income of household . In West Africa, ungerminated sorghum grains are generally
used for the preparation of "to", porridge and couscous. Malted
sorghum is used in the process of local beer "dolo" (reddish, cloudy
or opaque), infant porridge and non fermented beverages. Sorghum grains like
all cereals are comprised primarily of starch.
The aim and objective of this work is to
obtain diet low in sugars, with enriched nutrients intended for diabetics.
ORIGIN AND DISTRIBUTION OF SWEET POTATO
Sweet potato (Ipomoea
batatas) is a member of the convolvulaceae family
(purseglove, 1972). Approximately 900 different species of convolvulaceae in
400 genera have been identified around the world. Yen, (1974) and Austin
(1978,1988) recognized 11 species in the batatas, which includes sweet potato.
The closest relatives of the sweet potato appears to be ipomoea trifida that is found wild in
maxico, and ipomoeto tabascana.
Sweet potato has a chromosomes number for the genus ipomoea is 15, sweet potato
is considered to be a hexaploid. Most sweet potato cultivars are
self-incompatible, which means that when self pollinated, the cannot produce
viable seed. It is accepted that cultivated sweet potato originated in central
America or tropical south America. Sweet potatoes are cultivated where ever
there is enough water to support their growth: optimal annual rainfall for
growth range between 750-2000mm. sweet potato is a warm season annual,
requiring 20-25°C average temperatures and full sunlight for optimal
development. Sweet potato thrives in well drained loamy soils with high humus
content that provides warm and moist environment to the roots.
DESCRIPTION OF SWEET POTATO A. THE ROOT SYSTEM
When sweet potato is planted from stem
cuttings, adventitious roots arise from the cutting in a day or two. These
roots grow rapidly and form the root system of the plant. Research has shown
the roots of sweet potato can penetrate the soil to a depth of over 2m, the
exact depth attained being dependent on the soil condition (Onwueme, 1978 and
Kays, 1985). Based on its origin, the root system of sweet potato is divided
into the adventitious roots arising from subterranean nodes of a vine cutting
and lateral roots arising from existing roots. Kays (1985) subdivided the
adventitious roots into storage, fibrous and pencil roots. The lateral roots
are subdivided into primary, secondary and tertiary roots.
During the early ontogeny of young
adventitious roots emerging from the stem,
they are often separated
into (Togari, 1950). According to Wilson (1982) and Kays (1985),
thin roots are typically tetrarch in the arrangement of their primary vascular
tissue, i.e. four xylem and phloem poles found within the vascular cylinder.
The most important functional differences between these root types are their
capacity for storage root initiation in a specific region of the thick roots.
Several factors such as exposure of potential storage roots to long photoperiod
(Bonsi et al, 1992), water logged
soil conditions (Kays, 1985), high levels of nitrogen supply (Chua & Kays, 1981),
gibberellic acid application (McDavid
& Alamu, 1980), as
well as exposing the plant to long days (McDavid & Alamu, 1980; Du Plooy,
1989) encourage lignification and inhibit storage root development.
Alternatively high potassium supply (Isuno, 1971, Hahn
& Hozyo, 1984), the
absence of light (Wilson, 1982), as well as well aerated soil conditions, low
temperature and short days been demonstrated to encourage storage root
formation (Du Plooy, 1989).
Storage roots arise from pentarch or
hexarch thick young roots if the cells between the protoxylem point and the
central metaxylem cell do not become lignified, or if only a slight proportion
of these cells are lignified (Togari, 1950). The increase in storage root size
is attributed to the activity of the vascular cambium as well as the activity
of the anomalous cambia (Wilson, 1982). The initial sign of storage root
formation is the accumulation of photosynthetic consisting predominantly of
starch (Chua & Kays, 1982). Storage root initiation is reported to occur
between the periods of 35 to 60 days after planting (Agata, 1982, Wilson 1982).
But the work of Du Plooy (1989) indicated that storage root initiation might
occur as early as 7 days after planting. These conflicting results suggest the
need for further research on the storage root formation in sweet potato.
Agata (1982) reported that storage root
formation started about 30 to 35 days after planting and the roots dry weight
increased linearly until harvest.
Pencil roots are generally between 5
and 15mm in diameter, they are the least well defined of the adventitious root
emerging from the subterranean node of the culting. They develop mainly from
young thick adventitious roots under conditions not conducive for the
development of storage roots. In pencil roots lignification is not total, but
result in uniform thickening of the entire root.
According to Chua and Kays (1981),
fibrous roots develop mainly from tetrarch, thin adventitious roots. The
fibrous roots are generally less than 5mm in diameter and are branched with
lateral roots forming a dense network throughout the root zone constituting the
water and nutrient absorbing system of the plants. Fibrous roots have heavily
lignified steels and very low levels of vascular cambial activity. High
nitrogen and low oxygen within the root zone favors their formation (Chua &
The lateral roots of sweet potato
emerge from existing roots adventitious roots (storage, pencil and fibrous)
have a profusion of lateral roots at varying
densities along their axis. The primary
lateral roots emerge from adventitious roots. Lateral emerging from the primary
laterals are called secondary lateral and those emerging from the secondary
laterals are named tertiary laterals (Kays, 1985).
ABOVE GROUND PLANT ORGANS
Sweets potato has long thin stems
that trail along the soil surface and can produce roots at the nodes. Sweet
potato genotypes are classified as either erect, bushy, intermediate, or
spreading, based on the length of their vines (Yen, 1974, Kays, 1985). Stem
length varies with cultivar, and highly variable, ranging from a few
centimeters up to 10cm in length. Planting density has pronounced effect on the
internode length as well as on vine length (Somda & Kays, 1990a). The stem
is circular or slightly angular. Stem color is predominantly green, but
purplish pigmentation is often present.
Branching is cultivar dependent (Yen,
1974) and branches vary in number and length. Normally, sweet potato produces
three types of branches, primary, secondary and tertiary, at different periods
of growth. The total
TERMS AND CONDITIONS APPLY
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