COMPARATIVE STUDY OF SOME SELECTED COAGULANTS FOR SOY CHEESE (TOFU) PRODUCTION
COMPARATIVE
STUDY OF SOME SELECTED COAGULANTS FOR
SOY CHEESE (TOFU) PRODUCTION
1.0 CHAPTER ONE
1.1 INTRODUCTION
Cheese is the curd or solid substance
formed by the coagulation of milk of certain mammals by rennet or similar enzymes
in the presence of lactic acid produced by added micro organisms from which
part of the moisture has been removed by cutting warming and /or pressing,
which has been shaped in a mould and ripened by holding for sometime at
suitable temperatures and humidity (Frankhauser, 2007).
Frankhauser, (2007) used standard
cultures of Lactobacillus bulgaricus
and Streptococcus thermophilus as
starter cultures for cheese production.
Curdling is obtained at precise degree
of acidity called the Iso-electric point (Smith, 1995). During the cheese making
process, most of the milk proteins coagulates, trapping all the fat (Frankhauser,
2007).
Soy beans are excellent sources of high
quality protein that has many uses as human food (Liu, 1997).
Soymilk is a beverage derived from soya
beans, which is an alternative milk source for people suffering from lactose
intolerance and vegetarians who avoid cow’s milk, it provides the perfect plant
source replacement (Berk, 2000).
Soy milk is important to help people
reduce the risk for heart disease. Soy beans contain plant chemical called
isoflavones which assist in the lowering of cholesterol (Sacks et al, 2006).
Soy cheese (Tofu) is made by coagulating
soy milk and pressing the resulting curds. When the natural acidity of milk
increases, the protein curdles (Harold, 2004). The most important step in the
production of the soy cheese is coagulation and this process is accomplished
with the acid of coagulants. These coagulants are salts, acids or enzymes that
are added to soy milk to obtain a firm and silken curd (Shurtleff et al.,
2004).
Studies have shown that regular
consumption of soy cheese (tofu) provides an equivalent amount of energy,
protein, total fat, carbohydrates, alcohol and fibre of cheese. However, the
main health benefits of soy cheese is significantly lower in total cholesterol,
triglycerides and low–density lipoprotein (bad cholesterol) if eaten regularly
instead of meat (USDA, 2002).
Muyibi (2005) used moringa seed cake
extract and alum for the coagulation of water but this study intends to produce
soy cheese from soy milk using some selected coagulants. These coagulants
include tamarind seed, Moringa Oleifera seed cake extract, aqueous solution of
alum and lime juice.
A comparative analysis of the properties
of soy cheese produced from these coagulants will provide a basis for their
further development and use in the production of soy cheese.
1.1 AIMS AND OBJECTIVES
The general aim of this research is to
compare the effectiveness of Moringa Oleifera seed cake extract, tamarind
seeds, Aluminium sulphate (Alum) and lime as coagulant for soy cheese
production.
The specific objectives are:-
1. To
produce soy-cheese from soy milk using some selected coagulants namely:-
i.
Moringa oleifera seed cake extract
ii.
Tamarind seed
iii.
Alum (Aluminum sulphate)
iv.
Lime juice
2. To
determine the yield produced during curdling
3. To
determine the physio chemical properties of the soy cheese products
4. To
determine the proximate analysis of the soy cheese products.
5. To
determine the microbiological quality of the soy cheese products
6. To
assess the sensory qualities and acceptability of the products.
CHAPTER
TWO
2.0 LITERATURE REVIEW
2.1 HISTORICAL BACKGROUND OF SOYBEAN
The soybean (US) or soya bean (UK) (Glycine max) is specie of legume native
to East Asia, widely grown for its edible bean which has numerous uses. The
plant is classed as an oil seed rather than pulse by the United Nations Food
and Agricultural Organization (FAO).
Soybean
is one of the oldest cultivated crops believed to have originated from the
Northeast China. Soybean in China was originally known as “Shu” but is now
presently called “ta tou”, meaning the great bean (Salunkhe and Desai, 1986),
(Liu 1997).
They remain a major crop in China,
Japan and Korea. Prior to fermented products such as soy sauce, Tempeh, Natto and
Miso, soy was considered sacred for its beneficial effects in crop rotation.
Soy
was first introduced to Europe in the early 18th century and to
British colonies in North America in 1765, where it was first grown for hay.
Benjamin Franklin wrote a letter in 1770 mentioning sending soy beans home from
England. Soybeans did not become an important crop outside of Asia until about
1910. In America, Soy bean was considered an industrial product only, and were
not used prior to the 1920s. Soy bean was introduced to Africa from China in
the late 19th century and is now wide spread across the continent.
Soybean first arrived in South America in Argentina in 1882.
There
seemed to have been no interest in the production of soybean until after the
turn of the century (1900A.D). Some European countries especially England
started importing soybean from Manchuria in 1908, to supplement short supplies
of cotton seed and flax seed. The success in Europe engineered similar
experimentation in the United States, where the interest soon began to develop
for domestic processing of soybean (Daily mail international, 1983). In 1911,
the first crushing plant started operation based on beans imported from
Manchuria. The United States developed soybean into a major commercial crop at
the beginning of the twentieth century (Salunkhe and Desai, 1986), (Berk,
1992).
2.2 SOY: THE MAGIC BEAN
More
than five thousand years ago, early Chinese farmers discovered and began
cultivating a legume that would eventually become an essential food for much of
the world. This plant is known today as the ‘great bean’ in China, or as it is
known in the west as soy bean. During subsequent millennia, soybean use spread
across China, Korea, Japan, and Southeast Asia (Gissen, 1996). Soy beans yield
more protein per acres than any other crop. It has been a staple for many
societies.
Numerous
food products have been developed from soybeans including soymilk, Tofu (curdled
soymilk) and meat substitutes. Developed since two thousand years ago, today Tofu
is the world’s most popular soy food product. Infact, the average Japanese
person eats approximately a pound of Tofu every week (Liu, 1997).
Since
the introduction of soybean as food, it has gained a reputation for having
medicinal properties. The Chinese believe that soybeans are effective for
treating common cold, skin diseases, beriberi, diarrhea and toxemia of pregnancy,
constipation, anemia and leg ulcers (Gissen, 1996).
Soybean
curd (tofu) is made into a variety of product by frying, drying and freezing
and is consumed daily in the same manner as high protein foods in western
cultures. Soybeans are also prepared by fermentation with microorganisms to
form highly flavored food and seasoning. (AAFC, 2008).
2.2.1
COMPOSITION OF SOY BEANS
The soybeans (glycine max) is often called miracle crop and is the world’s foremost provider of protein and oil. Soy
beans are high in protein and contain beneficial photochemical such as
isoflavones. The mature soybeans is about
36.5% protein 30% carbohydrate 19.9%
oil and
14% moisture , ash and hull
(USDA, 2002.).
Soy beans contain
all three of the macro- nutrient
require for good
nutrition , complete protein carbohydrate and fat, as well as vitamin and
minerals , including calcium
folic acid and iron. Soybeans are the only vegetable that contain
complete protein (Riaz, 2006).
2.2.2 NUTRITIONAL
COMPOSITION OF SOY BEANS
Soy beans are
very rich in nutritive components. Beside
the very
high protein content, soy beans
contain a lot of fibre and
are rich in calcium, magnesium. The soy protein has a
high biological value and contains all the essential amino acid.
Soy beans are
rich in unsaturated fatty acids, and low in saturated fatty acids, which need
to be avoided.
Table 1: The nutritional value of soy beans per l00g
given below.
Water 8.5g
Energy 416kcal
Energy 1741kg
Protein
36.5g
Fat
(total lipid) 19.9g
Fatty acid saturated 2.9g
Fatty acid mono unsaturated 4.4g
Fatty acid poly unsaturated 11.3g
Carbohydrate 30.2
g
Fiber
9.3g
Ash 4.9g
Isoflavones 200mg
Calcium 277mg
Iron
15.7mg
Magnesium 289
mg
Phosphorus 704mg
Potassium 1797 mg
Sodium 2.0mg
Zinc
4.9mg
Copper 1.7mg
Manganese 2.52mg
Selenium
17.8µg
Vitamin
c (ascobic acid) 6.0mg
Thiamin
(vitamin B1) 0.87mg
Riboflavin
(vitamin B2) 0.87mg
Niacin
(vitamin B3) 1.62mg
Panthotenic
acid (vitamin B5) 0.79mg
Vitamin
B6 0.38mg
Folic
acid 375µg
Vitamin
B12 0.0µg
Vitamin
A 2.0µg
Vitamin
E 1.95mg
Source [USDA 2006 Nutrient Data base for standard
reference]
2.2.3 ANTI NUTRITIONAL COMPONENTS OF SOY BEANS
There
are a number of components present in soybeans that exert negative impact on the nutritional quality of
protein. These antinutritional, compound include; protease inhibitors phytate
& saponins (Liu 1997)
2.2.3.1 PROTEASE INHIBITORS
These are traditionally viewed as
anti-nutrients as the prevent the proper functioning of the enzymes responsible
for digesting protein in the diet (Gissen, 1996). This is the reason why
animals fed on soybeans do not grow properly. Heating and processing of soy
bean into its products prevents the problem of protease inhibitors since they
are broken down or removed (Gissen, 2004). It was recently discovered that
soybeans has the potential of inhibiting cancer in animals. The protease inhibitors
appear to have an anti-carcinogen mechanism of action whereby they prevent
normal functioning of protein involved in the activation of certain cancer
related genes. Large amounts prevent proper digestion of soy, however,
processed soy food contain only 5% or less of the naturally occurring protease
inhibitors. Since small amounts of protease inhibitors do not cause growth
suppression but do have anti cancer effects in animals, soy foods can be
consumed safely without fear of growth suppression (Gissen, 2004)
2.2.3.2 PHYTATES
Phytate,
a compound of inositol, is the storage form of mineral phosphorous in plants.
They are also considered as anti-nutrients due to the fact that they bind iron
and calcium preventing their proper absorption (Oboh et al., 2003). Phytates
are quite high in soybean and are considered beneficial due to its anticancer
properties and capability of preventing heart diseases. Inositol phosphates are
biochemicals that are in our cells and play a part in controlling cell growth
by their role as intracellular messenger. Dietary phytate are now thought of as
being able to alter the body’s pool of intracellular inositol phosphates and
may prevent cancer by controlling proliferic cell growth. It is also considered
to have antioxidant properties due to its ability to chelate iron, prevent both
irons reactivity and absorption (Gissen, 2004).
2.2.3.3 SAPONINS
Plants
saponins have been long considered as toxic. However, some human foodstuffs
have been found to contain significant amounts of saponins that posses little
toxicity (Oboh et al., 2002), soy beans is one of such foods. Saponins have
been suggested as possible anti-carcinogens having a mechanism of action which
include cytotoxicity immune modulatory effect, bile and binding and
normalization of carcinogen induced cell proliferation (Oboh et al.,1999). Soy
saponins particularly have been shown to inhibit human cancer cell growth
despite its low toxicity. Recent research has also suggested that saponins have
cholesterol lowering properties and diets high in saponins are associated with
lower rates of cardiovascular disease (Gissen, 2004).
2.3 SOY BEANS UTILIZATION
Soy
processors convert soybeans into product made from whole soybeans such as
soymilk, tempeh, miso, natto, soy sauce, soy flour, soy yoghurt, soy nuts and tofu
(soy cheese). Other soybeans destined for traditional products are graded,
cleaned, dried and cracked to remove hull. Soybean hulls are further processed
for animal feed or fiber additives for breads cereals and snacks (Theodore,
1995).
Processors
convert the remaining part of the soybeans after the hulls are removed into
full-fat flakes that may be used in animal feed or processed into full-fat for
a variety of commercial food uses. Immersing the full fat flakes into a solvent bath extracts
the crude soybean oil that is then degummed to separate lecithin from the oil.
Lecithin is an emulsifying agent and when further processed is used in baked
foods, dairy products and instant foods the extracted oil which is referred to
as soybean oil is used to produced cooking oil, margarine and shortening.
After the oil is extracted the solvent
is removed and recycled and the flakes are dried, creating an essentially oil
free, high protein product known as deflated soy flakes. Deflated soy flakes
are ground into soybean meal and used to produce feed for animals primarily
poultry, swine, cattle and aquaculture (Theodore, 1995).
2.3.1 SOY SAUCE
Soy sauce represent one of the
largest uses of soy beans. It is used as a condiment. It is a dark brown liquid
with a pleasant aroma produced by the fermentation of soy bean and carbohydrate
starchy cereal as rice or wheat.
2.3.2. SOY MILK
Soy milk is a beverage made
from soy beans, it is produced by grinding soaked dry soybeans. Soymilk is
obtained after filteration (Harold, 2014).
2.3.3. SOY YOGHURT
Soy yoghurt is produced using
soymilk adding yoghurt bacteria (Lactobacillus
bulgaricus and Streptococcus thermophillus),
sometimes adding sweetners such as fructose, glucose or sugar (Harold, 2014).
2.4 TOFU (SOY CHEESE)
Tofu is one of the most important and
popular food products in east and south Eastern state of Asian countries and is
gaining an “increasing popularity in western countries as well. Developed some
two thousand years ago. It has became the worlds’ most popular soy food product
(Gissen, 2004). There are many ways of preparing soymilk and tofu (Watambe et
al., 1997), (Liu 1997). Soy milk is commonly made by soaking soybeans in excess
water, draining and grinding with additional water extracting the raw soy milk
from the pulp residue and cooking soy milk (Liu, 1997). Tofu is an unfermented
soy product, also known as soy bean curd and is soft cheese –like food made
by curdling fresh hot soy milk with a
coagulant which is either a salt (CaCl2, CaS04) or an acid.
Traditionally the curdling agent used to make Tofu is Nigari compound found in
natural ocean waters or calcium sulfate (CaS04) (Prestamo et al.,
2002). The coagulant produce a soy protein gel which traps water, soy lipids
and other constituents in the matrix forming curds. The curds are then pressed
into solid cubes. The yield and quality of tofu are influenced by soy bean
varieties, soy bean quality (growth and storage environment dependent) and the
processing conditions of the coagulants (Prestamo et al., 2002).
The
yield and quality of tofu is affected by soy bean varieties, soy bean quality
and processing conditions. Coagulation is the most difficult to master, since
it relies on complete inter-relationship of the following variable; soy bean
chemistry, soy milk cooking temperature , volume solid content and pH,
coagulant type amount, concentration and the method of adding and mixing and
the coagulation temperature and time (Shurtleff and Aoyayi, 2002). The
variation in controlling all these variables greatly affect tofu yield quality.
Increasing coagulation temperature, stirring speed and coagulant concentration
increased tofu hardness but decrease tofu yield (Prestamo et al., 2002). Stirring
speed and time also had significant influence on tofu yield and quality
(Prestamo, 2002).
Most
studies available used small manual laboratory scale method to prepare tofu
from 5 to 300g soy beans. None of them applied a production scale method for
determing suitability of soybeans for tofu making. It does not depend only on processing parameters but
also on researchers skill in making tofu, particularly when a small manual
laboratory scale method is used. Variations in tofu making procedures and new
soybean can cause difficulties in comparing result among laboratories (Murphy et al., 1997) suggested that the
evaluation of soybean variety for suitability as a tofu cultivars tofu
preparation on a preparation scale.
A
small production scale method has been developed to evaluate the quality of
soybean variety for tofu making using an automatic tofu machine (Cai and Chang,
1998). The use of the automatic machine reduces variability of the manual
laboratory procedures. The tofu machine is an effective means of evaluating
suitability of existing commercial soy bean varieties and soy bean cultivars in
the final phases of breeding selection for tofu making. With the rapid
development of tofu market and new soybean
in the world, the need for more reproducible quantitative data on soy
milk coagulation in tofu production with a production scale method has become
necessary (Prestamo et al., 2003).
Coagulation
of soy milk is the most important step in the tofu process and the most
difficult to master since it relies on the complex interrelationship of the
following varieties. Soy bean chemistry, soy milk cooking temperature, volume,
solid content and pH, coagulant type, amount, concentration and the method of
adding and mixing and the coagulation temperature and time (Cai and Chang,
1999). Each of coagulant produces Tofu with different textural and flavor
properties (Poysa and Woodrow, 2002). The texture of Tofu should be smooth,
firm and coherent but not hard and rubbery. Since tofu is a soy protein gel,
the amount of soy protein used to make the soy milk is critical for tofu yield
and quality (Poysa and Woodrow, 2002).
Tofu
is available as three (3) major types which are firm, soft and silken tofu.
Firm tofu is dense and solid and has a higher protein and fat content than
other forms of Tofu. Firm tofu also contain higher calcium content. Soft tofu
is solid, but not firm while silken tofu is a creamy product (Shurtleff and Aoyagi, 2002).
2.4.1 TOFU COAGULANTS
Natural
calcium sulphate (gypsum) and magnesium chloride (nigari) are the most common
tofu coagulants used. They have been used for hundreds years in Japan and
China. Nigari is composed mainly of magnesium chloride but also contain other
minerals found in sea water, with the exception of sodium chloride (sea salt).
Gypsum is a naturally occurring calcium sulphate (Shurtleff and Aoyagi, 2002).
2.4.1.1.
SALT COAGULANTS
- Calcium sulphate:- The traditional and most widely
used coagulant to produce Chinese style tofu. It produces a tofu that is tender
but slightly brittle in texture. The coagulant itself has no perceivable taste.
Use of this coagulant also makes a tofu that is rich in calcium. As such many
tofu manufacturers choose to use this coagulant to be able to market their tofu
as a good source of dietary calcium (Shurtleff et al., 2008).
Ø Magnesium
chloride and calcium chloride: Both of these salts have high solubility rate in ware and affect soy
protein in the same way where as gypsum is only very slightly soluble in water
and acts differently in soy protein
precipitation the basis for tofu formation. These are the coagulants used to
make tofu with tender texture (Shurtleff et al., 2002).
2.4.1.2 ACID COAGULANT
Glucono
delta –lactone (GDL): A naturally occurring organic acid also used in cheese
making which produces a very fine textured tofu that is almost jelly like. This
coagulant is used especially for softer tofu, and confers an almost
imperceptible sour taste to the finished product (Shurtleff et al., 2008).
Ø Other
edible acids: Though they can affect the taste of tofu more and vary in
efficacy and texture, such as lemon juice, can also be used to coagulate
soymilk and produce tofu (soy cheese) (Harold, 2004).
2.4.1.3 ENZYME COAGULANTS
Among
enzymes that have been shown to produce tofu are papain and alkaline and
neutral proteases from micro-organisms. In the case of papain, the enzyme to
substrate ratio by weight, was held constant at 1:400. An aliquot of 1% crude papain was added to “uncooked”
soy milk at room temperature and heated to 90o -100oc
(shurtleff et al., 2008).
2.4.2 VARIETIES OF TOFU
There
is a wide variety of tofu available in both western and Eastern markets.
Despite the daunting variety tofu product can be split into two main
categories: fresh tofu which is produced directly from soymilk and processed
tofu, which is produced from fresh tofu. Tofu production also creates important
side products which are often used in various cuisines (shurtleff et al.,
2008).
2.4.2.1 FRESH TOFU
Depending
on the amount of water that is extracted from the tofu curds, fresh tofu can be
divided into three main varieties. Fresh tofu is usually sold completely
immersed in water to maintain it’s moisture content (Shurtleff et al, 2008)
2.4.2.2. FIRM TOFU
These
types of tofu are produced with sea water instead of nigari (magnesium
chloride) or using concentrated soy milk. Some of them are squeezed of excess
moisture using heavy weights. These products are produced in areas where
travelling is in convenient such as
remote islands, mountain villages, heavy snowfall areas and so on (Gissen,
2004).
2.4.2.3 CHINESE “DRY TOFU”
Tofu dried but is rather an extra
firm variety of tofu with a large amount of liquid pressed out of it. When
sliced thinly, this tofu can be crumbled easily. The skin of this form of tofu
has the pattern of the muslin used to drain and press it. Western firm tofu is
milled and reformed after the pressing and sometimes lacks the skin with its
cloth patterning (Harold 2014).
2.4.2.4 PROCESSED TOFU
Many forms of processed tofu exist due to the
varied ways in which fresh tofu can be
used. Some of these technique likely originate from the need to preserve tofu
before the days of refrigeration, or to increase its shelf life and longevity.
Other production techniques are employed to create tofu with unique texture and
flavor (Gissen, 2004).
2.4.2.5. DRIED TOFU
Two kinds of dried tofu are
produced in Japan. They are usually rehydrated (by being soaked in water) prior
to consumption. In their dehydrated state they do not require refrigeration.
They are:
·
Koya tofu is made using nigari
·
Kori tofu is freeze dried (Gissen 2004)
2.4.2.6 FRIED TOFU
With
exception of the softest tofu, all forms of tofu can be fried. Thin and soft
varieties of tofu are deep fried in oil until they are light and airy in their
core “bean bubble”. (describing the shape of the fried tofu as bubble).
Tofu such as firm Asian with their
lower moisture content, are cut into bile –sized cubes or triangles and deep
fried until they develop a golden –brown crispy surface. These may be eaten on
their own or with a light sauce or further cooked in liquids. They are also
added to hot dishes or includes as part of the vegetarian dish (Shurtleff and
Aoyayi, 2002).
2.4.3 NUTRITIONAL COMPOSITION OF TOFU
Tofu is rich in high quality protein, low
in saturated fat and cholesterol free. It is also a good source of B-vitamins
and minerals. Tofu also contain isoflavones which is a naturally occurring heterocyclic phenols
mainly in soy bean and its products (Gissen, 2004).
2.4.3.1 PROTEINS
Tofu is an excellent source of soy protein
(Liener, 1994). Proteins are polypeptides which are formed as a result of
condensation of amino –acids of the 20 amino acid utilized in protein syntheses.
Only 10 can be synthesized in the human system (non essential amino acid) while
the other 10 most necessarily be derived from food products (essential amino acid)
making the essential amino acids very important component of human diet.
Essential amino acids are isoleucine, leucine, lysine, methionine, phenyl
alanine, theonine, tryptophan and valine (for adults) arginine and histidine
are added to list for infants. Tofu contain all the above essential amino
acids. Tofu is a rich source of high proteins (Liener, 1994).
2.4.3.2. LIPIDS
Lipids
are organic compounds that are poorly soluble in water but readily dissolved in
organic solvents. Tofu contain low saturated fatty acids and has relatively
higher poly unsaturated fatty acid content. This makes tofu good nutritional
source of the poly unsaturated fatty acids. Also tofu is cholesterol free.
Although cholesterol is the major sterol in the body and is a structural
component results in a higher risk of cardiovascular diseases (Potler et al.,
1996).
2.4.3.3 CARBOHYDRATES
Tofu
contains carbohydrates and sugars. Sugar are often called carbohydrates,
carbohydrates are polymers of monosaccharides and disaccharides, they serve as
the immediate source of the energy in the body (Troll et al., 2000).
2.4.3.4 VITAMINS
Vitamins
are small organic molecules in the diet that either cannot be synthesized in
humans or are synthesized at a rate less than that consistent with health
(Troll et al., 2000). They generally serve as precursors of certain cofactors
/coenzymes necessary for enzymatic reactions in the body. Tofu contains a
number of vitamins which include ascorbic acid (vitamin c) thiamin, riboflavin,
niacin, panthothenic acid, vitamin A, B12, and folate (folic acids) (Troll et
al., 2000).
2.5 ISOFLAVONE CONTENT OF TOFU
Isoflavone are a group of naturally
occurring heterocyclic phenols found in soy bean and its products. (Jackson et
al., 2002). Isoflavone such as diadzen, geinsten, glycetein and their
derivative (glucosidic conjugates which are 9 in numbers) have been isolated
from soy beans and products.
They
are also referred to as soy phytoestrogen and have been credited for performing
several health promoting functions. These phytoestrogens have effects on
cardiovascular health and are noted for cancer prevention (Jackson et al., 2002).
The isoflavones in Tofu are not in high quantities compared to raw soy bean or
soy beverage (soy milk). The reduction of isoflavone content in tofu is as a
result of the loss during the processing of soy bean into tofu. Despite the
loss of isoflavone it still contains some amount of isoflavones, which is
better than not occurring at all. Recent
investigation shows that the total recovery of isoflavone in tofu was
about 36% based on dry matter (Jackson et al., 2002).
2.6 LIME
Lime is a citrus fruit. The juice fruit,
peel, and oil are used to make medicine, oil pressed from the crushed fruit is
known as distilled lime oil (Kanerva, 2000).
2.5.1 CHEMICAL/ INDUSTRIAL USES OF LIME
The chemical industry uses lime in the
production of variety of chemical including sodium alkalis, calcium, carbide,
cyanide, citric acid, petrochemicals, propylene, glycol glycerin, magnesia,
calcium hypo chlorite and many others. These chemicals are used in virtually
every product in the United States (Kanerva, 2000).
A growing use for lime is the production
of precipitated calcium carbonate, which is used in the production of paper,
paint, ink, plastic, rubber and purification of water (Kanerva, 2000).
2.6 MORINGA OLEIFERA SEEDS
Moringa oleifera seeds are produced
annually in the tropical and sub tropical countries of Asia and Africa. Like
the rest of the plant, they are highly valued, as they give us incredibly
nutritious moringa tree. The moringa oleifera tree also known as the tree of
life, and has a host of nutritive uses for both people and livestock alike.
2.6.1 USES OF MORINGA OLEIFERA SEEDS
Fresh
moringa seeds are usually quite soft and yield with strong pressure. If the
moringa seeds are to be used for oil extraction, the seeds are harvested and
immediately processed. The fresh soft seeds are broken into pieces and heated
with water, and they are pressed for oil. Moringa seeds contain between 30-42%
and the pressed cake obtained as a byproduct of oil extraction process contains
a very high level of protein some of these proteins are active cationic
polyelectrolyte that neutralize the colloids in muddy water since the majority
of these colloids have negative electric charge. This protein can therefore be
used in the purification of drinking water, (Zarkadas, 2005).
2.7 ALUM
Alum is a double sulphate of potassium
and aluminum with chemical formula K2SO4. Al2(SO4)3.24H2O
Alum are useful for a range of
industrial process. They are soluble in water; have a sweetish taste
2.7.1 INDUSTRIAL USES
Alum has been used at least since Roman
times for purification of drinking water and industrial process water. Between
30 and 40 ppm of alum for household waste water, often more for industrial
waste water is added to the water so that the negatively charged colloidial
particles clump together into ‘flocs’ and settles to the bottom of the liquid,
or can be more easily filtered from the liquid (Austin, 1984).
2.8
TAMARIND
Tamarind,
tamarindus indica is a multipurpose
tropical fruit tree used primarily for its fruits which are eaten fresh or
processed, used as a seasoning or spice, or fruits and seeds are a seasoning or
spice, or fruits and seeds are processed for non-food uses. Tamarind is known
as tsamiya in Nigeria and belongs to the dicotyledonous family leguminosae
which is the third largest family of flowering plants.
Whole
tamarind seed and kernels are rich in protein (13-20%) and the seed coat is
rich in fibre (20%) and tannins 20%.
It also contains 14-18% albuminoid
tannins located in the testa.
Tamarind seed is a by –product of the
commercial utilization of the fruit, however, it has several uses. In the past
the seeds have be wasted. In 1942, two Indian scientists, T.P. Ghose and S.
Krishma announced that the decorticated kernels contained 46-48% of a
gel-forming substance. Dr. G.R. Savur of the pectin Manufacturing company,
Bombay, patented a process for the production of a purified product, called
jellose; polyose; or pectin, which was found to be superior to other methods of
fruits preservation. The substance gelatinizes with sugar concentrates even in
cold water or milk (Savur, 1998). It has been recommended for use as a
stabilizer in ice cream, mayonnaise and cheese and as an ingredient or agent in
a number of pharmaceutical products (Savur, 1998).
CHAPTER
THREE
3.0 METHODOLOGY
3.1 MATERIALS
3.1.1. Samples: The samples were
obtained from Kakuri market. The samples included soy beans, coagulants (such
as lime juice, tamarind seeds, alum and moringa oleifera seeds) vegetable oil,
salt, pepper (fresh) onion, magi
3.1.2 EQUIPMENT
|
Cheese cloth
|
Nutrient agar
|
|
Thermometer
|
Potato dextrose agar
|
|
Electric blender
|
Pipette
|
|
Stove
|
Burette
|
|
Stirrer
|
Volumetric flask
|
|
Cooking pots
|
Cotton wool
|
|
Bowl
|
pH meter
|
|
Cooking spoon
|
Eosine methyline blue (EMB)
|
|
Knife
|
|
|
Oven
|
|
|
Murfle furnace
|
|
|
Weighing balance
|
|
|
Soxhlet apparatus
|
|
|
Dessicator
|
|
|
Petri dishes
|
|
|
Glass slide
|
|
|
Mortar & pestle
|
|
|
Sieve
|
|
|
Test tubes
|
|
|
Auto clave
|
|
|
Aluminum foil
|
|
|
Water bath
|
|
|
Centrifuge
|
|
|
Syringe
|
|
3.2 PREPARATION OF COAGULANTS
3.2.1 Moringa
oleifera seeds were dehulled after which it was weighed and was introduced into
a pot to be toasted for 3 minutes. The seeds were milled to powdered form, the oil
was extracted by the manual method. The seed cake was then used as a coagulant
PREPARATION
OF MORINGA SEED CAKE EXTRACT
Moringa oleifera seeds
Dehulling
Weighing
Toasting (3 minutes)
Milling
Extraction (hydraulic
press method)
Moringa oleifera seed cake extract
Flow
chart for the preparation of moringa oleifera seed cake extract
3.2.2.
TAMARIND SEEDS: The dry tamarind seeds also known as
tsamiya was sorted, then the seeds was soaked in water for 2 hrs. The seeds were separated from the juice and
the juice was used as a coagulant.
PREPARATION
OF TAMARIND SEEDS JUICE
Tamarind seeds
Sorting
Soaking (2hrs)
Sepeartion (removing the seeds
Tamarind juice
Flow
chart for the preparation of Tamarind (Tsamiya) seeds
3.2.3 LIME
The lime fruits were cut into halves and
the juice was extracted from the fruits by hand squeezing. The extract was
passed through a sieve and the collected filtrate was used as a coagulant.
3.2.4 ALUM
The alum was crushed and milled to
powdered form, which was then used as a coagulant.
3.3 PREPARATION OF SOY MILK
SOY BEAN SEEDS
SORTING
WEIGHING
|
STEEPING
DEHULLLING
CLEANING
WASHING
MILLING
|
FILTRATION
SOYMILK
Flow
chart for soy milk production
Source: (Harlord, 2004)
3.4 PREPARATION OF SOY CURDS
SOY MILK
|
PASTEURIZATION
 |
|||
 |
|||
COAGULATION
|
COOKING
DRAINING
|
|
MIXING
|
PRESSING
SOY CURD
CUTTING
PACKAGING
STORAGE
Flow
chart for soy curd production
3.4.1
METHOD OF PRODUCTION OF SOY CURD
a. SORTING: the soy beans were carefully
sorted manually by hand picking the
dirts stones and bad seeds on the tray
b. WEIGHING: 2kg of the sorted seeds was
weighed out with weighing scale
c. STEEPING: the sorted soybean was
steeped in water for six hours. This is done
to ease dehulling
d. DEHULING:- The seed coats of the
soybean was removed manually by rubbing
the soaked seeds between the palm in a bucket.
e) WET CLEANING: Rinsing and draining was carried out several times to ensure complete removal of see the seed
coats.
f) WET MILLING: it was then milled into paste using a milling machine
g) MIXING: water was added to the paste
and was mixed thoroughly using a wooden
stirrer to avoid lumps during extraction.
h) FILTRATION: the paste was passed
through a muslin cloth cheese cloth and
the soy milk was obtained as the
filtrate.
i) PASTEURIZATION: the soy milk was
transferred into a clean pot and was pasteurized
into a clean pot and was pasteurized at 900c for 5 minutes
j) ADDITION OF COAGULANT: prior to
Pasteurization the soymilk was divided
into equal portions, and to each portion a coagulator was used.
k) COOKING: after the addition of the
coagulant, the soymilk was allowed further cooking until there curd
formation
l) DRAINING: the curds formed at the top
were introduced into the muslin cheese clothe. The curds were allowed to
drain through the cheese cloth
m) MIXING: the curds, salt and spices were
mixed thoroughly in the muslin cloth
to allow even distribution of the spices in the curds.
n) PRESSING: the cheese clothe was folded
over the curd and it was pressed to expel
all the whey possible from it
0) CUTTING: the soy curd formed was cut
into regular shapes
p) PACKAGING: the soy curds was properly
wrapped in polyethylene bags.
q) STORAGE: the soy curds was stored in
the refrigerator at about until it is needed
for further analysis.
3.4.2
TABLE 2: TABLE OF FORMULATION FOR
PRODUCT
|
Coagulants
|
Used
|
Volume of soymilk
|
|
|
|
|
|
ASC
|
15g
in 1L (1000mls)
|
10
litres
|
|
MSC
|
200g
in 1L (1000mls)
|
10
litres
|
|
TSC
|
200g
in 1L (1000mls)
|
10
litres
|
|
LSC
|
200g
in 1L (1000mls)
|
10
litres
|
INGREDIENT
USED
|
Ingredients
|
ASC
|
MSC
|
TSC
|
LSC
|
|
|
|
|
|
|
|
Maggi
|
16g
|
16g
|
16g
|
16g
|
|
Onion
|
50g
|
50g
|
50g
|
50g
|
|
Pepper
|
50g
|
50g
|
50g
|
50g
|
|
Salt
|
5g
|
5g
|
5g
|
5g
|
3.5
PROXIMATE ANALYSIS ON TOFU (SOY CURD).
3.5.1
MOISTURE CONTENT DETERMINATION
About 2g of each tofu made from
different coagulants was weighed into pre weighed oven dried petridishes which
were later transferred into the oven and dried at 1000c for 5 hours.
The dried samples were cooled in the desiccator and the loss in weight was
expressed as percentage moisture (AOAC, 2000).
%MC = 
x 100
x 100
Where W1 = initial weight of
empty dish
W2 = weight of dish + sample before
drying
W3 = final weight of dish + sample
after drying
3.5.2
ASH CONTENT DETERMINATION
About 5g of each tofu coagulants was
weighed into pre weighed oven dried crucibles. The crucibles were placed in the
pre heated murfle furnace at 5500c. The sample was left for 3 hours
or more for complete ashing.
The crucible was removed and cooled in a
desiccator and weighed (AOAC, 2000)
% Ash = weight of ash residue after
ignition x 100
Dry
weight of sample
3.5.3 FAT CONTENT DETERMINATION
5g of each tofu samples was weighed
accurately into labeled thimbles. The boiling flasks was filled with about
350ml of petroleum ether (boiling print 40-60oc) The extraction thimble was
pluged lightly with cotton wool. The soxhlet apparatus was assembled and reflux
was allowed for 6 hours. The thimble was removed with care and the petroleum
either was collected in the top container of the set up and was drained into a
container for re-use. The samples were extracted for 15 minutes in boiling
position. This was cooled and reweighed (AOAC, 2000).
% fat = weight
of fat x 100
Weight of sample
3.5.4 PROTEIN DETERMINATION OF TOFU
Kjedahl nitrogen method was employed for
protein determination. 1g of the Tofu sample was weighed into the digestion
flask. Abort 5 tablets of Kjedahl catalyst was added to the samples. 20ml of
concentrated H2S04 acid was added to the sample and then
fixed for 8hours in the digestion unit [450oc) of the kjedahl
apparatus in fume cupboard. The digest pure yellow after cooling changed into a
colourless liquid that was transferred into 100ml volumetric flask and made up
the mark with distilled water. About 20ml of 4% boric acid solution was pipetted
into a conical flask. A drop of methyl red was added to the flask as indicator.
The sample was thereafter distilled with 7.5ml of distilled water. About 10ml
of the digest was made alkaline with 20ml of NaOH (20%) and distilled. The
steam exit of the distillatory was closed and the change of colour and solution
to green was timed. The mixture was distilled for 15 minutes (AOAC, 2000).
The
filtrate was then against 0.1 NHCl
%Nitrogen Titre x N acid x 0.014 x 100
Weight of sample
Where N acid = normality of acid
(0.1) N
%crude protein = N x (conversion
factor)
3.5.5 CRUDE FIBRE DETERMINATION
200ml of boiling 1.25% H2SO4
was added to about 2g of the sample. This was followed by boiling for 30
minutes. This was then filtered through poplin cloth by sunction using Buchner funnel.
Thereafter, it was rinsed with boiling water.
The samples were then retrieved into the flask, and 200ml boiling
water. The samples were returned to the
flask and 200ml boiling 1.25% NaOH was added. This was boiled for 30 minutes
and the samples were filtered and the washed with distilled water and twice
with methylated spirit and thrice with petroleum other. The residued was
transferred into an oven dried cruible of known weight, then placed in the oven
and dried at 105oc. It was cooled in a desiccators and the weight was
determined. Thereafter the samples were transferred into the murfle furnace at
about 450oc for about 3 hours. This was followed by cooling to room
temperature and the weight and
percentage were subsequently determined (AOAC, 2000).
%fibre = weight loss after incineration X 100
3.5.6. DETERMINATION OF CARBOHYDRATE
This was determined by subtracting from
100 the sum of the percentage moisture ash, fibre, protein and fat.
%Carbohydrate = 100 – (sum of moisture,
protein, ash, fibre and fats)
(AOAC,
2000)
3.6 PHYSIOCHEMICAL PROPERTIES ON TOFU
3.6.1 YIELD OF TOFU
The yield was expressed in volume of
fresh tofu obtained from 100g of soya beans. The yield of the total dry matter
and protein in tofu were calculated was follows (shurtleff et al., 2004)
% Total dry matter yield = Dry matter in tofu x 100
Dry matter in soya bean
3.6.2 PH MEASUREMENT
5g
of the soy curd (Tofu) was introduced into 50ml distilled water, and allowed to
stay for 30 minutes. In 40oc water bath. The pH was measured with a
pH meter (Onwuka, 2005).
3.6.3. DETERMINATION OF TOTAL TITRATIBLE ACIDITY
Acidity may be expressed in term of
hydrogen in concentration, a solution is being described as acidic if it’s
hydrogen ion concentration is greater than 10-7, a solution is
basic, if it’s hydrogen ion concentration is less than 10-7.
Acidity is more conveniently expressed
in terms of pH.
Procedure
10ml of the dissolves samples was
pipette into a conical flask. The sample was titrated against sodium hydroxide
(01N Na0H) using 2 drops of phenolphthalein as indicator (AOAC, 2005).
Titratable acidity T.A% = V x 0.007 x 100.
V= ml of NaOH Vs
3.6.4 CURDLING TEMPERATURE DETERMINATION
The
curdling temperature was determined when curdling was noticed with a
thermometer and the reading was noted (ONWUKA, 2005).
3.6.5 THE DETERMINATION OF COMPRESSION
The thickness of the soy curds samples
were noted before and after a known weight was placed on the samples.
% compression = difference in
thickness x 100
Original
thickness
% fibre = weight loss after incineration
x 200
3.7 MICROBIOLOGICAL ANALYSIS ON SOY CURD (TOFU)
3.7.1 STERILIZATION OF GLASS WARES AND MEDIA:-
All the glass wares were washed and
rinsed properly. All glass wares as well as other equipment coming in contact
with the samples were sterilized by autoclaving, until they are needed to be
used.
3.7.2 MICROBIAL ANALYSIS
The
standard method of WHO and FAO, 1986 was employed. About 1g of the soy curd
samples was aseptically weighed using a weighing balance and carefully
introduced into 9ml of sterile distilled water. This was shaken manually in
order to have a homogenous suspension. 1ml of this was taken and introduced
into the second tube, followed with series of dilutions up to 10-10
dilution. 1ml was taken 10-4 dilution and introduced into sterile
plates and molten agar (50oc) added by pour plate method using the
following agar and incubation periods.
Nutrient
Agar: This was used for the determination of total viable
bacteria in the sample. The plates were incubated at 37oc for
24-48hrs.
McConkey
Agar:- This was used for the enumeration of total coliform
organisms in the sample. The plates were incubated at 35oc for 24 –
48 hours.
Potato
Dextrose Agar:- This was used for the enumeration of
mould and yeast in the sample. The plates were incubated at 30oc for
24 hours for yeast and 2-5 days for mould.
3.8 SENSORY EVALUATION
Four
(4) samples of tofu (soy curd) were subjected to the test for sensory
evaluation base on appearance, aroma, texture, taste and overall acceptability.
The panelist composed of 15 judges which
include lecturers from the department and other departments assessed the
provided coded samples. The panelist were given a form to fill.
A
9. Point hedonic scale was used in the sensory evaluation. The scores ranged
from 9. like extremely; 8: Like very much; 7; Like moderately; 6; like
slightly; 5; Neither like nor dislike; 4; Dislike slightly; 3 Dislike slightly;
4: Dislike moderately: 2: Dislike very much; 1: dislike extremely.
4.0 CHAPTER
Four
4.1 RESULT
|
Figure 1: The soy cheese yield of selected coagulants  |
ASC- Alum coagulated soy cheese
MSC – Moringa seed cake extract
coagulated soy cheese
TSC- Tamarind coagulated soy cheese
LSC - Lime coagulated soy cheese
Table: 3 proximate composition of soycheese
produced with some selected coagulants
|
Sample
|
ASC%
|
MSC%
|
TSC %
|
LSC %
|
|
|
|
|
|
|
|
Moisture
|
59.0
|
61.5
|
69.0
|
64.0
|
|
Protein
|
15.3
|
20.4
|
17.0
|
18.7
|
|
Fat
|
4.9
|
6.2
|
5.5
|
5.2
|
|
Crude fibre
|
1.5
|
2.5
|
2.0
|
3.0
|
|
Ash
|
3.2
|
2.2
|
2.0
|
2.8
|
|
Carbohydrate
|
16.1
|
7.2
|
4.5
|
6.8
|
Table
4: Physico –chemical properties of the produced soycheese from some selected
coagulants
|
Sample
|
ASC%
|
MSC%
|
TSC %
|
LSC %
|
|
|
|
|
|
|
|
pH
|
5.26
|
5.67
|
5.00
|
5.62
|
|
Curdling temperature (oC)
|
100
|
100
|
100
|
100
|
|
Titratible acidity (%)
|
0.25
|
0.35
|
0.21
|
0.29
|
|
Compression (%)
|
73.0
|
78.5
|
64.0
|
76.0
|
|
Yield %
|
9
|
8
|
10
|
11
|
Table
5: Microbial results of or yeast and moulds of the produced soy cheese from
some selected coagulants
|
|
Sample code
|
Colonies
|
Cfu/g
|
Grams reaction
|
Identification of organism
|
|
|
ASC
|
47 x 101
|
4.7 x 102
|
Gram positive oval shaped cells
|
Yeast species
|
|
|
MSC
|
130 x 101
|
1.3 x 10-2
|
Gram positive oval shaped cells
|
Yeast species
|
|
|
TSC
|
7 x 101
|
<1.0 x 102
|
Gram positive oval shaped cell
|
Yeast species
|
|
|
LSC
|
22 x 101
|
2.2 x 102
|
Gram positive oval shaped cell
|
Yeast species
|
Code
ASC- Alum coagulated soy cheese
MSC- Moringa seed cake coagulated soy
cheese.
TSC- Tamarind coagulated soy cheese.
LSC- Lime coagulated soy cheese.
Table
6; microbial results for mesophibic bacteria on the produced soy cheese from
some selected coagulants
|
Sample code
|
Colonies
|
Cfu/g
|
Grams reaction
|
Organism isolated
|
|
|
|
|
|
|
|
ASC
|
10 x 101
|
1.0 x 102
|
Gram positive rod
|
Bacillus species
|
|
MSC
|
61 x 101
|
6.1 x 102
|
Gram positive rod
|
Bacillus species
|
|
TSC
|
12 x 101
|
1.2 x 102
|
Gram positive rod
|
Bacillus species
|
|
LSC
|
5 x 101
|
<1.0 x 102
|
Gram positive rod
|
Bacillus species
|
Table:
7 microbial result for coliform count
|
Sample code
|
colonies
|
Cfu
|
Grams reaction
|
Organism isolated
|
|
|
|
|
|
|
|
ASC
|
NIL
|
NIL
|
|
organism isolated
|
|
MSC
|
NIL
|
NIL
|
|
No coliform isolated
|
|
TSC
|
NIL
|
NIL
|
|
No coliform isolated
|
|
LSC
|
NIL
|
NIL
|
|
No coliform isolated
|
Table
8: sensory evaluation on soy cheese produced from some selected coagulants.
|
Sample
|
ASC
|
MSC
|
TSC
|
LSC
|
|
|
|
|
|
|
|
Appearance
|
8.20
|
8.67
|
6.73
|
8.67
|
|
Aroma
|
8.00
|
8.40
|
7.13
|
8.07
|
|
Texture
|
7.93
|
8.40
|
7.33
|
8.20
|
|
Taste
|
8.13
|
8.40
|
7.13
|
8.13
|
|
Overall acceptability
|
8.27
|
8.53
|
7.40
|
8.53
|
ASC: Alum coagulated soy cheese
MSC: Moringa seed cake coagulated soy
cheese
TSC: Tamarind coagulated soy cheese
LSC: Lime coagulated soy cheese
Soy curd is made by coagulation of soy
milk with salt or acid to produce soy protein gel, which traps water, soy
lipids and other constituents in the matrix.
The result of the tofu yield is shown in
figure 1, the result revealed that there was no significant difference in the
tofu yield by each of the coagulant, however lime gave the highest yield of soy
curd (11%), while moringa oleifera gave the least yield of soy curd. This is indication
that the selected coagulants under consideration may not differ substantially
in their coagulating ability, however, the slight difference could be as a
result of extraneous substance introduced by the coagulants.
The protein content of the soy curds
produced are 15.3%- 20.4% as shown in table 3. The high protein content of the
moringa oleifera seed cake extract (20.4%) coagulated soy curd could possibly
be attributed to the likelihood that the protein in the moringa seeds might
have been transferred into the soy curd unlike alum, which is salt.
Furthermore, the protein content of the
tofu produced using all these coagulants had higher protein content than that
of the commercial soy curd (12%) reported by Prestamo et al, (2002), this
variation could be as a result of the difference in the variety of soybean and
the condition under which the coagulation was carried out.
The fat content of moringa oleifera seed
cake extract soy curd was higher than that of lime (5.2%), tamarind (5.5%) and alum
(4.9%) coagulated soy curd. The higher fat content in the moringa soy curd is however lower than
the value (9%) reported by Prestamo et al, 2002 for some commercially purchased
tofu.
The ash content of the produced soy
curds are 3.2%, 2.2%, 2% and 2.8% for
alum, moringa, tamarind and lime respectively.
The result of the microbial analysis
shows that the prepared soy curds are acceptable for consumption with no
coliform bacteria isolated. The products are within the acceptable range of
consumption.
The result of the sensory evaluation is
shown in table 8. The result revealed that moringa oleifera seed cake extract
coagulated soy curd and that of lime is significantly different in overall
acceptability at P<0.05 level of significance than alum and tamarind
coagulated soy curd as typified by the appearance aroma, texture, and taste.
The low acceptability of tamarind coagulated tofu compared to others could be
attributed to the colour and taste on the soy curd.
The acceptability of the aroma of moringa
oleifera seed cake extract (8.4) is higher than lime (8.07), alum (8.00) and
tamarind (7.13) coagulated soy curd.
5.0
CHAPTER
FIVE
5.1
CONCLUSION
The result of the present study
indicated that moringa oleifera seed cake extract coagulated soy cheese when
compared to other coagulants is a better coagulant for the production of soy
cheese with high nutritional value and hypocholesterolemic effect.
Moringa oleifera seed cake extract and
lime coagulated soy cheese has the highest overall acceptability, while
tamarind coagulated soy cheese has the least. Therefore, further research will
be carried out on how to improve the sensory qualities of tamarind coagulated
soy cheese.
5.2
RECOMMENDATION
In view of the various health benefits
associated with soy cheese, it should be introduced into the Nigerian diet. Its
intake should be also be encourage in homes.
Soy cheese can be used as a functional
food to prevent oxidative stress due to its antioxidant properties and also in
the treatment of liver damage hypercholesterolemia and arteriosclerosis
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