PRODUCTION OF YOGHURT FROM LENTILS

PRODUCTION OF YOGHURT
FROM LENTILS
MURIMI RACHEL NJERI
AG 221-0005/2013
BSc. FOOD SCIENCE AND
TECHNOLOGY
JOMO KENYATTA UNIVERSITY OF
AGRICULTURE AND TECHNOLOGY
2016
ABSTRACT
The project involves making yoghurt from lentils “Lens culinaris” which are
highly nutritious. It aims at countering the problem of widespread malnutrition in
the drier parts of Kenya as well as increasing the utilization of the pulse. This will
also provide lactose intolerant people and those with milk protein allergies with a
new option for consumption. The activities to be carried out include:
Determination of the crude protein content through the Kjeldahl method,
measuring pH using a pH meter, determination of the acidity content through
titration against sodium hydroxide, mineral analysis by atomic absorption
spectroscopy and shelf life studies. The expected outcome of the study is to
provide information on a product that can be used in the battle against malnutrition
as well as increasing the utilization of lentils. The yoghurt is expected to have a
thick consistency and an earthy flavor. Both the milk and yoghurt should have a
creamish colour.
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1. INTRODUCTION
1.1. BACKGROUND INFORMATION
Lentils “Lens culinaris” are an edible pulse and are bushy annual plants that
belong to the legume family known for their lens-shaped seed. The lentil plant is
about 40 cm tall, and the seeds grow inside pods usually about two seeds in each
and every pod.
1.1.1 History
Lentils are believed to have originated in central Asia, having been consumed since
prehistoric times. They are one of the first foods to have ever been cultivated.
Lentil seeds dating back 8000 years have been found at archeological sites in the
Middle East. Lentils were mentioned in the Bible both as the item that Jacob traded
to Esau for his birthright and as a part of a bread that was made during the
Babylonian captivity of the Jewish people.
For millennia, lentils have been traditionally been eaten with barley and wheat,
three foodstuffs that originated in the same regions and spread throughout Africa
and Europe during similar migrations and explorations of cultural tribes. Before
the 1st century AD, they were introduced into India, a country whose traditional
cuisine still bestows high regard for the spiced lentil dish known as dal. In many
Catholic countries, lentils have long been used as a staple food during Lent.
Currently, the leading commercial producers of lentils include India, Turkey,
Canada, China and Syria.
Lentils have been part of the human diet since aceramic Neolithic times, being one
of the first crops domesticated in the Near East. Archeological evidence shows
they were eaten 9,500 to 13,000 years ago.
1.1.2 Growth conditions
Lentil plants are slender, semi-erect annuals with compound leaves (4 to 7 pairs of
leaflets) with a tendril at the tips. Plants normally range from 12 to 20 in. tall, the
taller plants resulting from cool growing season temperatures, good moisture and
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good fertility. Plants can have single stems or many branches depending upon the
population in the field.
Flowering begins on the lowest branches, gradually moving up the plant and
continuing until harvest. Each flower produces a short pod containing one or two
lens-shaped seeds. Flowers can be white, lilac or pale blue in color and are selfpollinated. At maturity plants tend to lodge because of their weak stems.
Lentil produced in North America has larger seeds than that from India and the
Near East. The seeds (2 to 7 mm in diameter) come in colors of tan, brown, or
black, and some varieties produce purple or black mottled seeds. Lentil seed
number varies from 15,600 to 100,000 seeds/lb.
Environment Requirements
Climate:
Lentil is adapted to cool growing conditions, and the young plants are tolerant of
spring frosts. This allows for early spring planting dates.
Lentils have been grown extensively in the semi-arid parts of the world, where
they have slightly lower yields, but good seed quality. High humidity and
excessive rainfall during the season encourages vegetative growth, which prevents
good yield and can reduce seed quality. 300-500 mm of annual rainfall will
produce high yields of good quality seed. Excessive drought and/or high
temperatures during the flowering and pod-fill period also reduce yields. Soil:
Lentil is adapted to all soil types, from sand to clay loam, if there is good internal
drainage. Lentil does not tolerate flooded or waterlogged soils, and does best on
deep, sandy loam soils high in phosphorus and potassium. Good drainage is
required, because even short periods of exposure to waterlogged or flooded field
conditions kill plants. A soil pH near 7.0 is best for lentil production.
Seed Preparation and Germination:
Unless nodulated field pea or lentil has been grown recently on a field, the seed
should be inoculated with Rhizobium leguminosarum just prior to planting (within
24 hours). Follow the instructions for inoculation, and protect treated seed from
high temperatures and drying winds until planted. Various forms of inoculant are
available, some of which can be placed in the furrow with the seed.
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Good quality lentil seed does not need to be treated with insecticides or fungicides,
because it germinates rapidly and seedlings emerge quickly. Seed treatment
compounds can interfere with the nodulation process.
Cultural Practices:
Seedbed Preparation:
A firm, smooth seedbed with most of the previous crop residue incorporated is best
for lentil. Uneven surfaces, large clods, rocks or protruding crop residue can
interfere with seed placement and complicate later swathing and combining.
Seeding Date:
Lentil should be seeded in late April to early Mail when small grain is being
planted. Later seeding dates produce shorter plants and late maturing pods which
increase harvest losses.
Method and Rate of Seeding:
Lentil should be planted 40cm deep, but this can be increased to 60 mm when the
upper layers of soil are excessively dry at planting time. Because of the small seed
size of some varieties, lentil cannot emerge if planted too deep or if the soil has
crusted extensively. Lentil has hypogeal emergence, which means that the growing
point emerges but the cotyledons remain in the soil.
Seeding rates vary depending upon seed size, but a target population of 400,000
plants/acre should be reasonable.
Because of the fragile growth habit of lentil and the fact that the crop does not
compete well with weeds, the best yields are from fields planted with a grain drill
which can ensure proper depth and distribution as well as good seed-soil contact.
Because of seed size variation, care must be taken to calibrate the drill properly.
Fertility and Lime Requirements:
Inoculation with the proper Rhizobium will provide the nitrogen requirements of
lentil. However, if available nitrogen is low (organic matter less than 2%), an early
nitrogen supplement of about 40 kg/ha is required to sustain the young plants until
root nodulation develops.
As for most legumes, sulfur needs are medium to high, and responses may be seen
on light colored sandy soils where manure has not been applied.
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Phosphorus and potassium are recommended for maximum yields on soils testing
medium or low. Optimum soil tests range 15 to 30 ppm for P and 90 to 120 ppm
for K for most soils. Band applications of P may be of some benefit on very low P
or high pH (above 7.6) soils.
Lime needs for lentil have not been well established. However, it is likely similar
to that of other leguminous vegetables - 6.0 on mineral soils and 5.6 on organic
soils.
Variety Selection:
Growers should consider maturity, growth habit, seed size and color as well as
yield potential when selecting a variety of lentil. Currently buyers prefer lentils
with larger seeds that are light in color and without mottling on the seed coat.
Weed Control:
Lentil is not very competitive (especially as seedlings) with many of the grasses
and/or broadleaf weed species that infest farm fields, so weed control before
planting and early in the growing season is critical.
Mechanical: Harrowing or rotary hoeing fields after emergence is recommended
only if there is a serious weed problem. Because of the slender early stem growth,
the plants are easily damaged at this time. If harrowing or hoeing is planned, be
sure to use the recommended seeding rates discussed earlier because the plant
stand will be reduced slightly along with the weeds. Rotary hoeing is normally
done 7 to 10 days after seeding.
Chemical: Glyphosate can be used as a preplow treatment to control quack grass.
Diseases and Their Control:
Ascochyta blight, Sclerotinia (white mold), Fusarium root rot and Rhizoctonia root
rot are possible disease problems for lentil. Since no effective treatment is
available for these diseases, crop rotation is the most effective method of
preventing a disease problem.
Avoid faba bean, fieldbean, field pea, mustard, canola, rapeseed, soybean,
sunflower, sugar beet and potato in too close a rotation, because these crops are
susceptible to the same diseases. Corn and small grains are good rotation crops in
conjunction with lentil. Some scientists feel a three to four-year rotation away from
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lentil is best for reducing disease problems. Always use good quality disease-free
seed to prevent introduction of disease into clean fields.
Insects and Other Predators:
Lentil can be attacked by aphids, thrips, Lygus bugs, seedcorn maggots and
wireworms, but major problems from these insects are seldom noted. If a serious
problem is developing in a field, you should consult your local Extension office for
information about obtaining threshold values and recommendations for control.
Harvesting:
Lentil should be swathed when plants begin to turn yellow and the lower pods
become brown to yellow-brown in color. This will occur within several days and
should be carefully watched, as pods can readily shatter. Lentil should be swathed
when there is sufficient moisture to toughen the pods. Swathing should not be done
during hot, dry periods of the day.
Lentil has a weak stalk and tend to lodge badly. This means that low cut is required
in order to minimize losses. Windrowing can be a very slow and difficult
operation. A dry field surface which is level, firm and free of stones is necessary to
reduce harvesting difficulties. A pick-up reel and lifter guards are very helpful
when windrowing. A floating cutterbar mounted on a windrower can further
minimize windrowing losses and difficulties.
Depending on the weather, windrowed lentil may take a week or more to dry
down. Since the lentil windrow has no strong stubble to hold it off the ground, air
circulation through the windrow is poor. This may result in seed discoloration and
mold development during periods of extended wet weather.
Lentils are considered dry at 14% moisture content. Combining at this moisture
level can result in high losses and damaged seeds. It may be advisable to combine
at a higher moisture content of 18 to 20%, and dry artificially.
If the field is uniformly mature, it is possible to combine lentil directly. This
should only be attempted at moisture levels of 18 to 20%, to prevent excessive
preharvest shattering. A combine equipped with a floating cutterbar should be used
to minimize header losses.
Once in the combine, lentils thresh easily. Compared to wheat settings a slower
cylinder speed is necessary to prevent cracking, and the concaves should be set
wider. Initial wind and sieve settings for wheat may be used.
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Drying and Storage:
If lentil seed is harvested at moisture contents greater than 14%, it will have to be
dried to prevent heating and molding in storage. It is best to let the seed dry down
in the field, if the drier plant material can be handled by the combines without
major losses due to shattering of the pods.
Lentils can be dried in heated air dryers, but a maximum temperature of 110°F is
recommended to reduce cracking of seed coats. Natural air drying has advantages
over heated air, but proper design of the system is necessary. The design must
ensure good airflow through the seed, which usually means that thinner layers of
the seed must be used in this process.
Yield Potential and Performance Results:
Yields vary with variety, management and environmental conditions. Under good
research management and excellent growing conditions, lentils may yield up to 500
kg/ha.
Yield of lentils can be calculated as follows:
Number plants per m2 x pods/plant x seeds/pod x seed mass (g) 100
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1.2PROBLEM STATEMENT
The main issues that this study is trying to combat includes:
 Widespread malnutrition especially in the drier parts of the country.
 Underutilization of lentils in Kenya.
 Lack of milk substitutes for lactose intolerant people and those with milk
protein allergies.
According to UNICEF, more than 1 million people remain food insecure in Kenya.
This includes 239,446 children suffering from moderate acute malnutrition (MAM)
and 2,600 children suffering from severe acute malnutrition (SAM) that are
receiving treatment every month. The main indicator of childhood malnutrition is
stunting—when children are too short for their age due to inadequate intake of the
required nutrients over a long period of time. Stunted children have poor physical
growth and brain development, preventing them from thriving and living up to
their full potential. With an estimated 2 million (26%) stunted children under the
age of 5, Kenya is facing a crisis of malnutrition. It mainly affects children from
Kitui, Isiolo, Marsabit and Turkana counties.
Underutilization can be due to lack of information on potential food uses. Lentils
are mainly consumed whole after boiling for about 30-45 minutes. The hard- to cook phenomenon of most legumes due to the hard testa of some of the legumes
has led to under-utilization of lentils. The presences of anti-nutritional factors such
as phytates which affect digestion and cause flatulence have also limited
consumption of lentils by people. Some research studies have shown that removal
of the outer testa will reduce some of these effects.
Cow’s milk is made up of lots of different components, for example proteins (such
as casein and whey), lactose and fat. The allergic reaction happens because the
immune system mistakes the proteins in cow’s milk to be a threat. It then releases
chemicals such as histamines and others which trigger the signs and symptoms of
an allergic reaction. However, lactose intolerance is triggered by the lactose sugar
in cow’s milk. In people with lactose intolerance, the digestive system can’t fully
digest this milk sugar, because it doesn’t make enough of the lactase enzyme. So
instead of being digested and absorbed, the lactose stays in the gut and feeds the
gut bacteria, which release acids and gases that cause the symptoms of lactose
intolerance.
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1.3 JUSTIFICATION
In order to curb the stated problems, there is a need for the study of production
of yoghurt from lentils. This is backed by the countless number of benefits that
can be gained from the legumes.
Lentils play an important role in human nutrition since they are rich and
economical sources of good quality protein, calories, certain minerals and
vitamins. They are inexpensive, nutrient dense sources of plant protein that can
be substituted for dietary animal protein. They also complement the lack of
some protein and micronutrients in most of the highly consumed cereals.
Due to the high nutritional content of lentils, malnutrition evident in a large
number of children may reduce especially for those that are under 5 years old.
Stunting and wasting may therefore become an issue of the past and more
children may be able to achieve good cognitive and physical body development
allowing them to live upto their full potential. Implications such as immune
disorders will also go down and children may be able to enjoy education and
their childhood in general.
Due to the lack of information of other lentil uses other than consuming them
whole, the study aims at providing knowledge on other ways of utilizing the
lentils without compromising on their great benefits to human health. This may
encourage improved production of lentils in the country which may even reach
commercialization levels. It is intended that household utilization of the lentils
may increase a well.
As an added advantage, the starch and proteins in lentils are very easily
digestible and are not known to cause any problems with digestion nor the
immune system. Therefore, use of this legume as a hypoallergenic alternative to
milk is a good idea for those suffering from lactose intolerance and allergies to
the milk proteins; casein and whey.
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1.4 OBJECTIVES
1.4.1 Main objective
The main aim of this study is to make yoghurt from lentils.
1.4.2 Specific objectives
The following are the other objectives of the study:
1.To determine the effect of soaking on the antinutritional factors present in
lentils.
2. To determine the temperature-time combination required to process lentil
yoghurt.
3. To determine the culture to be utilized in making of the lentil yoghurt.
4.To determine the quantities of additives that will make a good and flavourful
product.
5.To determine the period of consumption before spoilage microorganisms
grow in the lentil yoghurt.
6.To compare the yoghurt qualities of 2 different varieties of lentils.
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2. LITERATURE REVIEW
2.1 Taxonomy of lentils
Kingdom : Plantae
Subkingdom : Tracheobionta
Superdivision : Spermatophyta
Division: Magnoliophyta
Class : Magnoliopsida
Subclass: Rosidae
Order: Fabales
Family: Fabaceae
Subfamily: Faboideae
Tribe : Vicieae
Genus : Lens
Species : L. culinaris
2.2Types of lentils
Lentil colors range from yellow to red-orange to green, brown and black.[1] Lentils
also vary in size, and are sold in many forms, with or without the skins, whole or
split.
They include:
1.Beluga
2.Brown/Spanish pardina
3.French green
4.Puy lentils
5.Dark/Light Green
6.Indianhead
7.Yellow/tan lentils (red inside)
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8.Red Chief (decorticated yellow lentils)
9.Eston Green (Small green)
10.Richlea (medium green)
11.Laird (large green)
12.Masoor (brown-skinned lentils which are orange inside)
13.Petite crimson/red (decorticated masoor lentils)
14.Macachiados (big Mexican yellow lentils)
The most commonly known type of lentils are expounded below;
Brown Lentils - This is by far the most common variety of lentil.They can range
in color from khaki-brown to dark black, and generally have a mild earthy flavor.
They cook in about 20-30 minutes and hold their shape very well. Common
varieties are Spanish Brown, German Brown, or Indian Brown. The blackest and
tiniest lentils you find are usually Beluga lentils, which have a rich and deeply
earthy flavor.
Green Lentils - These can be pale green-brown in color with a glossy exterior.
They have a somewhat peppery flavor. Green lentils generally take the longest to
cook, upwards of 45 minutes, but they keep a firm texture even after cooking.
Red Lentils - With colors ranging from orange to red, these are the sweetest and
nuttiest of the lentils. They're somewhere in the middle in terms of cooking time
and are usually done in about 30 minutes. They tend to get mushy when cooked .
2.2Production
World production
World lentil production has almost quadrupled since 1980 at an average annual
percentage growth rate of 2.9 percent over the period 1980 to 2012.
Lentil production for the major lentil producing nations has been trending upwards
during the past 7 years, ranging from 2.1 million tonnes (Mt) in 2002-2003 to
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2.9 Mt in 2009-2010. Among the main producers, production has been trending
upwards in Canada, the US, and Australia, but has been highly variable and
trending down in India, Bangladesh, Syria and Turkey. In the US, production
increased sharply when lentils were first included under the loan program in 2002.
Although specific data is not available on the types of lentils grown, an estimated
70% of world lentil production is the red type, 25% green type and 5% brown and
other types. Canada and the US are large producers of the green type whereas the
rest of the world produces mainly the red type.
Canadian lentil production has increased in response to market signals, which has
contributed to the diversification of crop production in the Prairie Provinces,
especially in Saskatchewan. The increase in lentil production has proven to be
valuable in crop rotations which help to control weeds, diseases and insects and
improve soil texture and fertility. The higher production has also contributed to the
expansion of the pulse crops handling, marketing and processing industry, which
has increased employment opportunities in rural areas. The province of
Saskatchewan accounts for more than 95% of Canadian lentil production. The
balance is produced in Alberta where area is increasing.
Canadian production reached a record of 1.51 Mt in 2009-2010. Canada is the
main producer of the green type of lentils in the world, accounting for about
75% of world production. Production of the red type has been increasing over the
years as the large major importing countries consume mostly the red variety. The
production shift towards the red variety reflects the higher demand for the reds
over the past several years from the large import countries in the Middle East and
Asia and the development of varieties suited to production in Western Canada. The
Canadian lentil harvest generally occurs during the period from mid-August to
early October.
2.3 Nutrition Profile
Lentils are a powerhouse of nutrition. They are a good source of potassium,
calcium, zinc, niacin and vitamin K, but are particularly rich in dietary fiber, lean
protein, folate and iron. Lentils are considered to be a good source of proteins. This
high protein content makes them a significant food source for developing countries
and low income people.
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One cup of cooked lentils has about:
 230 calories

18 grams protein

15 grams of fiber

3.5 grams sugar

less than 1 gram fat

358 milligrams folic acid (90 percent DV)
1 milligram manganese(49 percent DV)
6.6 milligrams iron (37 percent DV)










356 milligrams phosphorus (36 percent DV)
0.5 milligrams copper (25 percent DV)
0.5 milligrams thiamine (22 percent DV)
731 milligrams potassium (21 percent DV)
71 milligrams magnesium (18 percent DV)
0.4 milligrams vitamin B6 (18 percent DV)
2.5 milligrams zinc (17 percent DV)
1.3 milligrams vitamin B5 /pantothenic acid (13 percent DV)\
DV=Daily Value
2.4 Health benefits
1.Great Source of Fibre
Lentils contain both insoluble and soluble fiber and help improve heart, digestive
and immune function by carrying waste, excess fat and toxins out of the body.
2. Protects Heart Health
Since they are one of the best sources of soluble fibre, lentils are very beneficial
for lowing bad cholesterol and preventing heart disease. Researchers have found
that diets high in lentils prevent hypertension and tend to produce more favorable
cholesterol levels than diets lower in lentils. Maintaining healthy cholesterol levels
reduces damage done to your arteries and prevents dangerous plaque buildup,
which greatly lowers your risk of having a heart attack or stroke. They are also
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very low in both fat and sodium, other key factors that make up a heart-healthy
diet. Diets lower in sodium favour healthy blood pressure levels, as do the many
nutrients that lentils provide like folate, potassium and magnesium. Folate can help
to lower homocysteine levels, which is known to be a serious risk factor for heart
disease, while magnesium and potassium help improve circulation and carry
adequate oxygen and nutrients around the body.
3. Improves Digestive Health
With such high levels of dietary fibre, lentils to promote regular bowel
movements. The high level of insoluble fiber found in lentils absorbs water in the
digestive tract, swelling up and carrying waste out of the digestive tract. This
makes lentils a great digestive regulator and helps prevent constipation,
IBS(Irritable Bowel Syndrome) inflammatory bowel diseases, and
even diarrhoea.
4. Helps Alkalize the Body and Balance Its pH Level
Lentils are one of the most alkaline protein sources there is, which is important for
balancing the body’s pH level and promoting a healthy gut environment. Lentils
help combat the acidic environment of the gut and promote healthy bacterial
growth, which is important for nutrient absorption, indigestion, constipation and
many other diseases, too.
5. Helps Manage Blood Sugar Levels
Research indicates that the high level of soluble fiber found in lentils traps glucose
from carbohydrates and slows down digestion. This means lentils can help stabilize
blood sugar levels, which is important for preventing energy dips, mood changes,
and serious conditions like diabetes, insulin resistance or hypoglycemia. One of the
keys attributes of lentils nutrition is their low starch content. Lentils contain only
about 35 percent digestible starch, and the remaining 65 percent is classified as
resistant starch, the type that essentially escapes digestion and absorption in the
small intestines because a high level of lentils’ carbohydrates and glucose cannot
be digested in the body. They have a very low impact on blood sugar compared to
refined grains and packaged carbohydrates.
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6. High Source of Plant-Based Protein
Lentils are considered one of the best sources of plant-based, high protein foods
there is.
7. Can Help You Lose Weight
Lentils are low in calories but high in protein and fiber, which helps make you feel
full. Another lentils nutrition benefit when it comes to weight loss is that they can
help control food cravings for sugar and refined carbohydrates since they help
balance your blood sugar levels.
8. Improves Immunity
Lentils help prevent deficiencies in critical minerals like iron, folate, zinc
and manganese that the body relies on to maintain a strong immune system.
2.5 Antinutritional factors
Pulses contain anti-nutritional components that limit their utilization. These
components include trypsin inhibitors, phytic acid, tannins and oligosaccharides.
Trypsin inhibitors are low molecular weight proteins capable of binding to and
inactivating the digestive enzyme, trypsin .
Phytic acid lowers the bioavailability of minerals and inhibiting the activity of
several minerals.
One of the major disadvantages of tannins in lentils is discolouration of the seed. In
addition to seed discolouration, tannins bind to proteins through hydrogen binding
and hydrophobic interactions, thereby reducing their nutritional quality. They can
crosslink with protein by reacting with lysine or methionine making them
unavailable during digestion.
While some efforts have been directed to minimize their contents in the seeds or to
minimize their effects through processes, little information on the effect of varietal
and environmental conditions on these antinutritional factors is available.
Physical and chemical methods employed to reduce or remove antinutritional
factors include soaking, cooking, germination, fermentation, selective extraction,
irradiation, and enzymic treatment.
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The application of a single technique is frequently insufficient for effective
treatment and so combinations are commonly employed .
Soaking could be one of the methods to remove soluble antinutritional factors
which can be eliminated with the discarded soaking solution. However, some
metabolic reactions can take place during soaking, affecting the content of some
compounds.
Cooking generally inactivates heat-sensitive factors such as trypsin and
chymotrypsin inhibitors and volatile compounds.
Germination has been documented to be an effective treatment to remove
antinutritional factors in legumes. It can lower the phytate content depending upon
the germination conditions.
Changes in the trypsin inhibitor activity and in the phytic acid, tannin, and catechin
content of lentils (Lens culinaris var. Vulgaris) were investigated after soaking in
distilled water, citric acid, and sodium bicarbonate solutions. The effect of
cooking, after the seeds were presoaked in the above-mentioned solutions and both
the soaking and cooking solutions were discarded, was also studied. Finally, two
varieties of lentils (L. culinaris var. Vulgaris and Variabilis) were germinated for 6
days, and the effect on the trypsin inhibitor activity and the phytic acid, tannin, and
catechin contents was also measured.
Soaking did not modify the trypsin inhibitor activity, decreased the phytic acid
content, and increased the tannin and catechin contents.
Cooking the presoaked seed brought about the total removal of trypsin inhibitor
activity, a reduction of the physic acid level, and an increase of the content of
tannins and catechins.
The trypsin inhibitor activity and the phytic acid content showed a large decrease
after 6 days of germination, while amounts of tannins and catechins in the two
lentil varieties studied increased.
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METHODOLOGY
3.1. RESEARCH SITE
The study is to be conducted at the JKUAT Main Campus laboratories in the Food
Science and Technology Department.
3.2 RESEARCH DESIGN
The experimental research design is to be used. This is because there are few or no
earlier studies to rely upon to predict an outcome. The focus is on gaining insights
undertaken when research problems, in this case, underutilization of lentils, are in a
preliminary stage of investigation. Exploratory designs are often used to establish
an understanding of how best to proceed in studying an issue or what methodology
would effectively apply to gathering information about the issue.
3.3 SAMPLING METHOD
Sampling method to be used is one whereby the lentils chosen will be purchased
from a specific supplier.
3.4 PRODUCT PREPARATION
 Weigh the sample of lentils.
 Wash the lentils thoroughly with clean water.
 Soak the lentils in a small amount of water for a period of 12 hours. The
water should slightly cover the lentils.
 Dispose the water.
 Blend the lentils with twice the amount of water as lentils until a fine meal is
produced and the water looks opaque.
 Strain the lentil milk using a strainer lined with a cheese cloth.
 Pasteurize the lentil milk.
 Cool the milk until a temperature of 45 degrees Celsius is obtained.
 Add the weighed sugar, stabilizers and culture to the lentil milk.
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 Incubate the yoghurt at 45 degrees Celsius until a thick viscosity is attained
or until it has set.
 Refrigerate the yoghurt.
 Pack the lentil yoghurt.
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3.5 LABORATORY METHODS
3.5.1 SPECIFIC METHODS
1) Determination of crude protein using the Kjeldahl method.
Materials and reagents
Beaker
Condenser
Volumetric flask
Sulphuric acid
Sodium hydroxide
Anhydrous sodium sulphate
Anhydrous copper sulphate
PROCEDURE
Digestion
1. Weigh approximately 1 g ground sample into digestion flask, recording weight
(W). Include reagent blank as check of correctness of digestion parameters. Weigh
a second subsample for laboratory dry matter determination.
2. Add 15 g sodium sulfate, 0.04 g anhydrous copper sulfate. Then add 20 mL
sulfuric acid.
3. Place flask on bunsen burner adjusted to bring 250 ml water at 25C to boil in 5
min.
4. Heat until white fumes clear bulb of flask, swirl gently, and continue heating for 90
min for copper catalyst .
5. Cool, cautiously add 250 ml distilled water and cool to room temperature .
Distillation
1. Prepare titration flask by adding appropriate volume accurately measured acid
standard solution to amount of water so that condenser tip is. For reagent blank,
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pipette 1 mL of acid and add approximately 85 mL water. Add 2 to 3 drops
indicator solution.
2. Slowly down side of flask, add sufficient 45% sodium hydroxide solution to make
mixture strongly alkali.
3. Immediately connect flask to distillation apparatus and distill at about a
temperature set to bring 250 mL water at 25oC to boil in 7.5 min until at least 150
ml distillate is collected in titrating flask.
4. Remove digestion flask and titrating flask from unit, rinsing the condenser tube
with distilled water as the flask is being removed.
Titration
1. Titrate excess acid with standard sodium hydroxide solution to endpoint and
record volume. Titrate the reagent blank (B) similarly.
The concentration of hydrogen ions (in moles) required to reach the end-point is
equivalent to the concentration of nitrogen that was in the original food. The
following equation can be used to determine the nitrogen concentration of a sample
that weighs m grams using a xM HCl acid solution for the titration:
(5)
Where vs and vb are the titration volumes of the sample and blank, and 14g is the
molecular weight of nitrogen N. A blank sample is usually ran at the same time as
the material being analyzed to take into account any residual nitrogen which may
be in the reagents used to carry out the analysis. Once the nitrogen content has
been determined it is converted to a protein content using the appropriate
conversion factor: %Protein = Factor x %N.
21
2) Determination of viscosity using the Ostwald viscometer.
Materials and reagents
Distilled water
Water bath
Funnel
Retort stand
Stop watch
Ostwald Viscometer
PROCEDURE
1. Rinse the viscometer with water and place it in position in water bath by
carefully clamping one limb. Check that it is vertical using a plumb line
2. Introduce exactly 20 ml (or the volume marked on the viscometer) of
water at 20°C into the bulb A with a syringe or pipette.
3. Leave for 5 min to equilibrate, then either apply positive pressure to the
wide limb (I) or gentle suction to the other limb (II) until the meniscus
rises above the upper graduation mark B.
4. Release the pressure and measure the time for the liquid to flow between
the two graduation marks B and C.
5. Repeat the process with the food sample.
3)Determination of acidity using the titration method.
Materials and reagents
Beaker
Volumetric flask
Pipette
Burette
Sodium hydroxide
Phenophthalein indicator
Food sample
22
PROCEDURE
1. Fill the burette with 0.1 N NaOH solution.
2. Mix the sample thoroughly by avoiding incorporation of air.
3. Transfer 10 ml sample with the pipette in conical flask.
5. Add equal quantity of glass distilled water.
6. Add 2-3 drops of phenolphthalein indicator solution and swirl.
7. Take the initially reading of the alkali in the burette at the lowest point of
meniscus.
8. Rapidly titrate the contents with 0.1 N NaOH solution continue to add
alkali drop by the drop and stirring the content with glass rod till first
definite change to pink colour which remains constant.
9.Note down the final burette reading.
Total titratable acidity is therefore calculated using the following formula:
% acid = [mls NaOH used] x [0.1 N NaOH] x [100]
grams of sample
4)Determination of pH using a pH meter.
A pH meter is a scientific instrument that measures the hydrogen-ion
concentration in a solution, indicating its acidity or alkalinity. The pH
of the yoghurt is monitored due to increase in acidity during
fermentation.
5)Analysis of minerals specifically iron using Atomic Absorption
Spectrometry and folic acid using High Performance Liquid
Chromatography (HPLC) technique.
6)Determination of shelf life using accelerated storage conditions.
The food sample is stored at various temperatures and parameters
such as changes in microbial counts, pH, titratable acidity and sensory
attributes are monitored during storage.
23
SENSORY EVALUATION
The sensory evaluation will be carried out using a sensory panel of 10-15 people.
The panel will consist of students and workshop technicians.
The tests will be used to evaluate the appearance, taste, texture and aroma of both
the flavoured milk and yoghurt.
STATISTICAL ANALYSIS
This will be done using Microsoft Excel and packages such as MaxStat software
package that will assist in analyzing the data that will be acquired.
EXPECTED OUTCOMES
The expected outcome is to provide information on the chemical, physical and
nutritional attributes of lentil yoghurt.
It is also expected that the knowledge acquired may be implemented in making
dairy product substitutes for the lactose intolerant and those with milk protein
allergies.
It may also provide a new method of utilization of lentil grains at a small scale and
even commercial level.
The yoghurt is expected to have a thick consistency and a vanilla and/or strawberry
flavour.
24
WORK PLAN
SEP
OCT
NOV
DEC
Sample
purchasing
and product
preparation
Shelf life
studies
Determination
of physical
and chemical
attributes
Progress
report with
project
supervisor
Determination
of nutritional
attributes
Sensory
evaluation
Project
presentation
25
JAN
FEB
MAR
APR
BUDGET
ITEM
UNITS
COST PER
UNIT
TOTAL COST
1. Lentils
5 kg
350
1750
2. Sugar
2 kg
150
300
3. Culture
1 pkt
1500
1500
4. Stabilizer and
starch
5. Flavourings
100 gm each
500
1000
-
-
500
6. Chemicals for
analysis
7. Packaging
bottles
-
-
3000
-
-
500
8150
TOTAL
26
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Hunbury, C., and Ryan, M. (2005) Temperature tolerance in legumes.
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Legume Research Conference (IFLRC IV), 18-22 October, 2005. New
Delhi, India, 21.
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July 2016
14. Williams, J.T., Sanchez, A.M.C., and Jachson, M.T., (1974) Studies on
lentil and their variation.I. The taxonomy of the species. Sabrao Journal
6, 133-145.
27
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28