EFFECTS OF NIGERIAN PREPARATORY
PROCEDURES ON THE THIAMIN
RIBOFLAVIN AND ASCORBIC AClD
CONTENT OF FOODS.

Thesis for the Degree of M. S;
MICHIGAN. STATE UNWERSITY
ADEOLA ABAELU
1 9 68

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EFFECTS OF NIGERIAN PREPARATORY PROCEDURES
ON THE THIAMIN RIBOFLAVIN AND
ASCORBIC ACID CONTENT OF FOODS

Adeola‘Abaelu

A THESIS

Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of

MASTER OF SCIENCE
Department of Foods and Nutrition

1968

ACKNOWLEDGMENT

The author wishes to acknowledge the invaluable help
and guidance given by Dr. Olaf Mickelsen, a man who was a
source of inspiration to me throughout my career here and
during the period of this study.

My gratitude goes to Dr. Dena Cederquist who arranged
for the facilities placed at my disposal to undertake the
study.

A thank you goes to Dr. Gaurth Hansen, who contri-
buted much for the study to take shape. A special thank
you is also due to Dr. Rae Schemmel for her technical aid,
advice, and encouragement throughout the period of this
study.

The concern and cordial relationship given by all
the members of staff and graduate students of the Nutrition
Department, especially Jenny Lou Taylor and Shirley Chen,
are much appreciated.

To Mrs. Mickelsen I give my regards and thanks for
the support and all she did to make the task easier during
the study.

I am indebted to the Institute of International
Agriculture and Nutrition and the Ford Foundation who made
the grant for this study available.

Finally, my thanks and deep gratitude go to my
Husband, John Nduka Abaelu, whose great sacrifice and care
made it possible for me to start and finish my studies at

Michigan State University.

ii

To My Father
Chief JOsiah O. Adedipe

For the value he placed on Education.

iii

TABLE OF CONTENTS

INTRODUCTION . . . . . . . . . . . . . . .
LITERATURE REVIEW . . . . . . . . . . . .
Studies Made in Nigeria . . . . . .
Studies Made in Other Parts
of the World . . . . . . . . . . .
MATERIALS AND METHODS . . . . . . . . . .
Preparation of Raw Samples for
Vitamin Analysis . . . . . . . . .
Storage of Samples . . . . . . . .
Washing Prior to Cooking . . . . .
Method of Sauce Preparation . . . .
Stew Preparation . . . . . . . . .
Sampling . . . . . . . . . . . . .
Analytical Procedures . . . . . . .
Food Analysis .'. . . . . . . . . .
Moisture and Nitrogen Determination
Conversion Factor for Calculation .
RESULTS . . . . . . . . . . . . . . . . .
Preliminary Study . . . . . . . .
The Second Study . . . . . . . . .

Vitamins Retained in Cooked Foods .

DISCUSSIONS . . . . . . . . . . . . . . .
Calculation of the Contributions of

the Foods to Nutrient Intake . . .

iv

Page

12

13
14
14
15
17
18
19
2O
2O
20
22
22
26
39

47

50

Page

SUMMARY . . . . . . . . . . . . . . . . . 54
LITERATURE CITED . . . . . . . . . . . . 57
APPENDIX . . . . . . . . . . . . . . . . 64

TABLE

LIST OF TABLES

Retention of Vitamins in the Three
Sauces at the End of Preparation

and After Storage at Room Temperature
for Various Times . . . . . . . . . .

Recovery of Thiamin, Ascorbic Acid
and Riboflavin During Preparation
of Spinach for gbe Efg I . . . . . .

Retention of Vitamins in gbe Efg I
During Cooking on Completion of
Cooking and After Storage at Room
Temperature . . . . . . . . . . . . .

Retention of Vitamins in gbg Efg II
During Cooking and on Completion of
Preparation . . . . . . . . . . . . .

Retention of Thiamin, Ascorbic Acid
and Riboflavin in the Cooked Sauces .

Vitamin Retention of Qbe Efg II
After Storage at Room Temperature . .

Preliminary Study . . . . . . . . . .
Mgs of Vitamin in 100 gms of each
of the Ingredients

vi

Page

23

27

28

36

45

46

64

TABLE Page

8 ng Efg I: Mgs Vitamin Contained
in the Raw Ingredients . . . . . . . . 65

9 ng EfQ II: Mgs Vitamin Contained

in the Raw Ingredients . . . . . . . . 66
10 Stew: Mgs Vitamin Contained in the

Raw Ingredients . . . . . . . . . . . 67
11 Second Study . . . . . . . . . . . 68

Mgs Vitamin in 100 gms of Each of
the Ingredients

12 gbe Efg I: Mgs Vitamin Contained
in the Raw Ingredients . . . . . . . . 69

13 Qbe Efg II: Mgs Vitamin in the

Raw Ingredients . . . . . . . . . . . 7O
14 Stew: .Mgs Vitamin Contained in
the Raw Ingredients . . . . . . . . . 71

Temperature Chart During Cooking

15 Qbe EfQ I . . . . . . . . . . . . . . 72
16 ng Efg II . . . . . . . . . . . . . 73
17 Stew . . . . . . . . . . . . . . . . 74

vii

LIST OF FIGURES

FIGURE Page

1 Thiamine Retention Immediately
After Cooking and During Storage
of QbeNEfg I, II, and the Stew

at Room Temperature . . . . . . . . . 25
2 Retention of Thiamin During

Cooking of ng Efg I . . . . . . . . 30
3 Retention of Ascorbic Acid During

Cooking of Qbe Efg I . . . . . . . . 32
4 Retention of Riboflavin During

Cooking of QbE Efg I . . . . . . . . 34
5 Retention of Thiamin. Riboflavin,

and Ascorbic Acid During Cooking

of gbg fifg II . . . . . . . . . . . 38
6 Ascorbic Acid and Riboflavin

Retention Immediately After
Cooking and During Storage of
Qbe Efg I at Room Temperature . . . . 42

7 Ascorbic Acid and Riboflavin
Retention Immediately After
Cooking and During Storage of
ng EfQ II at Room Temperature . . . 44

viii

INTRODUCTION

The importance of any food as a source of nutrients
depends on the amount of the nutrients present at the time
.of consumption. Riboflavin was found to be deficient in
Nigeria, which was accompanied by a low intake of thiamin
and ascorbic acid in prepared foods; even though plasma
levels of the latter vitamin were very high.

This study is devoted to determining the alteration
in thiamin, riboflavin and ascorbic acid content encountered
when vegetables and meats are made into soups and sauces
according to Nigerian methods of household cooking and what
contributions the foods make to the nutrient intake of the

Nigerian people.

LITERATURE REVIEW

In recent years, much attention has been paid by dif-
ferent groups of scientists to the nutrient contents of Afri-
can foods. This is a very important aspect of African nutri-
tion because a great deal has been published about the malnu-
trition in Africa, evident from the various nutritional
diseases found during investigations by different workers.
However,1ittle is known about the nutrient contents of African
foods and the alterations which might occur due to the native
‘methods of preparation and storage of foods. Knowledge of
this sort is necessary, to determine whether the malnourished
conditions found are due to a lack of essential nutrients in
the foods consumed or to a destruction or loss of the nutrients
during preparation or supply to an inadequate intake of those
foods which furnish the essential nutrients.

There is evidence that each of the three suppositions
' may be true to some degree and the summation of all three
factors may precipitate the final disease syndrome. For
instance, Dema (1965) observed that the ignorance of food
values and the nutritional needs of the different members of
the family lead to inequitable distribution of protein-rich
foods such as meat and fish. The dietary measurements made
at Ijana—Itarua (Ilesha, Nigeria) in FebruaryeMarch 1962
confirmed the popular view that the adult males eat the
richest portions, leaving the growing children with rela-

tively little.

The study mentioned above was made in Nigeria where it
was later observed that apart from imbalance of protein and
calories in diets, frank malnutrition is not observed in
adults but in children (1965, Nigerian Nut. Survey). The
same source noted that riboflavin-rich foods are limited in
supply.

There is,however, little information on the nutrient
content of the finished products after cooking and on how
much is lost during preparation. In the recent nutrition
survey carried out in Nigeria during February to April, 1965,
a comprehensive study was made to identify nutritional defi—
ciencies. The survey included dietary, biochemical and a
clinical evaluation of large segments of the population.

This was supplemented with a survey of agricultural practices,
food use and nutrient intake, as well as studies of the pos-
sible relation of nutrition to mental development, and to the
eye lesions found in the country.

The population studied included civilians, school
children, women in prenatal clinics, children at welfare cli-
nics, the military, and the police. The dietary survey in-
cluded the school lunch programme at Lagos.

In the dietary survey at the military school in Zaria,
observations showed that the most popular ways of preparing
foods in Nigeria involve either boiling or frying. For the
cadets, meat or fish was stewed or fried, or made into a
soup or sauce containing other ingredients like fresh or

dried chillies.

The following method was employed at the military school
for preparing the meat soup: The meat used was a less tender
cut, so it was boiled in water until tender (approximately 2-3
hours). The other ingredients were added to the meat and
broth near the end of this time. These included ground onions,
chillies, fresh tomatoes, melon, seed meal, palm oil and water.
Green vegetables were added to the fish or meat soup during
the later part of cooking. They were cooked for one hour or
more.

In the civilian dietary study, it was observed that food
prepared but not consumed at a given meal was usually eaten
at subsequent meals, especially in the case of stews and vege-
table sauces. These two dishes were often prepared in such
quantities as to feed the family for one, two or sometimes
three days.

Dietary information concerning the civilians indicated
that they received adequate amounts of iron, phosphorous, vi-
tamin A, niacin and ascorbic acid at the time of the survey.
However, protein, calcium and thiamin intakes were low in
several locations and riboflavin intake was low in most of
the locations.

In general, among all the groups studied, riboflavin
deficiency as evidenced by low dietary intakes and urinary
excretion levels was acute, while thiamin intake was low or
borderline in several cases; ascorbic acid intake was low in
a number of areas, though serum levels were uniformly high.

Prior to this study, Nicol (1954-1957) and associates
did a comprehensive survey of the types of foods consumed

with special attention to the caloric and protein intakes of

people in five vegetation zones. They observed (1956) that
80% of ascorbic acid is destroyed when foods such as yams and
other root vegetables are soaked, pounded and boiled into
"foofoo". The preparation of flour from cassava destroys
100%, while vegetable leaves and such fruits like peppers,
when boiled in an emulsion of oil and water loses on an aver—
age, 67% of the ascorbic acid present in the edible portion.

In another study on nutrient intakes of urban dwellers
in Lagos, Nigeria, J. Mc'fie (1967) referred to low intakes
of the B vitamins, notably riboflavin which resulted in the
appearance of angular stomatitis in a number of children.

0. L. Oke (1966) of Ibadan is chemically analyzing
many Nigerian foodstuffs. He observed appreciable amounts of
ascorbic acid is lost during processing of tubers and starchy
roots, but a negligible amount is lost when they are cooked.
He also observed that kolanuts appear to have as much ascor-
bic acid as spinach and citrus fruits.

In another study (1966) he obserVed that when liver,
spleen, kidney, lungs and heart of beef cattle were boiled
for ten minutes, losses of the ascorbic acid due to cooking
were highest in the spleen,resulting in an average destruction
of 69%. Other organs lost approximately 52%.

He (1967) also reported that most of the Nigerian vege-
tables in the raw state are rich sources of ascorbic acid
with values ranging from 18 mgs/lOO gms to 95 mgs/lOO gms of
ascorbic acid on fresh weight basis. An appreciable amount
is lost on boiling with losses ranging from 22% to 78%.

Turning to investigations in other parts of the world,

one finds that there is an enormous literature on the changes

in nutrient content of foods, caused by industrial and house-
hold handling and storage. Numerous studies on the vitamin
losses caused by washing, chopping into small pieces, frying,
boiling, holding at high temperatures or storing have been
done.

0. Mickelsen, g£_§l. (1934) found that stability of vi-
tamin B, in meats during cooking depended upon the method of
cooking. Frying produced the least change in B content as
shown by the almost complete preservation of vitamin in fried
beef round and fried ham. A 35%»loss was recorded for pork
loin and 45% in veal chops.

Roasting has a greater destructive action on the vitamin
B in the three samples. Fifty to 60% losses were recorded.
Broiled beef kidney showed a stability of the vitamin similar
to that of the broiled meat when cooked for 1 hr. 45 minutes.
The marked destruction of the vitamin produced by the above
preparatory procedures may be associated with the long time
and high temperature used in cooking.

E. Anghey, £E_El- (1940) showed that cooking destroyed
less of the B vitamin than was formerly supposed. They found
no loss of thiamin in 300 gms of carrots boiled for 23 minutes
in 100 mls of water, and also by the pressure cooker method.
Boiling whole potatoes in salt water for 36 minutes resulted
in 33% loss of thiamin. This loss was accounted for by 20%
destruction and 13% leached into the cooking liquid. When
55 gms of spinach was cooked for nine minutes, 30% loss of
thiamin was obtained out of which 8% of the loss was recovered

in the cooking liquid.

Roscoe (1930) discovered that spinach boiled for 15
minutes lost half its vitamin Bl content in the cooking liquid,
while Hoff (1933) reported more than 50% loss of vitamin Bl in
spinach cooked by ordinary household methods. Thus excessive
vitamin B1 losses reported by some investigators might have
been due to cooking with too large quantities of water or
cooking for long periods of time.

Latze and Hopper (1936) reported a 12% destruction of
Vitamin B1 in pork which had been ground and subsequently
stirred and cooked in a double boiler until it reached a
constant temperature of 90°C.

J. M. McIntire, §E_§1, (1943) studied retention of
thiamin, riboflavin and nicotinic acid in samples of pork
cooked by braising for 45 minutes at an internal temperature
of 87 degrees and roasting for 3-3 1/2 hours, they found
that the average retention of vitamin in the meat was 70%
for thiamin, after roasting and boiling, and 50% after
braising. For riboflavin, 85%»was retained by all methods
of preparation. Appreciable amounts of each of the vitamins
were found in the drippings, particularly from braised loin
cuts.

C. H. JOhnston,ԤE_al. (1943) recorded 30% retention
for thiamin in fresh peas, which were overcooked, with the
loss in the cooking water about 45%. Regardless of method
of cooking, 64-70% of the riboflavin remained in the peas
after cooking.

Effect of the amount of cooking water on vegetables

was studied by Martha Porgieter, et a1. (1950). They found

that with increase in the volume of cooking water more

ascorbic acid was lost from boiled kale. In that study, 25 gms,
312 gms and 600 gms quantities of water were used. Losses
varied from 22.2% for the smallest volume of water to 58.5%

for the largest volume. Increasing the cooking time resulted
in increased loss of ascorbic acid with all three cooking me-
thods. In the drained, boiled kale, there was a direct

linear relationship between the log of the cooking time and

the amount of the vitamin lost when three cooking times, 6,

9, and 13.5 minutes were compared.

Variations in cooking time, however, had much less ef—
fect than variations in volume of cooking water. Inclusion
of the ascorbic acid in the cooking water resulted in no
significant differences due to variations in cooking times.
Therefore, the increased losses with increased cooking time
were due to extraction of more of 'the vitamin from the kale.
Kale, cooked in the medium amount of water for a medium
length of time lost 28% thiamin as compared with 49% for
that cooked in the large amount of water for the same length
of time. Practically all the thiamin lost was recovered in
the cooking water. Kale boiled for the short and medium
times showed no significant difference in thiamin content
either in the drained kale or in the kale plus cooking water.
No additional loss was obtained for the long cooking time.

B. Barnes, EE.2l° (1943) also studied effects of vary-
ing amounts of water used in codking broccoli. Quantities
of water used were 100, 500 and 1000 gms. ‘With 100 gms of
cooking water, 10% ascorbic acid was leached into water
while 8.0% unaccounted for loss occurred. In 500 gms of

water, only 51% of ascorbic acid remained in the broccoli,

32%.went into solution and 1r% was lost. One thousand grams

of water gave only slightly greater loss into solution than
500 gms of water. Fifty-three per cent ascorbic acid remained
in the vegetable and 37%.went into solution.

McIntosh, Tressler and Fenton (1942) found the same
trend of vitamin loss with increase in amount of codking wa-
ter. From 1/4 to 1/2 of the ascorbic acid may be leached
from the vegetables when boiled in increasing amounts of
water. Broccoli was cooked for three different time inter-
vals resulting in undercooking in two minutes, just done in
five minutes and overcooking in 11 minutes. Percentage re—
tention of vitamin C was approximately the same for done and
overcooked, values were 57% and 55% respectively. Percentage
in solution was also about the same, 32% and 33%. The under-
cooked vegetable retained 64% of its vitamin but the taste
panel did not like it.

G. H. Bendix, §£_31.(l951) studied the effect of time,
temperature, and other variables on thiamin stability in
peas, corn, lima beans and tomato juice. At elevated tem-
perature and their normal pH when the log of percentage re-
tention was plotted against time, a negative linear rela-
tionship was shown for thiamin in peas, while in each of the
three other products the curves are characterized by a large
initial slope which leveled off with time.

More recently, Isabel Noble (1967) cooked six types of
vegetables till just tender, 5, 10, and 50 minutes overcooked
beyond the tender stage. She used both ordinary boiling and
pressure cooker methods. Average retention in the tissues

cooked for the longest and shortest periods in boiling water

10

and the pressure cooker were respectively 35% to 44% and 66%
to 78% of the original ascorbic acid. The unaccounted portion
amounted to about 15% for each cooking period.

J. C. Somogy (1964) made an extensive review of litera-
ture on effects of processing and storage on the composition
of foods. Therein, he reported that according to Doesburg
(1957), the retention of vitamin C in different vegetables,
especially spinach, stored at 20°C for 60 hours showed a
negative slope. When percentage retention was plotted
against time in hours, fresh spinach lost 48% and 75% of its
ascorbic acid content respectively in the first and second
day of storage at 20°C. The slope for the losses of ascor—
bic acid in sliced endives and sliced beans were not as
steep as that of spinach; sliced cabbage showed a slight
initial rise in the first twenty hours only to drop gradually
to about 88% retention by the end of 60 hours. This gave
rise to a curve with a concave shape.

Van Duyne, gt_al. (1954) showed that when 400 gms of
cabbage was boiled in 800 mls of water for seven minutes,
held in the refrigerator for 24 and 72 hours and reheated,
there were significant losses of ascorbic acid. Cabbage
tested immediately after cooking retained 57:2% of its as-
corbic acid. Retention after 24 hours storage in the refri~
gerator and reheating was 29:3%. Storage for 72 hours and
reheating gave 243% retention. The difference between the
ascorbic acid contents of the two reheated cabbage samples

is not significant.

11

More recently, Alfred Lopez (1967) studied the influence
of time and temperature on ascorbic acid stability during
storage in different types of orange juice including synthetic
orange juice to which ascorbic acid was added. The ascorbic
acid showed a remarkable stability; even at room temperature
there was no appreciable loss. Thus he recorded about 1-2%
difference in ascorbic acid content of fresh orange juice
stored for 24 hours and 48 hours at room temperature com-

pared with ascorbic acid values prior to storage.

MATERIAL AND METHODS

Food items were purchased at retail in two lots. Items
which were already processed like dried red pepper, dried
shrimps, peanut oil, were bought a few days before the actual
sauce preparation and were stored in the refrigerator at
2°C.

Perishable items like beef and spinach, fresh tomatoes
and onions were purchased early in the morning on the day of
sauce preparation. Tomatoes were immediately pitted, weighed
and homogenized in the one gallon Waring blendor for three
minutes. The homogenate was thoroughly mixed together and
samples were put into weighed one cup freezer jars. Grind-
ing or blending samples are acceptable methods for preparing
materials for vitamin analysis. Onions were treated simi-
larly except that after removal of the non-edible portion
they were homogenized with one quartertheir weight of dis-
tilled water.

The contents of all the fifteen packages of spinach
were weighed together on the Toledo balance which was ac-
curate to one gram. After the non-edible portion was re—
moved, the spinach was placed in a big container and mixed.
Samples for the determination of vitamin in the raw state
were taken from different parts of the whole batch. The
rest of the sample was divided into two portions for the
first and second vegetable sauces.

The meat was a beef chuck roast weighing seven pounds.

The meat was cut into stew size pieces after some of the

12

13

fat had been trimmed off and was again reweighed. By random
hand picking, the meat was divided into three equal portions.
One third was immediately weighed and placed in plastic bags
and frozen at -220C. From one of the two portions remaining,
some pieces were added to the other so that the pieces in the
stew were more than in the second vegetable sauce. The meat
in each portion was weighed and placed in covered plastic
bowls and kept in the cold room until needed.

The three bags of dried shrimps were pooled and ground
with the meat grinder. The ground shrimp was mixed and the
amounts needed for each vegetable sauce were weighed out.

Six tins of dried powdered red pepper were mixed by
rolling the powder up and down on a brown paper with the
aid of a spatula. The pepper was stored in the refrigerator

in quart jars at 2°C.

Preparation of Raw Samples for Vitamin Analysis

After the initial preparation of each ingredient as
described previously, the spinach, tomatoes, onions and
beef were prepared for ascorbic acid analysis by homogen-
izing them in the Waring blendor with 6% trichloroacetic
acid (TCA) in a one to one ratio.

Dried red pepper was first hydrated by blending it
with water using 25 gms of pepper to 50 gms of water. The
whole homogenatevwas again blended for two minutes with
75 gms of 6% TCA.

Fifty gms of dried ground shrimp were blended with
150 gms of water and the entire shrimp was again homogen—

ized with 200 gms of 6% TCA.

14

For riboflavin and thiamin, spinach was homogenized
with water in a one to one ratio in the waring blendor,
while the meat was put through the meat grinder three times.
Homogenates of tomatoes and onions prepared as described
previously, and powdered dried pepper and ground dried

shrimp were used for the analysis of these two vitamins.

Storage of. Samples

Because it was not possible to do the analysis imme-
diately after preparation, the samples were stored at -220C
until analysed. Storage at this temperature results in no
appreciable loss of vitamins even as long as seven months
of storage. Storage involved wrapping the bottles with
brown paper to protect the samples from light or any ultra—
violet light source which might destroy light sensitive ma-
terials like riboflavin. During preparation of samples for
analysis the light intensity in the room was reduced to a
minimum and care was taken to keep the samples away from

direct light of any kind.

Washing Prior to Cooking

Operations like washing of meats and leafy vegetables
in the raw state prior to cooking do not result in a signi-
ficant loss of vitamins. Because of this, samples were not
saved for analysis after these operations.

Van Duyne (1944) soaked shredded cabbage in water for
one and three hours and left it in air for one hour. He re-
corded 9412, 96:2 and 97: 2 ascorbic acid retention respect—

ively.

15

Holmquist, et al.(l954) found that with peas, washing
prior to blanching did not result in significant losses of

ascorbic acid, thiamin, riboflavin and niacin.

Method of Sauce Preparation

The three sauces consisting of a stew and two types of
vegetable sauces were prepared according to methods acceptable
to Nigerians. The methods of sauce preparation for the mili-
tary (1965) in the Nigerian nutrition survey at Zaria mess
were noted. Two other Nigerian cook books were consulted, as
well as three Nigerian women in residence at Michigan State
University at the time of the study.

The ingredients used in Qbe Efg I consisted of: a
leafy vegetable-spinach, fresh tomatoes, fresh onions, dried
shrimps, peanut oil, dried red pepper, monosodium glutamate
as seasoning and salt to taste.

Qbe EfQ II used essentially the same ingredients, except
that it had some meat added to it, while the stew contained
the same ingredients including meat but excluding spinach and

shrimps.)

Method of Sauce Preparation

ng Efg I: By weighing the sauce pan before and after
water was placed into it, the initial weight of water was ob-
tained as 1500 gms. When the water started to boil, its
weight was 1450 gms. Previously trimmed fresh spinach was
placed in the boiling water for four minutes. Since the quan-
tity of spinach was so large, boiling was done in two lots.

An average Nigerian woman is not particular about the

amount of water used. (0. L. Oke, 1967). She boils the

l6

spinach in a slight excess of water which is later discarded.

At the end of ten- minutes, the spinach was removed into
a container holding 1000 gms of cold tap water in which the
first rinsing was done for two minutes. Second rinsing was
carried out in another container of 1000 gms of cold tap
water. R. 0. Williams (1957) suggested preparing greens by
boiling in water until soft, removing them from the boiling
water into a collander or basket and running cold water over
them, or washing in a basin of cold water. The spinach was
removed from the second rinsing water and excess water was
removed by squeezing the spinach into balls.

The sauce base was prepared by heating the homogenized
onion, tomato, pepper and oil for 25 minutes before the cut-
up spinach was added. An additional cooking period of 18
minutes followed during which shrimp and salt were added to
taste thereof recorded.

gbe Efg II: (Spinach was not preboiled) One thousand
three hundred sixty four grams of cut-up and washed pieces of
beef meat were placed in a saucepan along with 649 gms of
water and salt and boiled for 25 minutes.

After this time, previously homogenized tomato,pepper
and onions were added. The weight of the pot both before and
after addition of each ingredient was recorded so that it was
possible to calculate how much of the ingredient was used.

Boiling continued for another 55 minutes at which time
1797 gms of trimmed, washed, raw cut-up spinach was added.
The spinach was mixed with the sauce and left to cook for 11
minutes. A sample was taken at this time. Shrimp, oil, mono—

sodium glutamate and salt were added 16 minutes later and the

17

sauce was left to cook for 20 minutes more. Total cooking

period for each item is recorded in table 16.

Stew Preparation (Alapa)

One thousand two hundred forty seven grams of washed
and cut-up chuck beef, 115 gms of water and salt were boiled
for one hour with occasional stirring with a large spoon to
ensure uniform cooking.

In another sauce pan, the oil was warmed for a few
minutes and onions, tomatoes,and pepper were added. After
cooking for 25 minutes the stock from the boiled meat was
also added along with the previously boiled meat. A little
water was used to rinse the sauce pan in which the meat was
boiled and this was also added to the sauce. The stew was
allowed to cook for 17 minutes more during which time more
salt was added to taste.

In a preliminary study the only samples of sauces
taken were immediately after preparation and six, 19, and 26‘
hours of storage at room temperature, 83°F.

However, in a second study as shown above, emphasis was
laid on stages prior to the end of preparation. Thus, for
Qbe Efg I, samples of water used for boiling and rinsing of
the spinach were saved for analysis of vitamins. Also, sam-
ple of the sauce was taken when shrimps were added before the
end of preparation, in addition to samples taken as soon as
the preparation ended and after 13 1/2 hours of storage at’

room temperature.

For Qbe Efg II, samples were taken 11 minutes after the

spinach was added and another sample as soon as the shrimp was

added. The usual sample, at the end of preparation, and after

18

17 and 22 hours of storage at room temperature were taken.

For the stew, only the samples immediately after prepara-
tion, 13 2/3 and 21 hours of storage at room temperature were
taken.

For all the sauces the temperature of the stove was
turned to high at the beginning and then down to medium when
the sauce began to boil. Occasional stirring was done to en—
sure uniform cooking. The temperature of the sauces were taken
from time to time to determine the average internal temperature

of the sauce during cooking.

8222121.:

In the case of Qbe Efg I,samples were taken immediately

after stirring and these were homogenized. gbe Efg II was

stirred and two pieces of meat, along with two spoonfuls of
the sauce, were taken as a sample. Four of such samples were
put into preweighed Waring blendor and reweighed so that the
weight of the sample was obtained prior to blending. Samples
were thus homOgenized and then placed into three weighed one
cup freezer jars. The stew was sampled in a similar manner.
It was not necessary to dilute samples with water because they
were all soft enough and maintained a good consistency. Homo-
genates were placed in two or three previously weighed screw
capped jars and were then reweighed. The bottles were then
ready for storage in the freezer at -22°C.

Preparation of samples for ascorbic acid analysis was as
for the raw samples.

Prior to analysis the samples were placed in the refrig—

o .
erator at 4 C to thaw overnight. Some samples, such as

19

tomatoes and onions which contained a lot of water and were
frozen into blocks of ice, needed to stand for one or two
hours at room temperature on the following day in order to ob-

tain representative aliquots of samples.

Analytical Procedures

Thiamin: The thiochrome method as outlined by Mickelsen
and Yamamoto (1958) was used to analyse the food samples with—
out any further modifications. The thiochrome method depends
on the in vitro oxidation of thiamin to thiochrome, which
fluoresces in ultraviolet light in the absence of other fluor-
escing substances.

Riboflavin: The fluorometric method as proposed by the
riboflavin Assay Committee (Andrew J. S., 1943) was applied
to food samples. The method is based largely on those of
Conner and Straub (1941) which used absorption of extract
on Florisil as a purification technique to remove interfer-
ing pigments formed in heated food samples and the compensa-
tory method of Hodson and Norris (1939) which involves meas-
urement of extracts before and after addition of a known
amount of riboflavin.

The riboflavin was measured as the difference between
the fluorescence before and after reduction of the Florisil
eluate with sodium hydrosulfite.

Ascorbic acid: Was determined by a method based on
that of Row and Osterling (1948). This method depends on the
oxidation of the ascorbic acid to dehydroascorbic acid and
then to diketogulonic acid which is later coupled with

2, 4 —dinitrophenylhydrazine to yield an orange insoluble

2O

osazone. The osazone is dissolved in conc-HZSO4 giving an
intense red solution, the absorbance of which is determined

spectrophotometrically.

Food Analysis

Each foodstuff that went into the sauce preparation was
analysed separately and the values obtained were used in the
calculation of the sauce composite. These values are shown
in tables 7-14.

There are considerable differences between the analysed
and calculated figures of the constituents of individual
diets as shown by Toscani (1948). Leverton (1960) also
showed that calculated food values only present an average
around which the analysed figures may fall. Since many
factors are taken into consideration in deriving the figures
in the food tables, they provide somewhat different informa—

tion about the product consumed.

Moisture Determination

 

The amount of moisture in every sample was determined
by drying at 70°C under vacuum for 48 hours in covered alum-

inum pans.

Nitrogen Determination
The sauces stored at room temperature for 13, 16 and 21
hours were analysed for Nitrogen by the Micro Kjeldah

technique.

Conversion Factor for Calculation

 

To get the amount of vitamins in 100 gms of the raw

21

materials as well as in the original ingredients, aliquots for
various analysis were corrected for the water added during the
preparation of the homogenates by multiplying the amount ob-
tained from vitamin analysis by the appropriate dilution
factor. Where the water used for blending was four parts of
ingredients to one part of water, then the conversion factor
would be 1.25. '

However, all the vitamin values for foodstuffs,both in
the raw and cocked samples were expressed on the dry weight

basis so as to have a common grounds for comparison.

RESULTS

Preliminary Study

 

Thiamin: gbe Efg I, at the end of preparation retained
only 40% of its initial thiamin. Storage for six and 19 hours
at room temperature (83°F) resulted in further losses to
values of 31 and 30% respectively. Qbe Efg II, when prepared,
had 50% of its initial thiamin. Storage at room temperature
for six, 21 and 26 hours resulted in an apparent rise in
thiamin content to 56, 59 and 58% respectively. The Stew
(Alapa) retained 99.8% at the end of its preparation while 73.
63 and 60% retention were recorded for the three storage
times at room temperature (Table l and Figure l). '

Ascorbic Acid: Not all samples were analysed. For
instance, complete destruction of ascorbic acid occurred in
Qbe Efg I at the end of its preparation. Analysis of the
sample stored for six hours gave no spectrophotometric
readings, and so, the sample stored for 19 hours was not
analysed. A

At the end of its preparation, Qbe EfQ II retained
13%, while storage of this sauce at room temperature for
six, 19, and 26 hours gave 6%, 5 and 6% retention respect-
ively. At the end of cooking, the stew (Alapa) retained
7% of its ascorbic acid.

In this study the volumes of water used in boiling and
washing the spinach in ng Efg I were not measured. It was
evident that interfering substances disturbed the ascorbic
acid analysis, therefore, in the second study, acid washed

Norit was used instead of bromine for oxidation and

22

23

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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24

.++++.++++++++++ Confirmatory Study

_ _ _.— Preliminary Study

Stew (Alapa)

Curve for Confirmatory Study
Oh

I (0'-

Preliminary Study 5f? II

 

Figure l._

Curve for Confirmatory Study
Obe Efo I
Curve for Preliminary Study

Thiamin retention immediately after
cooking and during storage of Obe Efo I,
Obe Efo II,and stew (alapa) at room
temperature. 1, 2, 3, 4, 5, and 6 repre-
sent thiamin retention of the sauces at

the end of cooking.

Figure 1.

(H6355)

 

 

 

 

 

 

 

 

 

 

L

100 80 6O 40

‘% Thiamin Retention

25

20

32

28

24

20

16

 

26

trichloroacetic acid instead of metaphosphoric acid in preci-
pitating proteins.

Since the preliminary study showed that the most preci-
pitous loss of ascorbic acid occurred during preparation of
all three sauces, and also the same thing obtains for thiamin
in Obe Efg I and II, further studies were concentrated on the
losses of these vitamins associated with the various stages
of preparation.

On the other hand, since the stew retained most of the
thiamin during preparation and it is seen from the raw compos-
ite, not to contribute much ascorbic acid, intermediate stage

sampling was not necessary.

The Second Study

Obe Efo I: The spinach used for this sauce was boiled
and rinsed twice in cold water. After the second rinsing.
the retention of thiamin, ascorbic acid and riboflavin in the
boiled spinach was 29, 41, and 43% respectively. There was
38¢H11 and 32% of thiamin ascorbic acid and riboflavin in the
water used for boiling the spinach, 8, 3, and 11% of the three
vitamins in the first rinse water and 8, 7, and 7% in the se-
cond rinse water respectively. Total recovery for thiamin.
ascorbic acid and riboflavin from the preceding were 83%, 62.
and 93% respectively (Table 2).

Immediately after the dried shrimps were added to Obe
Efg I, a sample was taken. At that stage, the sauce contained
50, 45, and 52% of the thiamin, ascorbic acid, and riboflavin

in the original ingredients (Table 3).

27

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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28

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29

Values are based on the thiamin in raw

spinach

Values are based on the thiamin in

preboiled spinach

Figure 2. Retention of Thiamine During Cooking

of Obe Efo I

 

 

;30

Figure 2 .

 

I I

_L

Cooking Time
I .

1

60

I...

 

30

 

 

100

80 60

% Thiamin Retention

4o

20

31

 

[j>

Figure 3.

Values are based on the ascorbic acid
in raw spinach
Values are based on the ascorbic acid

in preboiled spinach

Retention of Ascorbic Acid During

Cooking of Obe Efo I

32

Figure 3.

Cooking Time

(Minutes)

 

 

50

4O

3O

10

 

 

100

80 6O

% Ascorbic Acid Retention

40

20

33

——————1§r—————Values are based on the riboflavin in

raw spinach

Values are based on the riboflavin in

 

n
Ll

preboiled spinach

Figure 4. Retention of Riboflavin During Cooking

of Qbe Efg I

34

Figure 4.

Cooking Time
(Minutes)

 

 

6O

—

50

40

30

20

10

 

I L . I I O

 

100 80 6O 4O 20

‘% Riboflavin Retention

35

For Obe Efg II, sampling was done at only two stages;
one was 11 minutes after the spinach was added and the other
was immediately after the dried shrimp was added. For the
first sampling, retention of thiamin, ascorbic acid, and
riboflavin was 88.0%, 67%, and 85% respectively; while for
the latter time, retentions were 80%, 45%, and 65% respect-
ively (Table 4 and Figure 5).

For Obe Efo I, there was a sharp fall in the thiamin
content by the time the shrimp was added which was not af—
fected after 18 minutes of further cooking. When the com-
putation for thiamin was made on the basis of the vitamin
content of the preboiled spinach, the percentage retention
was much greater (Table 3, Figure 2).

For ascorbic acid, retention decreased markedly through-
out the preparation suggesting that ascorbic acid is more
easily destroyed than thiamine by this method of cooking
(Figure 3).

The retention of riboflavin was similar to ascorbic
acid except that the slopes were less steep. The difference
when retention was expressed on raw and preboiled spinach was
the largest for riboflavin. This means that by reducing the
loss of nutrients associated with such a procedure as pre-
boiling the spinach will markedly improve the nutritional
value of the food (Figure 4).

The destruction of vitamins in Obe Efg II was less
than in Obe Efo I. For thiamin, most of the loss occurred
during the last 15 minutes of cooking (Table 6 and Figure 5).
Ascorbic acid destruction was much greater than for thiamin.

Until the shrimp was added, the rate was almost a straight

36

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37

.1._0 Thiamin Curve

 

ll00 Riboflavin Curve

 

 

441.1, Ascorbic Acid Curve

Figure 5. Retention of Thiamine, Riboflavin and
Ascorbic Acid During Cooking of

9b: Efe II

 

38

Cooking Time

my
.. 140

120

-100

 

so

 

 

100 80 6O 4O 20

% Vitamin Retention

39

line, but it rapidly turned down after that. For riboflavin,
the graph was similar to that for ascorbic acid but much more

concave in nature.

Vitamins Retained in Cooked Sauces
When the cooking of the food was completed, the percent-
age retention for thiamin in Obe Efo I and II and the stew
were 48%, 63% and 88% respectively (Table 5). The corres-
ponding values for ascorbic acid were 25, 22, and 55%” while

for riboflavin, they were 40, 45, and 8T%.

Storage of Cooked Foods
at Room Temperature

In Nigeria, sauces not completely consumed on the day of
preparation are stored for one or two days. Since refrigera-
tion is limited, the sauce is usually stored at room tempera-
ture and rewarmed before use. These conditions were imitated
in the laboratory to find out how much of the vitamins were

destroyed during storage.

Preliminary Study: >

There was very little change in the thiamin content of
Obe Efo I during storage.The principal loss occurred during
preparation of the sauce (Figure 2).

For Obe Efo II, there was essentially no change with
storage (Figure l). The stew showed a gradual loss of these
vitamins. Where 27, 37, and 42% losses of thiamin were
recorded for the three storage times, 6, 21, 26 hours at

room temperature.

L.40

Second Study:

Storage of Obe Efo I for about 14 hours at room tempera-
ture resulted in no change in thiamin content. The value im-
mediately after preparation and after 14 hours storage, was
48% for the same time intervals. The values for the retention
of ascorbic acid were 25 and 26%, and for riboflavin, 40 and
37% respectively. These values are expressed on the basis of
the raw spinach (Figures 1 and 6).

Obe Efo II gave the following retention values imme-
diately after the sauce was prepared and after 17 and 22
hours of storage at room temperature: for thiamine, 63,
61, and.51%, for ascorbic acid, 22, 25, and 22%, and for
riboflavin, 58, 61, and 50% respectively (Table 6 and
Figures 1 and 7).

41

-—————IF—————Riboflavin Curve
——‘-—Ascorbic Acid Curve

Figure 6. Ascorbic acid and riboflavin retention
immediately after cooking and during

storage of Obe Efg I at room temperature

42

 

 

 

 

 

 

 

 

Figure 6

Time

(Hours)
_ 16

'T
_ 12
js
- 4
M4. 0
100 80 6O 40 20

'% Vitamin Retention

43

-—————4I——————Riboflavin Curve
———‘———Ascorbic Acid Curve

Figure 7.

Ascorbic acid and riboflavin retention
immediately after cooking and during
storage of Obe Efo II at room

temperature.

 

44

Figure 7.

Time (Hours)

 

 

32

Riboflavin Curve

Ascorbic Acid Curve

T _24

16

._12

 

 

 

 

 

 

.100 , so 60 4o 20

% Vitamin Retention

45

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47

DISCUSSION

‘OBE EFO I had the highest amount of each vitamin in
the raw composite, but it retained the least percentage of
each vitamin. However, in absolute term, the mg§_of vitamins
retained per 100 gms dry weight in this source was much higher
than in any of the other sauces (Tables 5. 6).

Despite this, the loss of nutrient in 'gbe Efg I is a
tremendous one. For example, the ascorbic acid which "disap-
peared" during the preparation of 'Qbe EfQ‘ I and 'Qbe Efg' II
and stew were 258, 109, and 27 mgs per 100 gms respectively.
Initially the sauce composite had 344, 140, and 79 mgs/100 gms
on dry weight basis.

From the foregoing, one can see that the severity of the
method of preparation resulted in a great loss of the nutrients
of gbe Efg I. Secondly, this sauce is composed mainly of
vegetables and fruits, all of which,except spinach, are homo-
genized and used in the sauce without any preliminary handling.
The spinach in the first vegetable sauce is more than half of
the total quantity of the ingredients in the sauce, and also
contains a high amount of all the vitamins; It is the item
that is preboiled and rinsed before incorporation into the
sauce.

The large amount of spinach in this sauce probably
accounts for a large share of the vitamin destruction which
occurred during the preparation of food. The preboiling of
the spinach resulted in a large loss of vitamin, partly due to

its high concentration of vitamins and to the large amount of

‘48

this vegetable incorporated in the sauce. The large surface
area of the spinach facilitated the destruction of the heat
labile nutrients. This can be shown by the fact that 95% of
the vitamin C was retained in asparagus during blanching,
while only 67% in spinach under similar conditions

(E. J. Cameron, 1964).

Spinach is the largest ingredient in ’gbe Efo‘ II.
followed closely by meat which contains less thiamin and ri-
boflavin than spinach and very little ascorbic acid. Thus,
meat dilutes the mgs thiamin/100 gms of the composite com-
pared with the first vegetable sauce. Since there is no
preboiling of the spinach for 'Qbe Efgd II, cooking time
is more important. Since the loss of vitamin during cooking
is gradual, it could be reduced considerably by shortening
the cooking time.

The stew retained the highest percentage of each vita—
min. However, because of the large amount of meat in it, the
amount of vitamin in the stew composite is much lower than
any of the vegetable sauces.' The methOd of cooking the stew
is similar to that employed for Obe Efg II except that
spinach was excluded. Since vitamin retention in the stew
remains high after cooking, it stresses the point that it
should be easy to reduce the loss of vitamin in Obeigfg II
by shortening the cooking period also.

The problem of storage needs further investigation.
However, from this study one can say that in the case of the
two vegetable sauces, especially “Obe Efgl I, the loss of
vitamin is already so great by the end of preparation that

there is not much left to be lost during storage. Therefore.

49

storage of Obe Efo I at room temperature for up to 19 hours
after preparation did not result in any appreciable change in
vitamin content. This was also true of Obe Efo II. Thus,
there was very little difference in vitamin content of
samples stored at room temperature for 21 hours.

Nitrogen values for Obe Efo I at the end of cooking
and after 13 hours of storage at room temperature were 3.42
and 3.17% respectively, while for Obe Efo II, values at the
end of preparation, and after 16 3/4 hours and 22 hours
were 6.52, 6.36 and 6.21% respectively under the same con-
ditions of storage.

These values showed a difference of approximately
3% for Obe_Efo I and 2% in the case of gbg Efg II. These
differences are within experimental error for the micro
kjheldah method, and moreover, they can be explained on the
basis of slight variations in aliquot samples. The nitrogen
in the sauces apparently did not show much change with
storage for the period of time studied. From the foregoing,
a few suggestions as to the ways of reducing the loss of vi—
tamins in these sauces during preparation can be made.

Much of the nutrient in Obe Efo I will be conserved
if the preboiling Oftfiugleafy vegetable, which contains the
highest concentration of vitamins, can be eliminated, or
the washing of these vegetables after preboiling. If pre-
boiling cannot be eliminated completely, the amount of water
used in boiling should be reduced considerably and so also
must be the length of time for which preboiling is done.

The practice of washing vegetables after boiling is to

remove sand and extraneous materials which accompanied these

vegetables from the farm. Thorough washing of vegetables

50

immediately after harvesting will go a long way to reduce
washings during household Cooking.

Loss of nutrients in Obe Efo II will be much reduced
if the cooking period is shortened, especially the time
after the spinach has been added.

In the study, the stew seemed to retain much of its
vitamin content at the end of preparation. However, consi-
dering that meats in Nigeria are of less tender cuts than
the one used in this study (Nigerian Nutrition Survey, 1965)
and thus they may be subjected to much longer periods of
cooking, then the length of the cooking period becomes an
important factor. The use of locally available meat ten-
derizers like enzymes from papaya and pineapples would help
in reducing cOoking time of the meats.

Calculations of the contributions of these foods to the
nutrients intake were made from data of dietary studies done
by different investigators at different times in Nigeria.
These calculations are based on the minimum daily requirement,
not the recommended daily allowance.

B. M. Nicol (1959) determined the calorie requirements
of Nigerians of different age groups in seven Nigerian villages.
Thiamin and riboflavin requirements are based on calorie in-
take. Based on Nicol's estimates, children 4-6 years and
weighing 12.90 kg require 1585 calories/day. Their minimum
thiamin, riboflavin, and ascorbic acid requirements will be
0.32 mgs, 0.63 mgs, and 30.0 mgs respectively. Seven to nine
year olds weighing 22.49 kg and consuming 1928 calories per
day will need 0.4 mg, 0.8 mgs, and 30 mgs of thiamin, ribofla-

vin, and ascorbic acid respectively. Ten to twelve year olds

51

of 30.47 kg body weight and receiving 2303 calories per day
need 0.46, 0.92, and 30 mgs of the three vitamins respectively,
while males who are 13-70 years old, of 57.27 kg body weight
and consuming 2527 calories per day will need 0.51, 0.76 and
30 mgs of the three vitamins respectively. Females of the
same age, weighing 49.94 kg and receiving 2036 calories per
day will need 0.41, 0.6l,and 30 of the vitamins as listed
above respectively. An adult male consuming 193.21 gms of
Obe Efo II with rice at a meal will receive 0.14, 16, and
0.21 mgs thiamin, ascorbic acid and riboflavin from the
sauce alone, and this will be approximately 28, 53, and 28%
of the minimum daily requirement for these vitamins respect-
ively (Nigerian Nutrition Survey, Table 10, page 82).

Seven to ten year olds receiving 67.36 gms of the stew
with rice in the school lunch program will receive 0.035,
11.52, and 0.053 mgs thiamin, ascorbic acid and riboflavin
respectively. This would furnish 9, 38, and 7% of the mi-
nimum daily requirements of these vitamins respectively.

Ten to twelve year olds receiving the same amounts as the
above children will have 8, 38, and 6% of their minimum
daily requirements furnished by the stew respectively (Ni-
gerian Nutrition Survey).

JOhn Mc'fie (1967) did a study on the nutrient intakes
of Urban dwellers in Lagos, Nigeria. From Table 3 of his
paper, it was possible to calculate how much vitamin the
civilians would be furnished by the items which go into each
of the three foods. These excluded fresh fruit but included
dried fish. The serving for Obe Efo I and stew were com-

bined because this is the way they would be eaten,with "foofoo."

52

According to his study, adult males eating 50 gms of
Obe Efg I, along with 91 gms of the stew will receive 16.0%.
76%, and 15%»of thiamin, ascorbic acid and riboflavin res-
pectively. While adult females consuming 40 gms of gbe Efg I
in combination with 71 gms of stew will receive 16%, 63%, and
15% thiamin, ascorbic acid, and riboflavin. Ten to twelve
year olds receiving 30 gms of Obe Efo I, along with 51 gms
of stew will be provided with 10%, 43%, and 7% of thiamin,
ascorbic acid, and riboflavin respectively. When 30 gms of
Obe Efo I in combination with 56 gms of stew is given to
seven to nine year olds, they will receive about 13% of
thiamin, 46% of ascorbic acid, and 9% riboflavin respectively.
Four to six year old consuming 30 gms of Obe Efo I and 55 gms
of stew will receive 15, 46, and 11 per cent of thiamin, as-
corbic acid, and riboflavin respectively. -One hundred forty
one grams of Obe Efo II would furnish 20, 39, and 53 per cent
thiamin, ascorbic acid, and riboflavin at one serving to
adult males. To seven to nine year olds, 79.41 gms of the
same food would furnish 15, 21, and 11 per cent of the three
vitamins respectively while ten to twelve year olds would be
provided with 13, 22, and 9 per cent of the three vitamins
respectively from the same amount of food.

On wet weight, Obe Efo II provides more thiamin and ri-
boflavin than Obe Efo I and the stew when eaten in combination.
while the latter provides more ascorbic acid.

These values, however, indicate that much of the ascorbic
acid consumed by the people must come from sources other than

the vegetable sauces and the stew. Kola nuts have been re;

ported to contain high levels of this vitamins, and so, are

53

fruits like oranges and mangoes, etc., which are eaten as
snacks during the day. Kola nut especially, is chewed by
more than half of the adult population, hence, the high

plasma levels of this vitamin found in the various nutri-

tion surveys.

54

SUMMARY

Many investigations have been done in Nigeria regarding
nutritional status of the people. It is evident from these
studies that riboflavin is deficient, thiamin inadequacy is
acute, while ascorbic acid is found to be adequate judged by
the high levels found in the plasma.

Various indigenous household cooking practices seem to
indicate that much of the nutrients in foods may be lost be—
fore they are actually consumed. One such practice is the
preboiling and washing of the vegetables after boiling before
incorporation into sauces. These operations are done to re—
move stones, and other unwanted materials from the green
vegetable, as well as reduce the greenish—brown colloidal
consistency which unwashed vegetables are said to impart to
the sauce, which makes the vegetable unacceptable to some
people if this is retained. This study was therefore devoted
to finding what alterations would occur to the nutrients,
namely, thiamin, riboflavin, and ascorbic acid when foods are
subjected to these methods of food preparation.

Three types of sauces were prepared, and chemically
analysed for these nutrients, namely, Obe Efo I and II,
which employed two methods of preparation and a stew.

Obe Efg I had the green vegetables preboiled and washed
in cold water twice. The vegetable was then drained and cut
up. It was later incorporated into a sauce base made from

homogenized tomatoes, onions, peppers, and oil, with salt to

taste.

55

The green vegetables in Qbe Efg II was cut up raw and

incorporated into a sauce base which comprised of the ingre-

dients used in Obe Efo I along with meat cut up into stew

sizes. The whole preparation lasted two and two—thirds

hours.

The stew was made from cut up meat which was boiled

for 50 minutes before the other ingredients were added;

they were the same as used for Obe Efo I. No leafy vege-

table was

(1)

(2)

(3)

(4)

(5)

used in its preparation.

The findings from the study show that alterations
in the nutrient contents of the foods depended
very much on the severity of the method of pre-
paration.

The effects of preboiling and excessive washing
of boiled vegetables which may lead to the des—
truction and leaching out of vitamins, as well as
effects of long cooking periods are marked in
those sauces Where such methods are employed.
They are much reduced in those sauces where less
prolonged treatment of the ingredients is done
prior to cooking.

gbe Efg I is subjected to all the three opera-
tions and so it lost the highest percentage of
its vitamins.

Qbe Efo II is exposed to a long cooking period
only and loss of vitamins is slightly reduced.
The stew employs long cooking periods but the

primary ingredient is meat whose vitamin content

I
is more stable due to the small surface area

(6)

.56

exposed to heat as against spinach in the other
sauces. For this reason, the percentage vitamin
retention in the stew is higher than in any of
the other sauces, but the mgs/100 gms is much
lower because of low initial amount in the raw
composite.

It appears that investigations concerning stor-
age of the sauces at room temperature will be—
come necessary if the losses of nutrients in the
sauces are reduced to a minimum by the end of

preparation.

57

LITERATURE CITED

Andrews, J. S. - A Collaborative Study of Riboflavin Assay
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Aughey, E. and Daniel, E. P. — Effect of Cooking on the
Thiamin Content of Foods. J. Nutr. 19, 285 (1940).

Barnes, B. Tressler, D. K. and Fenton, F. - Effect of Different
Cdoking Methods on the Vitamin C Content of Quick-
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Bendix, G. H., Herberlein, D. G., Ptak, R. P. and Clifcorn L.E.
- Factors Influencing the Stability of Thiamin
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Bowes, and Church. - Food Values of Portions Commonly Used.
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Cain, R. F. - Water Soluble Vitamins. Changes During Processing
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Fabuda, V. - Personal Communication

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of vegetables. 5. Cabbage. Food Res. 1, 247. (1936).

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Harding, R. S., Leveille, G. A., Baker III, E. M.,
Ziporin, F. F. and Sauberlich, H. E. - Biochemical
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Hodson, A. F. and Norris, L. C. - Fluorometric Method for
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Kaucher, M. Moyer, E. F., William, H. H., Macy, I. G. and
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6O

Leverton, R. M. and Whiting, M. G. - Reliability of Dietary
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The Retention of Vitamins in Meat During Cooking.
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61

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62

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Mc'Henry, E. W. 1964. A. P. New York and London.

APPENDIX

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