Download storage changes in tryptophan contents of some selected local foods

STORAGE CHANGES IN TRYPTOPHAN CONTENTS OF SOME SELECTED LOCAL FOODS
BY
EZEOFOR OGECHUKWU CHIDINMA
A PROPOSAL PRESENTED TO THE DEPARTMENT OFCHEMISTRY
FACULTY OF PHYSICAL SCIENCES, NNAMDI AZIKIWE UNIVERSITY, AWKA
IN PARTIAL FULFILLMENT OF THE REQUIREMENT FOR THE AWARD OF POST
DOCTORAL DEGREE (PhD) IN FOOD AND ANALYTICAL CHEMISTRY.
AUGUST 2015
ABSTRACT
The tryptophan contents of some locally consumed foods will be analyzed
and the effects of storage on this given parameter will be evaluated on
these studies. Fifteen food items (rice, beans, maize, garri, wheat and
millet, etc.) will be investigated for their tryptophan and lysine contents
and also for the effects of storage on their levels over a month period.
The objective of this studies is to carefully analyze the food items over a
month period and to be noted if there is any significant change in the
level of the essential amino acids; tryptophan over this period.
TABLE OF CONTENTS
 Introduction/literature review
 Objectives of the study
 Significance of the study
 Literature survey
 Experimental section
 Anticipated benefits of the study
 References
INTRODUCTION
 The importance of food composition data and security has long been recognized by
the Food and Agricultural Organization (FAO), and has received more attention in
recent years.
 A great emphasis has been laid on the role of traditional foods in improving the
nutritional status of the people. Many of these foods are nutritionally important in
the diet and can make a significant contribution in meeting the nutritional
requirements of a population, particularly those of low income and those living in
remote areas (Windham et al., 1983).
 Traditional diets in Nigeria are those diets related to food habits and culture of
Nigerian people and which are prepared locally and consumed in different regions of
the country (Dashati et al., 2001).
 Rice is considered to be the most known traditional dish in Nigeria, since 89% of
Nigerian families consume it as a main dish. Other foods consumed include yam,
garri, corn, semovita, etc.
 Tryptophan is one of the essential amino acids. The essential amino acids are those
which cannot be synthesized in the human body in amounts sufficient to meet
nutritional requirements. These amino acids must therefore be taken in through the
diets.
 The present study therefore addresses the tryptophan contents of some foods
consumed in Nigeria and effects of storage on the levels in the various foods.
 Tryptophan (Trp) is a difficult amino acid to determine in proteins and peptides
because it chemically decomposes during acid hydrolysis. Consequently, many
procedures have been developed for the independent preservation and determination
of this amino acid. Alkaline hydrolysis has also been studied and was shown to
produce higher Trp recovery than acid (Villegas, 1984).
 In this present study, spectrophotometric method will be used in determination of
the tryptophan content of the food items.
Functions of tryptophan
 In particular, Trp is the precursor of the neurotransmitter serotonin and plays an
important role in brain function and related regulatory mechanisms.
 Tryptophan is widely used in food industry. It is sometimes added to dietary and
feed products as a food fortifier in order to maintain the amino acid balance of the
food and correct possible dietary deficiencies.
 It helps to elevate mood and makes one sleep better.
 It helps regulate your appetite.
OBJECTIVE OF THE STUDY
 To determine the tryptophan content of selected food items.
 To study effects of storage on the levels of the various food items.
 To calculate amount of the various items that will meet the Recommended Daily
Allowances (RDA).
SIGNIFICANCE OF THE STUDY
 It is important for dietitians and nutritionist to know the nutrients composition and
nutritional quality of diets to enable them to set a menu for healthy people and
patients.
 The data obtained could be useful in food formulation at the home and institutional
levels to attempts directed at meeting RDA.
LITREATURE SURVEY
 According to the Encyclopedia of Medical Concept, food storage is defined as
keeping food for later consumption. food storage is both industrial and traditional
domestic skill and is important industrially.
 Based on this function of food storage, many authors have shown storage effect on
food stored over a period of time to determine whether storage of some raw food
affects its nutritional value. Amino acids are known to be denatured by heat and
different storage temperature(Wikipedia).
 The absorption spectroscopic methods of analysis of amino acids rank the most and
powerful tools for quantitative analysis. The use of a spectrophotometer to
determine the extent of absorption of various wavelengths of visible light by a given
solution is commonly known as Colorimetry (Rendina et al, 1999).
 This method of analysis is based upon the fact that compounds absorb light radiation
of a specific wavelength. In the analysis, the amount of light radiation absorbed by a
sample is measured.
 The Beer-Lambert law states that absorbance is proportional to the concentration (c)
of the absorbing molecules, length of light path through the medium (l) and molar
extinction coefficient(e).
A =ecl.
EXPERIMENTAL SECTION
 The food samples to be used in this study would be local samples of soyabeans,
beans (white), groundnut, walnut, yellow corn, white corn, semovita flour, millet,
guinea corn, wheat flour (white), wheat(raw), garri, rice, egg (white), egg (yolk).
Reagents to be used for the analysis
 4M sodium hydroxide: 4M NaOH would be prepared by dissolving 40g of NaOH in
250mL of distilled water.
 Reagent A would be prepared by dissolving 270mg FeCl3.6H2O in 0.5ml distilled
water and diluting with glacial acetic acid.
 Reagent B would be 30N Sulphuric acid (15M H2SO4).
 Reagent C would be prepared by mixing equal volumes of reagent A and B about
one hour before use.
Procedure:
 Sampling and grinding: A random sample of 20-30 seeds would be taken as a
representative of each sample and each sample will be grinded to a very fine
powder.
 Defatting: Each sample would be carefully transferred into a commercial filter
paper and 37g of each sample would be weighed out. The samples would be defatted
for 6hours with approximately 300ml of hexane per balloon in a Soxhlet type
continuous extractor and air dried to ensure that all hexane had evaporated.
 Digestion: In a hydrolysis tube, 0.1g (100mg) of each air dried, powdered and
defatted samples would be dissolved in 5ml of 4N NaOH solution respectively.
Instrumentation:
 The samples would be incubated at 1100C for 18hours. (This would be shaken at
least twice – one hour after being placed in an oven and one hour before it completes
its 18hours incubation).
 The hydrolysates would be aerated and cooled at 40C, then one milliliter of citrate
buffer (pH 2) would be carefully added to the hydrolysate in a glass tube and
allowed to stand for fifteen minutes.
 Samples would then be centrifuged at 3600g for 10min, allowing a very clear
supernatant which would be decanted into a glass tube.
 Colorimetric Analysis: one milliliter of the decanted supernatants would be
carefully transferred to a clean tube, and 4ml of reagent C (colorimetric reagent) will
be added. Samples will be thoroughly stirred and then incubated for 30mins at 600C.
The samples will be allowed to cool down at room temperature before reading its
optical density (OD)(absorbance) at 560nm in a UV-Visible Spectrophotometer.
Anticipated Benefits:
 It will help determine which of the food items has the highest level of the amino
acid, tryptophan.
 These studies will benefit various sectors of sciences but importantly help us to
understand if storage has effect on the tryptophan content of the analyzed food
items.
 It would also help us know the best method of food storage to benefit in a good food
security.
 This study would contribute immensely in food chemistry where food composition
data is important for calculating the Recommended Daily Allowance (RDA) of each
food item in our daily lives.