California State University, Northridge

CALIFORNIA STATE UNIVERSITY, NORTHRIDGE FOLIC ACID IN EYGYPTIAN VEGETABLES: EFFECT OF DRYING METHOD AND STORAGE ON FOLACIN CONTENT OF t1ULUKHIYAH (CORCHORUS OLITERIUS) A thesis submitted in partial satisfaction of the requirements for the degree of Master of Science in Home Economics by Sohair Saad August, 1980 The Thesis of Sohair Saad is approved: Tung-Shan Chen, Ph.D., Chairman California State University, Northridge i i DEDICATION To t~y Son Mike And ~1y Family ; ; ; ACKNOl~LEDGB1ENT I wish to thank those who worked closely with me and contri buted their knowledge and energy toward the achievement of this goal. I would especially like to acknowledge the members of my graduate committee: Dr. ~1arjory Joseph, to whom I owe my knowledge of statistical analysis, and who helped me to solve the statistical problems through out this research. Marjaret Anita King, who taught me initially how to assay for folacin and who gave encouragement and support throughout the duration of this research. Dr. Tung-Shan Chen, to whom I give special recognition for not only serving as my major advisor, but also for the patience, guidance, and assistance given to me throughout this research. I would like to thank Seija Hurme, Linh D. Nguyen, and Cliff Lui, who served as friends and coworkers, and with whom I was able to share ideas which helped to make this project a success. I gratefully thank my brother, Raed, who acted as a chemistry advisor, consultant, sounding board and optimist throughout this en terprise. And finally I especially thank my mother, Angele Yossef, with out whose patience, understanding, unqualified encouragement, and helping, I would never have attempted nor accomplished this project. iv TABLE OF CONTENTS Page DEDICATION ••• . iii AC KNOVJLEDGMENTS iv LIST OF TABLES • . vii LIST OF FIGURES • • • viii ABSTRACT ix Chapter I. INTRODUCTION 1 Objective • 2 Limitations 3 Definition of Terms 3 II. LITERATURE REVIEW Folacin • • • . 5 Dehydration . 8 Destruction of Vitamins During Drying and Storage • • • • • • • 10 Mulukhiyah ••••• . 18 III. MATERIALS AND METHODS . 19 Vegetable • . 19 ~~icroorganism . 19 Ba sa 1 Med i urn • • . 19 Chemical Reagents . 19 v Chapter Page Equipment • . 20 Methods 20 Sample Preparation . • 20 Drying r~ethods . 20 Storage Test . 22 Moisture Determination . 23 Folacin Determination . 23 Microbiological Assay Procedure 24 Data Treatment . 36 IV. RESULTS AND DISCUSSION Folacin Activities in Mulukhiyah . 38 Effect of Drying Methods on Weight Retention and Moisture Content of Mulukhiyah • • 41 Destruction of Folacin During Dehydration 45 Effect of Storage Condition on Folacin Retention in Dried Mulukhiyah ••• 62 V. SUt~MARY, CONCLUSIONS, AND RECOMMENDATIONS 77 REFERENCES . 80 APPENDICES A. Preparation of Chemical Solutions and Culture Media ••••••••••• 88 B. Preparation of Hog Kidney Conjugase 90 C. Preparation of Folic Acid STandard Solutions • 93 vi LIST OF TABLES Table Page 1. Sampling Schedule During Drying of Vegetable by Three Dehydration ~1ethods • . 21 2. Preparation of Assay Tubes for Folic Acid Standard Curve • . • • • • • • • • 28 3. Preparation of Folacin Assay Tubes for Mulukhiyah Samples • • • • • • • • • • • • • • • • • • 35 4. Folacin Content of t~ulukhiyah and Some other Folacin Rich Vegetables • • • • • • • • 39 5. Weight Retention and Changes in Moisture Content of Mulukhiyah During Drying and Process by Three Drying Methods • • • • • • • • • • • • • . • 42 6. Total and Free Folic Acid Content and Retention in Mulukhiyah During Freeze, Tray and Room Drying • • 46 7. Effect of Packaging Condition on Free and Total Folic Acid Retention in Dehydrated Mulukhiyah 69 8. Summary of Tukey's HSD for Comparison of Means of FFA and TFA Retention in Dried Mulukhiyah stored under Different Conditions at Various Storage Times • • • • • . • • . • • . • • • • • • • • • 75 vii LIST OF FIGURES Figure Page 1. Structure of Pteroylglutamic Acid • • • • 6 2. Schematic Diagram of Assay Procedure • • • • • • • 26 3. A Typical Folic Acid Standard Curve of L. casei 11 11 Linear Plot • • • • • • • • • • • • • • 31 4. Semi-log Plot of Folic Acid Standard Curve of L. casei • • • • • • . • • • • • • • • • • • 33 5. Semi-log Plot of Drying Time (hours) Versus Moisture Content g/g solid • • • • • • . • • 44 6. Percent Folacin Ret ntion in Mulukhiyah during Freeze Drying at 32 0 C • • • . • • • • • • • • 49 7. Percent Folacin R@tention in Mulukhiyah during Tray Drying at 50 C • • • • • • • • • • • • • • • 51 8. Percent Folacin Retention in Mulukhiyah during Room Drying at 25° C • • • • • • • • • • • • • 53 9. The Rate of Total Folic Acid Destruction Plotted Against the Percent Moisture Content • • • • • • . 56 10. The Effect of Drying on Folacin Retention in Mulukhiyah by the Three Drying Methods, Percent Total Folacin Retention Is Plotted Against Moisture Content • • • • • • • • • • • • • • • 61 11. Effect of Packaging Condition on TFA Content of Dried Mulukhiyah During Storage at Room Temperature • • • • • • • • . • • • • • • • • • 64 12. Effect of Packaging Condition of FFA Content of Dried Mul ukhiyah !).Iring Storage at Room Temperature • • • • • • • • • • • • • • • • • • 66 viii ABSTRACT FOLIC ACID IN EGYPTIAN VEGETABLES: EFFECT OF DRYING METHOD AI·JD STORAGE ON FOLACIN CONTENT OF ~ULUKHIYAH (CORCHORUS OLITERIUS) by Sohair Saad Master of Science in Home Economics The effect of three drying methods (room, tray, and freeze drying) moisture content, and packaging during storage on folacin con tent of mulukhiyah, which is one of the most common vegetables in Egypt, was investigated. It was found that fresh mulukhiyah contained 556 meg free folic acid (FFA) and 800 meg total folic acid (TFA) per 100 g fresh weight basis, and room dried mulukhiyah contained 662 meg FFA, and 1138 meg TFA per 100 g dry weight. Therefore, mulukhiyah is an excel lent source of folate in the Egyptian diet. The destruction of folic acid in mulukhiyah was high in all three drying methods studied. The retention of FFA ranged from 34 to ix 42 percent, and TFA ranged from 42 to 48 percent. Retention of TFA was always higher than that of FFA during drying because 70 percent of the TFA in mulukhiyah is FFA, which is more sensitive to heat than total folacin. Freeze drying method resulted in higher folacin reten tion than the other drying methods. Approximately 10 percent more TFA was preserved by the freeze drying method than that retained by the room drying method while the differences in folacin retention between the tray drying and the room drying methods was 7 percent. The retention of folacin in room dried mulukhiyah during storage varied depending on the packaging method. There was a signifi cant difference (r~O.Ol) in folacin retention between mulukhiyah packed in colored or clear jars under nitrogen or air atmosphere, and length of storage time. There was a significant decrease in folic acid retention with storage time of 48 weeks under all the conditions. Mulukhiyah stored in brown jars packed under nitrogen had the highest retention of folic acid followed by the brown jars with air. The clear jars with nitrogen had similar folic acid retention as that stored in brown jars with air. Severe destruction of folic acid occurred in clear jars with air atmosphere. It is recommended that room drying be continued as a home dehydration method for mulukhiyah because it causes insignificant higher folacin loss than the other methods. Tray drying might be ad opted on a commercial level while freeze drying would be too costly for the purpose of folacin retention. It is also recommended that dried mulukhiyah be stored in colored containers and, if possible, under nitrogen packing. X Chapter 1 INTRODUCTION A study carried out in countries of the Eastern Mediterranean region has shown that nutritional anemias are the most serious and widespread nutritional disorders in 9 countries of the region including Egypt (Rao, 1974). In the vulnerable groups such as infants and preg nant and lactating women, the proportion of anemic individuals seems to reach 70 to 90 percent. Although iron deficiency anemia is the pre dominant type, other types attributable to deficiencies of folate, vitamin s12 , protein, etc. are also prevalent. Halsted et al. (1969) reported that the anemia of Kwashiorkor in Cairo is usually megaloblas tic and is responsive to a combination of dietary protein with supple mental iron and folic acid. Green vegetables are generally considered to be good sources of folic acid. The only green vegetable consumed in large quantities in Arab Middle East is Jew's mallow (Corchorus oliterius) or mulukhiyah in Arabic (Patwardhan and Darby, 1972). This vegetable is popular all over Egypt. When available in season, it is bought in quantities, and the leaf separated from the stalk, dried, and stored. The dried muluk hiyah is soaked in water, cooked with salt and some sour lime juice, and eaten with bread or rice. Those who can afford it cook the vege table with meat. In spite of its popularity, information on folacin content of mulukhiyah is lacking. Folacin content of foods is greatly affected by conditions 1 2 associated with processing, storage and preparation (Malin, 1975). Since sun drying (or room drying) of vegetables is common in Egypt (Patwardhan and Darby, 1972), better drying methods for nutrient pre servation need to be developed. There are few studies on the effects of dehydration methods and storage conditions on folic acid retention in vegetables found in the literature. The purpose of this study was to generate quantitative

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