SELECTED NUTRIENT ANALYSES OF FRESH, FRESH-STORED, AND FROZEN FRUITS AND VEGETABLES by LINSHAN LI (Under the Direction of Ronald B. Pegg) ABSTRACT The objective of this two-year study was to determine and compare the status of targeted nutrients in selected fresh, fresh-stored, and frozen fruits and vegetables, while mimicking typical consumer purchasing and storage patterns of the produce. The nutrients analyzed were L- ascorbic acid (vitamin C), β-carotene (provitamin A), and folate, while the produce was blueberries, strawberries, broccoli, cauliflower, corn, green beans, spinach, and green peas. Analyses were performed in triplicate on representative samples using approved, standardized analytical methods and included a quality control plan for each nutrient; all data were analyzed by one-way ANOVA to determine the presence of significant difference in nutrient contents according to treatment (α=0.05). The findings demonstrated that fresh produce loses vitamins upon refrigerated storage over time, while their frozen counterparts retain these nutrients equally so or better. The consumers’ assumption that fresh food has significantly greater nutritional value than its frozen counterpart is misplaced. INDEX WORDS: Fresh Fruits and Vegetables, Frozen Fruits and Vegetables, Nutrients, Vitamin C, Vitamin A, Food Folate. SELECTED NUTRIENT ANALYSES OF FRESH, FRESH-STORED, AND FROZEN FRUITS AND VEGETABLES by LINSHAN LI B.E., Shanghai Ocean University, China, 2010 A Thesis Submitted to the Graduate Faculty of The University of Georgia in Partial Fulfillment of the Requirements for the Degree MASTER OF SCIENCE ATHENS, GEORGIA 2013 © 2013 Linshan Li All Rights Reserved SELECTED NUTRIENT ANALYSES OF FRESH, FRESH-STORED, AND FROZEN FRUITS AND VEGETABLES by LINSHAN LI Major Professor: Ronald B. Pegg Committee: Mark A. Harrison Ronald R. Eitenmiller Electronic Version Approved: Maureen Grasso Dean of the Graduate School The University of Georgia December 2013 DEDICATION This thesis is dedicated to my loving parents, Xiaoming Li and Zongqiong Ma, who love me and support me in every way. In addition this work is dedicated to my loving husband, Yi Chen, who supports and shares my hopes and dreams. iv ACKNOWLEDGEMENTS I would like to acknowledge my funding source, the Frozen Food Foundation, for providing me with this opportunity. I want to express my appreciation and gratitude to my major professor, Dr. Ronald B. Pegg, for all his constant encouragement and valuable guidance during my M.S. study. I appreciate the training he gave me to build my ability to research independently and corporately. In addition, he helped me in developing my critical thinking and English communication skills, which are very important in the journey of my life. I would also like to thank Dr. Ronald R. Eitenmiller and Dr. Mark A. Harrison for serving on my advisory committee and giving me valuable advice. Additionally, I want to thank most sincerely Vickie Wentzel, Dr. Ji-Yeon Chun, Sheena Patel, and Elizabeth Carr for their cooperation assistance in completing this research and thesis. v TABLE OF CONTENTS Page ACKNOWLEDGEMENTS .............................................................................................................v LIST OF TABLES ........................................................................................................................ vii LIST OF FIGURES ....................................................................................................................... ix CHAPTER 1 INTRODUCTION .........................................................................................................1 2 LITERATURE REVIEW ..............................................................................................9 3 L-ASCORBIC ACID CONTENT OF FRESH, FRESH-STORED, AND FROZEN FRUITS AND VEGETABLES ...................................................................................28 4 TRANS-β-CAROTENE CONTENT, AS A REPRESENTATION OF VITAMIN A, OF FRESH, FRESH-STORED, AND FROZEN FRUITS AND VEGETABLES .....57 5 FOLATE CONTENT OF FRESH, FRESH-STORED, AND FROZEN FRUITS AND VEGETABLES ..................................................................................................96 6 CONCLUSIONS........................................................................................................135 vi LIST OF TABLES Page Table 3.1: Accuracy and interday precision (%RSDr) determined by analysis of the L-ascorbic acid extracted from BCR® 431 ...................................................................52 Table 3.2: L-Ascorbic acid recoveries in frozen fruits and vegetables .........................................53 Table 3.3: L-Ascorbic acid content (mg AA/100 g, f.w.) in selected fresh, fresh-stored, and frozen fruits ..................................................................................................................54 Table 3.4: L-Ascorbic acid content (mg AA/100 g, f.w.) in selected fresh, fresh-stored, and frozen vegetables .........................................................................................................55 Table 3.5: L-Ascorbic acid content (mg AA/100 g, f.w.) in fresh, fresh-stored, and frozen green peas .....................................................................................................................56 Table 4.1: Accuracy and interday precision (%RSDr) determined by analysis of the trans-β-carotene extracted from BCR® 485 .................................................................83 Table 4.2: Trans-β-carotene recoveries in frozen fruits and vegetables .......................................84 Table 4.3.1: Trans-β-carotene content (μg/100 g, f.w.) in selected fresh, fresh-stored, and frozen fruits ..................................................................................................................85 Table 4.3.2: Trans-β-carotene content (μg/100 g, b.w.) in selected fresh, fresh-stored, and frozen fruits ..................................................................................................................86 Table 4.3.3: Vitamin A, RAE (μg/100 g, f.w.) in selected fresh, fresh-stored, and frozen fruits ..87 Table 4.4.1: Trans-β-carotene content (μg/100 g, f.w.) in selected fresh, fresh-stored, and frozen vegetables .........................................................................................................88 vii Table 4.4.2:Trans-β-carotene content (μg/100 g, b.w.) in selected fresh, fresh-stored, and frozen vegetables .........................................................................................................89 Table 4.4.3: Vitamin A, RAE (μg/100 g, f.w.) in selected fresh, fresh-stored, and frozen vegetables .....................................................................................................................90 Table 4.5.1: Trans-β-carotene content (μg/100 g, f.w.) in fresh, fresh-stored, and frozen green peas .....................................................................................................................91 Table 4.5.2: Trans-β-carotene content (μg/100 g, b.w.) in fresh, fresh-stored, and frozen green peas .....................................................................................................................92 Table 4.5.3: Vitamin A, RAE (μg/100 g, f.w.) in fresh, fresh-stored, and frozen green peas .......93 Table 5.1: Food/total folate content (μg/100 g, f.w.) in selected fresh, fresh-stored, and frozen fruits ................................................................................................................127 Table 5.2: Food/total folate content (μg/100 g, f.w.) in selected fresh, fresh-stored, and frozen vegetables .......................................................................................................128 Table 5.3: Food/total folate content (μg/100 g, f.w.) in selected fresh, fresh-stored, and frozen green peas .......................................................................................................129 Table 5.4: Accuracy and interday precision (%RSDr) determined by analysis of the ...................... folic acid extracted from BCR® 485 ..........................................................................130 viii LIST OF FIGURES Page Figure 2.1: General flow diagram for the processing of frozen vegetables ...................................27 Figure 4.1: Chemical structure of trans-β-carotene and its absorption spectrum in n-hexane.......94 Figure 4.2: Chemical separation of trans-β-carotene from α-carotene and other carotenoids in broccoli ........................................................................................................................95 Figure 5.1: Chemical structure of folic acid .................................................................................131 Figure 5.2: Layout of the microplate for the folate assay .............................................................132 Figure 5.3: An example of a typical standard curve generated in the microbiological assay of folate concentration versus absorbance. ....................................................................133 Figure 5.4: The quality control assessment of folic acid in enriched, all purpose-flour based on sixteen measurements ...........................................................................................134 ix CHAPTER 1 INTRODUCTION 1.1 Differences between fresh and frozen produce Is fresh produce significantly richer in nutrients when compared to its frozen counterparts? When selecting