DETERMINATION OF ALUMINUM CONTENT IN FOOD PRODUCTS AND TEXTURE PROFILE OF JELLYFISH PRODUCTS by CHAO XU (Under the Direction of Yao-wen Huang) ABSTRACT This study analyzed texture properties and mineral profiles of jellyfish products, which can provide valuable information for utilizing jellyfish as a potential food resource, as well as developing appropriate strategies to control the product quality. Desalting cured jellyfish in water is a critical step to create jellyfish a desirable texture. Inorganic elements in processed jellyfish were also under investigation. Fresh jellyfish are processed with mixture of salt and alum, and then the cured jellyfish are desalted in water before consumption. Very little is known about the inorganic constituents of jellyfish. In this study desalted jellyfish were examined for 7 elements, including Al, Ca, K, Mg, Na, Fe, and Zn, using inductively coupled plasma optical emission spectrometry. High amount of aluminum was found in cannonball jellyfish samples. High performance liquid chromatography (HPLC) with spectrophotometric detection using quercetin is developed to determine aluminum content. INDEX WORDS: Jellyfish, Texture, Mineral Profile, Aluminum, HPLC, Instrumental Texture Properties DETERMINATION OF ALUMINUM CONTENT IN FOOD PRODUCTS AND TEXTURE OF JELLYFISH PRODUCTS by CHAO XU B.S., China Agricultural 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 Chao Xu All Rights Reserved DETERMINATION OF ALUMINUM CONTENT IN FOOD PRODUCTS AND TEXTURE OF JELLYFISH PRODUCTS by CHAO XU Major Professor: Yao-wen Huang Committee: William L. Kerr Robert L. Shewfelt Electronic Version Approved: Maureen Grasso Dean of the Graduate School The University of Georgia August 2013 DEDICATION I would like to dedicate this to my parents for their love. iv ACKNOWLEDGEMENTS I would like to thank Dr. Yao-wen Huang for his great guidance and encouragement throughout this project. He has been a great source of inspiration throughout my education. I would like to thank Dr. William L. Kerr and Dr. Robert L. Shewfelt for their support and advice. Dr. Kerr gave me a lot of guidance at every step of my research. I am lucky to have Dr. Shewfelt as my committee member. He is extremely helpful in completing my research. I would like to extend my appreciation to Huiping Huang, Lu Shen, Jing Chen, Xiaomeng Wu, Carl Ruiz and Long Zou for their technical assistance and help. I would also like to thank Dr. Kong for letting me use the instrument in his lab. I would definitely want to thank Chi Zhang. Thank you for giving me the warmth and happiness I needed in difficult days. Last, but certainly not least, I would like to thank my parents and grandmother for their love and encouragement. v TABLE OF CONTENTS Page ACKNOWLEDGEMENTS .............................................................................................................v LIST OF TABLES ........................................................................................................................ vii LIST OF FIGURES ..................................................................................................................... viii CHAPTER 1 INTRODUCTION .........................................................................................................1 2 LITERATURE REVIEW ..............................................................................................6 3 TEXTURE PROFILE OF JELLYFISH PRODUCTS .................................................34 4 INORGANIC CONSTITUENTS IN PROCESSED JELLYFISH AND DETERMINATION OF ALUMINUM CONTENTS BY HPLC ...............................64 5 SUMMARY AND CONCLUSIONS ..........................................................................93 vi LIST OF TABLES Page Table 3.1 Mean values of force peaks and areas for single-blade shear test and moisture content for five commercial products .............................................................................................47 Table 3.2 Mean values of springiness (mm) for TPA ....................................................................48 Table 3.3 Correlation matrix between multiple-blade shear test and single-blade shear test of jellyfish ..............................................................................................................................49 Table 3.4 Mean values for single-blade shear for newly-processed sample under different heating conditions ...........................................................................................................................50 Table 3.5 Mean values for single-blade shear for refrigerator-stored sample under different heating conditions ..............................................................................................................51 Table 4.1 Calibration curve, LOD and LOQ data (n=5) ................................................................76 Table 4.2 Intra- and inter-day precision and accuracy for the quantitative determination ........... 77 Table 4.3 Changes of dry matter of jellyfish sample over 24 h .....................................................78 Table 4.4 Element concentrations of processed jellyfish samples (bought from Dalian, China) ..79 Table 4.5 Element concentrations of processed jellyfish samples (bought from Nantong, China)80 Table 4.6 Element concentrations of commercial jellyfish products bought from China .............81 Table 4.7 Element concentrations (mg/kg) of processed jellyfish samples (newly-processed) ....82 vii LIST OF FIGURES Page Figure 2.1 Diagram of jellyfish. .....................................................................................................22 Figure 3.1 Multiple-blade attachment with 16 blades (a) and a view of newly-processed sample placed in perpendicular direction to the attachment (b).....................................................52 Figure 3.2 Five different kinds of commercial products collected on the local markets. ..............53 Figure 3.3 Visual comparison between processed jellyfish and deslated jellyfish. .......................54 Figure 3.4 Moisture content of two kinds of samples soaking in water ........................................55 Figure 3.5 Force-time curves of samples soaking for 0, 2, 4, 6, and 8 h generated by single-blade attachment. .........................................................................................................................56 Figure 3.6 Single-blade shear force at the different locations on a sample ...................................57 Figure 3.7 Single-blade shear force (a) and area (b) of newly-processed sample and refrigerator- stored sample after soaking in water for 8 h. .....................................................................58 Figure 3.8 Multiple-blade shear force (a) and area (b)of newly-processed sample and refrigerator-stored sample after soaking in water for 8 h. .................................................59 Figure 3.9 Tension force (a) and area (b) of newly-processed sample and refrigeratore-stored sample after soaking in water for 8 h. ................................................................................60 Figure 4.1Typical chromatogram for Al-quercetin chelate ...........................................................83 Figure 4.2 Aluminum calibration curve; n=5. ...............................................................................84 Figure 4.3 Aluinum concentrations in newly-processed sample (a) and refrigerator-stored sample (b) soaking in water and 2% vinegar solution. ..................................................................85 viii Figure 4.4 Aluminum concentrations in dried refrigerator-stored sample soaking in water and 2% vinegar solution. .................................................................................................................86 Figure 4.5 Aluminum concentrations in soaking solutions. ..........................................................87 ix CHAPTER 1 INTRODUCTION Jellyfish is the common name of certain invertebrate animals of the phylum Cnidaria, which belongs to the Class Scyphozoa (Gibson and Barnes 2000). Several species with mild stings are edible, among which, Rhopilema esculentum Kishinouye is the most abundant and important species in the Asian jellyfish fishery (Hsieh, Leong and Rudloe 2001, Yu et al. 2006b). They have symmetrical soft bodies consisting of a gelatinous umbrella-shaped bell and trailing tentacles. Millions of jellyfish are found along the stretch of coast in the United States especially during the summer season. Jellyfish are regarded as a complex problem set by fish farmers since they sting swimmers, clog up fishing boats and interfere with fishing, aquaculture and power plant operations (Pastino 2007, Carpenter 2004, Owen 2006). Although in the water they are considered as a nuisance, several species of scyphozoan jellyfish with mild stings, about 12 of the approximately 85 species, are used as food in Asian countries for a long time owing to their unique textures (Huang 1988). Jellyfish production is a multi-million dollar business with an increase in the demand together with a reduction in the stock size (Hsieh et al. 2001). A large portion of the jellyfish body is called umbrella, composed of mesogloea and outer skin, and the upper surface is called the exumbrella and the lower surface is called subumbrella. The mouth is on the undersurface of