Food analysis plant proteins

Alongside protein biomarkers in human health, markers of food security even for plant proteins might become essential for the determination of food security and authenticity. In the actual world where products travel rapidly throughout continents, one of the main items for security is the traceability of products to try finding the origin of a possible health problem and make corrective actions. The case reported in June 2011 on the contamination of soya germs by a mutant of E. coli was symptomatic of what is the current risk for human health requiring a formal traceability of plant products and fully sensitive analysis. 

Whilst the updating aspect of the chapters is seen as the prime contribution of this book, an effort also has been made to include a summary of previous knowledge in the field to enable the reader to place new advances in this context. Chapters 1 and 2 review the application of contemporary isolation, quantification, and spectroscopic techniques in flavonoid analysis, while Chapter 3 is devoted to molecular biology and biotechnology of flavonoid biosynthesis. Individual chapters address the flavonoids in food (Chapter 4) and wine (Chapter 5), and the impact of flavonoids and other phenolics on human health (Chapter 6 and, in part, Chapter 16). Chapter 8 reviews newly discovered flavonoid functions in plants, while Chapter 9 is the first review of flavonoid-protein interactions. Chapters 10 to 17 discuss the chemistry and distribution of the various flavonoid classes including new structures reported during 1993 to 2004. A complete listing of all known flavonoids within the various flavonoid classes are found in these later chapters and the Appendix, and to date a total of above 8150 different flavonoids has been reported. 

Immunoaffinity columns are extremely versatile and have been used for the isolation and concentration of a diverse number of analytes from a wide array of matrices (2). Analytes may include macromolecules such as proteins and receptors or small molecules such as environmental toxins, antibiotics, or pesticides. Matrices may include animal tissues or excreta, plant extracts, cell culture medium, or virtually any milieu encountered in biological work. Because of its value as a research tool, immunoaffinity chromatography has found extensive use by the pharmaceutical industry to purify therapeutic proteins, the food safety community to purify small amounts of toxins from food and as a general tool for analytical chemists to purify analytes for subsequent instrumental analysis. 

Antioxidant-rich phytochemicals are micro-constituents in plants and agricultural food products. They differ from proteins, carbohydrates, and lipids, which are macro-nutrients that are abundant in plants and food products. The type and quantity of antioxidant-rich phytochemicals vary significantly from source to source. Different types of the antioxidant-rich phytochemicals may have different antioxidant and other biological activities and bio availability. Although most phytochemicals have UV absorption, using traditional spectrophotometeric methods to quantify the antioxidants is not practical as they could be significantly masked or interfered with by many other compounds in the sources. Thus, the analysis methods for antioxidant-rich phytochemicals are more complicated and sophisticated than the methods used for macro-nutrient compounds. 

Anion exchange chromatography coupled with ICP MS was used in the simultaneous speciation analysis of As, Se, Sb and Te compounds in extracts of fish [230]. Size exclusion chromatography (SEC) coupled with specific detectors is frequently used to analyse species of trace elements in protein-rich materials, such as extracts of meat and plant tissues. For instance, SEC hyphenated with ICP MS was used for the speciation analysis of Cu and Zn in samples of leguminous plants [191]. The same technique was applied to the speciation analysis of Cu, Cd, Zn, Se, As and Ca in fish [220] and Fe, Zn, Cu, Ag, Cd, Sn and Pb in mussels [189]. SEC HPLC coupled with GF AAS mmed out to be very useful for determining levels of Fe species in baby food [312]. With gel permeation chromatography (GPC) GF AAS, the speciation forms of Cd were determined in two kinds of vegetables contaminated with this element [216]. 

Osman, M.A. Chemical and nutrient analysis of baobab (Adansonia digitata) frait and seed protein solubility. Plant Foods for Human Nutrition. 2004, 59, 29-33. 

Thiamine (vitamin Bj) occurs in foods in free and bound forms, the free form predominates in cereals and plants, whereas the pyrophosphate ester is the main form in animal products. Acid hydrolysis is required to release thiamine from the food matrix. Enzymatic hydrolysis is then needed to convert phosphate esters to thiamine. Prior to CE analysis it is necessary to clean up samples by using ethanol to precipitate protein and by passing through an ion-exchange resin. Thiamine has been determined in meat and milk samples using MEKC with ultraviolet (UV) detection at 254 nm, obtaining comparable sensitivity to that achieved by HPLC using an ion-pair reversed-phase column with postcolumn derivat-ization and fluorescence detection. 

The advent of electrospray ionization certainly opened many new application areas for mass spec-trometric analysis. This is based on the ability to provide extreme soft liquid-based ionization. Perhaps the most important application area is the analysis of peptides and proteins. The possibility to perform rapid molecular-weight determination of proteins up to 200 kDa stimulated the commercial availability of MS instrumentation featuring atmospheric-pressure ion sources, equipped with electrospray ionization. Other application areas benefited from these developments. LC-MS has become an important analytical tool in many areas of drug development within the pharmaceutical industry, in the study of natural products in plants, in food and environmental analysis. It is about to enter the clinical application area for therapeutic drug monitoring, systematic toxicological analysis, and monitoring of inherited metabolic diseases. 

CSLM can provide focused images to a depth of up to several hundred micrometers, depending on the nature of the sample, so that sequential sections may be obtained for three-dimensional reconstruction of the image (Figure 2). In addition, several chemical components (e.g., protein and fat in cheese) can be identified and localized simultaneously using specific fluorescent labels. CSLM has been used for the quantitative analysis of cellular structures in plant material, the structural analysis of emulsions of different complexities, and the location of microorganisms in a wide range of food products. 

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