Proteome analysis

Proteins serve as the structural and functional entities in cells, contributing as catalysts, secondary messengers, transporters, receptors, etc., and are of considerable importance in cellular characterisation. The 'proteome' has been defined as the entire protein complement of a cell, or a tissue type (Wilkins et al., 1996). Proteomics is the large-scale study analysis of proteins. It involves the assessment of the total cellular protein content, in terms of protein type, nature and quantity,...

Principles of enzyme immunoassays

Immunochemical methods are based on the ability of antibodies (immunoglobulins) to recognise three-dimensional structures and play a major role in biochemical research. Being primarily a part of the immune system in most classes of vertebrates (Stanworth and Turner, 1979), immunoglobulins have been utilised as the key substances in any immunoassay for more than 40 years now. Molecules capable of inducing the production of immunoglobulins in a certain species are called immunogens or antigens....

Isotope terminology and delta scales

The electronic structure of an element primarily governs its chemical reactivity. Although, as a first approximation, the nucleus is responsible for its physical properties.2 All isotopes of a given element possess the same electronic configuration and consequently there are marked similarities in their behaviour. However, this similarity is not limitless. Natural variation in isotope abundance or fractionation is a physical phenomenon and is dependent upon thermodynamic equilibria and kinetic...

Delta notation and isotope reference materials

Differences in isotope effects mentioned in the previous section are usually of the order of a few percent. Consequently, changes in the isotopic ratio at natural abundance levels often occur around the third or fourth significant figure. Isotopic analysis therefore requires very precise measurement and this is achieved by measuring the ratio of the heavy and light stable isotopes in the test material and comparing it to a reference compound of nominal isotope ratio. This is done principally...

PCR based molecular markers

Random amplified polymorphic DNA (RAPDs) are in fact just one example of a whole set of PCR-based molecular markers, which have been collectively termed as MAAP, multiple arbitrary amplicon profiling (Caetano-Anolles, 1993). These approaches have in common the use of one, usually, or two primers of random sequence to amplify multibanded fingerprints from a complex genome (Fig. 1.8). The techniques differ in the length and sequence of the primers, number of amplification cycles, temperature of...

Fluorimetric control of food

Fluorescence spectroscopy has been used for a long time in the control of some food products like milk, meat and fish, but until now, because of the high cost of spectrofluorimeters and the difficulty of interpreting fluorescence spectra, it remains a marginal technique of food quality control. However, recent results with laser induced fluorescence spectroscopy on vegetable fats lead us to believe that spectrofluorimetry could be an important technique for food authentication within a few...

Multicomponent analysis of food products

While on-line moisture measurement using NIR technology remains the principal need within the food industry, other measurements are becoming increasingly important for a number of reasons. Legislation and product in-pack specification issues are becoming ever more important. The continuing trend to produce low fat oil products means measurement of this parameter is more important. While moisture control is practical through more or less drying in a process and therefore the benefit of...

Ultrasonic standing waves

When particles in suspension are placed in a stationary acoustic field (e.g., 13 MHz), they move towards and concentrate at half-wavelength intervals where there is minimum acoustic potential energy (Coakley, 1997). A number of different configurations have been used in order to separate particles and measure their efficiencies. These include the static banding cell, ultrasonic flow cell and ultrasonic. The reported efficiencies for the yeast Rhodotorula glutinans in the flow through design...

Online NIR Instrumentation

For an on-line NIR measurement to be acceptable in most industrial processes, severe constraints are imposed on the instrument design. For example, while most off-line analysers require the product to be carefully presented, pressed against a glass cell window, this is not practical in an on-line situation where a non-contacting system is much more appropriate. An on-line gauge must also be able to tolerate variations in operating conditions. Ambient temperature, relative humidity and the level...

Applications identifying flavour compounds

The chromatographic techniques employed for the analysis of macro- and microcomponents in foods and food products have been recently compiled and critically evaluated (Cserhati and Forgacs, 1999). These cover the differentiation of cassia, cinnamon, ginger, caraway fruits, turmeric powder, bell peppers, onion, garlic, wine, beer, hops, coffee, tea, dairy products, meat, fish, oils, juices, corn-based snacks and peanuts. An analysis of volatile compounds in different edible oils is often...

Near infrared absorption technology for analysing food composition

Benson, NDC Infrared Engineering, UK Near infra-red (NIR) measurement technology offers an amazingly diverse capability for the analysis of many different constituents or properties of food products. Moisture, fat, protein and sugar content are perhaps the most well known applications in products such as grain, flour, cereals, dairy products, snacks and coffee but NIR has also found application for the measurement of chocolate thickness on refiner rollers, the thickness of sausage...

Ultrafiltration and dialysis probes

Macromolecules (e.g., proteins and polysaccharides) in solution can be separated from low M.Wt. solutes (e.g., salts, amino acids) by dialysis which utilises a semipermeable membrane to retain macromolecules and allow small solute molecules to pass through (Fig. 12.8). An alternative way of separating macromolecules from low M.Wt. components is by ultrafiltration, in which pressure, vacuum or centrifugal force is used to filter the aqueous medium and low M.Wt. solutes through a semipermeable...

Essential oils

Quality and authenticity may be established by oxygen heterocyclic compounds such as coumarins, psoralens, and polymethoxylated flavones PMFs in citrus essential oils. Dugo P. et al.12 developed a HPLC method in combination with positive-ion atmospheric pressure chemical ionization-mass spectrometry PI-APCI-MS . Two specific PMFs in bergamot oil, one coumarin in lemon oil, and a different coumarin in bitter orange oil are identified. This method can be useful for authenticity and adulteration...

References

SCOT R.P.W., Techniques and Practices of Chromatography, New York, Marcel Dekker, 1995. 2. MEYER R.W., Practical High-performance Liquid Chromatography, New York, Wiley, 1994. 3. PARRIOTT D., A Practical Guide to HPLC Detection, New York, Academic Press, 1993. 4. NOLLET L.M.L., Food Analysis by HPLC, New York, Marcel Dekker, 2000. 5. HEA-JEUNG WHANG, SUNG-SOO KIM, KWANG-RO YOON, 'Analysis of organic acid in Korean apple juice by high performance liquid chromatography', Journal of the Korean...

Inline sampling

One of the main factors to consider when developing an in-line sensor for process application is the composition of a sample matrix, in particular potential interference e.g., due to background components, general turbidity, homogeneity, etc. that can seriously affect the sensor response and reduce both sensitivity and specificity of the measurement. Other major factors that affect sensor response include the effects of process variables e.g., temperature, pH, Aw, ionic strength, flow rate and...

Phenolic compounds polyphenols and dihydrochalcones

Phenolic compounds, a diverse class of compounds containing a hydroxyl group on a benzene ring, include, among others, flavones, flavonols, flavonoids, polyphenols, and chalcones. When quince is scarce the jam can be adulterated by apple and or pear puree. Silva B.M. et al.7 analyzed by reversed-phase HPLC the phenolic compounds and procyanidin polymers. The detection of arbutin, the characteristic hydroxyquinone of pear, in several samples suggests adulteration with pear puree. For the...

Advantages and disadvantages of the NMR technique

The first limitation in using NMR for food authentication and the most prohibitive one is the cost of the equipment. A new 500 MHz NMR spectrometer might cost 7-8 times as much as a new HPLC UV-DAD system. The second limiting reason is the relatively low sensitivity of NMR compared to other techniques such as HPLC or GC. However, the versatility of the technique means that the initial high cost may well be overridden by a number of advantages that other techniques may not provide. The first of...

J. Agric. Food Chem. 44 1996 2252-2259

Corps Gras, Lipides 5 4 293-295. BAETEN, V. and APARICIO, R. 2000 . Biotechnologie, Agronomie, Soci t et Environnement 4 4 196-203. BAETEN, V., MEURENS, M., MORALES, M.T. and APARICIO, R. 1996 . J Agric Food Chem 44 8 2225-2230 BARTLET, J.G. and MAHON, J.H. 1958 . F. Assoc. Offic. Agric. Chem. 41 2 450-459. BEWIG, K., CLARKE, M., ANDREW, D., ROBERTS, C. and UNKLESBAY, N. 1994 . J. Am. Oil Chem. Soc. 71 2 195-200. BOTTINI, E. and SAPETTI, C. 1958 . Ann. Sper....

Continuous flow Irms Cfirms

The combination of on-line or continuous flow preparation techniques with IRMS, and its origins and developments, has recently been extensively reviewed by Midwood and McGraw.24 It was the work of Preston and Owens25 in coupling an elemental analyser system with an IRMS that first permitted the dual-inlet to be bypassed. Continuous flow IRMS led to a significant evolution in on-line sample preparation techniques based around two principal instruments, the elemental analyser and the gas...

Related titles from Woodheads food science technology and nutrition list

Detecting pathogens in food ISBN 1 85573 670 5 Methods for detecting pathogens need to balance accuracy, specificity and speed. There have been major advances in techniques in all these areas. Detecting pathogens in food sums up the wealth of recent research, the range of techniques available and their applications. The first part of the book looks at general issues such as the role of microbiological analysis in food safety management, sampling techniques and ways of validating individual...