Food analysis fruit juices

USE Preserving foods, fats, fruit juices, alkaloidal solns, etc manuf benzoates and benzoyl compds, dyes as a mordant in calico printing for curing tobacco. As standard in volumetric and calorimetric analysis. Pharmaceutic aid (antifungal). 

The introduction of synthetic materials into natural products, often described as adulteration , is a common occurrence in food processing. The types of compounds introduced, however, are often chiral in nature, e.g. the addition of terpenes into fruit juices. The degree to which a synthetic terpene has been added to a natural product may be subsequently determined if chiral quantitation of the target species is enabled, since synthetic terpenes are manufactured as racemates. Two-dimensional GC has a long history as the methodology of choice for this particular aspect of organic analysis (38). 

To detect adulteration of wine. Bums et al. (2002) found that the ratios of acetylated to p-coumaroylated conjugates of nine characteristic anthocyanins served as useful parameters to determine grape cultivars for a type of wine. Our laboratory utilized mid-infrared spectroscopy combined with multivariate analysis to provide spectral signature profiles that allowed the chemically based classification of antho-cyanin-containing fruits juices and produced distinctive and reproducible chemical fingerprints, making it possible to discriminate different juices. " This new application of ATR-FTIR to detect adulteration in anthocyanin-containing juices and foods may be an effective and efficient method for manufacturers to assure product quality and authenticity. 

Although SPME was applied initially for the analysis of relatively volatile environmental pollutants in waters, rapid developments have enabled SPME to be successfully applied for the analysis of pesticides in water, wine and more complex food samples such as honey, fruit juice and pears, vegetables and strawberries. With food samples, most analysts recognize the need for some sample pretreatment in order to minimize matrix effects. The matrix can affect the SPME efficiency, resulting in a reduced recovery of pesticides. The most common method is simply to dilute the sample or sample extract with water. Simpltcio and Boas comminuted pears in water prior to the determination of pesticides. Volante et al. extracted over 100 pesticides... 

Figure 3.31 Analytical isotachophoresis. Ascorbic acid (vitamin C) is naturally present in many foods and is often added to others. Occasionally the cheaper isomer, is oascorbic acid, which has no vitamin action, is used and is distinguishable from the natural isomer by many analytical methods, (a) shows the analysis of a sample of commercial fruit juice while (b) shows the same fruit juice to which a known amount (4 nmol) of isoascorbic acid has been added. (Reproduced by permission of LKB, Stockholm, Sweden.)...

The AOAC 16 " edition describes a difference spectrophotometric method for the analysis of benzoic acid in various food preparations, such as jam, jellies, soft drinks, catsup, beverages, and fruit juices [14]. Before measuring any absorbance values, the sample is extracted four times with ether, and the ether extract purified by washing with solutions of HCl (1 + 1000) and 0.1 % of NH4OH. The maximum absorbance (at 272 nm) was subtracted by the average of the baseline absorbencies at -267.5 and 276.5 nm. 

Foods. The determination of antioxidants and food preservatives is a very active part of the gas chromatography field. Adaptations and sample types are almost limitless for example, analysis of fruit juices, wines, beers, syrups, cheeses, beverages, food aromas, oils, dairy products, decomposition products, contaminants, and adulterants. A detailed discussion of this field may be found in Chapter 9. 

JP Chaytor. The analysis of amino acids in fruit juices by high-performance liquid chromatography. J Sci Food Agric 37 1019-1026, 1986. 

In foods, the simultaneous HPLC analysis of several vitamins is feasible only under special conditions, for example, determination of fortified, free vitamins rather than endogenous ones, which are often bound to other food components, or determination of vitamins in relatively simple foodstuffs, such as fruit juice. The HPLC separation per se of multiple vitamins is not difficult it is their simultaneous, nondegradative extraction from foods that is problematic. Developing a single set of extraction conditions that satisfies the diverse physicochemical properties and stability requirements of several vitamins is a challenge. 

The solubility of NHDC in hot water, alcohol, aqueous alkali, acetonitrile, dimethyl sulfoxide, and alcohol/water mixture facilitates its selective extraction from food samples (20,91,94). It is extracted from jams, fruit juices, and dairy products with methanol (66,93) or acetone (95) and filtered or centrifuged. Chewing gum samples are dissolved in chloroform and extracted with water. The extract is centrifuged, and the clear supernatant is injected into the HPLC (95). If necessary, sample cleanup and concentration may be achieved by selective adsorption or desorption (20) on Sep-Pak Cl8 (96). Tomas-Barberan et al. (93) used Amberlite XAD-2 resin for purification of jam extract. Sugars, pectin, and other polar compounds were eluted with water, and NHDC was eluted with methanol. After concentration, the extract was further purified on a Sephadex LH-20 column prior to HPLC analysis. 

A method is described for the determination of the preservatives SA and BA in foods (including yogurt, soft drinks, and fruit juices) based on HPLC on a hydrogen-sulfonated divinyl-benzene-styrene copolymer column, isocratic elution with 0.01 N sulfuric acid/acetonitrile (75 25) mobile phase and UV detection at 220 nm (for BA) and 258 nm (for SA). Soft drinks and fruit juices merely require dilution and filtration before injection yogurt samples require treatment with potassium ferricyanide (III) and ZnS04 before analysis. Recovery of SA from yogurt was 95-110% the detection limit was 0.01 mg/kg. The recovery of BA from soft drinks and fruit... 

J Kantasubrata, S Imamkhasani. Analysis of additives in fruit juice using HPLC. ASEAN Food J... 

Phenolic compounds are of interest due to their potential contribution to the taste (astrin-gency, bitterness, and sourness) and formation of off-flavor in foods, including tea, coffee, and various fruit juices, during storage. Their influence on the appearance of food products, such as haze formation and discoloration associated with browning in apple and grape products, is also significant. Furthermore, analysis of these phenolic compounds can permit taxonomic classification of the source of foods. The importance of each phenolic compound and its association with the quality of various foods is described further in Sec. IV, on food applications. 

High-performance LC techniques are often applied to various fruit juices and drinks (158-161) to evaluate the antioxidative activity, which is attributed largely to the phenolics, such as flavonoids and phenylpropanoids. Analysis of food phenolics is gaining popularity with the growing evidence of possible health-promoting benefits of phenolics in foods, such as antioxidative, antimicrobial, tumor-inhibiting, free-radical scavenging, and other clinically relevant activities. 

Discrimination among all of these is a trivial exercise. Both B vitamins and C were easily quantitated in prepared mixtures as expected [59], but it was also relatively easy to measure each one after its simple extraction into aqueous buffer from pharmaceutical preparations, as well as (in the case of vitamin C) from extracts of fruit, fruit juices, and vegetables. A very thorough inventory of tests for possible interferences was run and the resultant analytical data for the vitamins compared extremely well with the labelled contents on the packages of pharmaceutical products and with the data in compendia that list the average compositions of vitamins and other essential products in plant food materials [33]. Analysis of the major fat soluble D2 and D3 vitamins (ergocalciferol and cholecalciferol) has not progressed with the... 

Price, W.J., and J.T.H. Roos. 1969. Analysis of fruit juice by atomic absorption spectrophotometry I. The determination of iron and tin in canned juice. J. Sci. Food Agric. 20 427-439. 

Wang, J., Sporns, P. (1999). Analysis of anthocyanins in red wine and fruit juice using MALDl-MS. /. Agric. Food Chem., 47, 2009-2015. 

Owing to its liability in acidic medium, enantioselective analysis of linalool (and its cyclic monoterpenoic derivatives) is not suitable as parameter in the origin assessment of acidic foods like fruits, fruit-juices, wines etc. 

Molecular model of benzoic acid, CgHjCOOH. Benzoic acid occurs widely in nature, particularly in berries. It finds broad use as a preservative in foods, fats, and fruit juices as a mordant for dying fabric and as a standard in calorimetry and in acid/base analysis. 

Chinnici, F., Spinabelli, U., Riponi, C., and Amati, A. 2005. Optimization of the determination of organic acids and sugars in fruit juices by ion-exclusion liquid chromatography. Journal of Food Composition and Analysis 18 121-130. 

Gas-selective electrodes are used to a hmited extent in food analysis although, in certain areas of food production their use is quite common. The oxygen-selective electrode is often used on the production hnes for fruit and vegetable juices, where a vacuum has been apphed to remove air before packaging, this in order to check the residual oxygen content. S02-selective electrodes are used to determine the SO2 content of wines and other S02-treated liquids either directly or after the acid conversion of a component such as NaHSOa to SO2. Other electrodes are available for similar measurements, such as nitrogen oxide (for nitrite contents) and carbon dioxide (for either CO2 directly or CO2 from acid-converted carbonate or bicarbonate salts). There are perhaps other more accurate ways of determining such analytes, but the gas-selective electrode is... 

L-Ascorbic acid is now produced in thousands of tonnes every year. It is used very extensively in the food industry and has its own E number (E300). Many foods have it added simply as a vitamin supplement, e.g. in fruit juices. In bread making it forms part of the baking process and is used as an antioxidant in a wide variety of foods. It is sold as an over-the-counter medicine in the form of pills and as a component of various multivitamin tablets indeed in shops in California it may be bought in 1 kg containers in powder form. It is clear, therefore, that as part of the quality control and assurance procedures it is necessary to have reliable and accurate analytical procedures. Much remains to be discovered about the role of vitamin C in living systems and as part of such studies analysis of very small quantities of the vitamin in many different matrices derived from both plants and animals will be required. 

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