Search

SUMMARY –Malonaldehyde has been identified as a component of commercial aqueous orange juice essences and a procedure for its isolation and identification is described. Fluorescence and phosphorescence spectra of the purified pink complex formed from the reaction of thiobarbituric acid with malonaldehyde exhibited several excitation and emission maxima in the region from 200–550 nm and proved to be a sensitive and highly selective method for confirming the presence of malonaldehyde in a sample. The method is applicable to all citrus essences and should be applicable to the evaluation of malonaldehyde from lipid autoxidation in other fruit juice essences.

Stable isotope ratio mass spectrometry has shown that pure frozen concentrated orange juices (FCOJ) of 63-67° brix possess a mean δ18 value of +14.28%o, with a standard deviation of 1.80. Beet invert syrups, which are produced using ground water, possess negative values. As a result, δ18 values decrease on addition of such syrups to FCOJ. Samples with values less than +8.9%o (3 standard deviations from the mean for pure FCOJs) can confidently be considered as adulterated. A collaborative study was conducted in which a pure FCOJ and 4 samples adulterated to various levels with medium beet invert syrup were sent to each of 6 collaborators. In all but 2 instances, juices containing more than 10% beet syrup would have been classified as adulterated by the collaborators; none would have classified pure juice as adulterated. The plot of mean δ18 values for all collaborators at each adulteration level has a correlation coefficient >0.999. The method has been adopted first action by AOAC International.

Carbohydrate analysis of 5 beet medium Invert sugar (BMIS) samples and 10 pure orange Juices was carried out using anion-exchange chromatography with a pulsed amperometric detector. This analysis revealed the presence of several oligosaccharides In BMIS that were in either low concentration or nonexistent in the orange juice samples. These oligosaccharides may be naturally present In sugar beets or synthesized during the acid and/or enzyme catalyzed hydrolysis of sucrose during the production of BMIS. BMIS was intentionally added to pure orange juice at levels of 5,10,15, and 20%. Subsequent liquid chromatographic (LC) analysis of these Intentionally adulterated samples revealed that detection of 5% BMIS In orange juice was possible.

Adulteration of frozen concentrated and single-strength orange juices with orange pulpwash (PW) have been detected regularly in samples obtained from the North American retail market. This practice is a direct economic fraud on the consumer and to the legitimate grower, processor and distributor. The addition of PW to frozen concentrated or single-strength orange juices may have a profound detrimental effect on the juice flavor and other quality factors. Turmeric, as colorant, alone and in combination with PW has been found in concentrated orange juice for manufacturing imported by some Florida processors. Sorbate preservative has been detected in single-strength orange juices from concentrate obtained from the retail market and packed out of Florida.

Visible and ultraviolet absorption and room temperature fluorescence excitation and emission spectra, obtained from alcoholic solutions of Florida orange juice (OJ) and orange pulpwash (PW), were used to characterize the collaborative study samples. The absorbance sum at 443, 325, and 280 nm and absorbance 443/325 nm ratio were used to estimate the percent total citrus material (TCM), OJ, PW, and dilution of the samples. Six laboratories participated in the study. Known samples of OJ and PW were given to each laboratory for familiarization and instrumental verification. Ten unknown samples (various combinations of OJ and PW) were analyzed by each laboratory. Three duplicate and 2 "closely matched pair" sample set combinations were reported. The results revealed that the method successfully detected the differences in sample formulations. The UV/vis and fluorescence spectrophotometric method has been adopted official first action for detecting adulteration of Florida orange juice with orange pulpwash.

A series of instrumental analyses is used for verification of the authenticity of orange juice: liquid chromatography for sugars, UV-visible spectrophotometry for absorbance measurements, stable isotope ratio analysis of δ13C and δ18O values, and atomic absorption spectrophotometry for potassium and sodium analyses. All authentic orange juices possess positive δ18O values, while those of ground water and water in beet invert syrups are negative. Hence, addition of either to orange juices decreases δ18O values, and allows detection of nonauthentic products.

The combined ultraviolet and visible absorption spectral characteristics of the juices of Florida Hamlin, Pineapple and Valencia oranges, harvested at approximately 2-wk intervals, were all found to be similar in shape but different in peak absorbance. Absorption maxima, recorded on alcoholic solutions of the juices, were observed at 465, 443 and 425 nm of the visible spectrum and at 325, 280 and 245 nm of the ultraviolet spectrum. Processing variables, such as maturity and extractor pressure, appeared to influence absorbance intensities

A colorimetric method for the quantitative determination of the aldehyde content of cold-pressed orange and grapefruit oils is described. The method employs N-hydroxybenzenesulfonamide and may be conducted in conjunction with the analyses of citrus essences and juices for total aldehyde content, since the same standards and reagents are used. Data for reproducibility, standard curves, and sample analyses are given and discussed. Equations are given for conversion of results to per cent decanal.

A procedure has been developed using anion exchange high pressure liquid chromatography (HPLC) which is capable of determining microgram quantities of two common food preservatives, sodium benzoate and sorbic acid, in citrus juices. The compounds are eluted from the column with a simple buffer system and detected with a variable wavelength spectrophotometer. Simultaneous determination is possible. Centrifugation and filtration are the only sample preparations required and HPLC analysis time is less than 10 min. Results, confirmed by ultraviolet absorption and phosphorimetric analyses, are accurate and reproducible. Analysis of fortified juice samples in the common ranges yields values within 5% of the prepared concentration.

Brix frozen concentrated orange juice (FCOJ) were prepared using a commercially prepared 65° Brix Valencia frozen concentrated orange juice as a base product and essences produced by three different Florida commercial citrus processors. The essences differed in odor and flavor characteristics and chemical composition. Essence was added to twelve of the packs on the basis of total aldehydes. Each of the three essences was added to obtain levels of 5, 15, 30 and 45 mg/l of total essence aldehydes in the reconstituted juices. The 13th pack contained no essence and was used as a control. All packs had coldpressed Valencia orange oil added to a level of 0.019% v/v in the reconstituted products. The packs were stored at −22.2°C. Flavor evaluations were made by twelve experienced taste panelists after storage periods of 1.5, 6, 9, 12, 15 and 30 months. Results indicate that essences produced by different recovery systems are distinct and differ in their chemical composition and strength. In some cases there is an optimum level of essence that can be added to a juice to improve its flavor, and higher levels can lower its flavor quality. Storage at −22.2°C had no effect on the flavor of products containing essence as a flavor enhancement material.