PubMed · 15210438
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2004. Orange juice evolution.. https://pubmed.ncbi.nlm.nih.gov/15210438/
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The caffeine content of selected herbal products and energy drinks available in the Saudi market was determined by HPTLC-UV densitometric analysis. Pre-coated HPTLC silica gel plates (20cm x 10cm) were used for the analysis. The solvent system consisted of ethyl acetate-methanol (85:15, v/v), and caffeine was detected at 275nm. The developed method was validated for specificity, repeatability (C.V. < 5%), recovery (98.90 +/- 3.46), and accuracy (99.84 +/- 2.87). The levels of caffeine were 4.76-13.29% (w/w) and 0.011-0.032% (w/v), for the herbal products and the energy drinks, respectively.
Several bioactive botanicals including St. John's wort (SJW; Hypericum perforatum L.) have been used to formulate functional foods and beverages. This study aimed to investigate the stability of SJW components in aqueous solutions and fruit-flavored drinks. Changes of active marker components (hypericin, pseudohypericin, hyperforin, and adhyperforin) as affected by pH and light exposure were determined by HPLC, and the degradation of hyperforin was analyzed by LC-MS/MS and NMR. SJW components were found to be unstable in acidic aqueous solutions. More changes occurred under light exposure, with hyperforin and adhyperforin decreasing the most. Less severe changes were observed in the drink sample as compared to the pH 2.65 solution. Major degradation products of hyperforin in acidic aqueous solutions were identified as furohyperforin, furohyperforin hydroperoxide, and furohyperforin isomer a. The latter was also found in the drink product containing SJW as an ingredient. Biological activities and potential quality and safety implications of these chemical changes are yet to be evaluated.
A method for the analysis of several volatiles compounds responsible for orange juice flavour (ethyl butanoate, limonene, linalool, alpha-pinene, geranial, neral and alpha-terpineol) has been developed. The isolation of this compounds was carried out by pervaporation (PV) followed by on-line gas chromatography-mass spectrometry (GC-MS). The coupling PV-GC-MS has been successfully applied to fresh hand-squeezed orange juices and frozen concentrated ones in order to establish differences in their flavour profile. Method has been validated with recovery spike experiments which showed its applicability for a wide range of concentrations.