33F-26 |
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C.-P. LIANG1, M. Wang2, J. E. Simon2, and C.-T. Ho1. (1) Dept. of Food Science, Rutgers, The State Univ. of New Jersey, 65 Dudley Rd., New Brunswick, NJ 08901-8520, (2) Dept. of Plant Biology & Pathology, Rutgers, The State Univ. of New Jersey, Center for New Use Agriculture & Natural Plant Products, New Brunswick, NJ 08901 Citral, a monoterpene aldehyde, contributes to the strong pleasant lemon-like aroma in fresh lemon juice and lemon oil. However, citral is not stable under acidic conditions thus limiting its application in beverage and fragrance industry. During degradation, citral undergoes series of cyclization and oxidation processes. Schieberle et al (1988) reported p-methylacetophenone was more responsible for the off-flavor in citral degradation than a,p-dimethylstyrene and p-cymene-8-ol. Phenolic compounds from plants are well known for their reactive oxygen scavenging activity. Under acidic condition, the formation of off-odor compounds from citral can be affected by the availability of oxygen, pH, temperature, and light. The objective of this study was to use commercially available plant extracts to inhibit the generation of off-odor compounds resulting from citral degradation. Four commercially available plant extracts (green tea, black tea, grape seed, and pomegranate seed extracts) were selected based on their high phenolic contents. 0.1 M citrate buffer (pH 3) containing 100 ppm citral and 200 ppm gallic acid equivalent plant extract was kept in airtight amber glass bottle and incubated in a 40 °C water bath. The reaction mixtures were analyzed by HPLC at 0, 6, 10, 13 and 16 days for monitoring degradation of citral and formation of a,p-dimethylstyrene, p-cymene-8-ol, and p-methylacetophenone. The addition of plant phenolic extracts neither slowed down nor inhibited citral degradation. However, all four plants extracts significantly inhibited p-methylacetophenone formation. The samples with the addition of plant extracts exhibited higher concentrations of a,p-dimethylstyrene and p-cymene-8-ol than the control. This is presumed to be due to the oxygen scavenging effect blocking the pathway from p-cymene-8-ol to p-methylacetophenone. These results suggested that the plant extracts act as antioxidants thus inhibite the generation of p-methylacetophenone regardless the types of the water soluble phenolic compounds exist in different plant extracts. HPLC offers a convenient way to monitor the degradation of citral and the formation of off-odor compounds without further generation or degradation of existing compounds during the analysis due to the increasing temperature.
Session 33F, Nutraceuticals & Functional Foods: Antioxidants and phytochemical analysis
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