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KMID : 0380919960250030441
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Journal of the Korean Society of Food Nutrition
1996 Volume.25 No. 3 p.441 ~ p.452
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Factors Affecting the Photooxidative Stability of Soymilk
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Lee Sang-Hwa
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Abstract
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The effects of chlorophyll, tocopherols(α-tocopherol, γ-tocopherol and δ-tocopherol), carotenoids(β-carotene and lutein), light sources, light intensities and storage temperatures on the photooxidative stability of soymilk were studied by measuring TBA value and depleted headspace oxygen(DHO) of soymilk. The samples were stored in the light storage box for 6 days and evaluated for the photooxidative stabilities. As the concentrations of chlorophyll increased, TBA value and DHO of the sample increased significantly(p＜0.05), indicating chlorophyll acting as a photosensitizer. However, as the concentrations of tocopherols(α-tocopherol, γ-tocopherol and δ-tocopherol) and carotenoids(β-carotene and lutein) increased, TBA values and DHO of the samples decreased significantly (p＜0.05). The light screening effects of carotenoids on DHO in the samples were not significantly different from the control at p＞0.05. Therefore, there was no light screening effects of carotenoids on the oxidative stability of soymilk. The results indicate that tocopherols and carotenoids reduce the photooxidative stability of soymilk. δ-Tocopherol was the most effective in photosensitized oxidation followed by γ- and α-tocopherols in the order of increasing stability. β-Carotene was significantly(p＜0.05) more effective than lutein in minimizing the chlorophyll-sensitized photooxidation of soymilk. Visible light was more effective than UV light in decreasing the photooxidative stability of soymilk. Therefore, photooxidation of soymilk containing chlorophyll is mainly due to photosensitized oxidation rather than photolysis reaction. As the intensities of fluorescence light increased, TBA values and DHO of the samples increased significantly at p＜0.05. However, as the storage temperatures increased, TBA values and DHO of soymilk did not change significantly at p＞0.05.
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KEYWORD
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tocopherol, carotenoid, storage conditions, soymilk
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