The antioxidant activities and total phenolics of 28 plant products, including sunflower seeds, flaxseeds, wheat germ, buckwheat, and several fruits, vegetables, and medicinal plants were determined. The total phenolic content, determined according to the Folin−Ciocalteu method, varied from 169 to 10548 mg/100 g of dry product. Antioxidant activity of methanolic extract evaluated according to the β-carotene bleaching method expressed as AOX (Δ log A 470/min), AA (percent inhibition relative to control), ORR (oxidation rate ratio), and AAC (antioxidant activity coefficient) ranged from 0.05, 53.7, 0.009, and 51.7 to 0.26, 99.1, 0.46, and 969.3, respectively. The correlation coefficient between total phenolics and antioxidative activities was statistically significant. Keywords: Antioxidant activity; phenolics; medicinal plants; oilseeds; buckwheat; vegetables; fruits; wheat products

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The effects of temperature and soluble solids on degradation of anthocyanins in sour cherry concentrate were determined over temperature ranges (-18 to 37)"C and 50 to 80°C. Anthocyanin degradation could be modeled as a first-order rate reaction, with rates of 33.97 X lo-' .hr-1 (lS"Brix), 59.19 X lo-' .I@ (45"Brix) and 97.14 X lo+ .hr-' (71"Brix) at 80°C. Temperature dependence of reaction was described by the Arrhenius relationship. Activation energy for a solids content of U-71' Brix ranged from 16.37-19.14 kcal.mole-' with an average of 17.45 kcaI.mole-1

The effect of microwave and conventional cooking methods on chlorophyll pigments and colour properties of squash, green beans, peas, leek, broccoli and spinach were studied, by HPLC and colorimetry, respectively. In five of six vegetables, chlorophyll a was found more heat resistant compared with chlorophyll b, except in peas. Chlorophylls in peas were retained to the 80-90%, the highest in all vegetables evaluated. Chlorophylls were retained to 19-100%, depending on the vegetable type and cooking method. Pheophytins increased in all vegetables after cooking. Highest chlorophyll a and chlorophyll b losses were observed in boiled leek while microwaved peas and boiled peas retained the most chlorophyll a and chlorophyll b, respectively. Pheophytin a and pheophytin b formation was highest at boiled squash and boiled green beans, which were fifty-ninefold and twentyonefold compared with fresh ones, respectively. Most of the pheophytin formations occurred in boiled and the least in microwaved vegetables. Surface colour changed depending on the type of vegetable and cooking method.

Black tea was extracted for 2, 8 and 18 h with absolute acetone, N,N-dimethylformamide (DMF), ethanol and methanol and their 50% aqueous solutions. The extracts were screened for total polyphenol contents, antioxidant and antibacterial activities. The polyphenol content of the extracts was found to be in the range of 0.44-114.01 mg gallic acid equivalents (GAE)/g dry weight tea, depending on the solvent used and the length of the extraction process. In general, aqueous acetone or DMF extracts displayed the highest polyphenol contents and antioxidant activity, while absolute acetone was the least efficient solvent. Antioxidant activities of tea extracts tested using the reducing power and 2,2-diphenyl-1-picryhydrazyl (DPPH) radical methods ranged from 0.09 to 1.18 and from 2.60 to 95.42 %, respectively, depending on the extraction conditions and the antioxidant activities correlated well with the polyphenol concentrations. Aqueous solvent black tea extracts also possessed antibacterial activity, depending on the solvent used and bacterial species tested. Staphylococcus aureus was found to be the most sensitive to all tea extracts, except for the methanol extract. Tea extracts were not effective against Y. enterocolitica, L. monocytogenes and E. coli O157:H7.

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