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Zhou J.,Hunan Agricultural University | Zhou J.,Hunan Provincial Key Laboratory of Food Science and Biotechnology | Chen X.,Hunan Agricultural University | Chen X.,Hunan Provincial Key Laboratory of Food Science and Biotechnology | And 6 more authors.
Journal of Chinese Institute of Food Science and Technology | Year: 2014

ORAC(oxygen radical absorbance capacity) and DPPH (1, l-diphenyl-2-picrylhydrazyl) assays have been received widely coverage and utilization in antioxidant and oxidative stress. But researches on antioxidant properties of 4 kinds of fermented teas in vitro both by ORAC and DPPH assays have not been reported. In this paper, 4 types of fermented teas (including 16 brands) from different floral origins were screened to quantify the polyphenos, catechins, theaflavins, gallic acid and total flavonoids contents, evaluate the antioxidant capacity and determine the correlations between the parameters analysed. Polyphenols contents were determined by ferrous tartrate method, catechins, theaflavins and gallic acid contents using HPLC, and total flavones contents using aluminium chloride method. Teas' antioxidant capacities were comparatively assessed by ORAC and DPPH assays. Results indicate that Green tea had significantly (P<0.05) higher polyphenlos and catechins [(5.221±0.707) and (3.520±1.025) mg/mL] compared to Oolong, Black and Dark teas. With the increase of the degree of fermentation, the contents of polyphenlos and catechins reduced remarkably. While the fermentation process significantly elevated the levels of theaflavins and gallic acid in Black and Dark teas. The antioxidant capacity as assessed by ORAC assay degreased in the order: Green tea > Oolong tea > Dark tea > Black tea. While using the DPPH assay the following antioxidant capacity was obtained: Green tea > Oolong tea > Black tea > Dark tea. The antioxidant capacities of teas both determined by ORAC and DPPH assays were significantly (P<0.05) correlated with polyphenols and catechins contents, indicating that phenolic compounds are the major contributors to the antioxidant properties of teas. Furthermore, theaflavins may also be contributed to the antioxidant capacities of Oolong, Black and Dark teas. Comparative analysis shows that ORAC is superior than DPPH method to detect the antioxidant capacity of tea. Source

Liu C.,Hunan Agricultural University | Liu C.,Hunan Provincial Key Laboratory of Food Science and Biotechnology | Yi W.,Hunan Agricultural University | Zhou H.,Hunan Agricultural University | Zhou H.,Hunan Provincial Key Laboratory of Food Science and Biotechnology
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering | Year: 2013

The viable probiotic count is the key factor to functionality of fermented milk. It is very important for the milk industry to improve the number of viable bacteria in its final products. Lactobacillus casei and Bifidobacterium were blended using them as a starter culture for fermented milk to achieve a high viable probiotic count. Lactobacillus casei and Bifidobacterium were studied and a high density culture technology of Lactobacillus was applied to increase the number of viable bacteria in the fermentation system. Determination of the absorbance method was used to assess the viable count of probiotics in fermented milk in which the calcium ion would combine with salt under alkaline conditions to make fermented milk dispersed evenly in a solution state. Ethylenediamine Tetraacetic Acid (EDTA) was selected as a chelating agent to chelate the calcium ion in the fermented milk, and to make the solution clarify. The OD value of the bacteria did not change significantly after entering the stable phase, and the number of viable probiotics count in the fermented milk achieved the maximum. The OD value of fermented milk in this study did not change significantly from the second day of fermentation. On this basis, OD value was measured for three consecutive days from the second day, and the average OD value was used as indicator of the viable probiotic count. Inoculation volume, ratio of probiotics strains, added glucose, added soybean peptide, and fermentation temperature were studied as a single factor affecting the number of viable bacterium in the fermented milk. Results show that the average OD value at different inoculation volume was not significant (P<0.01) while the other four factors were highly significant (P>0.01). The ratio of probiotics strains in blend culture, glucose level, soybean peptide level, and fermentation temperature were further studied using a Box-Benhnken design to optimize the fermentation technology. The results were analyzed with the software Design Expert to 8.0. Results indicated that the fermentation system model had an extremely significant effect on predicting the result of the test. The studied factors had significant effects on the average OD value of fermented milk. Results of the response surface optimization test showed that the optimal fermentation condition was: inoculation volume was 6%, the mass fraction of kim milk solid was 12%, the ratio of Lactobacillus casei and Bifidobacterium in blend culture was 3:1, glucose level was 2.9%, soybean peptide level was 0.8%, and fermentation temperature was at 34°C. The predicated average OD value was 1.076 with the optimal fermentation condition, and the verification tests demonstrated that the actual value was 1.087, the relative error was 1.0% compared with the predicated value. The verification tests also showed that the coagulation state of fermented milk was uniform, with less whey separation, and that there was a rich fermented milk flavor, pure without a peculiar smell. The maximum number of viable probiotics count was 4.1×1011 cfu/mL., which is 78.3% higher than the maximum number of viable count (2.3×1011 cfu/mL) before the optimization process. When stored under 4°C after 21 d, the number of viable probiotics count remained at 4.7×1010 cfu/mL. The research result could be used as a probiotic fermentation technology applied to production of probiotic beverages. In addition, it was applied to the industrialized production of probiotic strains used in common acid milk production. Thus, the result greatly increased the viable count of probiotic in the fermented milk and improved functional properties of the product. Source

Chen L.-L.,Hunan Agricultural University | Chen L.-L.,Hunan Provincial Key Laboratory of Food Science and Biotechnology | Yang Y.-L.,Hunan Agricultural University | Qing W.-Z.,Hunan Provincial Key Laboratory of Food Science and Biotechnology | And 4 more authors.
Modern Food Science and Technology | Year: 2015

The aerobic plate count (APC) and the bacterial population structure and diversity on the eggshell surface were studied on the basis of GB 4789.2-2010 and 16SrDNA sequence analysis using the Illumina Miseq Platform. The results showed that the APC values of eight samples ranged from 3.79±0.67 to 5.06±0.75 log CFU/eggshell±SD. The 163214 sequences of the eight samples belonged to Proteobacteria, Firmicutes, Actinobacteria, Bacteroidetes, Fusobacteria and Cyanobacteria, among which Enterococcus, Bacillus, Escherichia-Shigella, Pantoea, and Pseudomonas were dominant in eight samples. In each sample, Pseudomonas, Escherichia-Shigella, Acinetobacter, Bacillus, Stenotrophomonas, and Enterococcus showed the highest relative abundance, which were 67.89%, 36.15%, 68.08%, 40.12%, 21.59%, and 26.98%, respectively. The experimental results demonstrated that there were several bacteria and large bacterial populations present on the eggshell surface, and there were abundance differences for the given bacteria among different egg samples. Egg spoilage may be related to the presence of these bacteria on the eggshell surface and this aspect needs to be studied further. © 2015, South China University of Technology. All right reserved. Source

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