Hygienic quality and antioxidant activities of commerical microalgal products in Taiwan

• Main Authors: Yin-Ta Chen, 陳映達
• Other Authors: Yung-Hsiang Tsai
• Format: Others
• Language: zh-TW
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/91395817115735244058

碩士 === 大仁科技大學 === 環境管理研究所 === 94 === Six green algae products and 6 blue-green algae products sold in Taiwanese markets were tested to determine the chemical and microbiological quality, antioxdant activity and antibacterial activity. It was found that the average values of proximate composition in green algae products and blue-green algae products were protein: 40.78 % and 57.36 %, lipid: 14.28 % and 16.57 %, ash: 7.79 % and 8.07 %, moisture: 6.98 % and 7.15 %, carbonhydrate: 30.17 % and 10.79 %, respectively. The average carbonhydrate value of the green algae products was significantly (p < 0.05) higher than that of the blue-green algae products. In contrast, the average protein level in the green algae products was significantly lower than that of the blue-green algae products, except for BH-C and BH-S products. Among them, only one sample of green algae products and one sample of blue-green algae products had aerobic plate count (4.94 and 5.30 log CFU/g, respectively) greater than the Taiwanese regulatory standard limit of 4.70 log CFU/g. None of these samples contained total coliform and E. coli. The amounts of pheophoride a and heavy metals in all samples were below the Taiwanese regulatory level. Almost these tested samples were acceptable products based on Taiwanese regulatory standards with the chemical and microbiological quality in the samples. The antioxidant properties and antioxidant components of methanolic extracts from microalgal products were studied. Using the scavenging effect on 1,1-diphenyl-2-picryl-hydrazyl radicals, superoxide radicals and chelating effects on ferrous ions, the antioxidant activity of methanolic extracts from green alage products was similar as blue-green algae products. The green algae products showed significantly lower EC50 (50 % effective concentration, EC50) value than blue-green algae products in the reducing power (3.59 and 7.10 mg/ml, respectively). In contrast, the EC50 value of the scavenging effect on hydroxyl radical was lower for blue-green algae products than green algae products (0.07 and 0.11 mg/ml, respectively). Generally, methanolic extracts from green algae and blue-green algae products were good in the antioxidant properties tested. On the other hand, the ascorbic acid and β-carotene contents were similar for both microalgal products, except for GB-D product contained higher β-carotene content (50 mg/g). However, a higher average total phenols level at 4.7 mg/g was found in blue-green algae products than that at 2.5 mg/g in green algae products, whereas the average total chlorophyll content in green algae was higher than that of blue-green algae (24.3 and 12.2 mg/g, respectively). Although the average phycocyanin content at 29.6 mg/g was found in blue-green algae products, only one sample (GB-D product) of green algae products had 0.7 mg/g of phycocyanin. The methanolic extracts of commercial microalgae products were assayed with disc diffusion method for their antibacterial activity against pathogens: Staphylococcus aureus, Bacillus cereus, Escherichia coli and Pseudomonas aeruginosa. None of the green algae products inhibited the four pathogens. Only 2 of the blue-green algae products (FE-S and BH-S) inhibited the growth of S. aureus and B. cereus. The minimum inhibition concentration (MIC) and minimum bactericidal concentration (MBC) of the methanolic extract from FE-S product against S. aureus was 25 μg/ml and against B. cereus was 50 μg/ml, whereas the MIC and MBC of the methanolic extract from BH-S product against S. aureus was 125 μg/ml.