We investigated eight active natural antimicrobials for preservation of functional beverages that are usually degraded by yeasts rather than by bacteria due to a high sugar content and a low pH. Five strains of yeasts (S. cerevisiae, Z. bailii, P. membranaefaciens, C. albicans, and P. Anomala) were tested with eight natural antimicrobial agents (ε-polylysine, yucca extract, vitamin B1 derivative, scutellaria baicalensis extract, chitooligosaccharid, allyl isothiocyanate, sucrose-fatty acid ester, and oligosaccharide). The lowest minimal inhibitory concentrations (MIC) were 10 ppm for oligosaccharide and sucrose-fatty acid ester against S. cerevisiae and Z. bailii, 10 ppm for allyl isothiocynate against P. membranaefaciens and C. albican, and 10 ppm for allyl isothiocynate and oligosaccharide against P. anomala . No growth were observed for five kinds of yeasts in functional beverages containing sodium benzonate at concentration of 0.015% or higher. The resistance of S. cerevisiae, Z. bailii, and P. Anomala against natural antimicrobial agents was lower than those of P. membranaefaciens and C. albican. Allyl isothiocyanate, oligosaccharide, and sucrose- fatty acid ester showed the highest antimicrobial activities among the eight tested antimicrobials. These results can be applied to develop new natural antimicrobial agents to improve microbial quality of functional beverages.

Antifungal activity of seven natural antimicrobials, such as ε-polylysine, extract of Yucca shidigera, TLS (vitamin B1 derivative), BMB-FS, chitooligosaccharide, KDSP 001, and KDSP 002 were investigated for their applications in functional beverage. Five fungi including Aspergillus niger, Penicillium citrinum, Rhizopus oryzae, Fusarium moniliforme, and Mucor rouxii were applied as test fungi and mininum inhibitory concentrations (MICs) of antimicrobials were examined. TLS exhibited the strongst antifungal activity among tested antimicrobials and the growth of all fungi was inibited at 100 ppm. The antifungal activity of BMB-FS appeared different. The growth of Fusarium moniliforme was inhibited by BMB-FS at 100 ppm, but it exhibit antifungal activity on P. citrinum, and M. rouxii at 1000ppm. MICs of TLS appeared to be 60 ppm for four test fungi except A. niger (100 ppm). These results indicate the possible usage of TLS and BMB-FS as natural antimicrobials in functional beverage.

The purpose of this study was to investigate the antimicrobial activities of natural antimicrobials (10 formulas, F1~F10) against yeasts in functional beverages. The growth rates of yeasts were different with the ten different natural antimicrobial formulas tested. Yeasts grew for 14 days and the antimicrobial effect was observed between 14 and 18 days. Levels of S. cerevisiae, Z. bailii, and P. membranaefaciens were reduced to the limit of detection (ND) < 10 CFU/mL) after 28 days. Resistance against the antimicrobial effect was greatest for P. membranaefaciens, which grew to a level of 0.12~1.48 log10 CFU/mL after 14 days and was reduced to a level of 1.61~3.55 log10 CFU/mL after 28 days. The resistance of C. albicans was also high with a growth level of 0.13~1.28 log10 CFU/mL after 14 days and reduction to 1.51~5.30 log10 CFU/mL after 28 days. The antimicrobial effect of F10 was strongest for P. membranaefaciens. Every treatment reduced the microbial levels to 2.68~5.62 log10 CFU/mL after 6 months. F2, F4, F5, F6, and F10 reduced the C. albicans level to ND after 28 days while F1, F3, F8, and F9 reduced yeasts to the ND level after 6 months. The antimicrobial activities observed here will be useful for development of natural antimicrobials.

본 연구는 신선채소류의 대형매장과 재래시상에서의 청결도를 비교하기 위하여 시중에 유통 중인 상추, 깻잎, 오이를 시울과 경기남부의 15개 대형매장과 21개 재래시장에서 sampling하여 총호기성균, 대장균군, Escherichia coli 및 Listeria monocytogenes의 오염도 수준을 평가하였다. 대형매장과 재래시장에서의 상추, 깻잎, 오이의 총호기성균과 대장균군의 오염도는 유의차가 없었다(p>0.05). 그러나 3가지 채소에서의 총호기성균 오염수준은 상추, 깻잎, 오이 순으로 나타났으며 그 수준은 각각 평균 7.01±0.14 log_(10)CFU/g(대형)과 7.10±0.11 log_(10)CFU/g(재래)이었으며 6.69±0.20 log_(10)CFU/g(대형)과 6.44±0.13 log_(10)CFU/g(재래), 5.37±0.25 log_(10)CFU/g(대형)과 5.27±0.19 log_(10)CFU/g(재래)이었으며 대장균군의 오염 순위 또한 같은 양상을 보였다. E. coli검출률 역시 3가지 채소 모두에서 매장간의 유의적 차이는 없었으며(p>0.05) 상추와 깻잎은 대형매장과 재래시장 모두에서 30% 이상의 빈도로 검출되었으나, 오이에서는 10% 미만의 검출빈도를 보였다. L. monocytogenes는 모든 채소에서 검출되지 않았다(ND: 오이 <3 CFU/g, 상추, 깻잎<10 CFU/g. 따라서 본 연구에서 측정된 오염수준은 신성채소류의 미생물위해평가(MRA)프로그램 개발의 기초자료로 활용될 수 있을 것이다.