59D-32 |
Novel intelligent pH-sensitive microsphere to control quality of fermented foods |
S. K. PARK, S. I. Kang, and Y. H. Bae. Center for Biomaterials and Biotechnology, Department of Materials and Engineering, Kwangju Institute of Science and Technology, 1 Oryong-dong, Buk-gu, Kwangju, 500-712, South Korea Biopolymers have been developed for drug carriers and active film applications due to their remarkable functionalities. During fermentation, Kimchi, one of Korean fermented vegetable food, produced lactic acids that are responsible for their quality and spoilage. In our laboratory, pH-sensitive microsphere (MS) that contained nisin (100 mm/mL) as an antimicrobial was prepared. This pH-sensitive MS turns into hydrophilic as pH becomes low and release out antimicrobials into Kimchi system. The objectives of this study were to prepare chitosan MS as controlled release delivery systems to maintain fermented food quality at optimum pH 4.5, and investigate pH change, titratable acidity and anti-microbial activity of Kimchi during fermentation period at 15°C for a month. To obtain exact pH-sensitivity of MS, partial N-akylation of chitosan was required. Water solubility of MS as a function of pH was measured by the turbidity changes at 500nm. Then, pH-sensitive chitosan MS was made by the complexation between modified chitosan and nisin and its effects on Kimchi fermentation were examined. The changes of pH and titratable acidity of Kimchi during fermentation generally decreased and level off at pH 4.5 by releasing nisin from chitosan MS. It is explained that the surface of MS was swollen and eroded by the ionization of amine group in modified chitosan depending on pH. The greatest antimicrobial activity of chitosan MS was shown against Lactobacillus plantarum among various bacteria associated with Kimchi fermentation. The fermentation period of Kimchi reaching to the maximum number of cell counts was extended to 2 weeks as compared to control. Theses results suggest that our advanced controlled releasing technology for fermented foods could allow to be kept longer periods. In addition, because of the great diversity in fermented foods, especially Kimchi, the effects of controlled releasing technology could contribute to prolong maximum product quality.
Session 59D, Food Chemistry: Proteins and Physicochemical Properties
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