RESUMEN

This study investigated the extraction of polysaccharide from okra pulp (POP), its chemical components, and rheological properties. The results showed that the optimal extraction temperature, time, and the ration of water to material were 20-30 °C, 30 mins, and 150, respectively, giving a maximum yield of 29.4%. The POP extracted under the mild condition showed different properties. The molecular weight of POP varied from 6436 kDa to 7432 kDa. The GalA/Rha and Gal/Rha in POP suggests the domain of rhamnogalacturonan I with long galactose side chains. The POP presented pseudoplastic shear-thinning behavior, which can be described by the Ostward-DeWaele model. The apparent viscosity of POP decreased with temperature rising from 25 °C to 80 °C. In addition, sucrose, CaCl2, and NaCl led to the reduction of its apparent viscosity which was more sensitive to Ca2+ than to Na+ and sucrose. A closed hysteresis loop was obtained when the POP concentration reached to 6 g/L. The POP showed an elastic behavior (G' > G″) at concentration of 6 g/L, while it showed predominantly viscous response (G' < G″) at concentration of 2 and 4 g/L, over a wide range of frequencies (0.1-10 Hz). These results are potentially useful for the application of POP in food processing.

Asunto(s)

Abelmoschus/química , Fraccionamiento Químico , Polisacáridos/química , Polisacáridos/aislamiento & purificación , Reología , Fraccionamiento Químico/métodos , Cromatografía Líquida de Alta Presión , Elasticidad , Concentración de Iones de Hidrógeno , Extracción Líquido-Líquido , Peso Molecular , Monosacáridos/química , Espectroscopía Infrarroja por Transformada de Fourier , Temperatura , Viscosidad

RESUMEN

Kojic acid (KA) with antibacterial activities produced by fermentation was grafted onto konjac glucomannan oligosaccharide (KGO) composed of glucose and mannose linked by ß-1,4 glycosidic bonds. A novel KGO derivative, konjac glucomannan oligosaccharide kojic acid (KGOK) possessing both moisture retention and antibacterial activities was synthesized. The structure of KGOK was characterized and analyzed by thermogravimetric analysis (TG), XRD, UV-vis absorption, FTIR, and 1H NMR. The analysis results suggest that KA was linked to the KGO molecular chain through a covalent bond, and the reaction site of KA was the methylol group. The studies demonstrate that KGOK maintained the excellent moisture absorption and retention properties of KGO and the good antibacterial activities of KA. The minimum inhibitory concentration (MIC) of KGOK is 2 mg/mL for Staphylococcus aureus, Staphylococcus epidermidis, Shewanella putrefaciens, and Salmonella enterica, while its MIC is 3 mg/mL for Escherichia coli. The multi-functionality of the KGOK synthesized from natural sources provides a theoretical foundation for their potential applications in the preservation of food, beverage, aquatic, and cosmetic products.