ABSTRACT
Objective: Study on the influence of ζ potential on flocculating rate of Chinese herbs water-extract liquid. Methods: Chitosan of natural macromolecule flocculant was adopted to remove the flocculation impurity of the herb licorice (Glycyrrhizae Radix) extract, and the deep connection between ζ potential and liquid flocculating rate was proved by single factor experiment, orthogonal experiment, and granularity. Results: Under the influence of single factor conditions, absolute value of ζ potential of the system is lower, while the flocculation rate is higher. Based on orthogonal experiment, the optimum process condition of flocculating licorice extract is determined to be the flocculant dosage quantity of 0.347 g/L, pH value of 6, temperature of 30℃, and the system ζ potential of -1.67 mV, which is close to the isoelectric point among all the experiment. Whereas the flocculating rate was as high as 95.29%. The ζ potential of solution before flocculation is -14.78 mV, the average particle size is 17.12 μm; After the flocculation the ζ potential of clear liquid is -1.67 mV, the average particle size is 6.77 μm. The change of ζ potential affected the particle behavior of sol system and ultimately affected the liquid flocculating rate. Conclusion: In the process of flocculating herb licorice extract, the ζ potential has the important influence on the flocculation of herb extract. Absolute value of ζ potential of the system is lower, closer to the isoelectric point, the flocculation rate is higher. The ζ potential that reflects the flocculation essence provides a strong justification for the selection of flocculation conditions.
ABSTRACT
Preservation methods on the physiological and brewing technical characters in bottom and top brewing yeast strains were investigated. The preserved yeasts were reactivated after 24 months storage and grown up to stationary phase. The samples of filter paper storage indicated a higher cell growth and viability during propagation than those of nitrogen and lyophilization storage independent on propagation temperature. In addition, the filter paper storage demonstrated a faster absorption of free amino nitrogen and a highest level of higher aliphatic alcohols production during propagation than other preservation methods, which can be attributed to intensive cell growth during propagation. Moreover, the filter paper storage showed a faster accumulation for glycogen and trehalose during propagation, whereas, in particular, lyophilization storage noted a longer adaptation time regarding synthesis of glycogen and trehalose with delayed cell growth. In beer analysis, the filter paper storage formed an increased higher aliphatic alcohols than control. In conclusion, the preservation of filter paper affected positively on yeast growth, viability and beer quality independent on propagation temperature. In addition, in this study, it was obtained that the HICF and Helm-test can be involved as rapid methods for determination of flocculation capacity.