Abstract:

Chitosan-immobilized pectinase was applied to clarify maca juice in order to avoid turbidity caused by pectin,
water-soluble proteins and/or phenloics during storage. Three operating parameters including pectinase dosage, temperature
and time were optimized based on clarification efficiency by response surface methodology. A quadratic polynomial
regression model was developed indicating the effect of the three operating parameters on clarification efficiency. After
treatment with 43.50 g/L of the immobilized enzyme at 50 ℃ for 104 min, the clarity of maca juice was 95.78%. In
addition, the removal rates of pectin, water-soluble proteins and phenloics were 60.73%, 32.93% and 9.06%, respectively,
and glucosinolates, water soluble alkaloids, VC and total sugar, respectively, lost only 6.92%, 3.35%, 3.25% and 1.82% of
the original amounts, suggesting the major bioactive constituents in maca juice can be mostly retained under the optimized
clarification conditions. After ten cycles of repeated use, the immobilized pectinase provided a clarity of 75.49% when used
to treat a new maca juice, illustrating good repeated usability.

Key words: maca juice, chitosan-immobilized pectinase, clarification