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Co‐immobilization of pectinase and glucoamylase onto sodium aliginate/graphene oxide composite beads and its application in the preparation of pumpkin–hawthorn juice

Yang, Si‐Qi, Dai, Xiao‐Yan, Wei, Xiao‐Yi, Zhu, Qing, Zhou, Tao
Journal of food biochemistry 2019 v.43 no.3 pp. e12741
Crataegus, enzyme activity, fruit juices, glucan 1,4-alpha-glucosidase, graphene oxide, hydrolysis, pH, pectins, polygalacturonase, pumpkins, reducing sugars, sodium, sodium alginate, starch, sugar content, thermal stability, total soluble solids, transmittance, vegetable juices
Co‐immobilization of pectinase and glucoamylase onto sodium alginate/graphene oxide beads was achieved by N,N′‐dicyclohexylcarbodiimide/N‐hydroxysuccinimide as activating agent. The co‐immobilized pectinase‐glucoamylase (I‐PG) prepared under optimal conditions (pH 4.0, 40°C and 35 min) possessed pectinase activity of 1,227.5 ± 36.5U/g and glucoamylase activity of 1,027.2 ± 29.2U/g, with activity recovery of 73.8% and 85.2%, respectively. Both pectinase and glucoamylase in I‐PG possessed wider pH tolerance and superior thermal stability to those of their free counterparts. Reusability studies indicated that both enzymes in I‐PG retained over 60% of initial activity after six times of reuse. Conditions for the hydrolysis of the pumpkin–hawthorn compound juice by I‐PG were optimized using orthogonal experiments. After treatment with I‐PG, light transmittance, soluble solids, and reducing sugar content in the resulting juice increased significantly, whereas soluble protein and pectin content decreased appreciably. Therefore, the use of I‐PG provided an effective and feasible method for improving quality of the pumpkin–hawthorn juice. PRACTICAL APPLICATIONS: In order to overcome the drawbacks of using free pectinase and glucoamylase, an effective method for the co‐immobilization of these two enzymes onto sodium alginate/graphene oxide beads was developed. The co‐immobilized pectinase/glucoamylase developed in this study could be applied in the clarification of juice rich in pectin and starch.