Effect of Gelatin on Apple Juice Turbidity

Abstract

Clarification of apple juice by flocculation and precipitation with bentonite and gelatin is explained on a more systematic basis, essentially through the determination of turbidity and zeta-potential. Apple juice was also treated with Polyvinylpolypyrrolidone (PVPP) to remove total polyphenol. Gelatin-particle complex was evaluated as the increase in juice turbidity after the adding of tannic acid. The change of slope during Zeta potential determination indicated that electrostatic forces predominate at low gelatin content, and hydrophobic and hydrophilic interactions occur later at a higher gelatin content. Results also indicated that tannic acid test is useful for determining optimal gelatin concentration for clarification, as test was unaffected by soluble solids, acidity, or pectinase treatment. Gelatin consumption was mainly attributed to colloidal particles. Finally, results indicated that risk of haze by free gelatin in juice required at least 10 times more gelatin than the optimum dosage for clarification.