The cloud of pectinesterase active orange juice was stabilized by inhibiting pectinesterase competitively with pectic acid hydrolysates. Both chemically and enzymatically prepared hydrolysates with an average degree of polymerization of 8 to 15 proved to be suitable, inasmuch as their molecular weight is large enough to inhibit pectinesterase, but too small to cause juice clarification by coagulating themselves. The period of cloud stability of orange juices from various origins could be extended by a factor of 3 to 5 through the additions of 1 mg per ml of hydrolysate with a degree of polymerization of 12. The effect of delayed gelation in orange concentrates was found to be smaller, and higher concentrations of hydrolysates with a somewhat lower degree of plymerization had to be used. Measurement of methanol release proved that pectic acid hydrolysate, added to orange juice, inhibits pectinesterase.