Effect of juice extractor settings on juice cloud stability

Juice was extracted from Valencia oranges using three different extractor settings. Differential juice cloud stability was observed. Soft-extracted juice was the most stable, and hard-extracted juice was the least stable. The medium-extracted juice had intermediate cloud stability. Yearly (1997 versus 1998) differences were observed, but the relationship among the juices did not change. Addition of protein extracts, obtained from each juice, to pasteurized juice also resulted in differential cloud stability. Using pectinmethylesterase (PME) activity estimated at pH 4.5, the effects of the protein extract mirrored results from raw juice. Estimating PME activity at pH 7.5 produced contradictory results, indicating that predicting consequences of PME activity estimated at pH 7.5 is unreliable.