Abstract
During orange juice production, a half of fresh oranges weight is considered as production waste (peels, pulp, seeds, orange leaves and damaged orange fruits). An alternative for the management of these wastes is their treatment by addition of lime and a latter pressing, obtaining a press cake and a press liquor rich in sugars (10° Brix) and citric acid, protein, pectin and ethanol. For non-thermal concentration of press liquor to obtain citruss molasses (65°-70° Brix), the removal of pectin is necessary. Traditionally, depectinization of juices has been done by using pectinmethylesterase (PME) enzymes from external sources. In this work it performed the extraction of PME enzymes from orange peels to obtain the optimum extraction conditions. Two different methods of solventextraction were compared (conventional andultrasound-assisted methods). For the conventional extraction experiments, a central composite design with three variables ([NaCl], pH and time) and five replicates of the center point was used. For ultrasound-assisted extraction, experiments were done at pH = 5.5 and [NaCl] = 1.25M), varying extraction time (1-30 min). Response variables were PME activity, protein content and a ratio between them, named PME effectiveness (ηPME). At the same experimental conditions (pH =5.5, [NaCl] = 1.25 M, t = 15 min) it was found that conventional extractions led to slightly better results in terms of ηPME than ultrasound-assisted extraction method.
Highlights
During orange juice production only approximately the half of fresh oranges weight is transformed into juice [1] while the other half is considered as production waste [2]
It was obtained a wide range of values between 0.01 and 1.23 U/mg (d.b.)
The lowest PME activity was obtained at the lowest NaCl concentration and at center point conditions for pH and time
Summary
During orange juice production only approximately the half of fresh oranges weight is transformed into juice [1] while the other half is considered as production waste (peels, pulp, seeds, orange leaves and damaged orange fruits) [2]. The United States Department of Agriculture (USDA) forecasted a world production of orange juice of 2.2 × 106 metric tons (MT) [3] in 2010, which would lead to around 1.1 × 106 MT of solid wastes These wastes are, in most cases, spread on soil areas adjacent to the production locations, for a final use as raw material for cattle feed, or burned [4]. Based on results obtained by Garcia-Castello et al [8] and Garcia-Castello and McCutcheon [9] with synthetic press liquor solutions it would be expected a considerable improvement in the preconcentration yield of press liquor by membrane technology In this work it performed the extraction of PME enzymes from orange peels to obtain the optimum extraction conditions. Two different methods of solvent extraction were compared (conventional and ultrasound-assisted extraction)
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