Effect of pectic enzymes on cloud stability and soluble limonin concentration in stored orange juice

Abstract

Attempts to use pectic enzymes to stabilise the cloud and reduce the limonin content simultaneously in citrus juices were unsuccessful but led to several significant findings. Acid-catalysed reactions and residual effects of inactivated enzymes were shown to play a more important role in cloud stability than had been generally recognised. The maintenance of resuspended cloud, sometimes used as a measure of cloud stability during storage, was not always related to the actual retention of cloud; and although it was directly related to water-soluble pectin content, cloud retention was not. Factors controlling the solubility of limonin in orange juice appeared more complicated than previously thought and varied in their relative contribution from juice to juice. Other chemical reactions were involved besides the conversion of a non-bitter precursor to limonin, and the changes induced by endogenous pectic enzymes in unpasteurized juice had a more important effect on limonin solubility than the changes following the addition of fungal pectic enzymes to pasteurised juice. Finally, the separation of micro-crystalline limonin complicated limonin analysis of stored juices.

Effect of Assay Temperature on Activity of Citrus Pectinesterase In Fresh Orange Juice

“…At room temperature storage, cloud was lost at 0.25 X lo4 PEU/g single strength juice within 15 months when stored as single strength juice. Chandler and Robertson (1983) observed a continual decline in cloud density of pasteurized juice with storage time at 30°C and postulated that cloud loss was not due to residual enzyme activity but rather due to the result of PE activity before pasteurization and the physico-chemical reactions so initiated continued after pasteurization. Krop (1974) reported that a calcium pectate gel could be formed by high methoxyl apple pectin of 75% DE when the DE had only decreased by 5% when enzymatically deesterified.…”

Effects of High Pressure and Heat Treatment on Pectic Substances and Related Characteristics in Guava Juice

“…Guava juice (20 mL) was centrifuged at 800 ϫ g for 10 min. The turbidity of the upper layer solution was estimated by measuring the absorbance at 660 nm using a spectrophotometer, as described by Chandler and Robertson (1983). The viscosity (cps) was measured with a digital viscometer (Brookfield, USA) at the rotation speed of…”

Comparison of high pressure treatment and thermal pasteurization effects on the quality and shelf life of guava puree

“…Guava puree (20 mL) was centrifuged at 800 ϫ g for 10 min. The turbidity of the upper layer solution was measured as absorbance at 600 nm using a spectrophotometer as described by Chandler & Robertson (1983).…”