Chilled orange juices stabilized by centrifugation and differential heat treatments applied to low pulp and pulpy fractions

Thermal treatments of citrus juices to inactivate microorganisms and pectinmethylesterase (PME) must be as soft as possible to preserve fresh taste. PME, a cell wall enzyme associated with pulp, is more heat resistant than spoilage microorganisms. This paper analyzes fresh taste and storage stability of orange juices in which the pulp receives a heat treatment more intense than the rest of the juice. The products compared where: A) low pulp juice treated at 60 °C–15 s; B) aseptic blend of A and the corresponding pulpy fraction treated at 85 °C–15 s; C) non aseptic blend of non-treated low pulp fraction and the corresponding pulpy fraction treated at 85 °C–15 s. Product C was finally treated at 60 °C–15 s and packed under aseptic conditions. PME activity in A, B and C was around 10% of that in the original juice (1.30 nkat/ml).After 12 months at 3 °C, juices B and C retained the original fresh taste with minimal losses of color and cloudiness. Juice A maintained fresh taste but its color and cloud were not satisfactory.Industrial RelevanceThe procedures proposed in this paper can be applied to produce chilled orange juices without losses in fresh taste having in addition, higher stability than commercial juices. Other advantages when compared to non thermal emergent technologies are that can be carried out by regular equipments used in citrus industries with an important energy saving. These procedures imply energy savings of 22% to 38% when compared to thermal requirements of juice pasteurization at 85 °C.

Research Highlights
► Thermal treatments must inactivate microorganisms and enzymes in citrus juices.
► Pectinmethylesterase activity is mostly associated to pulpy fraction of juices.
► We evaluate orange juices with pulp fractions submitted to different heat treatments.
► Blend of pasteurized pulpy with low pulp fractions keep fresh taste, color and cloud.
► The blend pasteurized at 65 °C–15 s presented good stability at 3 °C for 12 months.