Orange juice is a highly valued product representing a significant source of vitamin C. During storage, orange juice undergoes a number of deteriorative reactions resulting in quality degradation of the product . Commercial chilled orange juice is usually produced from frozen concentrates reconstituted and thermally pasteurised
to achieve microbial stability and extend the shelf life of the product. Pasteurisation processes are designed to achieve a target shelf life of a few weeks for
the refrigerated product. Although conventional thermal treatment of fruit juices has been widely and efficiently used, the thermal process has a negative effect on the sensory and the nutritional characteristics of the juices
An important problem associated with orange juice quality is L-ascorbic acid loss during heat treatment or storage . During storage of the juice ascorbic acid is degraded, following two consecutive or parallel pathways, aerobically and anaerobically, at rates depending on storage conditions, packaging and the processing method employed during production High hydrostatic pressure (HHP) processing has been introduced as an alternative non-thermal technology
that causes inactivation of microorganisms and denaturation of several enzymes while minimally affecting quality and organoleptic characteristics Published data on the effect of high-pressure on ascorbic acid content is available for different food
systems . Kinetic studies of vitamin C degradation during HHP treatment have also been reported. Pressure alone was not found to significantly change vitamin C concentration of orangejuice. Only when temperature was above 60 ?C
ascorbic acid degradation was observed, during HHP processes.The effect of HHP on post processing quality loss of fruit juices is an important issue for study. The shelf life of a variety of fruit juices can be extended through the application of HHP compared to that of untreated ones with minimal product quality loss and a good retention of fresh-like flavour. Less than 20% ascorbic acid loss occurred during storage of orange juice at 4 ?C for three months and at 15 ?C for two months after processing at 800 MPa and 25 ?C for 1 min starting with fresh juice . Although several studies reported retention of the overall quality of high pressure processed orange
juice and increase of its shelf life compared to that of fresh juice, few works compare the effect of an alternative HHP process with that of a conventional heat pasteurisation on orange juice quality parameters during storage, studying only specific quality indicators, e.g. sensory characteristics or microbial growth The objective of the present work was to comparatively evaluate the effect of conventional thermal
pasteurisation and alternative HHP processing on the shelf life of reconstituted orange juice within the temperature range used for orange juice storage in two different oxygen barrier packaging types. The determination of shelf life was mainly based on post processing ascorbic acid loss kinetics, although a variety of other quality parameters such as sensory characteristics, colour and viscosity were also taken into
consideration.