Stabilisation of apricot juice by means of high-pressure treatments

High-pressure treatments are receiving a great deal of attention for the microbiological stabilisation of different food products such as fruit juices and nectars, jams, fresh-cut fruits, and sauces with reduced water activity. In this work, the physico-chemical effects of the high-pressure treatment (HPT) and anti-microbial potential on apricot puree samples were evaluated. Samples of apricot puree (earlier produced in pilot plant) without and with enzymes (pectinesterase, pectinliase, polygalacturonase) were prepared in laboratory conditions. The apricot nectars were treated at 90 °C and after a hot filling in glass bottles, maintained for 5 minutes in boiling water. After pasteurisation the samples were cooled, filled in plastic bags (approx. 1000 g) and frozen at - 20 °C. Research on HPT of apricot juice, processed from apricot fruit, variety S. Castrese, without and with enzymes, was performed at hydrostatic pressure of 400 and 700 MPa, and at temperatures of 20 °C and 50 °C, for 60, 150, and 300 seconds. Results of microbiological analysis showed that no samples contained Salmonella, entherobacteria or coliforms before or after HP treatments. The explanation for that can be that low pH (in apricot samples before HPT was between 3.40-3.60, and in HPT samples pH was between 3.22-3.68) did not support the outgrowth of any spores present. HPT apricot juices retained fresh-like flavour and appearance (colour), as well as rheological properties. In any of HP treated apricot juice samples polyphenol oxidase (PPO) activity was not determined, which means that all HP treatments inactivated enzymes. Combination of high pressure, mild temperature treatment and treatment time may be utilized to improve product safety. If high hydrostatic pressure is to be utilized as food preservation process, it is most likely to be used with another treatment (i.e. with elevated temperatures) in order to increase its effectiveness.