E. Kostrzewa (a), M. Fonberg - Broczek (b,c), A.Czarnecka (a), J. Danielczuk (a), A.Jakubowski (a), B. Sieliwanowicz (a), S.Skšpska, A. Witkowska - Gwiazdowska (a), D.Zdziennicka (a), J.Arabas (b), J.Szczepek (b).
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(a) Institute of Agricultural and Food Biotechnology, Rakowiecka 36, 02 - 532 Warszawa, Poland
(b) High Pressure Research Center Polish Academy of Sciences , Sokolowska 29/37, 01 - 142
Warszawa, Poland
(c) National Institute of Hygiene, Chocimska 24, 00 - 791 Warszawa, Poland
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Subject of this research was pulp juice produced from apples species Szampion, of low activity of poliphenoloxydase (PPO). Pulp juice contens: homogenised apple pulp - 80 %, sugar - 2,5% , citric acid - 0,05%, ascorbic acid - 0.06% , water - 17,39 %. Juice destined for high - pressure treatment was poured out to 100 ml polyethylene bottles.
Parameters of preservation. Pasteurisation: 850C, 20 min.; high pressure treatment: 450 MPa, 500C, 40 min.
Comparative quality assessment of pulp juice was carried out before treatment, immediately after pasteurisation or high - pressure treatment, as well as after 3 month - storage. The assessment comprised: microbiological investigation, sensorial evaluation of taste and flavour, determination of total extract, pH, total acidity, total contents of phenoles, flavonoids, chlorogenic acid and epicatechine, as well as instrumental colour values : "L" , "a" , "b" and ?.
It was found that directly after preservation and after 3 month storage both pasteurised and high- pressure treated juices complied with all microbiological requirements and did not reveal any activity of PPO. High - pressure treated apple juice retained the taste and flavour of fresh fruits; other quality parameters changed less than those of the pasteurised juice. The only exception was ascorbic acid contents, witch decreased by 90% in high - pressure treated juice after 3 month storage, while the corresponding reduction in the pasteurised juice was 50%.

Research was supported by National Committee of Scientific Research, Grant No PO6HG 02815.

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