Effect of high pressure treatment on cell wall polysaccharides of berries

High-pressure processing (HPP) is one of the prosperous techniques in food processing. Under HPP the activities and specificities of different cell wall affecting enzymes change [1]. In juice production cell wall degrading enzymes are used to soften the tissue and destroy a highly viscous pectin gel, which is formed after mechanical mashing of the berries. Thus, cell wall polysaccharides are key compounds for producing juice in higher yields and reduction of press cake quantities. The structure of cell wall polysaccharides is hardly affected by HPP directly, but the treatment might lead to improved enzyme control, giving a benefit for yield and colour of the juice. This is exemplified by Krebbers et al. [1] for two endogenous pectic enzymes affecting the viscosity of the mashed berries. They found a six fold higher activity of pectin methyl esterase after HPP of tomatoes, while the activity of polygalacturonase decreased by 70 %. The first step to show the influence of HPP on enzymatic activity was to analyse cell wall polysaccharides. Mechanically mashed bilberries and black currants were mechanically mashed and treated with 400 MPa at 32 – 43 °C for 15 min. Part of this mash was processed to juice. Cell wall polysaccharides were isolated from the mash, the juice, and the remaining press cake and analysed. The effect of HPP is shown by comparing the obtained data with the data from fresh berries and from juice and press cake of conventional processing [2]. This presentation shows how HPP affects the structure of cell wall polysaccharides. Consequences of the use of enzymatic activity and specificity (endogenous and exogenous) before and after HPP will be discussed. REFERENCES: 1. Krebbers, B., Matser, A.M., Hoogerwerf, S.W., Moezelaar, R., Tomassen, M.M.M., and Van den Berg, R.W., IFSET, 4(4), 377-385 (2003). 2. Hilz, H., Bakx, E.J., Schols, H.A., and Voragen, A.G.J., Carbohydr. Polym., submitted (2004).