COMPARISON OF SOME ADDITIVES USED IN THE PREPARATION OF FREEZE-DRIED LEMON JUICE CANDIDATE REFERENCE MATERIALS

The stability, storage, and distribution of certified reference materi als which consist of liquid or frozen fruit juices is rather problemat ic. As a better alternative a stable orange juice powder has been obta ined by freeze-drying to a moisture content below 0.4%. However, freez e-drying lemon juices resulted in unstable materials which collapsed i nto lumps after standing some weeks in brown bottles under argon. An a dditive was sought which can be used to obtain stable lemon juice powd ers without influence on important analytical parameters as amino acid s, sugars, organic acids, minerals and flavanone glycosides. The addit ives pectin, hydroxy ethylcellulose? and hydroxypropyl methylcellulose were examined. Powders containing pectin quickly showed a loss of str ucture (collapse) and resulted in non-acceptable changes in amino acid s, sugars or minerals compared to the original lemon juice. The additi on of up to 3% hydroxypropyl methylcellulose seemed more promising, al though some minor changes in the sugar and sodium concentration occurr ed.