Water activity as it is well known, the stability and safety of foods does improve if a_w of the product decreases. The aw of foods influences the multiplication, metabolic activity, resistance and survival of the organisms present (Leistner et al., 1981). Reported that the reduction of aw to about 0.93 would be enough to suppress the growth of most pathogenic bacteria (Chirife & Favetto, 1992) with the exception of Staphylococcus aureus, which may grow aerobically at aw values down to 0.86. Most mould and yeast strains are inhibited between 0.88 and 0.80, although some osmophilic yeast strains can still grow down to 0.6 (Iglesias & Chirife, 1982). The osmotic pretreatment was more efficient in reducing aw as a considerable amount of water was removed during osmosis and an incorporation of sugars occurred. The sample without pretreatment did not lower aw to a safe value.