| Summary: | The background of this experiment was the use of uncontrollable preservative in commercial jam which was unsafe for human health. The aim of this research was to improve shelf life pineapple jam through decreasing water activity (Aw), increasing glass transition temperature (Tg) by the addition polyol.
The jam was made by mixing 1000 gram pineapple slurry and 1200 gram sucrose, heating at boiling point about 45 minutes to get a thick mixture. After that, glycerol and sorbitol were added at the level 6%, 7% and 8% respectively. The jam then was cooled down to 80°C and added with 18 ml 50% citric acid. The jam was analyzed Aw, Tg, pH, soluble solid, reduction sugar, sensory test, mold and yeast viability. The growth of mold and yeast was evaluated during 6 months storage.
The result showed that the addition of polyol ( glycerol and sorbitol) at 6%,7% and 8% level was able to improve shelf life of pineapple jam. The Aw of treated pineapple jam decreased from 0,83 for control to 0,81 - 0,69 for the addition of 6% - 8% glycerol, and the Tg increased from 23,85 °C to 25,76 °C - 27,77°C. The addition of sorbitol at the level of 6% - 8% was decreasing Aw from 0,83 to 0,81 - 0,68 and increasing Tg from 23,85 °C to 25,44 °C - 27,93 °C. The treated pineapple jam shelf life at ambient temperature was 18 - 20 weeks, whereas for untreated pineapple jam only stored for 2 weeks.
Keywords: pineapple jam -glycerol -sorbitol.
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