Effect of different pretreatments before hot air drying of onion on its powder quality during storage

Dried and powdered onionshave many applications in food production.But during onion drying, nonenzymatic browning reaction happens which decreases its quality. In this study, different pretreatments before onion drying were used to prevent destructive reactions. After pealing and grating the onions, they were treated with three treatment methods of sodium metabisulphite 0.5%, citric acid with pH=4 and 10% salt (NaCl) for two minutes. Then, the treated onions were dried at cabinet dryer at two temperatures of 800C and 900C till reaching moisture content of 6 and the produced powders were kept for two months at room temperature and qualitative tests were carried out on them at days 1,30 and 60. Results showed that the pretreatments had significant effects(p