The use of carbonyl analysis to follow the main reactions involved in the process of deterioration of dehydrated dairy products: prediction of most favourable degree of dehydration

摘要

Carbonyl analysis was used in order to follow the main reactions involved in the process of deterioration of milk powders. This method was applied after the milk had been processed using microfiltration and ultrafiltration, freeze-drying or spray-drying. Themilk powders were then stored at a temperature of 45 oC and aw ranging from 0.7, 0.11, 0.23 and 0.33 to 0.5 for a period of twenty days.Water adsorption was influenced by powder composition on one hand, with a maximum water adsorption of whey proteins at 0.20 aw, and by the physical state of molecules on the other hand. At certain conditions such as 45 oC and 0.33 aw, amorphous lactose released the water molecules and turned into crystallised lactose. All powders studied exhibited a minimum deterioration, except those rich in lactose, at 0.20 ± 0.5 aw. For the products rich in lactose this minimal deterioration was observed at two awvalues: 0.10 and 0.30. The determination of the monolayer moisturewas carried out either theoretically with the BET model or experimentally so as to predict the most favourable degree of dehydration of dehydrated products.