Journal of Food Engineering, Vol.252, 18-27, 2019
The influence of the structure on the sorption properties and phase transition temperatures of freeze-dried gels
The effect of a tailored structure on sorption properties and phase transition temperatures of freeze-dried gels with low-methoxyl pectin and a mixture of xanthan gum and locust bean gum was investigated. Gels were aerated for 3, 5, 7 and 9 min which together with hydrocolloid type diversified the porous structure of samples. Shrinkage value was in the range 3.5-11.9% for gels with low-methoxyl pectin, and higher for samples with the mixture of xanthan gum and locust bean gum (34.1-40.5%). This structure had impact on the sorption kinetics and isotherms as well as phase transition temperatures. The larger free spaces and smaller shrinkage value lowered the sorption properties. Samples with xanthan gum and locust bean gum aerated by 5 min had the lowest sorption properties related to their structure. The GAB model fitted well with moisture sorption isotherms. The course and shape of DSC curves were affected by the type of gel ingredients, whereas the aeration time did not have any impact on them.