LACTULOSE FORMATION DURING BATCH MICROWAVE TREATMENT OF DIFFERENT TYPES OF DAIRY-PRODUCTS

Whole and skim milk, skim milk retentate and skim milk permeate were h eated by batch microwave at 100 degrees C for 10, 20 and 30 min. The e valuation of the heating intensity was estimated by measurement of lac tose isomerization to lactulose. Conventional heat treatment assays un der the same conditions were carried out in order to compare the heat treatment effect. In the microwave heated samples higher levels of lac tulose were observed as compared to those found in the conventionally heated samples. The highest values of the relative standard deviation were those corresponding to the microwave treatments. The differences found in the lactulose formation among the samples studied seem to be due to the equipment design rather than to their composition.