USE OF DRY WHEY AND LACTOSE HYDROLYSIS IN YOGURT BASES

Nine batches of yogurts were prepared from nonfat dry milk (NDM) with 3 levels of sweet dry whey (SDW) used in replacement for an amount of NDM and 3 levels of lactose hydrolysis in one experimental series which were replicated 5 times. It was feasible to manufacture yogurt with reconstituted NDM and with 25 % of the NDM replaced with SDW. Fifty % replacement of NDM with SDW resulted in lower flavor scores and affected body and texture. Seventy-five % lactose hydrolysed (LH) batches with 6 % SDW were preferred over unhydrolysed or 50 % LH batches with the same formulation. LH yogurts produced higher titratable acidity. Viscosities of yogurts decreased as the SDW contents of yogurt bases were increased. Water soluble nitrogen (WSN) was higher in yogurts containing SDW and in LH batches. A higher WSN in LH yogurts indicated proteolytic activity of the yeast derived lactase. Proteolytic activity by the culture organisms was also observed.