A procedure was developed to entrap culture bacteria using a twophase (water/oil) system. It consisted of 3% sodium alginate mixed with microbial cells and suspended in an oil bath containing 0.2% Tween 80. While stirring at 200 rpm, calcium chloride (O.OSM) solution was added to break the water/oil emulsion and form calcium alginate gel. The calcium alginate beads containing microbial cells had mean diameters of 25-35 pm (range S-100 pm). The entrapped microbial cells were released completely from the drop shaped beads by gentle shaking in O.lM phosphate solution (pH 7.5) for 10 min. About 40% more lactobacilli survived freezing of ice milk when they were entrapped in calcium alginate than when they were not entrapped.
Microstructure was studied on spray‐dried microcapsules with wall systems consisting of mixtures of whey protein isolate (WPI) and maltodextrins (DE 5, 10, 15) or corn syrup solids (DE 24). Structure of microcapsules was appreciably affected by type of carbohydrate and by the WPI‐to‐carbohydrate ratio. The extent of surface indentation was inversely related to the proportion of WPI in the wall system. Ratio of low‐to‐high molecular weight solutes in the wall system affected structure. At a WPI‐to‐carbohydrate ratio of 1:1 or higher, whey proteins improved the surface‐smoothness and decrease surface indentation of maltodextrin‐based microcapsules. Combinations of WPI with high‐DE value carbohydrates were more effective than those with carbohydrates of low DE value in limiting surface‐dents formation.
Lactobacillus bulgaricus cells were entrapped in beads of calcium alginate and evaluated for their ability to survive freezing processes. Cells survived freezing (without agitation) in ice milk mix much better than in distilled water, and more entrapped cells survived than did cells that were not entrapped. Glycerol and mannitol were cryoprotective, but glucose was not, when each was added (6%) separately to the beads. Entrapment protected the lactobacilli in batch frozen and continuously frozen ice milk mixes. The percentage of survival for entrapped and unentrapped cells in continuously frozen ice milk approximated 90 and 40%, respectively. Lactobacilli survived better in beads with mean diameters > 30 microns than in those averaging 15 microns. Addition of entrapped lactobacilli had no measurable effect on the sensory characteristics of the ice milk.
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