Adsorption methods for debittering skim milk hydrolysates were compared in an attempt to develop acid-soluble milk solids for fortification of beverages which appear and taste like the original beverages after fortification of the milk solids up to the level of skim milk. Preliminary studies using casein hydrolysates indicated that the bitter peptides were mostly hydrophobic as they were almost completely eliminated by hydrophobic chromatography on hexylepoxy Sepharose. Activated carbon, talc, and fl-cyclodextrin were more effective in adsorbing bitter peptides than Sephadex G-10. With skim milk hydrolysate, it was observed that activated carbon, glass powder or fiber, Sephadex LH-20, and phenoxyacetyl cellulose were effective in this order in reducing the bitter flavor of skim milk hydrolysate. 100% carbon vs protein completely eliminated the bitterness of Pronase-or ficin-hydrolyzed skim milk; the carbon requirement was reduced by 70% when Pronase hydrolysates were pretreated with glass fiber. About 60% of the riboflavin and less than 5% of the protein were lost during treatment; no substantial decrease in lactose, calcium or ash content was observed. The essential amino acid pattern compared well with the FAO/WHO (1973) provisional reference pattern except for the total aromatic amino acid content which was 81% that of the reference pattern. Sensory analysis of the product indicated that orange crush, orange juice, and grapefruit soda were not significantly preferred over beverages containing 10% hydrolysate solids, while apple juice was preferred to the fortified juice due to a faint whey-like salty flavor of the fortified juice. No difference in the appearance was detected between the fortified and the original beverages except a slight turbidity developed when clear apple juices were fortified. The two bitter peptides were isolated from the butanol extract of the activated carbon used in debittering Pronase-hydrolyzed skim milk. It is likely that these peptides were derived from casein especially cY,l-casein.

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