Some Functional Properties of Succinylated Single Cell Protein Concentrate

Single cell protein concentrate was prepared by extracting dried Candida utilis with 0.2 N NaOH at 95 C for 10 min. The soluble protein was precipitated at pH 3.5, washed, and lyophilized. Portions of the protein isolates were succinylated so that 84% of the free amino groups were blocked. Alkaline extractions under optimum conditions gave a yield of 25 to 30% of total solids. Nucleic acid content of the isolates was 10.4% whereas protein comprised 67.3%. Succinylated (SI) and nonsuccinylated (NSI) single cell protein concentrate exhibited similar solubilities above pH 4, the apparent isoelectric point. At pH values below 4, SI was quite insoluble whereas NSI was very soluble at pH 2. Digestibilities as measured by percentage of lysine released from the protein by pepsin and pancreatin were 32.7%, 18.6%, and 3.3% for NSI, whole egg, and SI, respectively. Stabilities of emulsions prepared from corn oil (20–50%) tended to be lower when gelatin was used at the 1% level compared to NSI and SI. However, higher levels of gelatin tended to yield more stable emulsions compared to NSI and SI. Stabilities of emulsions prepared from NSI and SI tended to be comparable with NSI being slightly better. Viscosities of emulsions increased with increasing oil content and increasing emulsifier concentration.