Processing of microbial protein for food use

Hargrave, A.L. (1977). Processing of microbial protein for food use. University of Birmingham. Ph.D.

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Abstract

Processes were investigated for the production of protein fibres from Bakers’ yeast, suitable for food use. Cell disruption by sonication followed by protein extraction at pH 11 and precipitation at pH 3*8 resulted in high protein yield (70% for 100% disruption) but an unacceptably high nucleic acid content (13%w/w DM) in the isolate. Nucleic acid removal was attempted, the main emphasis being on endogenous nuclease methods.
Heat shock (70°C, 6 secs) followed by incubation (55°C, 2 hours, yfeti/v NaCl) of 10%w/v DM fresh whole yeast suspensions resulted in a 95% reduction in the nucleic acid content. However, when this process was followed by disruption, alkaline extraction and acid precipitiation the protein yield in the isolate was only 12% of that without heat treatment.
Incubation of 10%w/v disrupted yeast suspensions at 50°C, 30 mins with 3%w/v NaCl led to an isolate with a protein to nucleic acid ratio (P/NA) of 14, but a protein yield only 37% of that without incubation.
Incubation at 50°C, 2 hours, pH 6 with 3%w/v NaCl, of the alkaline extracted material followed by acid precipitation resulted in an isolate with a P/NA of 23, without loss of yield. However the isolate was rather insoluble and did not yield good fibres on spinning.
Isolates produced by alkaline extraction and acid precipitation from disrupted yeast suspensions were mixed with 3 N NaOH to give dopes which were spun through capillaries into an acid / salt coagulating bath. The strongest fibres were obtained using dopes of 20%w/w DM at pH 10.0. Spinning did not in itself lead to loss of nucleic acid.
Incubation of spun fibres (50°C, 2 hours, pH 6.0, 3%w/v NaCI) with the supernatant fluid separated following acid precipitation gave a product with a P/NA greater than 30« There was no loss in yield and fibre strength was not impaired.
By drying these fibres at room temperature and rehydrating in boiling water a texture similar to that of meat was obtained.

Type of Work:	Thesis (Doctorates > Ph.D.)
Award Type:	Doctorates > Ph.D.
Licence:	All rights reserved
College/Faculty:	Faculties (to 1997) > Faculty of Science
School or Department:	Department of Chemical Engineering
Funders:	Other
Other Funders:	Science Research Council
Subjects:	Q Science > QD Chemistry T Technology > TP Chemical technology
URI:	http://etheses.bham.ac.uk/id/eprint/13204

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