GB596847A - Process for producing yeast extract and food preparations made from yeast - Google Patents

Abstract

A yeast extract is prepared from compressed fresh baker's yeast containing about 75 per cent of water by mixing with 2-4 per cent of its wet weight of sodium chloride, heating to 57-67 DEG C., maintaining at that temperature for at least 40 hours and then separating the resulting extract from the yeast cell residue and evaporating to a desired consistency. The extract may be separated continuously by a centrifuge and the cell residue further centrifuged after adding wash water and if necessary heating by steam. A peeling or sedimentation centrifugal machine may be used with discontinuous separation of the cell residue. Separation may be effected also by filtration either by forcing the liquid up through a filter of compressed cellulose, e.g. by means of a saturated solution of sodium chloride, or by a suction pipe containing the filter being lowered in the liquid. The primary extract and all further extracts obtained by washing the cell residue are evaporated separately or together in open vessels at atmospheric pressure. If evaporation takes place in vacuo, fat is added to reduce foaming. The cell residue may be mixed with finely-divided vegetables e.g. mashed, boiled turnips after evaporating water, and mixing in lactic acid, lactic acid bacillus or Yoghurt-micro-organisms fermenting and, if desired, pasteurising. Beet juice, celery and small amounts of tomatoes may be added. The cell residue can also be utilized by plasmolysing it with sugar or malt and, if desired, proteolytic enzymes. Alternatively, the cell residue may be hydrolysed, e.g. with hydrochloric or sulphuric acid, and after neutralizing boiling the mixture with steam to assist the separation of the remaining cell walls from the mixture by centrifuging, sedimentation or filtering. A suitable method is to hydrolyse one half of the cell residue with acid and treat the other half with sodium hydroxide or lime at 50-60 DEG C. at such concentration that upon mixing the two portions a neutral mixture is obtained. In an example, to 50 kg. of fresh baker's yeast in narrow glass cylinders is added a saturated solution of NaCl at 100 DEG C. corresponding to 3 per cent NaCl on the total mixture and stirred, the temperature becoming 62 DEG C. at which the mixture is maintained for 60 hours. The mixture is raised to 90 DEG C. by steam and centrifuged. Hot water is added to the residue which is centrifuged. The extract and washing water are mixed and first evaporated at atmospheric pressure in a rapidly revolving evaporator and then in a vacuum evaporator. The cell residue is heated for about 24 hours with an amount of H2SO4 corresponding to 3 per cent of the mixture and then neutralized p with chalk and lime, filtered or centrifuged and then evaporated separately or together with the primary extract. 1 per cent of fat is added in portions during vacuum evaporation when foaming is worst.