Conversion of whey solids to an edible yeast cell mass

Claim 2

The process of claim 1 in which said first stage terminates in about 3 to 8 hours.

Claim 3

The process of claim 1 in which said medium on completion of said second stage contains less than 1% of the starting whey protein unincorporated in said yeast cells.

Claim 4

The process of claim 1 in which said fermentation medium at the start of said first stage fermentation contains at least about 22% solids by weight including at least about 3% of said undenatured whey protein and at least about 15% of said lactose.

Claim 5

The process of claim 1 in which said yeast species include at least one yeast species capable of utilizing both lactose and lactic acid from each of the genera Candida, Saccharomyces, and Torulopsis.

Claim 6

The process of claim 1 in which said medium is inoculated with at least four of said bacterial species, including at least two different species from the genus Lactobacillus, and at least one species each from the genus Streptococcus and, from the genus Leuconostoc.

Claim 7

The process of claim 1 in which said fermentation medium during said first stage is aerated by passing intimately dispersed air therethrough at an aeration rate ranging from about 85 to 135 milliliters of air per minute per liter of fermentation medium per each 1% of initial lactose content.

Claim 8

The process of claim 8 in which the air employed for said aeration is enriched with oxygen, and said aeration rate is decreased by 15% for each 20% increment increase in oxygen content over the 20% oxygen content of atmospheric air.

Claim 9

A process for converting the lactose and protein in whey to edible yeast cells, comprising in combination the steps of: a. preparing an aqueous fermentation medium containing essentially undenatured whey protein, lactose, minerals, and added nutrients to provide a balanced medium for promoting the growth of yeasts and bacteria, said medium having a solids concentration of at least 16% by weight inclUding at least 1.5% of said undenatured whey protein and at least 10% of said lactose; b. cool sterilizing said medium without denaturing said whey protein by treatment with hydrogen peroxide and decomposing any residual hydrogen peroxide; c. inoculating said sterile fermentation medium with a lactose-utilizing dairy starter culture including a plurality of different bacterial species capable of converting lactose to lactic acid, said bacterial species including at least one species selected from each of the genera Lactobacillus, Streptococcus, and Leuconostoc, and also inoculating said substrate with a food acceptable yeast culture including a plurality of different yeast species capable of utilizing both lactose and lactic acid, said lactose and lactic acid utilizing yeast species including at least one species selected from each of the genera Candida, Saccharomyces, and Torulopsis; d. subjecting said inoculated medium to a first stage aerated fermentation at an initial pH of in the range of 5.1 to 5.5, said fermentation medium decreasing in pH with the build-up of lactic acid therein during said first stage wherein both said bacteria and said yeasts are growing actively until the pH of said medium has fallen to a minimum pH within the range from 4.4 to 4.9 inhibitory to the growth of said bacteria, said first stage being completed in about 3 to 8 hours; and e. thereafter subjecting said fermentation medium to a second stage aerated fermentation during which essentially only said yeasts are growing, the pH of said fermentation medium increasing during said second stage due to the utilization of said lactic acid by said yeasts until a pH above 6.0 has been reached, said second stage being continued until said medium is composed essentially of yeast cells at a concentration of about 7 to 25% by weight yeast cells on a dry basis, said yeast cells containing therein essentially all of said starting whey protein.

Claim 10

The process of claim 10 in which said fermentation medium is sterilized by treatment with said hydrogen peroxide at a temperature of 60* to 70*C. in the presence of a protein-protective agent selected from dextrins and pectins.

Claim 11

The process of claim 10 in which said fermentation medium at the start of said fermentation contains at least about 22% solids by weight including at least about 3% of said undenatured whey protein and at least about 15% of said lactose.

Claim 12

The process of claim 10 in which said fermentation medium during said first and second stages is aerated by passing intimately dispersed air therethrough at an aeration rate ranging from about 85 to 135 milliliters of air per minute per liter of fermentation medium per each 1% of initial lactose content.

Claim 13

The process of claim 13 in which the air employed for said aeration is enriched with oxygen, and said aeration rate is decreased by 15% for each 20% increment increase in oxygen content over the 20% oxygen content of atmospheric air.

Claim 14

A process for converting the lactose and protein in whey to edible yeast cells, comprising in combination the steps of: a. preparing an aqueous fermentation medium containing essentially undenatured whey protein, lactose, minerals, and added nutrients to provide a balanced medium for promoting the growth of yeasts and bacteria, said medium having a solids concentration above 16% by weight including at least 1.5% of said undenatured whey protein and at least 10% of said lactose; b. cool sterilizing said medium without denaturing said whey protein by treatment with hydrogen peroxide in the presence of a protein protective agent selected from dextrins and pectins and decomposing any residual hydrogen peroxide; c. inoculating said sterile fermentation medium with a lactose-utilizing dairy starter culture including a plurality of different bacteRial species selected from the genera Lactobacillus, Streptococcus, and Leuconostoc, said dairy starter culture bacteria being capable of converting lactose to lactic acid and including at least two different species from the genus Lactobacillus, and at least one species each from the genus Streptococcus and from the genus Leuconostoc, and also inoculating said substrate with a food-acceptable yeast culture including a plurality of different yeast species selected from the genera consisting of Candida, Saccharomyces, and Torulopsis, said yeast species being capable of utilizing both lactose and lactic acid and including at least one species selected from each of the genera Candida, Saccharomyces, and Torulopsis; d. subjecting said inoculated medium to a first stage aerated fermentation at an initial pH above 5.0 favorable to the growth of both said bacteria and yeasts, said fermentation medium decreasing in pH with the formation of lactic acid therein during said first stage wherein both said bacteria and said yeasts are growing actively until the pH of said medium drops to a pH below 5.0 inhibitory to further growth of said bacteria, thereby terminating said first stage, said lactic acid-induced inhibitory pH occurring within about 3 to 8 hours from the start of said first stage fermentation; and e. thereafter subjecting said fermentation medium to a second stage aerated fermentation during which essentially only said yeasts are growing, the pH of said fermentation medium increasing during said second stage due to the utilization of said lactic acid by said yeasts until a pH of 6.5 to 8.5 has been reached, said second stage being continued until said medium is composed essentially of yeast cells at a concentration of about 7 to 25% by weight cells on a dry basis, said medium containing less than 1% of the starting whey protein unincorporated in said yeast cells.

Claim 15

The process of claim 15 in which said hydrogen peroxide treatment is carried out at a temperature of about 60* to 70*F. and during said treatment a protein-protective concentration of canary dextrin is present in said medium.