Inoculation Of Milk Research Articles

Lyophilized Lactic Acid Starter Culture Concentrates: Preparation and Use in Inoculation of Vat Milk for Cheddar and Cottage Cheese

A method to concentrate and lyophilize milk-grown cultures of lactic streptococci which produced cells active in fermentation is described. Inoculated nonfat milk was maintained at pH 6.3 by continuous addition of 30% aqueous sodium carbonate. After growth for 15 to 18h at 30C, the pH was adjusted to 6.9, and 4.5% sodium citrate was added to allow recovery of the cells by centrifugation. The cells were resus-pended in a medium of 10% sucrose, 5% sodium citrate, 5% gelatin, and 2% monosodium glutamate to l/20th the original culture volume, and were frozen and lyophilized. Vials containing the dry concentrate were sealed under vacuum, stored at −22C and +22C, and examined for cell viability and activity. Activity was assayed by simulating cottage and Cheddar cheese making procedures and measuring the final pH. Several lyophilized cultures maintained activity similar to conventional culture for storage of up to 3 mo. Cheddar and cottage cheese were made in 363-kg capacity vats with lyophilized and conventional cultures, and the dry concentrates performed as well as conventional cultures.

Salmonella Survival During Spray Drying and Subsequent Handling of Skimmilk Powder. I. Salmonella Enumeration

Quantitative recovery of Salmonella organisms added to skimmilk powder was investigated with a method based upon recommended procedures for the isolation of Salmonella from dried milk and other foods. The sensitive detection method with a brilliant green pre-enrichment, a brilliant green-sodium sulfathiazole-tetrathionate broth enrichment, and bismuth sulfite for selective platings yielded quantitative results by performing the method in replicate and estimating Salmonella by the Most Probable Number technique. Known levels of added Salmonella were recovered quantitatively from skimmilk powder containing a normal mixed flora. Neither age of cultures, level of inoculum, nor heat shocks given the cultures before milk inoculation affected quantitative recovery of added Salmonella. This method is adaptable and suitable for investigations of Salmonella survival during spray drying and subsequent handling of skimmilk powder

Survival and activity of frozen starter cultures for cheese manufacture.

A study has been conducted on the effect of freezing and storage in liquid nitrogen on 13 strains of lactic streptococci. Cultures were frozen in droplet form and collected in mesh bags. After rapid thawing, the activity of the frozen cultures was compared with a culture of the same organism of the age usually used in cheese-making. The activities of the test and control cultures were traced simultaneously by continuous recording of the pH changes in inoculated milks. Viable counts were performed before and after freezing in liquid nitrogen and after storage in liquid nitrogen. There was no decrease in viable count or loss in activity of the cultures due to freezing and storage. Frozen cultures of some strains showed a shorter lag period after inoculation of milk than control cultures. Frozen concentrated cheese-starter cultures behaved normally in the manufacture of Cheddar cheese.

Survival and Activity of Frozen Starter Cultures for Cheese Manufacture

A study has been conducted on the effect of freezing and storage in liquid nitrogen on 13 strains of lactic streptococci. Cultures were frozen in droplet form and collected in mesh bags. After rapid thawing, the activity of the frozen cultures was compared with a culture of the same organism of the age usually used in cheese-making. The activities of the test and control cultures were traced simultaneously by continuous recording of the pH changes in inoculated milks. Viable counts were performed before and after freezing in liquid nitrogen and after storage in liquid nitrogen. There was no decrease in viable count or loss in activity of the cultures due to freezing and storage. Frozen cultures of some strains showed a shorter lag period after inoculation of milk than control cultures. Frozen concentrated cheese-starter cultures behaved normally in the manufacture of Cheddar cheese.

237. Lactic acid bacteria in relation to cheese flavour. II. Observations on the inoculation of the milk employed in cheese manufacture with lactobacilli

Attempts to improve the flavour of cheese by inoculation of good quality cheese-milk (pasteurized) with selected strains of streptobacteria gave the best results when relatively small inocula were employed. Large inocula imparted a sharpness to the flavour of the cheese during the early stages of ripening, and this sharpness often persisted when the cheese was mature.Several possible methods suitable for the propagation of lactobacilli under factory conditions were investigated. The most convenient procedure consisted in the incorporation in the starter “mother” culture (enriched with a vegetable extract) of suitable strains ofSbm. plantarum; these strains were found to grow better in association with some starters than with others.