Proper Grip Research Articles

The Bacteriology of Swiss Cheese: V. The Use of Streptococcus thermophilus in Ripening Milk for Swiss Cheese

Summary Attempts were made to ripen milk for Swiss cheese by inoculation with Str. lactis or Str. thermophilus and holding over night at 20 to 25° C. Inoculation of the kettle milk with Str. lactis was also attempted. About one-fifth of the milk to be used in making Swiss cheese was heated to 50° C, inoculated with Str. thermophilus and held for varying periods at that temperature before it was mixed with the rest of the milk for the cheese. Cheeses made with this milk were compared with cheeses made from untreated milk. The experiments led to the following conclusions: 1.Ripening milk by inoculating it with Str. lactis or Str. thermophilus and holding it over night at 20 to 25° C. did not produce satisfactory results, nor did the addition of Str. lactis to the kettle milk. 2.A temperature of 50° C. with a holding time of from 30 to 60 minutes has been satisfactory for ripening the milk with Str. thermophilus. 3.Str. thermophilus introduced into the kettle milk by addition of milk ripened with this organism increased in numbers to a greater extent in thekettle than did Str. thermophilus added as a starter, but grew slightly or not at all in the press. 4.Ripening with Str. thermophilus usually improved the quality of the cheese when the methylene blue reduction time of the kettle milk was 5 to 6 hours or longer, but was not helpful if the milk had a shorter reduction time. 5.pH values of the interior of the cheeses made with milk ripened with Str. thermophilus were lower in the early hours that the cheeses were in the press and higher after 21 hours in the press than the pH values of cheeses made with unripened milk. 6.Ripening part of the cheese milk with Str. thermophilus may be used to improve the quality of Swiss cheese when the kettle milk acts dead, that is, the curd does not have the proper grip or consistency in the kettle.

Aerodynamics for Engineers

IN these articles an attempt will be made to provide an introduction to a large subject specially serviceable to engineers. Restrictions on space make themselves felt in various ways. Proper acknowledgments cannot be given for the sources of information beyond mention of the books of Bairstow, Lamb, Cowley and Levy, and Glauert, to which frequent reference has been made. No account can be included of the fascinating and often instructive historical development of the science; it must be assumed that proofs of various essential theorems will be sought in text‐books of Engineering, Mathematics and Physics; lastly, there can occur little opportunity for the working of illustrative examples upon which a proper grip of the subject greatly depends. The engineer of experience will detect much that, with slight generalisation, could be made capable of important use in other branches of his profession, but in this treatment we shall keep closely in view the scientific aspect of aircraft design, structural strength apart.