240 PRACTICAL DAIRY BACTERIOLOGY 



cheese. Swiss cheeses also suffer from gas production, but the 

 phenomenon is totally different from the one which produces 

 the ordinary holes so familiar in that type, and is caused by 

 different species of bacteria. 



Remedies for gassy cheese are chiefly in the way of pre- 

 vention, not of cure. Indeed, it may be stated concerning all 

 the defects of cheeses that, after they have once made their 

 appearance, there is practically no remedy. They are slow in 

 developing, and usually are not seen until the cheese is so 

 far ripened that the injury is beyond repair. The cheese 

 makers' defence is in guarding against them; and for this 

 purpose various methods are within his reach. One of the 

 most satisfactory is the use of a large, vigorous starter of 

 common lactic acid bacteria. The protecting power of this 

 type of bacteria will prevent the growth of many others, and 

 if the non-gas-producing acid organisms are present in the 

 milk in sufficient quantity, the gassy organisms will be held 

 in check. A vigorous culture of slimy whey is said to be 

 efficient in preventing swelling of Edam cheeses, and it will 

 do the same in other types of cheese. 1 A second factor in 

 preventing gas formation is the use of low temperatures. As 

 pointed out on a previous page, the gas-producing organisms 

 develop readily at high temperatures, 80 to 100. At lower 

 temperatures, on the other hand, they do not grow very 

 readily, while the Bact. lactis acidi type does grow vigorously. 

 If, therefore, the curd is kept at low temperatures, the develop- 

 ment of the gassy curd and the gassy cheese is much lessened. 2 

 Cheeses that will become gassy at 75 will not do so at 60. 

 It is possible by a cool temperature so to check the develop- 

 ment of gas that a fair cheese may be produced from milk, 

 which contains enough of gas bacteria to ruin it. A third 

 \ partial preventive is the use of more salt in the cheese, for this 



1 Bockhaut and Vries. Cent. f. Bact., II., xii., p. 89, 1904. 



2 Spallanzani. Rev. Gen. d'Lait. IV., p. 477, 1905. 



