Lactobacilli are found in large numbers in cheeses of many varieties, and it is therefore believed that they are concerned with the development of flavour. In investigating this, Mabbitt(1) made cheese without starter, adding strains of lactobacilli to the cheese millr to determine whether flavour would then develop. The serological types of the lactobacilli were known, and the present paper describes the serological methods of identifying the strains of lactobacilli which were recovered from the cheese with those which were added.

1. The serum prepared by subjecting Cheddar cheese to pressure becomes inhibitory to the growth of lactobacilli as the cheese ripens.

2. One factor responsible for the inhibitory phenomena is the increasing osmotic pressure of the serum due mainly to the increasing amounts of amino-acids present.

3. Observations made during the ripening of a normal Cheddar cheese suggest that other factors, e.g. amino-acid imbalance, are also important.

Kizer, Hankin, Speck & Aurand(1) have observed that the impurities associated with proteolytic enzymes are stimulating to lactic acid bacteria, and they have suggested that these substances may accelerate the ripening of dairy products. In view of these observations and suggestions an experiment begun in March 1954, on the preparation of cheese with crystalline rennin, is reported below. The results are in agreement with the suggestions of Kizer et al.

A variability study of ball-compressor readings on the upper faces of 10 Cheddar cheeses has shown that:

1. Percentage elasticity readings were generally less discriminating than total deformation readings.

2. As measured by the total deformation, there were firmness gradients across the faces of the cheeses, which tended to increase in firmness from the centre outwards.

Further experimentation to determine consistent firmness differences on cheeses has been recommended and meanwhile, from preliminary examination of firmness discrimination, it is suggested that four total deformation readings may give sufficient accuracy for many routine purposes.