Date of Award:

1949

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Agricultural Systems Technology and Education

Abstract

In many countries of the world and in some parts of the United States milk is produced which has a high bacterial contamination. Such milk of undesirable quality is frequently delivered to factories engaged in the manufacture of cheddar cheese. This milk commonly contains large numbers of lactic acid-producing bacteria or other types of microorganisms which cause objectionable flavors and textural defects in the cheese. The improvement of the quality of milk supply under some conditions is a matter of great difficulty so that the manufacture of inferior quality milk into cheese is a problem often encountered.

In the United States pasteurization of milk is used to reduce the bacterial content and give the cheese maker control over the manufacturing process. Public health officials favor pasteurization as a protection against pathogens; however, in many areas of the world pasteurization is not available. Although pasteurization of milk for cheddar cheese offers certain advantages such as destruction of pathogenic bacteria which may be present, and control of certain undesirable fermentations, experience has shown that pasteurized milk cheese develops flavor slowly and, even with extended ripening, does not have as satisfactory a flavor as good raw milk cheese. The slow ripening usually is attributed to the destruction by heat of certain essential bacteria and enzymes normally present in milk.

Pasteurization, however, destroys many enzymes indigenous to milk as well as some beneficial organisms; consequently, cheese made from pasteurized milk ripens more slowly than cheese made from raw milk. For years, leading dairy technologists have been laboring assiduously but quite unsucessfully to produce cheese free from undesirable organisms yet comparable in flavor and in the rapidity of ripening to the best quality of raw milk cheese. Pursuant to these objectives a number of methods such as replenishing the enzymes in milk destroyed by pasteurization, the use of select ripening cultures, and the use of mixtures of various percentages of raw and pasteurized milk have been tried but without complete success.

These objectionable features of pasteurization led to interest in another method such as the treatment of milk with edible hydrogen peroxide to control fermentation by means of its germicidal and inhibitory action.

This comparative study was conducted to determine the effect of the germicidal properties of hydrogen peroxide in treating raw milk for cheddar cheese making in relation to the flora, quality, and ripening of the cheese.

This study was concerned with the remedial measures which can be applied to milk to overcome some defects in the cheese.

The antiseptic and germicidal properties of hydrogen peroxide are well known. A study involving the use of hydrogen peroxide and catalase has many possibilities in the dairy industry, and the practical aspects of this problem are numerous. Some phases are herewith indicated:

1. If hydrogen peroxide could be used to improve the general quality of cheddar cheese, it would be a boon to the industry and should have a value in the manufacture of cheddar cheese for shelf curing purposes, canning, processing, and for natural ripening in transparent packages.

2. It was believed that the use of hydrogen peroxide and catalase would increase the safety of raw milk cheese. (Kernsman, 1934, found that 0.1 percent of hydrogen peroxide killed E. coli, E. typhi and staphilococcus.)

3. If hydrogen peroxide could be used for destroying organisms harmful in milk and thus for preventing undesirable fermentation, yet leave intact more of the natural enzymes than is possible in accepted pasteurization procedures, the cheese treated with hydrogen peroxide and catalase might ripen faster than pasteurized-milk cheese and have a finer and more pronounced flavor.

4. If approved by public health authorities in the United States, treating milk with hydrogen peroxide would be a simple method of reducing bacterial content in small communities and rural areas. Such procedure would be very practical in preventing growth of bacteria in milk produced under unsanitary conditions.

5. If the use of hydrogen peroxide could be proved practicable, a beneficial program in most countries and especially in the Middle East where dairy equipment and pasteurizers are not readily available and where the production of unsanitary milk predominates might be established.

6. Since this process does not require special equipment it might prove economical and might become, in the future, a useful method of reducing the bacterial content of milk and preserving some of the natural characteristics of the raw milk for cheese making.

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