[Advances in Food Research] Advances in Food Research Volume 7 Volume 7 || Chlorine in Food Plant Sanitation

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  • Chlorine in Food Plant Sanitation

    BY WALTER A. MERCER AND IRA I. SOMERS

    Western Research Laboratory, National Canners Association, Berkeley, Calijornia

    Page I. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130

    11. Historical Review. 130 111. The Germicidal Ac ne . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133

    1. Mechanism of Microbial Death from Chlorine.. . . . . . . . . . . . . . . . . . . . . 133 2. The Germicidal Agent in Chlorine Solutions. . . . . . . . . . . . . . . . . . . . . . . 134 3. The Pattern of Bacterial Death from Chlorine.. . . . . . . . . . . . . . . . . . . . 136 4. Evaluation of the Germicidal Activity of Chlorine Solutions. . . . . . . . . 140

    IV. The Application of Chlorine in Food Plant Sanitation.. . . . . . . . . . . . . . . . . . 141 1. Definition of Chlorination Terms.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141 . a. Available Chlorine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141

    b. Chlorine Dosage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142 c. Chlorine Demand.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142 d. Total Residual Chlorine.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143 e. Free Available Chlorine.. . . . . . . . . . . . . . . . . . . . 143 f. Combined Availab e . . . . . . . . . . . . . . . . . . . . . . 143 g. Marginal Chlorina . . . . . . . . . . . . . . . . . 143 h. Break-Point Chlor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143

    2. Chlorine Compounds Commonly Used.. . . . . . . . . . . . . . . . . . . . . . . . . . . 145 . . . . . . . . 145

    c. Chloramine Compounds. . . .

    a. In-Plant Chlorination. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158 b. Chlorination of Can-Cooling Waters.. . . . . . . . . . . . . . . . . . . . . . . . . 158 c. Chlorination of Waters Reused for Purposes Other

    V. The Effects of Food Plant Chlorination.. . . . . . . . . . . . . . . . . . . 1. Effect of Chlorination on Plant Sanitation. . . . . . . . . . . . . 2. Effect of Chlorination on Containers and Equipment. . . . 3. Effect of Chlorination on Quality of Foods., . . . . . . . . . . .

    VI. Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

    129

  • 130 WALTER A. MERCER AND IRA I. BOMERS

    I. INTRODUCTION

    Chlorine compounds, correctly used in food plant sanitation, have proved to be safe and dependable germicides. The addition of chlorine to waters used for washing and conveying raw food products, for cleansing food-handling equipment, and for cooling heat-sterilized cans of food has been of inestimable esthetic and practical value in food processing. The ability of chlorine in water solution, even in trace amounts, to destroy microorganisms has made possible longer periods of continuous plant operation under conditions which have enabled the food processor to prepare and package foods which meet the highest standards of sanitation.

    11. HISTORICAL REVIEW

    Chlorine compounds were used long before the element itself was discovered in 1774 by Scheele, who named it I dephlogisticated muriatic acid. In 1785, Berthollet, because of the method used in preparing chlorine, considered it a compound of hydrochloric acid and oxygen. He called it oxygenized muriatic acid. Sir Humphry Davy, in 1810, proved that chlorine was an element and gave it the name by which it is known today.

    The value of chlorine in preventing disease was recognized before the germ theory of disease was established and before the cause of fermenta- tion and decay was known. In 1846, Semmelweis, using chloride of lime, succeeded in eradicating puerperal fever from his medical clinic. Koch, in 1881, made the first investigation of the bactericidal properties of hypo- chlorites. Five years later, the American Public Health Association issued a report favorable to the use of hypochlorite solutions as disinfectants.

    Chlorine compounds began to be widely used as disinfectants during World War I when Dakins Solution (Dakin, 1915) was introduced for the irrigation-disinfection of wounds. The irritating action of this hypo- chlorite solution on living tissue caused Dakin and his associates (1916, 1917) to search for other chlorine-bearing compounds which would be effective as germicides yet would not harm tissue. p-Toluene sulfon- chloramide, now known as chloramine-T, was their final choice.

    As early as 1850, chlorinated lime was used for treating water, and in 1854 a report by the first Royal Sewage Commission of Great Britain referred to the use of chlorinated lime as a deodorant in London sewage (Phelps, 1909). It is probable, however, that Traube (1894) first focused attention on the disinfecting properties of chlorine compounds when added to water supplies. The first attempt in North America to purify water by chlorination was that by Johnson (1911). He reported very satisfactory results when 1.5 parts per million chlorine was added to the

  • CHLORINE I N FOOD PLANT SANITATION 131

    effluent from the Bubbly Creek Filter Plant in Chicago. These results led to the first permanent chlorination installation in this country, when, in 1908, hypochlorites were added to the Boonton, New Jersey, water supply of Jersey City. From this time, the use of hypochlorites for water purification rapidly increased and by 1911 it was estimated that 800,000,- 000 gal. of water per day were being chlorinated. In 1913, Darnall com- pleted development of equipment for chlorinating water supplies by the introduction of gaseous chlorine. Today unchlorinated municipal water is rarely found.

    Among food processors the dairy industry was the forerunner in utilizing the germicidal and deodorant properties of chlorine. I n 1912, Whittaker and Mohler referred to the use of calcium hypochlorite as a sanitizer for milk bottles. Subsequently, many others studied and reported on the uses of chlorine compounds in cleansing dairy farm and milk plant equipment. Prucha (1927) and Loveless (1934) were among the early workers to compare and report on the effectiveness of various methods of applying chlorine solutions to milk-handling equipment, Johns (1930, 1934), Myers (1930), and others studied the comparative germicidal efficiency of the different chlorine products available for use in dairy sanitation. I n 1939, the United States Milk Ordinance and Code recommended chlorine as one of the agents for the bactericidal treatment of milk equipment between each usage.

    The use of chlorine in the canning, freezing, and dehydrating of foods began with its addition to the water used for washing and rinsing equipment during routine cleaning periods. In 1931 (Scott, 1937) the canning industry began to experiment with the addition of chlorine to water used for cooling heat-sterilized cans. Can spoilage caused by aspiration through apparently normal seams of minute amounts of con- taminated cooling water was an annoying and costly problem. The results of experimental chlorination (Merrill et al., 1938) of can-cooling waters soon demonstrated that this leaker spoilage could be drastically reduced by chlorine.

    Development of the principles of break-point chlorination (Griffin, 1946) indicated the possibility of more extensive use of chlorine in food plants. In 1946, Hall and Blundell reported on the beneficial results obtained by chlorination beyond the break-point of the general water supply for a pea cannery and a vegetable freezing plant. This method of chlorination became known as in-plant chlorination. It provided a continuous application of germicidal chlorine to the food preparation equipment during its operation. Critical surveys (Zuch and Somers, 1946; Vaughn and Stadtman, 1946) of the results obtained showed that the use of chlorinated water sprays a t selected points on the preparation

  • 132 WALTER A. MERCER AND IRA I. SOMER9

    lines greatly reduced or prevented the accumulation of microbial slimes. Washing and conveying the raw product in chlorinated water resulted in much lower bacterial counts in the finished product. Odors of fermenta- tion were avoided and the time required for satisfactory plant cleaning shortened.

    Generally, the food processing industry approached with considerable caution the widespread use of in-plant chlorination (Cameron, 1939). Additional information was needed on (1) the possibility of chlorine causing off-flavors in the product, (2) the effect of chlorine on metal equipment, and (3) the concentrations and the costs of chlorine required to maintain satisfactory sanitary conditions.

    In 1946 and 1947 several in-plant chlorination installations were made. Geographically, these installations were widespread and in plants han- dling a considerable variety of fruits and vegetables. The reported results from the use of chlorine in these plants served as a basis for a preliminary evaluation of in-plant chlorination. Conclusions regarding the advantages of this method of chlorination were set forth in a conference in December 1946 (Ritchell, 1947) a t which various food processors, the National Canners Association, and a manufacturer of chlorinating equipment were represented.

    The conclusions reached by this conference are virtually unchanged today. Essentially they were as follows:

    1. The use of chlorine prevents or greatly reduces the accumulation of microbial slimes on all equipment surfaces which are continuously or frequently washed with chlorinated water. Odors due to fermentation and decay are prevented.

    9. Use of chlorinated water permits longer hours of operation by reducing the time required for cleanup.

    3. Total bacteria counts on the finished product are reduced if the raw product is washed in chlorinated water and conveyed over prepara- tion lines bathed with chlorinated water.

    Q. No apparent corrosion of metal equipment occurs from continuous contact with water having a chlorine content normally used in food plant operation.

    6. Chlorine must not be applied indiscriminately. The following precautions should be taken: (a) It must be determined that the flavor of the product will not be adversely affected by chlorine; (b) fruit canning sirups should not be made with chlorinated water; (c) compounds con- taining phenol or related chemicals should not be present in a plant using chlorinated water; (d) frequent tests should be made of the chlorine concentration in the water; (e) standard industrial safety measures should be observed in the use of chlorine.

  • CHLORINE IN FOOD PLANT SANITATION 133

    These conclusions formed on the basis of preliminary studies and observations were confirmed by a succession of studies carried out under varied conditions of food plant operation (Harris, 1946; Brownlee et al., 1947; Scarlett and Martin, 1948; Haynes and Mundt, 1948; Stanley, 1948; Mercer, 1951; Filice, 1953). I n 1951, Somers reported that in the United States there were 230 known installations of in-plant chlorination. Of these, 165 were in fruit and vegetable canning or freezing plants and 57 were in fish processing plants. Today it is estimated that only a small percentage of the canning plants in the United States do not use chlori- nated water a t some point in their operations.

    111. THE GERMICIDAL ACTIVITY OF CHLORINE

    The most remarkable characteristic of chlorine in aqueous solution is its ability even in trace amounts to exert rapid germicidal action. The mechanism of this action is not thoroughly understood despite the long and wide use of chlorine in sanitation. Much of the confusion in this regard resulted from the difficulties experienced by early workers in identifying and measuring the germicidally active chlorine in their work- ing solutions.

    1. Mechanism of Microbial Death from Chlorine

    Many early workers were of the opinion that the killing action of chlorine was due to oxidative reactions involving nascent oxygen which was assumed to be liberated in a union of chlorine with the hydrogen of water. The nascent oxygen, in turn, was supposed to combine with unsaturated components of the cell protoplasm. Well-founded objections to this theory have been brought forth. Oxygen from sources other than chlorine does not kill bacteria as readily as does the amount of chlorine theoretically necessary to yield an equivalent amount of nascent oxygen. Chlorine is also known to have germicidal activity under conditions which exclude direct oxidation of bacterial protoplasm.

    Experimental proof is lacking also for other hypotheses advanced to explain the bactericidal action of chlorine. These include suggestions that bacterial proteins are precipitated by chlorine; that cell membranes are altered by chlorine to allow diffusion of cell contents; and that cell membranes are mechanically disrupted by chlorine.

    More acceptable theories conceive of the direct chemical combination of chlorine with the protoplasm of the bacterial cell. Chlorine would replace one or more hydrogen atoms in amino groups to produce chlora- mines which would be toxic to the cell and eventually cause its death.

    Rudolph and Levine (1941) concluded on the basis of results from their studies with hypochlorite that two phases exist in the death of the

  • 134 WALTER A. MERCER AND IRA I. SOMERS

    bacterial cell: (1) the penetration of the active principle into the cell, and (2) the chemical union of this principle with the protoplasm which is directly responsible for the death of the cell. The majority of investigators now apparently believe that bacterial death by chlorine is a poisoning process in which a form of chlorine combines chemically with the proto- plasm of the bacterial cell to produce toxic organic complexes. If penetra- tion of undissociated chloramines or perhaps intracellular chlorination of nitrogen compounds occurs, it is assumed to be followed by dissociation of the chloramine to produce more specific inhibiting reactions. More recent theories are concerned principally with the mode of the chemical combination.

    The small amounts of chlorine needed to cause effective killing of cells in a bacterial suspension has led to recent theories that chlorine must attack certain oxidizable radicals in essential enzymes. Because of the marked bactericidal efficiency of chlorine in water in concentrations of 0.2 to 2.0 p.p.m., Green and Stumpf (1946) and Knox et al. (1948) con- sidered chlorine a biologically active trace substance. They found experimentally that a precise parallelism existed between the effect of chlorine on bacterial growth and its effect on the rate of glucose oxidation by certain bacteria.

    This corre...

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