POTENTIAL MICROBIAL CONTAMINANTS 139 volving pasteurized milk both in the swabs and in age Temperatures on the Growth of Psychrophilic Organisms the first milk through the equipment. The frequent in Sterile and Laboratory Pasteurized Skimmilk. J. Dairy occurrence of micrococci might logically be taken Sci., 37:1164. 1954. 5. Macaulay, D. M., Hawirko, R. Z., and James, N. Effect as an omen of potential· hazards of food poisoning of Pasteurization on Survival of Certain Psychrophilic Bac if negligent handling of the products should follow. teria. Appl. Microbial., 11:90. 1963. 6. Marth, E. H. and Frazier, W. C. Bacteriology of Milk AcKNOWLEDGMENT Held at Farm Bulk Cooling Tank Temperatures. III. Psy The generous cooperation of the Omaha-Douglas County chrophiles Found and Their Growth. J. Milk and Food Health Department and the Roberts Dairy Company is grate Techno!., 20:93. 1957. fully acknowledged. 7. Maxcy, R. B. and Shahani, K. M. Cleaning and Sani· tization of Welded Line Systems for Handling Milk. J. Milk and Food Techno!., 24:122. 1961. REFERENCES 8. Mundt, J. 0. and Rai, B. N. Rapid Detection of Faecal 1. American Public Health Association. Standard Methods Coliform Bacteria in the Food Processing Plant. J. Milk and for the Examination of Dairy Products. 11th ed. Am. Pub Food Techno!., 26:46. 1963.. Downloaded from http://meridian.allenpress.com/jfp/article-pdf/27/5/139/2396558/0022-2747-27_5_139.pdf by guest on 27 September 2021 lic Health Assoc., Inc. New York, N. Y. 1960. 9. Schultze, W. D. and Olson, J. C. Jr. Studies on Psy 2. Baumann, D. P. and Reinbold, G. W. Enumeration of chrophilic Bacteria. I. Distribution in Stored Commercial Psychrophilic Microorganisms. J. Milk and Food Techno!., Dairy Products. J. Dairy Sci., 43:346. 1960. 26:81. 1963. 10. Thomas, S. B., Jones, Mena, Hobson, Phyllis M., Wil 3. Kaufmann, 0. \V. and Andrews, R. H. 'The Destruction liams, G., and Druce, R. G. Microflora of Raw Milk and Rate of Psychrophilic Bacteria in Skimmilk. J. Dairy Sci., Farm Dairy Equipment. Dairy Ind., 28:212. 1963. 37:317. 1954. 11. Trout, G. M. Official Acceptance of Homogenized 4. Lawton, W. C. and Nelson, F. E. The Effect of Stor- Milk in the United States. J. Dairy Sci., 46:342. 1963.
SANITARY STUDIES ON MALTED MILK SHAKES' V. D. FoLTZ2 AND Ross MICKELSEN" Kansas Agricultural Experiment Station, Manhattan (Received for publication No'\ember 27, 1963)
SUMMARY tralized ice cream-ice milk mix processing followed One hundred samples of vanilla flavored malted milk shakes by distribution over distances of several hundred were analyzed for the incidence of staphylococci and coliform miles to soft-serve stores could permit considerable organisms. Eighty-one samples contained coliform organisms growth of organisms of the coliform group. Thus, and ten samples contained coagulase positive phage typable the significance of coliform organisms in soft-serve strains of staphylococci. A discussion of bacterial sanitary frozen dairy products, as far as post-pasteurization standards for products such as "malts" and "shakes" is pre sented. contamination is concerned, would seem to be the presence or absence of the organism, and not its Several types of dairy products have been examined total numbers. However, the soft-serve industry by the authors in recent years to determine the might well consider the number of coliform organisms presence of potentially pathogenic staphylococci (2, along with total plate count as an index of mix 4, 5). The findings indicate that post pasteurization quality. contamination may play an important role in intro ducing staphylococci into some dairy products. At ExPERIMENTAL PROCEDURE tempts have been made to correlate the presence of coliform organisms and staphylococci, since the coli One hundred samples of vanilla flavored malted form test is often used as an index of post-pasteuri- milk shakes were collected from malt shops, Sice cream mix ed within 150 miles of Manhattan, Kansas. Samples, at temperatures as low as 4.4 C over prolonged purcha11ed as an ordinary consumer might purchase holding periods (3). Present day practices of cen- them, were immediately transferred to sterile sample jars and refrigerated with dry ice until returned to the laboratory. Analysis of samples was begun with' 'Contribution No. 406, Department of Bacteriology, and Con in 12 hours of collection. tribution No. 323, Department of Dairy Science, Kansas Agricultural Experiment Station, Manhattan; supported in Isolation, enrichment and identification of staphy part by research grant E-3157 from the National Institutes of Health and the Public Health Service. lococci were carried out as previopsly described 2Departmeut of Bacteriology; "Department of Dairy Science. (2). Bacteriophage typing was done at the RegionaJ 140 SANITARY STUDIES ON MALTED MILK
Bacteriophage Typing Center, Kansas State Board of Health Laboratories, Topeka. TABLE 3. RANGE OF COLIFORM COUNTS IN 100 SAMPLES OF Coliform counts were made on Violet Red Bile MALTED MILK SHAKES Agar ( Difco). Confirmation of isolates was done Number of samples Number of coliform present using the methyl red reaction, production of acetyl 19 None methyl carbinol ( Voges-Proskauer reaction) and utili 20 1 to 10 5 11 to 20 zation of citrate (Koser citrate). Additionally, lac 4 21 to 50 tose fermentation, Gram's stain and morphological 7 51 to 100 characteristics were utilized as confirmatory criteria. 8 101 to 200 6 201 to 300" RESULTS 3 301 to 400 4 401 to 500 Qualitative data from examining samples of malted 8 501 to 1000 milk shakes for coliform organisms are presented in 2 1001 to 2000 Downloaded from http://meridian.allenpress.com/jfp/article-pdf/27/5/139/2396558/0022-2747-27_5_139.pdf by guest on 27 September 2021 Table 1. Table 2 contains similar data, quantitative 10 2001 to 5000 1 5001 to 10,000 in nature. 1 10,001 to 20,000 2 20,000 TABLE 1. QUALITATIVE DATA OBSERVATIONS ON COLIFORM ORGANISMS IN MALTED MILK SHAKES •when new standards are proposed, they usually are set at Number of samples a point so two-thirds of the operators qualify. Using the data reported here and such standards would permit 300 per Coliform free 19 ml. Containing coliform 81 Containing Escherichia coli only 14 Containing Aerobacter aerogenes only 42 Containing both Escherichia coli and TABLE 4. RELATIONSHIP BETWEEN THE PRESENCE OR ABSENCE Aerobacter aerogenes 25 OF CoLIFORM ORGANISMS AND Staphylococcus aureus IN MALTED MtLK SHAKES TOTAL 100 Number of Samples containing samples Staphylococcus aureus TABLE 2. QuANTITATIVE DATA OBsERVATIONs oN CoLIFORM Free of colifonn 19 3 ORGANISMS IN MALTED MILK SHAKES Escherichia coli only 14 1 Aerobacter aerogenes only 42 3 Number of Counts samples per mla Both Escherichia coli and Containing Escherichia coli only 14 4100 Aerobacter aerogenes 25 3 Containing Aerobacter aerogenes only 42 1640 Containing Escherichia coli and TOTAL 100 10 Aerobacter aerogenes 25 849
Coliform positive 81 1820 "TABLE 5. PHAGE PATTERNS OF Staphylococcus aureus CuLTURES Coliform negative 19 Pattern Malt sample (No.) Average for 100 samples 1470 3A 10 •Mean arithmetic average. 6, 43E, 47, 53, 83A, 81 16 6, 42E, 45, 83A 16 Table 3 presents the range of coliform counts in 3B, 3C, 71 18 the samples examined. ~D 25 Ten samples contained coagulase positive phage 80, 81 32 80, 81 35 typable strains of staphylococci. The distribution of 29, 52, 79, 80 58 coliform organisms in the ten samples is presented in 6, 7, ~E, 47, 54, 75, 42D 82 Table 4. 79, 80, 3C, 6, 7, 42E, 47, 54, 75, 83A, 81 82 The chi square test showed the relationship between 6, 42E, 47, 77, 81 82 coliform organisms and S. attreus in malted milk 6, 42E, 75, 77, 42D 82 29, 81 89 shakes to be nonsignificant. Thus, the presence or 29, 7, 81 90 absence of coliform organisms is not necessarily a good index as to whether staphylococci will be pres 13 Phage patterns 10 samples ent. The bacteriophage pattern for the ten samples con taining coagulase positive staphylococci is presented DISCUSSION in Table 5. Thirteen separate phage patterns were Standard plate counts were not made. Past ex noted among the ten samples that contained coagu perience indicates that many samples with high lase positive staphylococci. standard plate counts would have been found. In- SANITARY STUDIES ON MALTED MILK 141 terest was directed toward the hvo groups of bacteria mit a coliform count not exceeding one in two of reported. five samples and not exceeding 10 in the other three In the process of pure culture isolation procedures, (1). Some states have no bacterial standards for ice many yeasts were noted in several samples. Counts cream and related products. were not tabulated but the yeasts are a significant Table 7 presents the percentage breakdown of malt index of general sanitary practices. samples that meet indicated arbitrarily-assigned stand Most states have total plate and coliform count ards for both coliform organisms and staphylococci. standards for ice cream and related products. How ever, specific standards for products such as "malts" and "shakes" are not included in most cases so at TABLE 7. PEBCEJ'