Bacteriological Survey of the Frozen Prepared

Transcription

1 APPLIED MICROBIOLOGY, Jan., 19 Copyright 19 American Society for Microbiology Vol. 14, No. 1 Printed in U.S.A. Bacteriological Survey of the Frozen Prepared Foods Industry I. Frozen Cream-Type Pies BERNARD F. SURKIEWICZ Division of Microbiology, Food and Drug Administration, U.S. Department of Health, Education, and Welfare, Washington, D.C. Received for publication 21 June 195 ABSTRACT SURKIEWICZ, BERNARD F. (Food and Drug Administration, Washington, D.C.). Bacteriological survey of the frozen prepared foods industry. I. Frozen cream-type pies. Appl. Microbiol. 14: During Food and Drug Administration inspections of 12 imitation cream pie producers, 453 finished product samples and 35 line samples were collected and analyzed bacteriologically. Sanitary conditions in the plants varied from good to poor and, in general, were reflected in the bacteriological results. The survey revealed that, in the great majority of cases, frozen imitation-cream pies produced in plants operating under good conditions of sanitation had the following bacteriological content: (i) a most probable number (MPN) of fewer than three Escherichia coli cells per gram (i.e., absent from all tubes in the methodology employed), (ii) an average MPN of fewer than 5 coliforms per gram ( or more pies), (iii) the absence of coagulase-positive staphylococci in.1-g portions, and (iv) an aerobic plate count of fewer than 25, per gram (geometric mean of or more pies). In 1957, the Association of Food and Drug Officials of the United States (AFDOUS) instructed a committee to undertake a bacteriological survey of the frozen precooked foods industry. The Food and Drug Administration participated in this program. A report of the Food and Drug Administration's survey during the period from March 1958 to June 1959 was issued in 19 (2). The report dealt with 81 frozen food products collected from 3 firms. Each food product was not considered individually, but was placed in one of four groups of foods according to the amount of cooking which the product may be expected to receive in the home and according to the cooking received by the product at the time of manufacture. The report revealed that sanitary conditions and operating practices in many of the plants were below the desired level. The impact of the survey and voluntary corrective measures of the industry resulted in some improvement in the conditions which had been found during the early stages of the survey. This is the first of a series of papers supplementing the 19 report. Each paper will deal with a specific type of frozen food and will attempt to provide information regarding the 21 microbial content of the product when produced under sound commercial practices. We are reporting here only that portion of the FDA survey dealing with imitation-cream pies. Because of the absence of dairy cream and eggs, this report refers to the product as "imitation-cream" pies. The principal component is a base consisting of vegetable oils, stabilizers, emulsifiers, and water. Varying amounts of sugar, coloring, artificial flavor, dried milk powder, and starch are added to the base. The incorporation of chocolate, extracts, or purees results in the various flavors of pies produced. Except for heating during the manufacture of the pie base (in some cases, the base is purchased by the processor), this type of pie is not cooked or baked. Prebaked pie shells, or a graham-cracker mixture pressed into the form of a pie shell, are filled mechanically with the cold-blended, aerated fillings. The purchaser consumes the product either in its frozen state or after it has thawed in the refrigerator. MATERIALS AND METHODS Collection of samples. A two-man team, consisting of a bacteriologist and an inspector, conducted official inspections of the plants. During each inspec-

2 22 SURKIEWICZ APPL. MICROBIOL. tion, line samples of the ingredients of the pies, line samples during various stages of manufacture, and samples of the finished pies were collected aseptically. When available, samples of pies produced on a date prior to the inspection were collected, also. Immediately upon collection, the samples were placed in the firm's freezer. Upon termination of the inspection, the samples were transported under Dry Ice to the laboratory. In general, analysis was begun 2 weeks from the date of collection. A total of 453 finished-product samples and 35 line samples were collected from 12 imitation-cream pie producers in nine states. Analytical procedure. The methodology recommended by the Frozen Food Subcommittee of AFDOUS was followed (1). A 5-g portion of each sample was weighed into a sterile blending container and 45 ml of sterile buffered phosphate diluent was added. The mixture was blended 2 min. Decimal dilutions were prepared by using 9 ml of a sterile diluent plus ml of the previous dilution. Samples were employed for the following determinations: (i) Aerobic plate count (APC). Duplicate plates of each of three dilutions (1:, 1:1,, 1:,) in Plate Count Agar (Difco) were incubated at 35 C for 48 hr. (ii) Most probable number (MPN) of coliforms. Lauryl sulfate lactose broth (LST) in a three-tube series was inoculated with each of three dilutions (1:, 1:, 1:1,) and incubated at 35 C for 48 hr. Readings were made at the end of each 24-hr period. Gaspositive tubes were loop-transferred to 2% brilliant green lactose bile broth (BGLB) and incubated at 35 C for 48 hr. The MPN was computed from the gas-positive BGLB tubes. (iii) MPN of Escherichia coli. Gas-positive LST tubes were loop-transferred to E C (Difco) broth and incubated for 48 hr at 45.5 C (.5 C) in a water bath. Readings were made at the end of each 24-hr period. Gas-positive E C tubes were loop-streaked on Levine's E M B Agar (Difco) plates from which colonies developing after 24 hr at 35 C were transferred to slants. The isolates yielding IMViC patterns of or were classed as E. coli. (iv) Coagulase-positive staphylococci. Decimal dilutions were planted in single tubes of Trypticase (BBL) soy broth (TSB) to which NaCl had been added to a final concentration of %. After 48 hr of incubation at 35 C, the TSB was loop-streaked on Staphylococcus Medium No. 1 plates. The plates were incubated for 48 hr at 35 C, after which representative colonies were picked and coagulase-tested by means of dehydrated coagulase plasma. REsuLTS Tables 1 to 3 summarize the results of the bacteriological examinations of finished pies as collected from the manufacturer. Each line of the tables represents pies produced on the same date. The plants listed in Table 1 operated under poor conditions of sanitation. In Plant D, the housekeeping was very lax; sugar, flour, starch, etc., were spilled on the floor in many areas. Fruit ffies, roaches, and ants were seen in the processing area, and rodent droppings were noted along the walls. Many of the window screens were in need of repair. Equipment was cleaned only at the end of the 8-hr work shift and employees routinely handled equipment and then the foods, without washing or sanitizing their hands between such diverse operations. Finished pies were cased before freezing, and the cases were stacked with no air space to facilitate rapid freezing. Many of the same objectionable conditions prevailed in Plant E. However, the cream pie operation was relatively small, and three employees handled the product expeditiously, completing the preparation and packaging within 2 hr. Accordingly, the results on the final product failed to reflect truly the observed insanitary practices, although line samples readily demonstrated the inadequacies of equipment cleaning. The pie filling was free of coliforms and had an APC of 1, per gram prior to entry into the filling machine, after which it had a coliform count of 15 per gram and an APC of 47, per gram. Although Plant M conducted an adequate clean-up during the lunch hour and after completion of the day's operation, the employee practices were very poor. No hand-sanitizing solutions were provided, and food handlers used sponges to wipe their fingers and equipment during the weighing and packaging operations. The sponges were rinsed occasionally in water, but were not sanitized throughout the work shift. Finished pies were cased before freezing and stacked without air space in the freezer. Line samples demonstrated that coliforms entered the product from the premixed cocoa and starch powders and remained fairly constant throughout the process, but increased significantly in the finished pies. The APC of the finished product was higher than in samples collected along the processing line. The primary objectionable condition noted in Plant K was the routine practice of employees performing multiple tasks with no attention to sanitation. Employees engaged in packaging finished pies often left their stations to help handle the pie-crust mix and various nonsanitized objects, such as cartons and machinery, and returned to the packaging operation without first washing and sanitizing their hands. As a result, and particularly toward the end of the work shift, coagulase-positive staphylococci appeared in the pie-crust mix, the pie topping, and the finished pies. The influence of inadequate and delayed cooling, combined with failure to clean equipment properly, is illustrated by lines 1 and 2 of Plant C. There was no provision for a rapid chilling of freshly prepared pie base; rather, it was stored in

3 VOL. 14, 19 BACTERIOLOGY OF FROZEN CREAM-TYPE PIES 23 TABLE 1. Results of anialyses of pies collected at plants operating under poor sanitary conditions Plant Type of pie No. of pies Coliforms (MPN Escherichia coli Sh o Aerobic plate avg/g) (MPN avg/g) OCCL countb D c 23, 22. -, ()d 2, , , 3. 22, > 1,. 15. (15).1 (1) 9, (2) 2,4, (1) 33, 2. 2.(1) 4, E (1).1(1) 14, 8. _ 9, M 43..7(2) 28, 91..1(1) 47, K (4) 5 f 12.1 (4) 1, ~.1 (3) C Lemon > 1,. 2,2, Lemon >1,. _ 2,7, Lemon 87. 4, , 225. _ 5, > 1,. 1, a Highest dilution in which coagulase-positive staphylococci were found. b Geometric mean of the aerobic plate count per gram. c Dash indicates negative in the lowest dilution tested. d The numeral in parentheses indicates the number of pies positive. TABLE IA. Aerobic plate counts of some line samples collected at Planit C Sample description Aerobic plate count per gram Final mixture of pie base after heating to 1 F.< Pie base, after overnight storage.14, Ingredients for pie topping (to be mixed with pie base). Final mixture of pie topping (sample 2 plus sample 3).4, Pie topping, after being pumped to a holding tank.9, Pie topping, being deposited on pies.,, milk cans in a cooler so that 24 hr was required for the temperature of the material to drop from 9 to 4 F. An occasional failure to sanitize the milk cans, coupled with the prolonged holding time at incubation temperature, resulted in increased bacterial counts in some batches of pie base. The subsequent use of this pie base in even a single batch of pie filling or pie topping contaminated the continuous processing line where pie shells were filled. The cycle was completed and maintained by the lack of cleaning the equipment of the processing line throughout a day's production. Table 1A shows the APC of line samples collected during inspection of this firm and illustrates the condition noted. The management of Plant C was made aware of the bacteriological contamination resulting from these conditions and, at a considerable expenditure of funds, replaced the milk cans with an efficient plate-cooler and stainless-steel refrigerated holding tanks. Concurrently, the firm adopted the policy of cleaning equipment during the lunch period. As a result, subsequent samples (lines 3 to, Table 1) had acceptable plate counts; however, the noon clean-up was observed to be very inadequate and led to significant coliform counts of the product.

4 24 SURKIEWICZ APPL. MICROBIOL. TABLE 2. Results of analyses of pies collected at plants operating under marginal sanitary conditions Plant Type of pie No. of pies Coliforms/MPN geschegchiaoli Staphylococcia APCb F 48 -c 73, 5 1, 4 _ 2 H Strawberry (4)d 5, Strawberry 2, , , B ,4 5 1, (1) 18, a Highest dilution in which coagulase-positive staphylococci were found. b Geometric mean of the aerobic plate count per gram. c Dash indicates negative in the lowest dilution tested. d The numeral in parentheses indicates the number of pies positive. TABLE 2A. Results ofanalyses ofsome line samples collected at Plant B Aerobic Sample-description Coliforms MPN/g count plate per gram Gelatin... < Sugar plus dry milk powder. - 1,3 Pie base.< Combination of above ingredients from mixing vat , * Dash indicates negative in the lowest dilution tested. The results shown in Table 2 are of samples collected at plants where the operations were borderline, with fewer and less pronounced insanitary practices, or with procedures which could result in the contamination of the product. Plant F was newly organized and just beginning production. The equipment was modem in design and could be cleaned and sanitized readily. The product was prepared in small batches to avoid long holding periods. The employees, not yet properly trained, engaged in practices which led to coliform contamination and high APC. A particularly objectionable practice by a few of the employees was the use of the same piece of cloth to wipe equipment, utensils, and hands. Subsequent inspections (lines 2 and 3) demonstrate a bacteriological improvement in the product as a result of the training received by the employees in the proper handling of foods. Housekeeping in Plant H was very good, and, thus, the plant had a neat, clean appearance. However, separate handwashing and sanitizing facilities were not provided in the processing area and were conducted in a sink used for washing small utensils. The periodic cleaning of equiipment was inadequate, consisting only of a brief cold and warm water rinse. Line samples collected in connection with the chocolate pies shown in line 4 (Table 2) were free from coliforms until contact with the automatic aerating and depositing devices, whereupon 93 coliforms per gram were added to the product. Plant B is a sanitation-conscious firm with a program of routine clean-up of equipment, including posted step-by-step instructions on the proper procedure for clean-up. However, because of the lack of close supervision, the cleaning of the equipment was conducted carelessly. The line samples, listed in Table 2A, show that coliforms were absent in the individual ingredients but appeared in the mix after contacting a mixing vat. The management of Plants A, J, L, and G (Table 3) were aware of the need for sanitation and the means of achieving it. Separate sanitizing solutions for equipment and for use as a hand dip by the employees were available and were maintained at effective concentrations. The employees were trained to utilize these solutions conscientiously. Regular programs of periodic and thorough cleaning of equipment were followed. Plant G deviated from its sound program of sanitation in that a holding tank for the pie base was not always emptied prior to the addition of subsequent batches. The firm's bacteriologist acknowledged the bacterial counts occasionally increased at this site, particularly near the end of a work period. It is highly probable that the counts represented by line 8 (chocolate pies produced prior to the date of inspection) reflected this condition.

5 VOL. 14, 19 BACTERIOLOGY OF FROZEN CREAM-TYPE PIES TABLE 3. Results of analyses of pies collected at plants operating under good sanitary conditions Plant A J L G Type of pie Banana Banana Banana Strawberry Strawberry Lemon Lemon Lemon Strawberry No. of pies 9 12 * 8 13 Coliforms (MPN avg/g) Escherichia coli (MPN avg/g) -c.4(1 )d I.i cn Aerobic plate countb 24, 19, 5,5 4,5 11, 2,5 5, 9, 1, 3 3 2, 3 5 8, 3,,, 35, ahighest dilution in which coagulase-positive staphylococci were found. bgeometric mean of the aerobic plate count per gram. c Dash indicates negative in the lowest dilution tested. dthe numeral in parentheses indicates the number of pies positive. a- a.' -. I B be I... Cs. 't 4.) N 9.. v) b. xxxxxxxxx -N so't ot 't - *~.~.n - C o -- - C1 4 T" N en xxxxxxxxx (' r-n N m) ON Cs - a; o II I -C 'ot- Fi~~ AAA '. o oo z - -^ 25 DIscussIoN As expected, insanitary practices at the plant level are reflected in the bacteriological results of samples collected in the plant. Those firms with sound programs of sanitation manufactured products of a superior bacteriological quality. There is not always, of course, a good correlation of insanitation with bacteriological results. Insanitary practices are routes of contamination which may not always lead to measurable contamination. The examination of only 5-g portions as representative of hundreds of pounds of heterogeneous foodstuffs handled daily at a plant may not always be sufficient to present a true indication of insanitary conditions. Nevertheless, a reinspection and the collection of additional line samples generally led to a better correlation of bacteriological results to factory conditions. It was found that a schedule of collecting samples of individual components of the product, *.' C-. C.' *.' m- bo o PS.i Cd cn E A AAAAA A A A A A A. '.e OI1 1 rr-a-is' ~E EEEEE E B u - Bu uu u,._ N a), a) a. C-a c) S.) B B Z z

6 2 SURKIEWICZ APPL. MICROBIOL. samples at each step of the processing procedure, and samples of the finished product is essential for a reasonable evaluation of the bacteriological data. Examination of component parts of the product ("raw" ingredients) may disclose a source of contamination. Sampling before and after each step of the food-processing operation often verifies observed insanitation. For example, an objection to the lack of washing and sanitizing a container before each use becomes irrefutable if shown that foodstuffs increased in bacterial count as a result of contacting that container. Samples of the finished product reveal its bacteriological quality when offered for sale by the producer and, in addition, may reflect objectionable conditions during the final steps of packaging and freezing. Imitation-cream pies are produced by means of equipment that can be cleaned and sanitized readily. The fillings and toppings are processed in a series of stainless-steel tanks (mixers, homogenizers, coolers, aerators, and automatic dispensers) connected by means of stainless-steel or plastic pipes. Pie shells on a continuous conveyor belt pass rapidly under the dispensers, where they are filled mechanically. The fillings and toppings are dispensed while still chilled, so that the desired fluffy consistency is maintained. The almost complete automation eliminates extensive human contact with the product, and the rapid flow of chilled material eliminates significant periods of incubation. The results of this survey show that, because of these inherent favorable factors, pies of low bacterial content can be produced readily. E. coli was isolated from only 22 (4.9%) of the 453 pies collected during this survey, and only one of the 172 pies in Table 3 (plants operating under good sanitary conditions) contained E. coli. Coagulase-positive staphylococci were isolated from only 1 (3.5%) of the total of 453 pies ollected, and were not recovered from the 172 pies in Table 3. These microorganisms were reccvered from line samples just as infrequently. Fifty-one groups of pies, each group representing a different production date, were collected from 12 firms. Only 15 groups had average APC greater than 25, per gram, and 9 of these groups were manufactured by the same firm (Plant D, a firm that operated under poor sanitary conditions). Low levels of coliforms (3. to 23. per gram) appear in the pies even when they are produced under good conditions of sanitation. However, for this product, it was found that the coliform group is a good indicator of insanitation. When improper or infrequent cleaning of equipment existed, significant numbers of coliforms (more than per gram) appeared in the pies before a significant increase of APC could be noted. The results of a brief test demonstrating that imitation cream pies support bacterial growth are tabulated in Table 4. Nine pies, collected at the plant level and with no inoculation of bacteria in the laboratory, were examined while frozen (zero time) and after 24 and 48 hr at room temperature. After 24 hr, the pies had no organoleptic changes, with the exception of some "weeping" in the cavity produced by the withdrawal of the zero time sample. Every pie had a sour odor after 48 hr at room temperature. The survey revealed that, in the great majority of cases, frozen imitation-cream pies produced in plants operating under good conditions of sanitation had the following bacteriological content: (i) An MPN of fewer than three E. coli per gram (i.e., absent from all tubes in the methodology employed). (ii) An average MPN of fewer than 5 coliforms per gram ( or more pies). (iii) The absence of coagulase-positive staphylococci in.1-g portions. (iv) An APC of fewer than 25, per gram (geometric mean of or more pies). ACKNOWLEDGMENTS This investigation could not have been accomplished without the whole-hearted cooperation of a number of inspectors and microbiologists in the field districts of the Food and Drug Administration. Field bacteriologists who assisted in the analysis of samples included Theodore J. Wazenski, John Feldman, Eugene H. Peterson, James B. Hyndman, Ralph W. Johnston, and Daniel Kokal. Thanks are given to Ralph Groomes and Adriano Padron, of the Division of Microbiology, for their technical assistance in the analysis of a majority of the samples. LITERATURE CITED 1. FROZEN FOOD STANDARDS COMMITTEE Report of frozen food standards committee. Quart. Bull. Assoc. Food Drug Officials U.S. 22:4, SHELTON, L. R., JR., H. V. LEININGER, B. F. SUR- KIEWICZ, E. F. BAER, R. P. ELLIOTT, J. B. HYND- MAN, AND N. KRAMER. 19. A bacteriological survey of the frozen precooked food industry. U. S. Department of Health, Education, and Welfare, Washington, D. C.