Bacteriological Survey of the Frozen Prepared Foods Industry: IV. Frozen Breaded Fish

During sanitation-inspections of 23 breaded-fish processors, 573 finished product units and 604 line samples were collected and analyzed bacteriologically. Data for finished product units processed on the same data are presented in groups; most of the groups consisted of 10 units. Groups of frozen, raw-breaded fish produced under good and poor conditions of sanitation were studied. No more than 20% of the units in each group produced under good conditions of sanitation were positive for Escherichia coli or coagulase-positive staphylococci. Groups of frozen, fried-breaded fish produced under good and poor sanitary conditions were also studied. No more than 10% of the units in each good-sanitation group were positive for E. coli or coagulase-positive staphylococci. However, approximately 30% of the groups processed under poor sanitary conditions also did not exceed these viable bacterial counts because of the lethal effect of the terminal fry to which the product is subjected. It was found that line samples collected from the processing lines reflected the sanitary conditions of the plant and provided bacteriological support for inspectional evidence of plant insanitation.     

Bacteriological Survey of the Frozen Prepared Foods Industry: III. Potato Products

[This corrects the article on p. 1327 in vol. 15.].     

Bacteriological Survey of the Frozen Prepared Foods Industry: II. Frozen Breaded Raw Shrimp

During inspection of 21 frozen breaded raw shrimp processors, 861 finished product units (retail packages) and 778 line samples were collected and analyzed bacteriologically. The bacteriological results for the finished product samples collected in plants with poor and good sanitary controls are presented and compared. The samples consisted of 4 to 38 units (retail packages) of the finished product as offered for sale by the processors. Frozen raw breaded shrimp collected from plants operating under good conditions of sanitation had the following bacterial contents: 85% of the samples had an average (geometric) aerobic plate count of less than 1,000,000 per gram; all of the samples had an average (geometric) most probable number of less than 1,000 coliforms per g; 81% of the samples contained less than 20% Escherichia coli-positive units; 57% of the total number of units in 0.1-g portions were negative for coagulase-positive staphylococci, and 95% of the units had less than 1,000 coagulase-positive staphylococci per gram.     

Bacteriological Survey of the Frozen Prepared Foods Industry: III. Potato Products

During sanitation-inspections of 29 potato-processing firms, 2,544 finished product units and 1,654 samples were collected and analyzed bacteriologically. The results of the bacteriological examination of finished French fries, fried potato cylinders, and dehydrated potatoes usually did not reveal the conditions of cleanliness under which they were produced. This was most likely due to the lethal effect of the terminal fry to which the French fries and potato cylinders are subjected, and because of the lethal effect of the dehydration temperatures used in processing the dehydrated potato products. However, as in most food-processing firms, line samples collected at each processing step reflect sanitary conditions and provide bacteriological support of inspectional evidence of plant insanitation. Most of the frozen stuffed baked potatoes examined were produced under poor sanitary conditions. But because this product is usually processed while hot, bacteriological examination of the finished product did not usually reveal the conditions of cleanliness under which they were produced. Again, inspectional observations were necessary for a full evaluation of the conditions of production. In contrast, frozen potato patties and frozen hash brown potatoes were more likely to reveal the conditions of sanitation under which they were produced as evidenced by the varying bacterial counts.     

Coliform Behavior in Frozen Foods: I. Rapid Test for the Recovery of Escherichia coli from Frozen Foods

An assortment of 496 samples of frozen foods consisting of fish or marine products, variety types, and cream pie desserts were subjected to four parallel examinations for the recovery of Escherichia coli. The test procedures consisted of two low-temperature (35 C) and two high-temperature (44 C) presumptive tests, followed by an E C confirmatory test at 45.5 C. Of all the test methods examined, a single Lauryl Sulfate Tryptose (LST) presumptive test at 44 C gave best E. coli recovery (425). This recovery compared favorably with the lengthier Association of Official Analytical Chemists test with which only 420 E. coli cells were recovered. The LST (44 C) test saves much time, since it renders a follow-up 48-hr confirmatory test unnecessary. Moreover, since 96% of all the E. coli are recovered within 24 hr by LST (44 C), it is essentially a 24-hr test. The results of this study also confirmed earlier findings, in that it is possible to describe a specific coliform bacteriological test method by simple reproducible productivity ratios. E. coli recovery dilution data and coliform group behavior were also examined.     

Bacteriological Survey of the Blue Crab Industry

During sanitation inspections of 46 crabmeat processing plants on the Atlantic and Gulf Coasts, 487 samples of whole crabs immediately after cooking, cooked crabs after cooling, backed or washed (or both) crab bodies and whole crab claws, as well as 1,506 retail units of finished product were collected and analyzed bacteriologically. The 1,506 retail units (1-lb [373.24-g] cans) included 518 cans of regular (special) meat, 487 cans of claw meat, and 501 cans of lump meat. Statistical analyses showed that crabmeat from plants in Mississippi, Louisiana, and Texas had higher counts in 19 of 24 cases for the four bacteriological indices than crabmeat from plants located along the Atlantic Coast and the Gulf Coast of Florida. Aerobic plate counts of retail units collected from a previous day's production were significantly higher than those collected on the day of inspection. Regular crabmeat had consistently higher aerobic plate counts than claw or lump meat. When the product was handled expeditiously under good sanitary conditions, the bacteriological results were significantly better than the results from plants operating under poor sanitary conditions. Crabmeat produced in plants operating under good sanitary conditions had the following bacteriological content: (i) coliform organisms average most-probable-number values (geometric) of less than 20 per g; (ii) no Escherichia coli; (iii) coagulase-positive staphylococci average most-probable-number values (geometric) of less than 30 per g in 93% of the plants; (iv) aerobic plate count average values (geometric) of less than 100,000 per g in 93% of the plants, with the counts from 85% of these plants below 50,000 per g.     

Bacteriological Survey of Frozen Meat and Gravy Produced at Establishments Under Federal Inspection

During visits to 34 federally inspected establishments producing frozen meat and gravy, 541 production line samples and 535 finished product units were collected for bacteriological analyses. It was found that more than 70% of the sets of finished product (10 units/set) produced under good manufacturing practices had: (i) four or fewer coliform-positive units, (ii) two or fewer Escherichia coli-positive units, (iii) three or fewer Staphylococcus aureus-positive units, and (iv) an aerobic plate count of fewer than 50,000/g (geometric mean of 10 units). All finished product units were negative for salmonellae.     

Staphylococci in Competition: I. Growth of Naturally Occurring Mixed Populations in Precooked Frozen Foods during Defrost

In chicken pot pies, it was not possible to promote the growth of appreciable numbers of staphylococci under any condition of defrost. The pies spoiled under the same conditions, however. In macaroni and cheese dinners, tremendous numbers of saprophytic bacteria developed, but only after extended incubation at room temperature in which even spoilage was carried to an extreme. Under these conditions, staphylococci also multiplied vigorously. At the extreme temperature of 37 C, rank spoilage of such an advanced state as to render the product completely inedible was reached in less than 24 hr. Staphylococci grew very well under these extreme conditions.     

Fate of Staphylococci and Enteric Microorganisms Introduced into Slurry of Frozen Pot Pies

A slurry was prepared from six frozen pot pies diluted 1:5 with distilled water, two chicken, two turkey, and two beef pies of different brands. This slurry formed a reference sample and was placed in sterilized jars, frozen, and used as needed throughout the experiments. A second slurry was prepared in a similar manner from a frozen beef pot pie and a chicken pot pie, and was used as a control in only one experiment. The total count of microorganisms and the number of coliforms, Escherichia coli, salmonellae, and coagulase-positive staphylococci per gram were determined. Samples of slurry were inoculated in decimal dilutions with one or more of the following: Salmonella typhimurium, E. coli, and a strain of staphylococcus that causes food poisoning. The natural flora was found to exert an inhibitory effect upon the growth of the added microorganisms after incubation at 35 C for 18 hr. The inhibitory effect on growth was in part due to pH. The predominating organism isolated from the natural flora after incubation was a lactobacillus, which, when added in mixture with the test organisms in sterilized slurry, did not exert the profound inhibitory effect observed in the case of the natural flora. Some factors which may be concerned with the inhibition were investigated.     

A Bacteriological Survey of the Domestic Environment

The results of a survey of the bacterial flora in many sites in 21 homes are discussed. In all areas both wet and dry, coagulase negative, Gram positive cocci and Bacillus spp. were found. Wet areas such as kitchen sinks and drains contained large numbers of Escherichia coli and sometimes Klebsiella pneumoniae , Citrobacter and Enterobacter spp. In toilet areas, little evidence was found of contamination with organisms of faecal origin. Of 47 samples taken from teacloths and towels 22 were contaminated with Staphylococcus aureus although the actual numbers of this organism were low. Pseudomonas aeruginosa was isolated from several sites in one home only.     

Measurement of Temperature-dependent Ice Fraction in Frozen Foods

Ice fraction was measured for solutions containing glucose, sucrose, gelatin, and egg albumin at various concentrations at temperatures from 0 to -20°C. For glucose and sucrose solutions, the ice fraction was accurately measured from phase diagram, which could be interpreted by solution thermodynamics with two parameters. The ice fractions of these sample solutions increased with decreases in both temperature and concentration. Because of the limited applicability of the phase diagram method only to systems with low molecular weight materials, the DSC method was also used for ice fraction measurement. The DSC method, corrected for temperature-dependent latent heat of ice and corrected with Pham’s equation, provided a good approximation for ice fractions with general applicability. The DSC method was used to measure the ice fractions of gelatin and egg albumin gels as a function of solute concentration. The freezing point and bound water of gelatin and egg albumin gels were described as a function of concentration. Effects of the differences in molecular structure on ice fraction were analyzed for various carbohydrate solutions at the same concentration. The ice fraction proved to be strongly dependent on the colligative properties of the solution with nonideal behavior.     

DSC Measurement of Frozen Water in Liquid Foods

We investigated the state of water in frozen liquid foods, supposed to influence the performance of freeze-drying, by DSC. The amount of unfreezable water in milk was constant irrespective of the initial water content. As expected from the phase equilibrium, the water content of the non-ice part of CAS was constant among the samples with different initial water contents. The volume fraction of ice crystals, which should be known in the analysis of the freeze-drying rate, was significantly smaller at the low initial water content than the one usually estimated with the assumption that the water was all freezable.