In a comparative study to determine their effectiveness for early detection of prolific histamine-producing bacteria from tuna samples, Niven's medium proved to be superior to three modifications of the medium. Presumptive colonies could be detected in 24 h on Niven's agar surface-plated and incubated at 35°C. Following confirmatory histamine determination with high performance liquid chromatography of the tuna fish infusion broth inoculated with presumptive histamine-producers and non-producers, detection rates of 95.8 and 93.9% were obtained from temperature-abused and bacteria-spiked tuna samples, respectively, using Niven's agar. The other three modifications provided much lower detection rates and higher false-positive and false-negative results than did Niven's agar.

Samples of flour, corn meal, ground meat and carrots were analyzed by standard procedures for presence of fungi using both Dichloran-Rose Bengal (DRBC) and Plate Count agar with antibiotics. Bacterial contamination was so extensive with ground meat and carrot samples on DRBC that meaningful fungal counts could not be obtained. Therefore, DRBC is not recommended for routine enumeration of fungi in foods.

Sixty samples each of oysters ( Crassostrea virginica ), clams ( Mercenaria mercenaria ), striped mullet ( Mugil cephalus ), and blue crab ( Callinectes sapidus ) were analyzed for the presence of salmonellae within 4 h of harvesting from an east and west coast location in Florida. Mullet was the only seafood from which salmonellae were not recovered. Clams from the west coast location had the highest incidence (43%) of salmonellae. Eleven serotypes of Salmonella were recovered and identified from the samples. In quantitative MPN studies, the number of salmonellae present in west coast oysters was 2.2 organisms per 100 g of oyster meats. The variety of serotypes isolated, coupled with consistent recoveries throughout the year, suggests that salmonellae may represent a portion of the natural background flora in these seafoods rather than recent single source contamination.

Nineteen eels ( Anguilla rostrata ), collected from the Suwannee River estuary in Florida, were examined for Vibrio cholerae . Nonagglutinable V. cholerae were isolated from 11 of the eels for an isolation rate of 58%. Isolates from 6 of the eels were confirmed by the Smith serotyping system and found to be types 17, 68 and 175.

Selected biochemical and microbial changes in Penaeus shrimp inoculated with Planococcus citreus were examined to determine the potential of this organism to contribute to spoilage of shrimp. Biochemical and microbial studies were conducted following storage of Penaeus shrimp at 5 C for 0, 4, 8, 12 and 16 days. Three samples, a control (raw shrimp), an irradiated (600 Krad) control and an irradiated (600 Krad) sample inoculated with P. citreus , were analyzed for changes in aerobic plate count, pH, total volatile nitrogen/amino acid nitrogen (TVN/AA-N) ratio, trimethyl amine-nitrogen (TMN) and total extractable protein (TEP). P. citreus counts increased in the inoculated shrimp from 3.0 × 10 3 bacteria/gram at 0 day to 1.5 × 10 8 bacteria/gram at the 16th day. By the 16th day of storage, the pH of the inoculated shrimp was significantly higher than the pH of the other samples. P. citreus inoculated onto irradiated shrimp was able to produce a TVN/AA-N ratio of 1.3 by the 10th day of storage, about the same time as that developed by the natural flora on raw shrimp. The increase in TMN content of the control (raw shrimp) and the inoculated sample were not significantly different. P. citreus was also able to bring about a significant decrease in the percent TEP of shrimp during storage. These changes indicate the capabilities of P. citreus in lowering the overall quality of Penaeus shrimp.

Tostones (fried plantains) are consumed by a large segment of the Latin population in Florida. In addition, their use in specialty restaurants is on the increase. However, little is known about the microbial and nutritional quality of this product, particularly as affected by processing. Tostones are prepared by peeling and cutting the plantains into slices; soaking slices in a salt brine; frying, drying and flattening the slices; and refrying them until golden brown. Protein, ash, crude fiber and carbohydrate content increased during preparation as a result of moisture loss during processing. Fat content increased due to uptake during frying. Phosphorus, Na, Hg, Se and Zn content also increased, whereas that of K and Fe decreased. Changes in water activity and pH were not significantly pronounced. Bacillus and Penicillium species were the only organisms isolated from laboratory-prepared samples. The finished product contained 48.0% carbohydrate, 26.5% moisture, 21.5% fat, 2.5% protein, 1.0% ash, 0.5% crude fiber and 395 Kcal/100 g.

Fifty-three retail samples of seafood were examined for members of the family Enterobacteriaceae , using violet red bile agar with 1% glucose. Isolation and identification of 99 typical colonies showed them all to be members of the family Enterobacteriaceae . Enterobacter species were most frequently isolated with Erwinia , Klebsiella , Hafnia , Proteus , Serratia , Escherichia and Yersinia recovered with decreasing frequency.

To determine the effect of delayed heading on shrimp quality, shrimp were stored on ice with and without heads for 10 days. Some shrimp were delay-headed after 5 days and returned to ice for the remainder of the storage period. Microbiological studies were conducted at 0, 5 and 10 days of storage. Total aerobic plate counts were done using Standard Plate Count agar with an added 0.5% NaCl. Incubation was at 20 C for 5 days. Analyses indicated similar counts on shrimp tails stored with or without heads and those delayed-headed. Counts ranged from 2.4 × 10 6 bacteria/gram at 0 day to 1.6 × 10 9 bacteria/gram on the 10th day. Identification of the flora present revealed that the same major groups of organisms predominated on shrimp tails subjected to the different storage treatments and the head did not alter development of the usual flora. Flavobacterium , Pseudomonas , Planococcus , Moraxella and the Vibrio/Aeromonas group were the major genera encountered. A shift in bacterial populations was observed during storage. Flavobacterium species predominated during the first 5 days of storage; however, after the fifth day Pseudomonas species predominated. Sensory panel data revealed no differences in acceptability between shrimp tails stored with or without heads and those delay-headed.

Gentamicin, chloramphenicol and chlortetracycline were evaluated singly and in combination for their ability to control bacteria in media to enumerate yeast and molds. No single antibiotic tested at 50 or 100 ppm was totally effective in controlling bacteria. Chlortetracycline in combination with either chloramphenicol or gentamicin inhibited the contaminating bacteria as long as the antibiotics were added after autoclaving. It is recommended that for routine use, reliance not be placed upon a single antibiotic to control bacteria when enumerating fungi.

Twenty samples of cold ready-to-eat cereal were analyzed for total organisms using the pour plate and Most Probable Number technique (MPN). Nine samples enhibited growth in MPN tubes but not on pour plates. Of the 28 isolates obtained from the MPN tubes, 16 were members of the genus Bacillus and the remainder were predominately other gram-positive organisms. The data support the working hypothesis that aside from the mathematical bias associated with the MPN procedure, microbial recovery is more favorable in a liquid environment than in an agar medium.

Shrimp dipped in sodium bisulfite solutions of 1.25 and 5.0% were analyzed for residual bisulfite during iced storage for up to 15 days. Most of the bisulfite was located on the shell and was readily leached away by the melting ice. A further reduction in bisulfite occurred when shrimp were rinsed in either water or hypochlorite solutions after storage, with the greatest reductions occurring during the hypochlorite rinses.

The microbial flora of rock shrimp ( Sicyonia brevirostris ) taken off the East Coast of Central Florida was studied. Gram negative bacteria, particularly the Flavobacterium-Cytophaga group, represented most organisms isolated from the fresh shrimp. Gram positive organisms were found in greater number after iced storage, with Planococcus increasing from 10% of the isolates on fresh shrimp to 40% on the red samples. Examination of the fungal population showed only yeasts to be present, with members of the genus Rhodotorula being the only survivors of iced storage.

It was possible to compare recovery of yeasts and molds from 30 food samples by three methods, employing plate count agar and broth with added antibiotics. Although the pour plate and surface plate methods gave comparable results, the Most Probable Number (MPN) procedure consistently yielded the highest counts. With some of the samples, the MPN method was the only one in which recovery occurred. It thus appears that this procedure is practical for detection of fungi and may be of use in survey work or when analyzing foods containing low numbers of microorganisms.

The most probable number (MPN) technique is extensively used in food microbiology. However, because statistics involved often are cumbersome and it is difficult to obtain some of the widely scattered literature, many individuals are not able to delve into the subject to gain a thorough understanding of the method. To overcome these inherent difficulties, this review and discussion was prepared as an introduction and aid in presenting the MPN method to students and individuals working in food microbiology.

Five media, with added antibiotics, were compared for their ability to recover yeasts and molds from 31 foods. Overall, no significant difference in recovery was found among Mycophil, Plate Count, Malt, or Potato dextrose agars but all were superior to Sugar Free agar. On the basis of recovery of organisms, availability, ease of management, and cost, Plate Count agar with antibiotics is recommended for routine enumeration of yeasts and molds in foods.

Twenty-five health foods were compared to traditional foods with respect to color, flavor, texture, odor, and overall acceptance. None of the health foods was found to be superior on the basis of overall acceptance, but three of the items were individually preferred for color or odor. Many traditional foods, however, were preferred for color, odor, flavor, and texture as well as overall acceptance.

Health and traditional foods ( 24 of each) were compared for proximate composition, cost, microbial content, pesticide levels, and polychlorinated biphenyl (PCB) contamination. Only minor differences were detected for proximate composition and microbial content. No pesticides were detected but 7 samples of health and 3 of traditional foods contained PCBs. The major difference between the samples was the greater cost of the health foods.