Bacterial Spoilage of Citrus Products at pH Lower than 3.51

A strain of Lactobacillus brevis, L-3, was isolated from a blown can of grapefruit segments in sugar syrup; it caused spoilage of citrus products having pH values lower than 3.5. When inoculated into orange (pH 3.38) and grapefruit (pH 2.99) juices, after 5 h at 30 C L-3 produced 15 and 22 μg diacetyl/ml, respectively, and off-flavor was detectable. L-3 grew in APT broth acidified to pH 3.0 with citric, hydrochloric, phosphoric, or tartaric acid. However, its growth was inhibited at pH 3.6 if the acidulant was lactic acid, while with acetic acid inhibition occurred at a pH between 3.7 and 4.0. The thermal resistance of L-3 in orange serum (pH 3.4) was studied in the temperature range of 52 to 60 C: a z value of 8.3 was obtained. A simple and reliable capillary technique for studying the thermal resistance of gas-producing organisms in liquid foods and media is presented.

Electronic Somatic Cell Count—Chemical Method, DMSCC, and WMT Tests for Raw Milk

The Direct Miscroscopic Somatic Cell Count — field method (DMSCC), Wisconsin Mastitis Test (WMT), and Electronic Somatic Cell Count (ESCC) were studied to determine variability and relationship to each other. The coefficients of variation computed at a DMSCC count near one million were 15.6% (DMSCC), 6.3% (WMT), and 4.2% (ESCC). Linear regression equations were determined for predicting DMSCC results by WMT and ESCC. The approximate width of the 95% confidence intervals for ESCC predicting DMSCC were ± 275,000 and for WMT predicting DMSCC were ± 600,000. The prediction of square root and log transformations of DMSCC by WMT exhibited narrower confidence intervals for low somatic cell counts, but wider intervals for high counts (greater than 1,000,000).

The Microflora of Parsley

Commercially available parsley is a heavily contaminated product. The possible public health significance of this observation is discussed. Parsley with the roots intact is also heavily contaminated. However, microorganisms indicative of fecal contamination could be found much less frequently and less numerously. For this reason it is concluded that standards for Escherichia coli and/or D-streptococci might serve as a useful public health precaution.

Contribution of KH2PO4 to Toxicity in Phosphate Buffered Dilution Water Systems

It appears that different sources of KH2PO4 used to prepare phosphate buffered dilution water have various effects on the ability of the dilution water to maintain a stable bacterial population. When the water used to prepare the dilution water is of either very good or very poor quality, the KH2PO4 source is of no consequence. However, if water of an intermediate quality is used, the KH2PO4 source becomes of consequence in the over-all quality of the system.

Destruction of Food Spoilage, Indicator and Pathogenic Organisms by Various Germicides in Solution and on a Stainless Steel Surface1

Representative food spoilage, indicator, and pathogenic organisms were exposed to newly developed imported iodophors and widely used representative domestic germicides that included iodophors. The organisms used in these experiments included Salmonella derby, Escherichia coli, yeast of the genus Candida, Pseudomonas aeruginosa, Staphylococcus aureus. Streptococcus lactis, and spore of Bacillus licheniformis. Results of the germicide experiments showed generally similar effectiveness by iodophor and hypochlorite. Both were superior to the quaternary ammonium compounds (QAC) when used at much lower concentrations (12.5 and 25 for the halogens and 50 and 200 ppm for the QAC). The iodophors exhibited a consistently greater rate of destruction of yeast cells than the hypochlorite when low concentrations of germicide were used. A procedure to more closely simulate actual use of germicides in food and dairy industries also was employed in this study. Special polished metal strips were inoculated with organisms and exposed to an iodophor, a sodium hypochlorite, and a QAC for 15, 30, 60, and 300 sec. Again the halogen compounds were superior to the QAC in destroying the bacterial cells, especially against gram-negative species including Salmonella.

Microbiology of Fresh Comminuted Turkey Meat

Standard plate counts, coliform plate and most probable number (MPN) counts, Escherichia coli plate and MPN counts, Staphylococcus aureus MPN counts, and fecal streptococcus counts were determined for 75 samples of fresh ground turkey meat purchased from retail markets in the San Francisco Bay Area. The presence of Clostridium perfringens was determined by both direct plate count and enrichment techniques. Salmonellae were isolated using selective enrichment procedures. Samples were screened for presence of enteroviruses. Aerobic gram-positive and gram-negative organisms were isolated and identified. Clostridium perfringens and Salmonella sp. were isolated from 52% and 28% of the samples, respectively. The mean standard plate count was 84,000,000 per gram. The mean count for E. coli determined by the MPN method was 19 per gram. Fecal streptococci were isolated from 95% of the samples with a mean count of 18,000 per gram. Staphylococcus aureus was isolated from 80% of samples analyzed with a mean count of 34 per gram.

Mathematical Model Describing the Relationship of Fat, Protein, and Lactose to the Total Solids—Its Application in Milk Testing

California dairy farmers producing and selling Grade A milk for pasteurization receive payment based on milkfat and solids-not-fat content of raw milk. In 1970, the concept of using electronic methods for testing of milk and its components was accepted by the California Department of Food and Agriculture. The InfraRed Milk Analyzer (IRMA) with its ability to measure fat, protein, and lactose, using a predetermined factor for the unmeasured solids, appeared to fill the need for a rapid, accurate, and economical method. After comparing IRMA results with chemical tests of known accuracy for several seasons, it appeared the ash factor could vary seasonally and geographically, as well as with individual dairy herds. It was decided to study the accuracy and calibration stability of InfraRed Milk Analyzers (IRMA), as well as the use of a constant value for the ash factor. By applying a multiple regression technique to milk sample data, it was possible to generate a model describing the relationship of fat, protein, and lactose to total solids (and solids-not-fat).

Coagulation of Milk with Immobilized Proteases: A Review

Enzymatic coagulation of milk by immobilized proteases, and their potential application to cheese manufacture, is reviewed. Particular emphasis is given to the immobilized protease catalyst and to the reactor design for coagulation of milk. Pepsin and chymotrypsin retained more activity and greater stability than the other immobilized proteolytic enzymes. Porous glass beads, several anion exchange resins, and the copolymer ethylene-maleic anhydride gave best results among the support materials that were evaluated. Covalent attachment of enzyme to support is preferable to adsorption techniques but may be too costly. Perhaps the best catalyst is one using a lengthy procedure for covalent immobilization of enzyme on glass beads but good results were also obtained with simpler adsorption techniques. Catalysts varied greatly in initial activity but all lost activity upon exposure to milk. Stirred tank, packed bed, and fluidized bed reactor designs were used. Continued research is required to make enzymic milk coagulation with immobilized proteases economically feasible.

Foodborne Disease Outbreaks Traced to Poultry, United States, 1966–1974

To determine the epidemiologic characteristics of foodborne disease outbreaks traced to poultry, we reviewed records of all 352 such outbreaks reported to the Center for Disease Control 1966–1974; 217 (62%) outbreaks were traced to turkey, 129 (37%) to chicken, 5 (1%) to both turkey and chicken, and 1 (0.3%) to cornish hen. Outbreaks from poultry accounted for 12% of all foodborne disease outbreaks reported from 1966 through 1974, but the number and percentage has been decreasing since 1969; these outbreaks involved 30,606 cases of gastrointestinal illness (20% of all cases of foodborne disease) and 14 deaths. Food-service establishments were responsible for mishandling the food in 79% of outbreaks, homes in 19%, and food-processing establishments in 2%. In 85% of the outbreaks, the food-handling error was storage of food at improper holding temperatures. In outbreaks reported 1972–1974 in which an etiologic agent was indentified, Salmonella spp. were responsible for 44%, Clostridium perfringens for 26%, and Staphylococcus aureus for 26%. The number of reported outbreaks from turkey increased dramatically during the Thanksgiving-Christmas holiday season. The downward trend in the number and percentage of poultry outbreaks since 1969 may reflect public education efforts.

Interval Plating: A Simplified Method to Determine Suitability of Distilled Water as a Dilution Fluid

A simplified procedure has been developed for routine evaluation of distilled water used in milk, food, and water service laboratories. It is simple to do, requires no additional equipment or reagents, and can be done along with the routine daily workload. It requires no “control” water, and has a sensitivity which is appropriate for the intended use of the distilled water.