Spherical Lactic Acid-producing Bacteria of Southern-grown Raw and Processed Vegetables.

The frequency and levels of population of the spherical lactic acid-producing bacteria were determined on raw and processed yellow summer and zucchini squash, a variety of greens, green beans, okra, southern peas, and butter and lima beans, and on fresh cucumbers and corn flowers. Six taxa occurred consistently: Leuconostoc mesenteroides, yellow-pigmented streptococci, Streptococcus faecium, Aerococcus viridans, and S. faecalis and S. faecalis var. liquefaciens. The same taxa occurred with the same order of frequency on processed, frozen vegetables, but with a marked decrease in the occurrence of S. faecalis var. liquefaciens. S. lactis, S. cremoris, S. equinus, S. bovis, and pediococci were isolated infrequently. No other member of the viridans group of the streptococci and no member of the pyogenic group was isolated. Approximately 88% of the cultures were identified. Total counts of the lactic-acid-producing bacteria rarely exceeded 10 per gram of sample, and there was a reduction by 90% during the second year of study, probably because of drought. Only one bacterial species was found on 40% of the raw and 34% of the processed vegetable samples. Two or more species or taxa were present on the remainder of 153 raw and 56 processed vegetable samples. A. viridans was present on squash, greens, okra, and southern peas, and its frequency of occurrence on vegetables suggests that plants are its natural habitat.

Microbial Spoilage of Mexican-Style Sauces.

The objective of this study was to determine causes for spoilage of Mexican-style sauces prepared "in-house" by restaurants, and to suggest improvements in handling to eliminate this problem. A microbial profile was determined for spoiled enchilada and hot and mild taco sauces. There was no indication of a potential health problem associated with spoiled sauces since Salmonella was absent and Clostridium perfringens and Staphylococcus aureus were present only in low numbers. Spices used in preparing sauces had plate counts ranging from log 4.1 to log 7.7 bacteria per gram. Spoiled sauces had bacterial counts up to log 6.6 per gram. The enchilada and hot sauces which contained the greatest amount of spices had higher bacterial numbers and spoiled more rapidly than the mild taco sauce. Use of ethylene oxide-treated spices, prompt refrigeration of sauces and thorough sanitation reduced counts by 4 log cycles and eliminated spoilage problems.

Growth of lactic acid bacteria in waste waters of vegetable-processing plants.

Waters used in washing, blanching, cooling, and conveying vegetables during processing for freezing were filtered, sterilized, and inoculated with Streptococcus faecalis, S. lactis, or Lactobacillus plantarum. The contents of total nitrogen and total solids were determined, and ninhydrin tests and Benedict's tests for reducing sugars were performed. Substances positive to the ninyhydrin tests and also capable of supporting the growth of the bacteria to high levels of population were found in waters used to blanch cut green beans, but not in the cooling or conveying waters. They were found only in waters following slicing of blanched whole beans. They were also present in waters used in processing purple hull peas at all stages, but only in the waters used to blanch and cool lima beans. The substances were present in waters used to wash and blanch squash, but only in the waters used to blanch greens; they were not found in the cooling waters during the handling of either vegetable. No waters used in the processing of okra yielded a positive ninhydrin test, nor did they support the growth of the lactic acid bacteria.

Microbial Changes in Sweet Sorghum (Sorghum bicolor) Juices.

Juice freshly expressed from Sorghum bicolor for making sweet sorghum syrup contained 10 microorganisms per ml. The dominant bacterium was Leuconostoc mesenteroides, followed by gram-negative rods. Lactobacilli, yeasts, and nonfecal coliform bacteria each comprised about 1% of the microbial population. Spoilage of juice, manifested by a sour odor, discoloration, and foaming, occurred between 5 and 12 h at ambient temperatures. Spoilage was correlated with a drop in pH from 4.9 to 4.5 L. mesenteroides was the dominant spoiling agent at 20 degrees C, and Lactobacillus plantarum was the dominant spoiling agent at 32 degrees C, as determined by pure culture studies. Juice may be stored for 14 days at 4 degrees C if promptly refrigerated.

Description and Microbiology of Home-Canned Tomatoes and Tomato Juice.

Home canners completed questionnaires and submitted 378 jars of tomatoes and 382 jars of tomato juice for analysis. Nearly 50% of the containers were non-canning jars, and 25 jars had held food items such as instant tea or coffee or jelly. A few closures were reused from grocery stock; the remainder were the two-part rim and lid or zinc cap and ring. The headspace in 14% of the jars was below 16/32 inch and in 17% between 31/32 and 64/32 inch. Serum layers in 70% of the jars of tomato juice ranged from 20 to 64% of the volume. Eleven percent of the samples were processed with the method of hot fill and seal only, 66% were processed in boiling water, and 23% in the pressure canner. Vacuums of 13 to 15 inches of mercury were most frequently recorded in jars processed with any of the three methods. The pH ranged from 3.5 to 4.7. The average titratable acidity as citric acid, of tomatoes was 0.444% and of tomato juice 0.471%. Microorganisms were recovered from 33% of the jars of tomatoes and from 15% of the tomato juice; however, the percentage of recovery decreased during the period of analysis, suggesting autosterilization. The microorganisms recovered included three fermentative yeasts, one Rhodotorula , three filamentous fungi, 15 Bacillus licheniformis , and the remainder were Klebsiella pneumoniae . It is concluded that directions given to home canners are adequate for home preservation of tomatoes and tomato juice, and that most canners engage in good canning practices.

Modification of the Processing Method for Home-Preservation of Tomato Juice.

A modification (low water level bath, LWL) of the recommended water bath (high water level bath, HWL) procedure was used to process tomato juice in quart jars. The LWL bath contained one-fifth the amount of water recommended for the HWL bath. Use of the HWL bath required 59 min and 1838 watt-hours of electricity to heat the bath and process hot packed (92°C) juice for 15 min. In comparison, 34 min and 1065 watt-hours of electricity were required when the LWL bath was used. Samples of juice were inoculated with log 3.0 Bacillus coagulans per ml, processed in each of the two baths, and stored up to 12 weeks at 27°C. Aerobic mesophiles were found only in juice processed in the HWL bath and stored 4 weeks and in juice processed in the LWL bath and stored 0 weeks. The aerobic mesophile count (log10) of juice processed in the HWL bath and stored 4 weeks was a mean log 1.4 per ml. Similar juice processed in the LWL bath had a mean log 1.3 aerobic mesophiles per ml. Juice processed in both water baths and stored for 8 and 12 weeks exhibited mesophilic counts of <1 log per ml. None of the inoculated, processed samples had a mean count greater than 1 log per ml of juice for aerobic, acid forming mesophiles; aerobic thermophiles; anaerobic mesophiles and thermophiles; and mold. Using temperature values and microbiological measurements, one may conclude that the LWL bath was as effective as the HWL bath for processing tomato juice while allowing for a substantial saving of time and electricity.