Custy F. Fernandes

Anticarcinogenic and Immunological Properties of Dietary Lactobacilli

Consumption of Lactobacillus products and supplements containing viable lactic acid bacteria results in their establishment in the gastrointestinal tract. Their presence in the intestinal tract has been suggested to be prophylactic. They may reduce risk associated with dietary onset of carcinogenesis directly due to the reduction of procarcinogenic substances or indirectly due to the reduction in the level of enzymes that convert procarcinogens to carcinogens. In short-term studies, feeding as well as intraperitoneal administration of lactic acid bacteria suppress tumors implanted in rodents. The suppression is probably mediated by lactic acid bacteria through activation of host defense system. The activation of host defense system has been hypothesized to augment the immune system. Transient increase in the host immune defense system has been observed following feeding of cultured dairy products, but the biological significance of these changes has not yet been elucidated.

Influence of processing schemes on indicative bacteria and quality of fresh aquacultured catfish fillets.

Fresh aquacultured catfish fillets were obtained from three processors using different processing protocols in summer, autumn, winter, and spring and evaluated for microbial quality. Twenty freshly processed fillets were randomly selected and each fillet was placed in a sterile polyethylene bag. The fillets were transported on ice-pack overnight by air immediately after processing. Five fillets were randomly selected for microbial assays. Each fillet was weighed and an equal volume of sterile 0.1% peptone water at 0 to 1 degrees C was added aseptically. The fillet was massaged (or rinsed) for 120 s and the rinse was used to determine microbial quality. Aerobes (incubation at 35 degrees C for 48 h) and psychrotrophs (incubation at 20 degrees C for 96 h) were enumerated using 3M Petrifilm Aerobic Count plates. Escherichia coli (incubation at 35 degrees C for 24 to 48 h) and total coliforms (incubation at 35 degrees C for 24 to 48 h) were enumerated on 3M Petrifilm E. coli Count plates. Staphylococcus aureus counts were determined on Baird-Parker agar (incubation at 35 degrees C for 48 h). Significant differences (P < or = 0.05) in aerobic, psychrotrophic, total coliform, E. coli, and S. aureus counts due to temperature effects during production and variations in processing protocols were observed. E. coli and S. aureus counts were significantly different during the four seasons. E. coli and S. aureus counts were high during summer and low during winter weather. There was a significant difference (P < or = 0.05) in aerobic, psychrotrophic, and total coliform counts among the three processors during warm weather; however, these differences were significantly (P < or = 0.05) reduced in cold weather.

Fermented Dairy Products and Health

Humans around the globe have ingested fermented milk products (FMP) for nutrition and good health for a very long time. Since 1966, FMP consumption has been chronicled, by the International Dairy Federation (IDF). During the last 10 years, the global annual per capita consumption of FMP has increased according to the 29 participating members (IDF, 1989) (Table 1). In the US during the last 18 years, the per capita sales of yoghurt have increased steeply from 0.6 kg to 1.9 kg while the per capita sales of buttermilk have declined from 2.4 kg to F8 kg (Fig. 1). More recently, however, per capita sales of yoghurt declined by 8.7% and of buttermilk by 4.9% between 1988 and 1989. Nevertheless, the overall consumption of FMP has expanded over the last decade. Yoghurt consumption has escalated significantly, presumably because of its perceived health benefits. The processing technology has undergone considerable modifications as consumers are demanding a variety of yoghurts. Further, yoghurt with a characteristic sour taste has been transformed into a wholesome and natural food with the addition of sweeteners and fruit preparations. Additionally, in some parts of the world yoghurt is being pasteurised to enhance its shelf-life with concomitant destruction of lactic acid bacteria (LAB).

Role of Organic Acids during Processing To Improve Quality of Channel Catfish Fillets

A microbial preparation derived from aquacultured channel catfish fillets (Ictalurus punctatus) was acidified with 0, 1, 2 and 4% (vol/vol) weak organic and held in an ice bath at 0 degree C to simulate the chilling process. Additionally, catfish fillets were sprayed under varying pressures at 15 degrees C with organic acids to evaluate the efficacy of concentrations of organic acids and spray pressures to ameliorate the microbiological quality. To determine plate counts, the dilution fluid was neutralized to pH 7.2 with 1.0 M NaOH. The aerobic plates counts of microorganisms in the chilling water were monitored over a 20-min interval. Aerobic plate counts were found on the channel catfish fillets before and after spray washing with organic acids. Plates were incubated at 35 degrees C for 48 h. The addition of organic acids tot he microbial preparation used in simulating the chilling process significantly (P < 0.05) reduced the number of bacterial surviving. The number of surviving bacteria in the chilled water decreased with increasing concentration and time of exposure to organic acids. Propionic acid had the most detrimental effect on organisms present in the microfloral preparation followed by acetic and lactic acids. Spray washing of catfish fillets with water did not significantly (P < 0.05) affect the microbial quality of fillets. However, catfish fillets sprayed with organic (lactic and propionic) acids significantly (P < 0.05) reduced the microbial counts by 10-fold. Lactic and propionic acids were not significantly (P > 0.05) different in influencing the aerobic counts of the catfish fillets.

Growth of inoculated psychrotrophic pathogens on refrigerated fillets of aquacultured rainbow trout and channel catfish.

Aquacultured rainbow trout (Oncorhynchus mykiss) and channel catfish (Ictalurus punctatus) fillets were inoculated with the psychrotrophic pathogens Listeria monocytogenes and Aeromonas hydrophila: cell populations were monitored during refrigerated storage at 2 to 4 degrees C. Fillets of both species were placed individually in sterile plastic bags and inoculated with cell suspensions (10(4.7) CFU/100 g of fish) of either A. hydrophila or L monocytogenes or of both A. hydrophila and L. monocytogenes, for a total of three treatments for each species of fish. Each inoculum and fillet were mixed to ensure uniform distribution and then stored at 2 to 4 degrees C. A. hydrophila, L. monocytogenes, and aerobic cell populations were determined on days 1, 3, 6, 8, 10, 13, and 15. Individually inoculated A. hydrophila and L. monocytogenes grew on catfish and trout fillets during the 15-day study. There was no inhibition of either pathogen by the natural flora on the fillets. Both psychrotrophic pathogens grew equally well in catfish and trout fillets inoculated with a combination of A. hydrophila and L. monocytogenes. In all three treatments, the counts of the psychrotrophic pathogens were lower than the aerobic plate counts. The growth of the psychrotrophic pathogens L. monocytogenes and/or A. hydrophila during refrigerated storage on aquacultured fish fillets could increase the food hazard risk, particularly where there is a possibility of cross-contamination with ready-to-eat food products.

Comparison of quality in aquacultured fresh catfish fillets. II. Pathogens E. coli O157:H7, Campylobacter, Vibrio, Plesiomonas, and Klebsiella

Aquacultured channel catfish ( Ictalurus punctatus ) were evaluated for the presence of human pathogenic bacteria. Fresh catfish fillets procured from three catfish processors in the southeastern United States during the four annual seasons (e.g., summer, fall, winter, and fall) were screened for selected human pathogens. At each sampling time point, 20 freshly processed catfish fillets were randomly selected from each processor during each season. Five catfish fillets were randomly selected for aerobic plate counts and all 20 fillets were screened for five pathogenic bacteria viz. Campylobacter jejuni/coli , Escherichia coli O157:H7, Klebsiella pneumoniae subsp. pneumoniae , Plesiomonas shigelloides , and Vibrio cholerae . There was a significant difference (P < 0.05) in the aerobic plate counts due to differences in unit processing operations and processing season. C. jejuni/coli , E. coli O157:H7 and K. pneumoniae subsp. pneumoniae were not isolated. Only P. shigelloides and V. cholerae were isolated during the warm weather.

Effect of Lactobacillus Acidophilus on Growth of Ehrlich Ascites Tumor in Swiss Mice

The role of Lactobacillus acidophilus LA 15 in reducing the proliferation of Ehrlich ascites tumor (EAT) was studied in Swiss male mice, over a period of 8 days. EAT cells were implanted intraperitoneally into mice on day 1 and the mice were subsequently treated intraperitoneally with whole cells of L. acidophilus. The mice were sacrificed on the eighth day to determine the effect of L. acidophilus on the proliferation of EAT cell growth. Control mice were injected with an equal volume of phosphate-buffered saline. There was a significant reduction in the proliferation of EAT cell due to L. acidophilus treatment. Three strains of L. acidophilus were efficacious in reducing the proliferation of EAT cell growth but the differences among L. acidophilus strains were not significant. Cell wall solids, but not non-cell wall solids reduced proliferation of EAT cells. Although L. acidophilus whole cells reduced proliferation of EAT cells, they were not as efficacious in decreasing proliferation of EAT cells in hy...