Control of Alicyclobacillus acidoterrestris in fruit juices by enterocin AS-48

Alicyclobacillus acidoterrestris is a spoilage-causing bacterium in fruit juices. Control of this bacterium by enterocin AS-48 from Enterococcus faecalis A-48-32 is described. Enterocin AS-48 was active against one A. acidocaldarius and three strains of A. acidoterrestris tested. In natural orange and apple juices incubated at 37 degrees C, vegetative cells of A. acidoterrestris DSMZ 2,498 were inactivated by enterocin AS-48 (2.5 microg/ml) and no growth was observed in 14 days. In commercial fruit juices added of AS-48 (2.5 microg/ml) and inoculated with vegetative cells or with endospores of strain DSMZ 2,498, no viable cells were detected during 90 days of incubation at temperatures of 37 degrees C, 15 degrees C or 4 degrees C, except for apple, peach and grapefruit juices inoculated with vegetative cells and incubated at 37 degrees C which were protected efficiently for up to 60 days. Remarkably, in all commercial fruit juices tested, no viable cells were detected as early as 15 min after incubation with the bacteriocin. Endospores incubated for a very short time (1 min) with increasing bacteriocin concentrations were inactivated by 2.5 microg/ml AS-48. Electron microscopy examination of vegetative cells and endospores treated with enterocin AS-48 revealed substantial cell damage and bacterial lysis as well as disorganization of endospore structure.     

Survival and growth of Enterobacter sakazakii on fresh-cut fruits and vegetables and in unpasteurized juices as affected by storage temperature

Enterobacter sakazakii is an emerging foodborne pathogen that has caused illnesses and deaths in infants and elderly immunocompromised adults. Outbreaks of E. sakazakii infection have been associated with infant formulas, but the documented presence of this pathogen in a wide variety of ready-to-eat foods, including lettuce and other raw vegetables, makes it important to learn more about its behavior in these environments. We investigated the survival and growth characteristics of E. sakazakii on fresh-cut apple, cantaloupe, strawberry, watermelon, cabbage, carrot, cucumber, lettuce, and tomato and in juices prepared from these fruits and vegetables. Produce and juices were inoculated with E. sakazakii at 2 to 3 log CFU/g and 1 to 2 log CFU/ml, respectively, and stored at 4, 12, or 25 degrees C. Populations either did not change or gradually decreased in fresh-cut produce and juices stored at 4 degrees C but grew at 12 degrees C on fresh-cut apple, cantaloupe, watermelon, cucumber, and tomato and in all juices except apple, strawberry, cabbage, and tomato juices. All fresh-cut fruits and vegetables except strawberry supported growth of E. sakazakii at 25 degrees C. Growth occurred in all juices except apple, strawberry, and cabbage juices, followed by decreases in population to < 1 CFU/ml after 48 to 72 h, which coincided with decreases in pH and an increase in the population of lactic acid bacteria. Increases in total counts occurred in all juices except strawberry juice stored at 25 degrees C and apple and strawberry juices stored at 12 degrees C. Total counts increased in cantaloupe, carrot, cucumber, and lettuce juices stored at 4 degrees C. Populations of molds and yeasts increased in apple and tomato juices stored at 25 degrees C but decreased to <1 CFU/ml in cabbage, lettuce, and cucumber juices. Further characterization of the behavior of E. sakazakii on fresh produce and in unpasteurized juice as affected by commercial packaging and handling practices is needed.     

Enhanced bactericidal effect of enterocin AS-48 in combination with high-intensity pulsed-electric field treatment against Salmonella enterica in apple juice

The effect of the broad spectrum cyclic antimicrobial peptide enterocin AS-48 combination with high-intensity pulsed-electric field (HIPEF) treatment (35 kV/cm, 150 Hz, 4 micros and bipolar mode) was tested on Salmonella enterica CECT 915 in apple juice. A response surface methodology was applied to study the bactericidal effects of the combined treatment. The process variables were AS-48 concentration, temperature, and HIPEF treatment time. While treatment with enterocin AS-48 alone up to 60 microg/ml had no effect on the viability of S. enterica in apple juice, an increased bactericidal activity was observed in combination with HIPEF treatments. Survival fraction was affected by treatment time, enterocin AS48 concentration and treatment temperature. The combination of 100 micros of HIPEF treatment, 30 microg/ml of AS-48, and temperature of 20 degrees C resulted in the lowest inactivation, with only a 1.2-log reduction. The maximum inactivation of 4.5-log cycles was achieved with HIPEF treatment for 1000 micros in combination with 60 microg/ml of AS-48 and a treatment temperature of 40 degrees C. Synergism between enterocin AS-48 and HIPEF treatment depended on the sequence order application, since it was observed only when HIPEF was applied in the presence of previously-added bacteriocin. The combined treatment could improve the safety of freshly-made apple juice against S. enterica transmission.     

The growth of Propionibacterium cyclohexanicum in fruit juices and its survival following elevated temperature treatments

This study investigated the growth of Propionibacterium cyclohexanicum in orange juice over a temperature range from 4 to 40 degrees C and its ability to multiply in tomato, grapefruit, apple, pineapple and cranberry juices at 30 and 35 degrees C. Survival after 10 min exposure to 50, 60, 70, 80, 85, 90 and 95 degrees C in culture medium and in orange juice was also assessed. In orange juice the organism was able to multiply by 2 logs at temperatures from 4 to 35 degrees C and survived for up to 52 days. However, at 40 degrees C viable counts were reduced after 6 days and no viable cells isolated after 17 days. The optimum growth temperature in orange juice over 6 days was 25 degrees C but over 4 days it was 35 degrees C. The growth of P. cyclohexanicum was monitored in tomato, grapefruit, cranberry, pineapple and apple juices at 30 and 35 degrees C over 29 days. Cranberry, grapefruit and apple juice did not support the growth of P. cyclohexanicum. At 30 degrees C no viable cells were detected after 8 days in cranberry juice or after 22 days in grapefruit juice while at 35 degrees C no viable cells were detected after 5 and 15 days, respectively. However, in apple juice, although a 5 log reduction occurred, viable cells could be detected after 29 days. P. cyclohexanicum was able to multiply in both tomato and pineapple juices. In tomato juice, there was a 2 log increase in viable counts after 8 days at 30 degrees C but no increase at 35 degrees C, while in pineapple juice there was a 1 log increase in numbers over 29 days with no significant difference between numbers of viable cells present at 30 and 35 degrees C. The organism survived at 50 degrees C for 10 min in culture medium without a significant loss of viability while similar treatment at 60, 70 and 80 degrees C resulted in approximately a 3-4 log reduction, with no viable cells detected after treatment at 85 or 90 or 95 degrees C but, when pre-treated at intermediate temperatures before exposure to higher temperatures, some cells survived. However, in orange juice a proportion of cells survived at 95 degrees C for 10 min without pre-treatment and there was no significant difference between numbers surviving with and without pre-treatment. The results from this study demonstrate that P. cyclohexanicum is able to grow in a number of juices, other than orange juice, and able to survive a number of high temperature procedures. Therefore, if initially present in the raw materials P. cyclohexanicum might survive the pasteurization procedures used in the fruit juice industry, contaminate and consequently spoil the final product.     

Effect of enterocin AS-48 in combination with high-intensity pulsed-electric field treatment against the spoilage bacterium Lactobacillus diolivorans in apple juice

Enterocin AS-48 was tested in apple juice against the cider-spoilage, exopolysaccharide-producing strain Lactobacillus diolivorans 29 in combination with high-intensity pulsed-electric field (HIPEF) treatment (35 kV/cm, 150 Hz, 4 μs and bipolar mode). A response surface methodology was applied to study the bactericidal effects of the combined treatment, with AS-48 concentration and HIPEF treatment time as process variables. At subinhibitory bacteriocin concentrations, microbial inactivation by the combined treatment increased as the bacteriocin concentration and the HIPEF treatment time increased (from 0.5 to 2.0 μg/ml and from 100 to 1000 μs, respectively). Highest inactivation (4.87 logs) was achieved by 1000 μs HIPEF treatment in combination with 2.0 μg/ml AS-48. While application of treatments separately did not protect juice from survivors during storage, survivors to the combined treatment were inactivated within the following 24 h of storage, and the treated samples remained free from detectable lactobacilli for at least 15 days at temperatures of 4 °C as well as 22 °C. The combined treatment could be useful for inactivation of exopolysaccharide-producing L. diolivorans in apple juice.     

Inhibition of Listeria monocytogenes by enterocin EJ97 produced by Enterococcus faecalis EJ97

Enterocin EJ97 from Enterococcus faecalis EJ97 showed a concentration-dependent antimicrobial activity against Listeria monocytogenes CECT 4032. Activity of enterocin EJ97 against L. monocytogenes CECT 4032 increased slightly at 4 degrees C, and cold-adapted cells did not show any increased resistance. Sensitivity of L. monocytogenes CECT 4032 to enterocin EJ97 was not modified by the addition of sodium benzoate, sodium acetate, NaCl or sodium tripolyphosphate. Anti-listeria activity was enhanced by potassium nitrate, and especially by sodium nitrite at concentrations of 50 microg/ml or above. E. faecalis EJ97 produced bacteriocin activity during cocultivation with L. monocytogenes CECT 4032 at 37 degrees C and also at 15 degrees C, but not at 4 degrees C. Growth of L. monocytogenes CECT 4032 was inhibited by bacteriocin produced during cocultivation at 37 and 15 degrees C, and the degree of inhibition was influenced by the incubation temperature and the initial concentrations of enterococci and listeria. E. faecalis EJ97 also produced bacteriocin during cocultivation in half-skimmed milk, although its capacity to control L. monocytogenes was limited to populations of 10(3) CFU/ml or lower.     

Effect of low-temperature, high-pressure treatment on the survival of Escherichia coli O157:H7 and Salmonella in unpasteurized fruit juices

The destructive effect of high pressure (615 MPa) combined with low temperature (15 degrees C) on various strains of Escherichia coli O157:H7 and various serovars of Salmonella in grapefruit, orange, apple, and carrot juices was investigated. The three-strain cocktail of E. coli O157:H7 (SEA13B88, ATCC 43895, and 932) was found to be most sensitive in grapefruit juice (8.34-log reduction) and least in apple juice (0.41-log reductions) when pressurized at 615 MPa for 2 min at 15 degrees C. Correspondingly, no injured survivor was detected in grapefruit and carrot juices under similar treatment conditions. No Salmonella spp. were detected in a 2-min pressure treatment (615 MPa, 15 degrees C) of grapefruit and orange fruit juices. Except for Enteritidis, all four serovars tested in the present study have viability loss of between 3.92- and 5.07-log reductions when pressurized in apple juice at 615 MPa for 2 min at 15 degrees C. No injured cells were recovered from grapefruit and orange juices, whereas the same treatment demonstrated reduction in numbers of Salmonella serovars Agona and Muenchen in apple juices and to a lesser extent with Typhimurium, Agona, and Muenchen in carrot juice. The present study demonstrated that low-temperature, high-pressure treatment has the potential to inactivate E. coli O157:H7 strains and different Salmonella spp. in different fruit juices.     

Effect of storage in juice with or without pulp and/or calcium lactate on the subsequent survival of Escherichia coli O157:H7 in simulated gastric fluid

A study was conducted to evaluate the effect of storing Escherichia coli O157:H7 in fruit or vegetable juices with or without pulp and/or calcium lactate, on the bacterial resistance to a simulated gastric fluid (SGF, pH 1.5). Apple, carrot, orange, and tomato juices containing pulp or freed from pulp by filtration were used in this study. Calcium lactate at about 1.4 g/l was added to juices to obtain calcium supplemented juices. Juices with or without pulp and/or calcium lactate were inoculated with E. coli O157:H7 and then were stored at 7 degrees C for 0, 1, 2, or 4 days. The acid resistance of cells stored in juices with or without pulp and/or calcium lactate was determined by incubating in SGF for 90 or 240 min at 37 degrees C. Cells stored in apple juice for 4 days, carrot juice for 2 days, and orange juice for 4 days with pulp only had greater acid resistance, while all cells stored in tomato juice with pulp had greater acid resistance than cells stored in juice without pulp. The D-values of cells stored in supplemented apple and orange juices with calcium lactate declined 1.7-3.5 fold, whereas D-values of cells stored in supplemented tomato juice decreased by about 1.4-fold when compared to cells stored in juice without calcium lactate after exposure in SGF. These results indicate that storing E. coli O157:H7 in juices with pulp had little or no effect on the acid resistance of cells during subsequent exposure in SGF. Calcium lactate supplemented into juices could dramatically decrease the ability of E. coli O157:H7 to survive in SGF, possibly reducing the risk of foodborne illness by juice products.     

Efficacy of enterocin AS-48 against bacilli in ready-to-eat vegetable soups and purees

The broad-spectrum bacteriocin enterocin AS-48 was tested for biopreservation of ready-to-eat vegetable foods (soups and purees) against aerobic mesophilic endospore-forming bacteria. By adding AS-48 (10 microg/ml), Bacillus cereus LWL1 was completely inhibited in all six vegetable products tested (natural vegetable cream, asparagus cream, traditional soup, homemade-style traditional soup, vegetable soup, and vichyssoise) for up to 30 days at 6, 15, and 22 degrees C. A collection of strains isolated from spoiled purees showed slightly higher resistance to AS-48 in the order Paenibacillus sp. > Bacillus macroides > B. cereus, although they were also completely inhibited in natural vegetable cream by AS-48 at 10 microg/ml. However, cocktails of five or eight strains composed of B. cereus (three strains), B. macroides (two strains), and Paenibacillus sp., Paenibacillus polymyxa, and Paenibacillus amylolyticus showed higher bacteriocin resistance with AS-48 of up to 50 microg/ml required for complete inactivation in natural vegetable cream stored at 22 degrees C. Repetitive extragenic palindromic sequence-based PCR (REP-PCR) analysis showed that paenibacilli (along with some B. cereus) was the predominant survivor in the cocktails after bacteriocin treatment. To increase the effectiveness of enterocin AS-48, the bacteriocin was tested (at 20 microg/ml) against the eight-strain cocktail in natural vegetable cream in combination with other antimicrobials. The combination of AS-48 and nisin had a slight but significant additive effect. Bactericidal activity was greatly enhanced by phenolic compounds (carvacrol, eugenol, geraniol, and hydrocinnamic acid), achieving a rapid and complete inactivation of bacilli in the tested puree at 22 degrees C.     

Inhibition of toxicogenic Bacillus cereus in rice-based foods by enterocin AS-48

The antimicrobial effect of the broad-spectrum bacteriocin enterocin AS-48 against the toxicogenic psychrotrophic strain Bacillus cereus LWL1 has been investigated in a model food system consisting of boiled rice and in a commercial infant rice-based gruel dissolved in whole milk stored at temperatures of 37 degrees C, 15 degrees C and 6 degrees C. In food samples supplemented with enterocin AS-48 (in a concentration range of 20-35 mug/ml), viable cell counts decreased rapidly over incubation time, depending on the bacteriocin concentration, the temperature of incubation and the food sample. Enterotoxin production at 37 degrees C was also inhibited. Heat sensitivity of endospores increased markedly in food samples supplemented with enterocin AS-48: inactivation of endospores was achieved by heating for 1 min at 90 degrees C in boiled rice or at 95 degrees C in rice-based gruel. Activity of enterocin AS-48 in rice gruel was potentiated by sodium lactate in a concentration-dependent way.     

Effects of high pressure and mild heat on endogenous microflora and on the inactivation and sublethal injury of Escherichia coli inoculated into fruit juices and vegetable soup

The objective of this study was to determine the effects of high-pressure treatments and mild temperatures on endogenous microflora and Escherichia coli CECT 515 artificially inoculated into orange and apple juices and vegetable soup. In general, the viability of aerobic bacteria was significantly reduced as pressure and temperature increased. Although the greatest reduction in the concentration of aerobic mesophilic vegetative cells was reached at 350 MPa and 60 degrees C, the same reduction occurred in fruit juices at 350 MPa and 20 degrees C. Yeasts and molds were below the level of detection (1 log CFU/ml) for the fruit juices and did not exceed 2 log CFU/ml for vegetable soup. Foods inoculated with E. coli were subjected to several treatments as indicated by the mathematical model applied in response surface methodology to obtain the maximum information with the minimum number of experiments. The number of tests for a range of pressures (150 to 350 MPa) and temperatures (20 to 60 degrees C) was limited to 11. The models were considered adequate because of satisfactory R2 values. The optimum process parameters (pressure and temperature) for a 6-log reduction of E. coli were obtained at 248.25 MPa and 59.91 degrees C in orange juice, 203.50 MPa and 57.18 degrees C in apple juice, and 269.8 MPa and 59.9 degrees C in vegetable soup. Sublethal injury of E. coli occurred as pressure and temperature increased. Nearly all of the E. coli cells were injured at 350 MPa and 20 degrees C in fruit juices and after all treatments in vegetable soup.     

Portable, low-cost equipment for small-scale fruit juice processing

Simple, low-cost portable equipment to extract citrus juice, and pasteurize it and other fruit juices by passing through a coil of stainless steel tube in boiling water was designed, constructed and tested. Temperature reached was varied by altering the hydrostatic feed height, and the product was directly hot-bottled and capped. Pasteurization was microbiologically effective, and had little effect on ascorbic acid, furfural and colour of freshly prepared pineapple orange, Valencia orange and apple juices, and an orange squash drink, and only the expected changes occurred on storage at 21°C for periods up to 6 months, although with no indication of microbial activity. Taste panel ratings showed a loss of liking for treated orange juice, but not for apple. The equipment is suitable for improved utilization of crops by community technology in less-developed areas.     

Survival of SA11 rotavirus in fresh fruit juices of pineapple, papaya, and honeydew melon

Survival of rotavirus in fresh fruit juices of papaya (Caraca papaya L.), honeydew melon (Cucumis melo L.), and pineapple (Ananas comosus [L.] Merr.) was studied. Clarified juices were prepared from pulps of ripe fruits and sterilized by ultrafiltration. One milliliter of juice from each fruit was inoculated with 20 microl of 1 x 10(6) PFU of SA11 rotavirus and sampled immediately (0-h exposure) and 1 and 3 h later at 28 degrees C. Mean viral titers in juices of papaya (pH 5.1) and honeydew melon (pH 6.3) at 1 and 3 h were not significantly different from titers at 0-h exposure. Mean viral titers in juices from pineapples with ripening color indices of 3 (pH 3.6) and 6 (pH 3.7) at 1-h exposure (color index 3: 4.0 +/- 1.7 x 10(4); color index 6: 2.3 +/- 0.3 x 10(5)) and 3-h exposure (color index 3: 1.1 +/- 0.4 x 10(4); color index 6:1.3 +/- 0.6 x 10(5)) were significantly lower than titers at 0-h exposure (color index 3: 5.7 +/- 2.9 x 10(5); color index 6: 7.4 +/- 1.3 x 10(5)). Virus titers in pineapple juices of color index 3 were significantly lower than titers of the virus in juices of index 6. In cell culture medium (pH 7.4), SA11 titer remained stable over 3 h at 28 degrees C. However, at pH 3.6, the virus titer was reduced to a level not significantly different from that of the virus in pineapple juice of color index 6 (pH 3.7). In conclusion, papaya and honeydew melon juices, in contrast to pineapple juice, have the potential to transmit rotavirus. Inactivation of SA11 virus in pineapple juice can be possibly attributed to low pH and constituent(s) in the juice.     

Application of a multi-pass high-pressure homogenization treatment for the pasteurization of fruit juices

This work evaluates both the effects of a multiple-pass high-pressure homogenization treatment on the microbial inactivation of selected microbial strains (Saccharomyces cerevisiae, Lactobacillus delbrueckii, Escherichia coli) inoculated into commercial fruit juices (orange, red orange, pineapple) as well as the application of this non-thermal technology to the pasteurization of fresh juices (Annurca apple juice). The pressure level ranged from 50 to 250 MPa, the number of passes from 1 to 5 and the inlet temperature from 2 to 20 °C.Preliminary tests in distilled water showed that the efficiency of the multiple-pass treatment significantly depends on both the homogenizing pressure as well as the microbial species. The subsequent extension of the multiple-pass treatment to the inactivation of S. cerevisiae inoculated into three different fruit juices (orange, red-orange and pineapple juice) highlighted that the inactivation induced by the high pressure treatment did not depend on the properties of the tested juices and was not statistically different from inactivation in water (p value < 0.05). These findings were supported by the comparison of two different mathematical models used to fit the inactivation kinetics, whose fitting parameters were not significantly different for water and the fruit juices for any pressure level applied.Three homogenization passes at 150 MPa and 25 °C, which resulted to be optimal for yeast inactivation in fruit juices, were effective for the stabilization of the endogenous microbial load of fresh Annurca apple juice. The treated apple juice showed a minimum shelf-life of 28 days under refrigerated conditions, during which the natural qualities of the fresh juice were completely preserved.     

Inhibition of Bacillus cereus and Bacillus weihenstephanensis in raw vegetables by application of washing solutions containing enterocin AS-48 alone and in combination with other antimicrobials

Enterocin AS-48 is a broad-spectrum cyclic antimicrobial peptide produced by Enterococcus faecalis. In the present study, the bacteriocin was tested alone and in combination with other antimicrobials for decontamination of Bacillus inoculated on alfalfa, soybean sprouts and green asparagus. Washing with enterocin AS-48 solutions reduced viable cell counts of Bacillus cereus and Bacillus weihenstephanensis by 1.0–1.5 and by 1.5–2.38 log units right after application of treatment, respectively. In both cases, the bacteriocin was effective in reducing the remaining viable population below detection levels during further storage of the samples at 6 °C, but failed to prevent regrowth in samples stored at 15 or 22 °C. Application of washing treatments containing enterocin AS-48 in combination with several other antimicrobials and sanitizers (cinnamic and hydrocinnamic acids, carvacrol, polyphosphoric acid, peracetic acid, hexadecylpyridinium chloride and sodium hypochlorite) greatly enhanced the bactericidal effects. The combinations of AS-48 and sodium hypochlorite, peracetic acid or hexadecylpyridinium chloride provided the best results. After application of the combined treatments on alfalfa sprouts contaminated with B. cereus or with B. weihenstephanensis, viable bacilli were not detected or remained at very low concentrations in the treated samples during a 1-week storage period at 15 °C. Inhibition of B. cereus by in situ produced bacteriocin was tested by cocultivation with the AS-48 producer strain E. faecalis A-48-32 inoculated on soybean sprouts. Strain A-48-32 was able to grow and produce bacteriocin on sprouts both at 15 and 22 °C. At 15 °C, growth of B. cereus was completely inhibited in the cocultures, while a much more limited effect was observed at 22 °C. The results obtained for washing treatments are very encouraging for the application of enterocin AS-48 in the decontamination of sprouts. Application of washing treatments containing AS-48 alone can serve to reduce viable cell counts of bacilli in samples stored under refrigeration, while application of combined treatments should be recommended to avoid proliferation of the surviving bacilli under temperature-abuse conditions.     

Moulds and yeasts in fruit salads and fruit juices

Thirty-eight fruit salad samples including cantaloupe, citrus fruits, honeydew, pineapple, cut strawberries and mixed fruit salads, and 65 pasteurized fruit juice samples (apple, carrot, grapefruit, grape and orange juices, apple cider, and soy milk) were purchased from local supermarkets in the Washington, DC area and tested for fungal contamination. The majority of fruit salad samples (97%) were contaminated with yeasts at levels ranging from <2.0 to 9.72 log10 of colony forming units per gram (cfu/g). Frequently encountered yeasts were Pichia spp., Candida pulcherrima, C. lambica, C. sake, Rhodotorula spp., and Debaryomyces polymorphus. Low numbers of Penicillium spp. were found in pineapple salads, whereas Cladosporium spp. were present in mixed fruit and cut strawberry salads. Twenty-two per cent of the fruit juice samples tested showed fungal contamination. Yeasts were the predominant contaminants ranging from <1.0 to 6.83 log10 cfu/ml. Yeasts commonly found in fruit juices were C. lambica, C. sake, and Rhodotorula rubra. Geotrichum spp. and low numbers of Penicillium and Fusarium spp. (1.70 and 1.60 log10 cfu/ml, respectively) were present in grapefruit juice.     

Adaptation of Salmonella spp. in juice stored under refrigerated and room temperature enhances acid resistance to simulated gastric fluid

The objective of this study was to evaluate the acid resistance of Salmonella spp. adapted in juices stored under refrigeration and room temperatures to simulated gastric fluid (SGF, pH 1.5). Five Salmonella serovars, Agona, Gaminara, Michigan, Montevideo, and Poona were used in this study. Apple, orange, and tomato juices inoculated with five serovars were stored at refrigeration (7 degrees C) and room temperature (20 degrees C) for 24 h for adaptation. Acid resistances of serovars adapted in juice were determined in SGF at 37 degrees C. All acid-adapted Salmonella serovars in juices displayed enhanced survival time compared to non-adapted controls. Among serovars, S. Poona adapted in apple at 20 degrees C and orange juices at 7 and 20 degrees C showed >2.0 log cfu/ml survivors, while the other serovars decreased to non-detectable level or <2.0 log cfu/ml for 100 s in SGF. Unlike apple and orange juices, all serovars adapted in tomato juice survived with >2.0 log cfu/ml for 100 s. For D-values, all Salmonella serovars adapted in apple and tomato juice enhanced their acid resistances compared to orange juices. S. Agona adapted in tomato juice at 7 degrees C and S. Poona in apple juice at 20 degrees C had the highest D-values with 82.9 and 82.5s, respectively. Results showed that the adaptation in juice increased acid resistance in SGF and varied by serovar, juice type, and adaptation temperature. Therefore, this study indicates that the introduction of Salmonella spp. to an acidic juice environment during processing can enhance their ability to survive in a human stomach, possibly increasing the risk of a Salmonella outbreak by juice.     

Development and optimisation by means of sensory analysis of new beverages based on different fruit juices and sherry wine vinegar

BACKGROUND: Despite the long history of sherry wine vinegar, new alternatives of consumption are being developed, with the aim of diversifying its market. Several new acetic‐based fruit juices have been developed by optimising the amount of sherry wine vinegar added to different fruit juices: apple, peach, orange and pineapple. Once the concentrations of wine vinegar were optimised by an expert panel, the aforementioned new acetic fruit juices were tasted by 86 consumers. Three different aspects were taken into account: habits of consumption of vinegar and fruit juices, gender and age. RESULTS: Based on the sensory analysis, 50 g kg^?1 of wine vinegar was the optimal and preferred amount of wine vinegar added to the apple, orange and peach juices, whereas 10 g kg^?1 was the favourite for the pineapple fruit. Based on the olfactory and gustatory impression, and ‘purchase intent’, the acetic beverages made from peach and pineapple juices were the most appreciated, followed by apple juice, while those obtained from orange juice were the least preferred by consumers. CONCLUSION: New opportunities for diversification of the oenological market could be possible as a result of the development of this type of new product which can be easily developed by any vinegar or fruit juice maker company. © 2012 Society of Chemical Industry     

Heat-resistant fungi in Nigerian heat-processed fruit juices

Sixty packaged heat-processed Nigerian fruit juices consisting of 15 each of mango, orange, pineapple and tomato, were screened for the presence of heat-resistant fungi after storage at approximately 28°C for 30 days. The resulting fungal growth was purified on potato dextrose agar. Approximately 17% of all the fruit juice packages and 27% of mango and tomato juices contained heat-resistant fungi. These were identified as Paecilomyces variotii, Aspergillus tamarii, A. flavus and A. ochraceus , the latter being predominant.     

Enterocin 416K1, an antilisterial bacteriocin produced by Enterococcus casseliflavus IM 416K1 isolated from Italian sausages

Enterococci (118) from Italian sausages were tested for the production of antimicrobial substances. Of these, 7.6% showed antibacterial activity against one or several closely related microorganisms used as indicators. Enterococcus casseliflavus IM 416K1 in particular produced a bacteriocin (Enterocin 416K1) with strong anti-listerial antagonistic activity. The bacteriocin withstood heating at 90 degrees C for 120 min and storage at 4 degrees C for 6 months. The mode of action was identified as bactericidal. The crude activity of Enterocin 416K1 was linked to a molecule with an apparent molecular weight smaller than 5 kDa. Plasmid analysis of E. casseliflavus IM 416K1 revealed the presence of four plasmids with different molecular weights (34, 11, 7 and 3.3 MDa). All the Bac- variants produced by curing experiments showed loss of the single plasmid of 34 MDa. Bacteriocin activity and immunity production may be linked to genes located on that same plasmid.