Evaluation of thermotolerant capacity of lactic acid bacteria isolated from commercial sausages and the effects of their addition on the quality of cooked sausages

The thermotolerant capacity of several lactic acid bacteria strains isolated from cooked commercial sausages was determined. Four strains were positively identified as Lactobacillus plantarum, Lactobacillus curvatus, Pediococcus pentosaceus and Pediococcus acidilacti, after surviving thermal treatment (70 °C during 60 minutes). Thermotolerant strains were inoculated in sausage batters before cooking in order to determine their effect on color, texture, acceptance and inhibition of Enterobacteria during 12 days at 8 °C. No significant effect of the inoculated strains was detected on color parameters. Textural profile parameters, cohesiveness and resilience, were not affected by the inoculation of thermotolerant lactic acid bacteria, but L. curvatus sausages resulted softer than the rest of the treatments. Samples inoculated with L. curvatus also obtained the lowest scores for the sensory attributes evaluated, with the remaining treatments causing no unfavorable effects on sausage acceptance. There was a reduction in enterobacterial counts after 12 days of cold storage in inoculated samples. The performance of inoculated lactic acid bacteria strains can be explained in a similar way as that of starter cultures in dry-fermented sausages, where the growth in nests impairs other pathogenic microorganisms present in the rest of the sausage, since environmental conditions and the early inoculation of these thermotolerant strains favor them to become the dominant flora.

Quality of mussels cultivated and commercialized in Ubatuba, SP, Brazil: monitoration Bacillus cereus and Staphylococcus aureus growth after post-harvest processing

Aiming at improving the quality of Perna perna mussels cultivated and commercialized in Ubatuba, SP, Brazil, the growth and elimination of Staphylococcus aureus and Bacillus cereus artificially inoculated in mussels were studied. The inoculation was carried out in "in natura" and pre-cooked mussels for 30 min, and after that the mussels were kept for 10 hours at room temperature (25 ± 1 °C) and under refrigeration (7 ± 1 °C). Six thermal treatments were evaluated: three using steam (5, 10 and 15 minutes) and three in boiling water (5, 10 and 15 minutes), in order to find the best time/temperature binomial to provide pathogenic control. Yield and physical-chemical and sensory characteristics were evaluated. All thermal treatments were efficient to eliminate microorganisms in 2 logarithmic cycles. However, the boiling water treatments presented better results than the steam treatments. The physical-chemical and sensory analyses did not show statistical differences among the thermal treatments studied. The best performances were reached in the shortest times of heat exposure. Overall, the treatments in boiling water presented better results than the steam treatments.

Bacterial ecology of tilapia fresh fillets and some factors that can influence their microbial quality

The purpose of research was to investigate the bacterial ecology of tilapia (Oreochromis niloticus) fresh fillets and some factors that can influence its microbial quality. Samples of fish cultivation water (n = 20), tilapia tegument and gut (n = 20) and fresh fillets (n = 20) were collected in an experimental tilapia aquaculture located in the city of Lavras, Minas Gerais, Brazil. Staphylococcus spp., Aeromonas spp., Enterococcus spp. and Enterobacteriaceae were quantified using selective plating. For the enumeration of Pseudomonas spp., the most probable number technique (MPN) was utilized. Bacterial colonies (n = 198) were identified by Gram strain and biochemical tests. Aeromonas spp., Pseudomonas spp., Enterococcus spp. and Enterobacteriaceae were found in the cultivation water (water from a fishpond cultivation), tegument, gut, and fresh fillets. Staphylococcus spp. was not isolated in the cultivation water. Salmonella spp. was not detected. The count variable of 10 to 10³ CFU or MPN.(g or mL)-1. Associated to freshwater tilapia fillet processing, there is a large variety of microorganisms related to foodborne illnesses and fish products deterioration.

Chemical characterization and antimicrobial activity of essential oils of salvia L. species

In this work, the essential oils of S. officinalis, S. sclarea, S. lavandulifolia and S. triloba were chemically analyzed by gas chromatography coupled to a mass spectrometry detector (GC/MSD), and their antimicrobial activity was tested against 10 microorganisms using the disk diffusion method and the Minimum Inhibitory Concentration (MIC) technique. The following major compounds were identified in the essential oils: α - and β-thujone, camphor and 1,8-cineole, except in S. sclarea, where linalool, linalyl acetate and α-terpineol were the major constituents. The antimicrobial activity showed significant differences (p < 0.05) only when obtained by the MIC method. Gram-positive microorganisms presented larger sensitivity for the essential oils. The lowest MIC was observed when Staphylococcus aureus was exposed to 2.31 mg.mL-1 of S. lavandulifolia essential oil, while the highest MIC value was obtained when Shigella flexneri was exposed to 9.25 mg.mL-1 of the same essential oil, thus demonstrating that this essential oil may be effective as a bacteriostatic agent against Gram-positive microorganisms.

Quality of minimally processed guava with different types of cut, sanification and packing

The purpose of this project was to evaluate the sanitization effect on the quality of minimally processed guava. Initially, research was carried out with consumers in a supermarket to verify preferences of packaging for guava. Following this, the guava cv. Paluma underwent two sanitization sequences using dehydrated sodium dichloroisocyanurate compound, in 50 ppm concentration, sanitization prior to (S1) and after (S2) being cut; removal of excess water; conditioning in PET packaging and PSPVC and storage at 3 ºC ± 1 ºC. Physicochemical analysis - [pH, total soluble solids (SST), total labeled acidity (ATT), ascorbic acid (AA), total sugars (AT) and reducers (AR)], textural sensorial and microbiological analyses were used to monitor the quality of the products. The consumers preferred the guava cut in halves with pulp and packed in PET, although this packaging promoted condensation of water vapor on the inner surface of the lid, compromising the appearance of the product. The two sanitization sequences and the two kinds of packaging did not significantly affect the pH, SST, ATT, SST/ATT, texture and AA values. The AT and AR tenors increased significantly in the MP guavas stored in the PSPVC package. Both sanitizations were efficient in the bacterial control of the indicators of the hygienicsanitary conditions, although the S1 sanitization proved to be more efficient in the control of autochthonous aerobic microbiota (aerobic mesophylic microorganisms). It can be concluded that guava cv. Paluma packed in PSPVC can be conserved for 6 days when stored at 3 ºC.

Effectiveness of cleaning and sanitizing procedures in controlling the adherence of Pseudomonas fluorescens, Salmonella Enteritidis, and Staphylococcus aureus to domestic kitchen surfaces

The effectiveness of cleaning and sanitizing procedures in controlling Staphylococcus aureus, Salmonella Enteritidis, and Pseudomonasfluorescens adhered to granite and stainless steel was evaluated. There was no significant difference (p > 0.05) in the adherence of pure cultures of these microorganisms to stainless steel. The numbers of P. fluorescens and S. Enteritidis adhered to granite were greater (p < 0.05) than the numbers of S. aureus. Additionally, the adherence of P. fluorescens was similar to the adherence of S. Enteritidis on granite surface. In a mixed culture with P. fluorescens, S aureus adhered less (p < 0.05) to stainless steel surfaces (1.31 log CFU.cm-2) than when in a pure culture (6.10 log CFU.cm-2). These results suggest that P. fluorescens inhibited the adherence of S. aureus. However, this inhibition was not observed in the adherence process for granite. There was a significant difference (p < 0.05) between the number of adhered cells before and after pre-washing for S. aureus on stainless steel and granite surfaces, and after washing with detergent for all microorganisms and surfaces. The efficiency of the cleaning plus sanitizing procedures was not significantly different (p > 0.05) between the surfaces. However, a significant difference was observed (p < 0.05) between the sanitizer solutions. Sodium hypochlorite and peracetic acid were more bactericidal (p < 0.05) than a quaternary ammonium compound. With regard to microorganisms, S. aureus was the least resistant to the sanitizers. These results show the importance of good cleaning and sanitization procedures to prevent bacterial adherence and biofilm formation.

β-carotene biotransformation to obtain aroma compounds

Carotenoids are important constituents of food due to their color and because their degradation products generate important volatile compounds in foods. Aroma compounds derived from carotenoids are widely distributed in nature, and they are precursors of many important aromas in foods such as fruits and in flowers as well. They present high aromatic potential and are therefore of great interest to the industries of aromas and fragrances. In this study, more than 300 previously isolated microorganisms with potential for biotransformation of β-carotene present in the culture medium were selected using the plate method; about 80 strains presented capacity to produce aroma compounds and 7 strains were selected by an untrained panel of tasters to generate aroma compounds. The β-ionone was the main compound produced by CS1 (34.0 mg.L-1) and CF9 (42.4 mg.L-1) microorganisms at 72 and 24 hours of fermentation, cultured with and without pre-inoculation, respectively. The β-damascone and pseudoionone were found in low concentrations, 1,1,6-trimethyl-1,2,3,4-tetrahydronaphthalen (TTN) was tentatively identified and other compounds such as apocarotenoids, apparently obtained from the cleavage of the central part of the carotenoid, were detected.

Microbial profile of a kefir sample preparations: grains in natura and lyophilized and fermented suspension

Probiotics are supplementary foods developed by microbial strains that improve animal health beyond basic nutrition. Probiotics are consumed orally, regardless of being considered as normal inhabitants of the intestines, able to survive in enzimatic and biliary secretions. Kefir is a probiotic originated from the old continent, fermented by several bacteria and yeasts, encapsulated in a polyssacharide matrix, and resembles jelly grains. Kefir is also presented as its sourish product both in sugary or milky suspensions containing vitamins, aminoacids, peptides, carbohydrates, ethanol, and volatile compounds. Kefir is known to have a diverse microbial content depending on the country and fermentative substrates, which cause distinct probiotic effects. In this sense, the purpose of this work was to isolate, identify, and quantify the microbial content of a native sugary kefir sample (fermented suspension and lyophilized natural grains). Serial dilutions were plated on Rogosa agar (AR) and De Man, Rogosa and Sharpe (MRS), for Lactobacillus; Brain Heart Infusion (BHI), for total bacteria; Sabouraud-Dextrose-Agar (SDA), for yeasts and filamentous fungi; Thioglycolate Agar (TA), for Streptococcus, Acetobacteria and Leuconostoc; and Coconut Water Agar (CWA), and CWA supplemented with yeast extract (CWAY), for various genera. Genera and species for all strains were identified through biochemical reactions and specific API systems. The microbial profile of kefir was different from other sources of grains despite the presence of similar microorganisms and others which have not been reported yet. The data obtained with the CWA and CWAE media suggest that both substrates are alternative and salutary media for culture of kefir strains.

Detection of enterotoxins produced by B. cereus through PCR analysis of ground and roasted coffee samples in Rio de Janeiro, Brazil

Coffee is one of the most appreciated drinks in the world. Coffee ground is obtained from the fruit of a small plant that belongs to the genus Coffea. Coffea arabica and Coffea canephora robusta are the two most commercially important species. They are more commonly known as arabica and robusta, respectively. Two-thirds of Coffea arabica plants are grown in South and Central America, and Eastern Africa - the place of origin for this coffee species. Contamination by microorganisms has been a major matter affecting coffee quality in Brazil, mainly due to the harvesting method adopted. Brazilian harvests are based on fruits collected from the ground mixed with those that fall on collection cloths. As the Bacillus cereus bacterium frequently uses the soil as its environmental reservoir, it is easily capable of becoming a contaminant. This study aimed to evaluate the contamination and potential of B. cereus enterotoxin genes encoding the HBL and NHE complexes, which were observed in strains of ground and roasted coffee samples sold in Rio de Janeiro. The PCR (Polymerase Chain Reaction) results revealed high potential of enterotoxin production in the samples. The method described by Speck (1984) was used for the isolation of contaminants. The investigation of the potential production of enterotoxins through isolates of the microorganism was performed using the B. cereus enterotoxin Reverse Passive Latex Agglutination test-kit (BCET-RPLA, Oxoid), according to the manufacturer's instructions. The potential of enterotoxin production was investigated using polymerase chain reaction (PCR) methods for hblA, hblD and hblC genes (encoding hemolysin HBL) and for nheA, nheB and nheC genes (encoding non-hemolytic enterotoxin - NHE). Of all the 17 strains, 100% were positive for at least 1 enterotoxin gene; 52.9% (9/17) were positive for the 3 genes encoding the HBL complex; 35.3% (6/17) were positive for the three NHE encoding genes; and 29.4% (5/17) were positive for all enterotoxic genes.

Culture alternative medium for the growth of extreme halophilic bacteria in fish products

Halotolerant or halophilic (Archaeabacteria) microorganisms can be found in salted and ripening fish products that are not affected by salt. They can be moderate or extremely halophilic bacteria. The extremely halophilic bacteria require between 15-30% of NaCl for growth. The extremely halophilic archaeobacteria may be selectively isolated in different media. The aim of this work was to determine the effectiveness of the Salt-Agar-Milk medium, a medium modified in our laboratory through the addition of MgSO4 and KCl - named SAMm, and its effect on the bacterial growth by means of comparison with other media, with and without milk, determining time of incubation and counting. Two samples of salted fish from local fish salting factories and two laboratory strains were used. The factory samples were matured anchovy and anchovy fillets in oil, and the laboratory strains were: Haloarcula spp. (proteolytic) and Halococcus spp. (non-proteolytic). The following media were alternatively used for the isolation of extremely halophilic bacteria: IRAM; Formulation of Gibbons and collaborators, Cod Milk agar, and SAMm. IRAM and Gibbons were also used enriched with milk. In the SAMm medium, there were obtained count values similar or higher than the ones of the traditional media; besides the simplicity of its elaboration, the possibility to obtain positive results two or three days earlier also added to its benefit. Consequently, it can be considered an alternative to the media traditionally used for the studied halophilic bacteria.

The influence of different combinations of probiotic bacteria and fermentation temperatures on the microbiological and physicochemical characteristics of fermented lactic beverages containing soybean hydrosoluble extract during refrigerated storage

Lactic beverages containing probiotics were prepared with whole UHT milk, whey of Mozzarella cheese, soybean hydrosoluble extract and sugar. Three formulations were studied, each one containing a different combination of probiotic/starter bacteria, fermented at two different temperatures (37 and 45 °C). The aim of this work was to verify the influence of these variables on the viability of probiotic microorganisms and on the physicochemical stability of lactic beverages during storage under refrigeration (21 days at 7 °C). The results indicated that the fermentation temperature had a significant effect on the viability of probiotic bacteria. Counts for Lactobacillus acidophilus were affected by storage time, resulting appropriate after 21 days only for the beverage fermented at 37 °C. Physicochemical parameters did not exhibit drastic variations - proving the stability of formulations during storage. Cells of Bifidobacterium spp. showed high survival ability, probably due to the presence of growth promoters from soybean and cheese whey. The fermentation temperature of 37 °C allowed counts above the minimum limit for all the studied microorganisms, being preferred to the temperature of 45 °C. The inclusion of soybean hydrosoluble extract, a prebiotics source, resulted in a symbiotic product with more benefits to the health of consumers.

Ocurrence of Vibrio spp., positive coagulase staphylococci and enteric bacteria in oysters (Crassostrea gigas) harvested in the south bay of Santa Catarina island, Brazil

The aim of this study was to assess the contamination of oysters (Crassostrea gigas), harvested in six different regions of the South Bay of Santa Catarina Island, with Coliforms at 45 ºC, Escherichia coli, Vibrio spp., positive coagulase staphylococci, and Salmonella sp. over a period of one year. One hundred eighty oyster samples were collected directly from their culture sites and analyzed. Each sample consisted of a pool of 12 oysters. All of the samples analyzed showed absence of Salmonella, 18 (10%) samples showed presence of Escherichia coli, 15 (8.3%) samples were positive for V. alginolyticus, and Vibriocholerae was detected in 4 samples (2.2%). The counts of positive-coagulase staphylococci varied from <10 to 1.9 x 102 CFU.g-1, whereas the counts of Coliforms at 45 ºC and E. coli ranged from <3 to 1.5 x 102 MPN.g-1 and <3 and 4.3 x 10 MPN.g-1, respectively. Counts of V. parahaemolyticus and V. vulnificus ranged between <3 and 7 MPN.g-1, for both microorganisms. This suggests the need for monitoring these Vibrios contamination in oysters. Based on the results of the microbiological assays, the samples analyzed showed acceptable bacteriological quality, i.e., they were within the parameters established by Brazilian Legislation.

Synergistic and antimicrobial properties of commercial turmeric (Curcuma longa) essential oil against pathogenic bacteria

Several studies have shown the antimicrobial and antioxidant properties of turmeric (Curcuma longa), widely used in food industry as a colorant, among other functions. The aim of this study was to determine the antioxidant and antimicrobial properties of turmeric essential oil against pathogenic bacteria and to study the influence of the addition of ascorbic acid on the prevention of polyphenols oxidation. The commercial turmeric essential oil alone did not show bactericidal activity against the microorganisms studied, Listeria monocytogenes and Salmonella typhimurium, but when combined with ascorbic acid, it showed significant antibacterial activity. The highest antimicrobial activity of turmeric essential oil against Salmonella typhimurium was 15.0 ± 1.41 mm at the concentration of 2.30 mg.mL-1 of essential oil and 2.0 mg.mL-1 of ascorbic acid. With regard to Listeria monocytogenes, the largest zone of inhibition (13.7 ± 0.58 mm) was obtained at the same concentrations. The essential oil showed antioxidant activity of EC50 = 2094.172 µg.mL-1 for the DPPH radical scavenging method and 29% under the concentration of 1.667 mg.mL-1 for the β-carotene bleaching method.

Evaluation of the use of PetrifilmTM EB count plates for the enumeration of Enterobacteriaceae in poultry samples

A test that is rapid, simple, accurate, not expensive, gives rapid results, and is sensitive enough to detect low levels of microorganisms would be the most suitable for food industry routine laboratories, or even for a public health laboratories. A ready-to-use alternative, commercially available method is the PetrifilmTM EB method. The aim of this study was to evaluate whether there is a statistically significant difference between the conventional methods based on Violet Red Bile Glucose Agar and the alternative 3M TM Petrifilm (EB) method for the enumeration of Enterobacteriaceae in poultry carcasses. This study also assessed whether the alternative method showed ability to produce results that were directly proportional to the concentration of the target (approximately 270 colony-forming unit.mL-1). A total of 120 poultry carcasses samples showed a significant difference (p < 0.05) between the populations obtained by the two methods, and the conventional method showed low proportionality between the dilutions. On the other hand, the PetrifilmTM EB quantification system showed the capacity to produce results that are proportional to the concentration of the analyte in samples in the concentration range from 1 to 256 colony-forming unit.mL-1.

An alternative method for screening lactic acid bacteria for the production of exopolysaccharides with rapid confirmation

The accumulation of exopolysaccharides (EPS) produced by microorganisms occurs in the presence of excess substrate and limiting conditions of elements that are essential to growth, such as nitrogen, phosphorus, sulfur, and magnesium. The presence of EPS produced by bacterial cells contributes to slime colonies formation in solid medium and increased viscosity in liquid medium. This paper proposes an alternative method for screening EPS-producing lactic acid bacteria using solid medium-containing discs of filter paper that are saturated with active cultures. The screening was carried out under different culture conditions varying the type of sugar, pH, and temperature. EPS production was visualized by the presence of mucoid colonies on the discs, which was confirmed by the formation of a precipitate when part of this colony was mixed with absolute alcohol. The established conditions for obtaining a high number of isolates producing EPS were 10% sucrose, pH 7.5 and 28 ºC. This method proved to be effective and economical because several strains could be tested on the same plate, with immediate confirmation.