Antimicrobial effectiveness of oregano and sage essential oils incorporated into whey protein films or cellulose‐based filter paper

BACKGROUND: In this study the antimicrobial effectiveness of oregano and sage essential oils (EOs) incorporated into two different matrices, whey protein isolate (WPI) and cellulose‐based filter paper, was analysed. RESULTS: Antimicrobial properties of WPI‐based films containing oregano and sage EOs were tested against Listeria innocua, Staphylococcus aureus and Salmonella enteritidis. Oregano EO showed antimicrobial activity against all three micro‐organisms. The highest inhibition zones were against L. innocua. However, sage EO did not show antimicrobial activity against any of the micro‐organisms. Antimicrobial activity was confirmed for both EOs using cellulose‐based filter paper as supporting matrix, although it was significantly more intense for oregano EO. Inhibition surfaces were significantly greater when compared with those of the WPI films. This finding is likely due to the higher porosity and diffusivity of the active compounds in the filter paper. CONCLUSION: The interactions between the EOs and the films have a critical effect on the diffusivity of the active compounds and therefore on the final antimicrobial activity. As a result, to obtain active edible films, it is necessary to find the equilibrium point between the nature and concentration of the active compounds in the EO and the formulation of the film. Copyright © 2010 Society of Chemical Industry     

The effects of ratio of cow's milk to soymilk,probiotic strain and fruit concentrate on qualitative aspects of probiotic flavoured fermented drinks

The effects of proportion of cow's milk to soymilk (100:0, 75:25, 50:50, 25:75, 0:100), probiotic bacteria (Lactobacillus acidophilus LA‐5 or Lactobacillus casei L‐01) and natural fruit concentrates (strawberry, apricot, peach and pear) on quality characteristics of soy‐based probiotic drink were investigated. The parameters were analysed at the end of fermentation and during 21 days of storage at 5 ^°C. The highest viability was observed when the equal proportion of cow's milk and soymilk and L. casei was used (50:50‐CY). During chilled storage, the flavouring apricot had the highest stimulatory effect on the survival of L. casei in 50:50 treatment. In general, the treatment 50:50‐CY was realised as the best one overall.     

Effects of Mentha longifolia L. essential oil and Lactobacillus casei on the organoleptic properties and on the growth of Staphylococcus aureus and Listeria monocytogenes during manufacturing,ripening and storage of Iranian white‐brined cheese

This research evaluated the effects of Mentha longifolia L. essential oil (EO) in concentrations 0, 50, 150 and 300 ppm and Lactobacillus casei (10⁸–10⁹ CFU/mL) on the growth of Staphylococcus aureus and Listeria monocytogenes during the manufacturing, ripening and storage of Iranian white‐brined cheese. The growth of the two pathogens was significantly reduced (P < 0.01) by both EO concentrations ≥50 ppm and probiotic and their combination in the standard manufacturing and storage process conditions of the cheese. Furthermore, the treatment containing 150 ppm of this EO combined with probiotic had a favourable inhibitory effect on the growth of two pathogenic micro‐organisms and also was the most appropriate treatment in sensory assessment. The synergistic effects of the above‐mentioned concentration level between the essential oil and probiotic were significant compared to other treatments, including essential oil and probiotic only. Thus, a lower concentration of this EO can be used when it is combined with this probiotic.     

Antimicrobial activity of whey protein based edible films incorporated with oregano,rosemary and garlic essential oils

The use of edible films to release antimicrobial constituents in food packaging is a form of active packaging. Antimicrobial properties of spice extracts are well known, however their application to edible films is limited. In this study, antimicrobial properties of whey protein isolate (WPI) films containing 1.0–4.0% (wt/vol) ratios of oregano, rosemary and garlic essential oils were tested against Escherichia coli O157:H7 (ATCC 35218), Staphylococcus aureus (ATCC 43300), Salmonella enteritidis (ATCC 13076), Listeria monocytogenes (NCTC 2167) and Lactobacillus plantarum (DSM 20174). Ten millilitres of molten hard agar was inoculated by 200 μl of bacterial cultures (colony count of 1 × 10⁸ CFU/ml) grown overnight in appropriate medium. Circular discs of WPI films containing spice extracts, prepared by casting method, were placed on a bacterial lawn. Zones of inhibition were measured after an incubation period. The film containing oregano essential oil was the most effective against these bacteria at 2% level than those containing garlic and rosemary extracts (P < 0.05). The use of rosemary essential oil incorporated into WPI films did not exhibit any antimicrobial activity whereas inhibitory effect of WPI film containing garlic essential oil was observed only at 3% and 4% level (P < 0.05). The results of this study suggested that the antimicrobial activity of some spice extracts were expressed in a WPI based edible film.     

Study of the effects of spray‐drying on the functionality of probiotic lactobacilli

Three probiotic lactobacilli strains were spray‐dried in 20% (w/v) skim milk and submitted to a simulated gastrointestinal digestion. Fresh or spray‐dried cultures were administered to mice for 5 and 10 days, and Immunoglobulin A (IgA)‐producing cells were enumerated in the small intestine by immunohistochemistry. Spray‐drying significantly enhanced the resistance of Lactobacillus paracasei A13 and Lactobacillus casei Nad to a simulated gastrointestinal digestion (0.96 and 1.95 log orders, respectively), compared with fresh cultures. Also, a significant higher number of IgA‐producing cells were induced by spray‐dried cultures compared with fresh cultures. Spray‐drying is a suitable, but strain‐dependent, technological process for the development of probiotic cultures in skim milk with increased functionality.     

Effects of encapsulation on the viability of probiotic strains exposed to lethal conditions

The effect of microencapsulation on the viability of Lactobacillus casei, L. paracasei, L. acidophilus Ki and Bifidobacterium animalis BB‐12 during exposure to lethal conditions (25% NaCl, pH 3.0 and 55–60 °C) was evaluated. Results demonstrated that survival of probiotic strains to the imposed lethal stress conditions was strain dependent. With the exception of exposure to 25% (w/v) NaCl, L. acidophilus Ki (free and encapsulated cells) demonstrated the highest survival rates through exposure to lethal conditions of temperature and pH. For this probiotic strain exposed to heat, microencapsulated cells expressed a higher heat tolerance at 55 °C than free cells. For the other tested bacteria, in general, encapsulation had no positive effect on survival through the tested lethal conditions.     

Potential for prevention of non‐O157 Shiga toxin‐producing Escherichia coli contamination in traditionally fermented African maize gruel by fermentative probiotic Lactobacillus plantarum

Non‐O157 Shiga toxin‐producing Escherichia coli (STEC) are a frequent cause of STEC‐related infections such as diarrhoea. Fermentation by presumptive probiotic Lactobacillus plantarum strain B411 isolated from cereal fermentation was investigated to prevent the growth of acid‐adapted (AA) and non‐acid‐adapted (NAA) non‐O157 STEC in traditionally fermented maize gruel, a widely used complementary food in Africa. L. plantarum strain B411 possessed probiotic characteristics and antimicrobial activity against selected pathogenic bacteria. Growth of AA and NAA non‐O157 STEC strains was substantially inhibited by 3.6 and 4.8 log reductions, respectively, in the maize gruel fermented with the L. plantarum B411, while their growth was only inhibited by 1.0 and 1.2 log reductions, respectively, by traditional fermentation alone. Inclusion of fermentative strains of L. plantarum exhibiting probiotic activity is a feasible method to ensure safety of traditionally fermented African cereal porridges through inhibition of non‐O157 STEC.     

Proteolysis of reconstituted goat whey fermented by Streptococcus thermophilus in co‐culture with commercial probiotic Lactobacillus strains

Reconstituted goat whey was fermented with the starter Streptococcus thermophilus TA‐40 in co‐culture with four probiotic adjuncts (independent treatments): Lactobacillus casei BGP93 (T1), Lactobacillus paracasei BGP1 (T2), Lb. paracasei LPC37 (T3) and Lactobacillus rhamnosus LR32 (T4). Lactobacillus populations were higher than 7 log cfu/mL after fermentation and storage. Proteolysis increased significantly (P < 0.05) during fermentation in all trials. Relative amount of low‐molecular‐weight protein fractions (<6.5 kDa) increased in goat whey trials with T1, T3 and T4 during fermentation and storage. The goat whey powder was considered a potential substrate for starter and probiotic cultures, which raised the opportunities to upgrade this by‐product into a functional food.     

Survival during storage and sensory effect of potential probiotic lactic acid bacteria Lactobacillus acidophilus Bauer and Lactobacillus casei Bif3′/ IV in dry fermented pork loins

The objective of this work was to study the survival of two potential probiotic strains (Lactobacillus acidophilus Bauer and Lactobacillus casei Bif3′/IV) in pork loins both with the verification of the possibility of fermented loin development in relation to sensory and microbiological criteria. Six different samples of loins were prepared while as 3 weeks of ripening process and 6 months of storage. The obtained results indicated that highest sensory quality of fermented pork loin after storage was observed in the case of sample produced with L. acidophilus Bauer and with 0.2% glucose addition. The highest count of lactic acid bacteria was observed in the case of the sample with L. casei Bif3′/IV. The results of the study demonstrate that application of probiotic strain L. acidophilus Bauer for pork loins fermentation could assure the satisfying quality regarding sensory and microbiological criteria and can be used for dry fermented loin production.     

Probiotic potential of lactic acid bacteria from fermented Malaysian food or milk products

This study investigated the probiotic characteristics of lactic acid bacteria (LAB) isolated from 14 Malaysian fermented food or milk products. In total, 22.3% (121 of 542) of the LAB isolated from the local fermented products exhibited antibacterial activity against Micrococcus luteus. Twelve LAB that demonstrated better antibacterial activity against M. luteus as compared to a commercial strain Lactobacillus casei strain Shirota (LABPC) were selected for further characterisation. Based on 16S rRNA gene sequence, the LAB were identified as pediococci (seven) and lactobacilli (five). All 12 LAB showed bile tolerance, but only eight were acid tolerant at pH ≥ 3.0. The highest level of adhesion to HT‐29 cells was observed among the Lactobacillus sp. LAB 1 and 10. The LAB also showed antimicrobial activity against Escherichia coli and Staphylococcus aureus through the production of organic acids. LAB isolated from Malaysian fermented food and milk products, especially fermented tapioca, contains potential probiotic candidates.     

Survival and activity of 5 probiotic lactobacilli strains in 2 types of flavored fermented milk

The viability of 5 probiotic lactobacilli strains (Lactobacillus acidophilus LA-5, Lactobacillus casei L01, Lactobacillus casei LAFTI L26, Lactobacillus paracasei Lcp37, and Lactobacillus rhamnosus HN001) was assessed in 2 types of probiotic flavored drink based on fermented milk during 21 days of refrigerated storage (5°C). Also, changes in biochemical parameters (pH, titrable acidity, and redox potential) during fermentation as well as the sensory attributes of final product were determined. Among the probiotic strains, L. casei LAFTI L26 exhibited the highest retention of viability during refrigerated storage period, while L. acidophilus LA-5 showed the highest loss of viability during this period. The decline in cell count of probiotic bacteria in strawberry fermented milk was significantly greater compared to peach fermented milk. In an overall approach, peach fermented milk containing L. casei LAFTI L26 was selected as the optimal treatment in this study in both aspects of viability and sensory accpeptibility.     

Production of a whey‐based functional beverage supplemented with soy isoflavones and phytosterols

Reconstituted whey beverages were prepared from whey powder by adding either soy isoflavones or phytosterols as functional compounds (at levels of 0%, 0.25%, 0.50% or 1.0% w/v) and probiotic bacteria (Lactobacillus acidophilus LA‐5 or Lactobacillus casei LBC‐81). The addition of nutraceuticals did not change the basic composition of the products. However, a time‐dependent increase in sedimentation/phase separation and acidity of fermented functional beverages was observed. Samples supplemented with phytosterols were more preferred by the panel group than the samples supplemented with isoflavones, and no considerable differences were noted between the control and phytosterol‐added samples in terms of overall perception.     

Development of antimicrobial gummy candies with addition of bovine colostrum,essential oils and probiotics

The aim of this study was to develop antimicrobial properties of gummy candies based on bovine colostrum (BC), essential oils (EOs), lactic acid bacteria (LAB) strains and their combinations. In addition, the heteropolysaccharide (agar), as a multifunctional polymer, was used for the antimicrobial candies preparation. The antimicrobial activities of BC, EOs (C. reticulata L., Eugenia caryophyllata, C. paradisi L., Thymus vulgaris), LAB strains (Lactobacillus plantarum LUHS135 and Lactobacillus paracasei LUHS244) and their combinations against pathogenic bacteria (Pseudomonas aeruginosa, Proteus mirabilis, Escherichia coli, Salmonella enterica, Staphylococcus aureus, Enterococcus faecalis, Streptococcus mutans) were investigated. The highest antimicrobial activities were demonstrated by Thymus vulgaris and Eugenia caryophyllata EOs and their emulsions (12%), and the best formulation of components for antimicrobial gummy candies production would incorporate the BC fermented with L. paracasei LUHS244 in combination with Thymus vulgaris or Eugenia caryophyllata EOs, which inhibited growth of all the tested pathogenic microorganisms (except Pseudomonas aeruginosa). Gummy candies formula consisting of the fermented BC (up to 3%) and thyme EO (up to 0.2%) with mandarin or grapefruit EOs (up to 0.2%) for taste‐masking, allowed obtaining good texture and high overall acceptability products containing desirable antimicrobials, thus antimicrobial gummy candies could be consumer preferred form of nutraceuticals.     

Proteolysis in dry‐aged loins manufactured with sonicated pork and inoculated with Lactobacillus casei ŁOCK 0900 probiotic strain

Selected parameters related to proteolysis were evaluated in dry‐aged loins manufactured with sonicated pork and inoculated with Lactobacillus casei ?OCK 0900 probiotic strain. Dehydration, pH, water activity and total nitrogen content were not affected by ultrasound treatment. Neither sonication nor inoculation has an influence on L* and a* colour parameters. Sonication significantly influenced the pattern of proteolysis providing higher nonprotein nitrogen content (NPN) and proteolysis index (PI). The highest intensity of proteolysis, as assessed by NPN and PI, occurred in an inoculated sample. Neither sonication nor inoculation with L. casei had a significant effect on total viable counts. Loins inoculated with L. casei had the highest lactic acid bacteria count, followed by the sonicated and nonsonicated control. This research shows that sonication followed by inoculation with L. casei ?OCK 0900 could be used as an effective measure to speed up the proteolytic changes in dry‐aged meat cuts.     

Physical,antimicrobial and antibiofilm properties of Zataria multiflora Boiss essential oil nanoemulsion

It was evaluated physical, antibacterial and antibiofilm properties of Zataria multiflora Boiss essential oil (ZEO) and its nanoemulsion. Long‐term stability of nanoemulsion prepared by emulsion phase inversion was satisfying based on low narrow size distribution (polydispersity index ?0.2) and low droplet size (200 nm) over 21 days of storage. Nanoemulsion showed lower minimum inhibitory concentration (MIC) on Listeria monocytogenes (2500 µg mL^?1) than Salmonella Typhimurium (5000 µg mL^?1). Killing kinetics study revealed that nanoemulsion was more effective in inhibiting the growth of bacteria in milk than culture media. Both bacteriostatic and bactericidal effects were observed depending on the type of bacteria, nanoemulsion concentration and the time of exposure. Nanoemulsion at 4×MIC concentration reduced 64% and 75% of one‐day‐old biofilm of L. monocytogenes and S. Typhimurium, respectively. In conclusion, nanoemulsion revealed antimicrobial activity, but converting the ZEO to nanoemulsion did not improve its antibacterial activity; however, antibiofilm properties were enhanced.     

Evaluation of in vitro probiotic potential of phytase‐producing bacterial strain as a new probiotic candidate

Sixty‐three phytase‐producing bacterial strains were isolated from natural sources, and their probiotic potential was evaluated. Of these, only fifteen strains were selected on the basis of confirmatory plate assay. Among these, five phytase‐producing strains exhibiting potent probiotic properties were identified as Bacillus cereus P1, Bacillus subtilis P6, B. subtilis P7, Pseudomonas aeruginosa P12 and P. aeruginosa P15 on the basis of morphological, biochemical and molecular characteristics. Maximum phytase activity (2.74 EU mL^?1) with potential probiotic properties, that is more than 70% survivability at pH 2.0, up to 2.0% bile salt tolerance, sporulation efficiency of more than 80% and survival in anaerobic condition (94.31%), was revealed by B. subtilis P6 as compared to the well‐established commercial probiotic strains Lactobacillus sporogenes and Lactobacillus casei. Thus, phytase‐producing B. subtilis P6 with promising probiotic features can be used in food and animal feed applications for betterment of mankind after further validation.     

Effect of cryoprotectants,prebiotics and microencapsulation on survival of probiotic organisms in yoghurt and freeze-dried yoghurt

The survival of probiotic microorganisms including Lactobacillus acidophilus, Lactobacillus casei, Lactobacillus rhamnosus and Bifidobacterium spp. was evaluated in yoghurt and freeze-dried yoghurt after processing and storage. The effectiveness of microencapsulating probiotic organisms as well as adding cryoprotectants and prebiotics in improving their viability was also investigated. The viability of Bifidobacterium infantis 17930 and L. rhamnosus GG was reduced by 0.07 log, while that of L. casei 1520 and Bifidobacterium longum 1941 was reduced by 0.28 and 0.39 log, respectively. There was a 7% improvement in the viability of L. casei 1520 when cryoprotectant ‘Unipectine™ RS 150’ was added at 2.5% (w/v). The prebiotic ‘Raftilose^®P95’ when added at 1.5% w/v to yoghurt improved the viability of the combined selected probiotic organisms by 1.42 log during four weeks of storage at 4 °C. Microencapsulation with alginate improved viability of combined selected probiotic organisms by 0.31 log in freeze-dried yoghurt stored at 21 °C.     

Antimicrobial Activity and Hydrophobicity of Edible Whey Protein Isolate Films Formulated with Nisin and/or Glucose Oxidase

The use of edible antimicrobial films has been reported as a means to improve food shelf life through gradual releasing of antimicrobial compounds on the food surface. This work reports the study on the incorporation of 2 antimicrobial agents, nisin (N), and/or glucose oxidase (GO), into the matrix of Whey protein isolate (WPI) films at pH 5.5 and 8.5. The antimicrobial activity of the edible films was evaluated against Listeria innocua (ATCC 33090), Brochothrix thermosphacta (NCIB10018), Escherichia coli (JMP101), and Enterococcus faecalis (MXVK22). In addition, the antimicrobial activity was related to the hydrophobicity and water solubility of the WPI films. The greatest antibacterial activity was observed in WPI films containing only GO. The combined addition of N and GO resulted in films with lower antimicrobial activity than films with N or GO alone. In most cases, a pH effect was observed as greater antimicrobial response at pH 5.5 as well as higher film matrix hydrophobicity. WPI films supplemented with GO can be used in coating systems suitable for food preservation.     

Development of novel species‐specific primers for species identification of the Lactobacillus casei group based on RAPD fingerprints

BACKGROUND: It is difficult to clearly distinguish and identify specific species of the Lactobacillus casei group using phenotypic and genotypic (16S ribosomal DNA sequence analysis) techniques alone. Some species of this group are probiotic and are widely used in the food and feed industries. The objective of this study was to develop species‐specific primers based on randomly amplified polymorphic DNA (RAPD) fingerprinting for species identification within the closely related L. casei group of bacteria. RESULTS: Three random primers termed OPT‐14, OPA‐11 and OPT‐16 were developed for analysis. The primer pairs each produced a species‐specific band found only in the tested Lactobacillus rhamnosus, Lactobacillus paracasei subsp. tolerans and Lactobacillus zeae isolates respectively. These specific fragments were then sequenced for further analysis. The species‐specific primers were designed according to cloned sequencing, which was employed for polymerase chain reaction (PCR) with the template DNA of Lactobacillus strains. Single 102, 179 and 451 bp species‐specific bands were found only in L. rhamnosus, L. paracasei subsp. tolerans and L. zeae respectively. CONCLUSION: Using PCR, the novel species‐specific primers have been shown to rapidly, accurately and effectively identify species of L. rhamnosus, L. paracasei subsp. tolerans and L. zeae from within the L. casei group of probiotic bacteria. Copyright © 2009 Society of Chemical Industry     

Functionality of different probiotic strains embedded in citrus pectin based edible films

The inclusion of probiotics into the packaging films has emerged as a novel approach to provide edible packaging with new functionalities. In this study, probiotic films were developed by embedding four different probiotics (Lactobacillus casei, Bifidobacterium bifidum, Lactobacillus acidophilus, and Lactobacillus rhamnosus) into citrus pectin films and their viability was checked at 25 and 4 °C for 30 days. A reduction of 0.44, 1.04, 0.32, and 1.0 log CFU g⁻¹ was observed in probiotic films containing L. casei, B. bifidum, L. acidzophilus, and L. rhamnosus respectively during drying process of film’s formation. The viability of all probiotics (except B. bifidum) was decreased from 10⁹ to 10⁶ CFU g⁻¹ in 30 days storage at 25 °C. Whereas, only 2 log reduction was observed for films stored at 4 °C during 30 days. The physical and optical properties of the films were affected slightly by inclusion of bacterial cells. The presence of live cells in films made them less resistant to elongation and less stretchable. All bacterial films inhibited the growth of L. monocytogenes by 1.5 logs compared to control. The results suggest the entrapment of probiotics in pectin can be used as an effective packaging technology for ensuring food safety.