Addition Of Antimicrobial Agents Research Articles

Effects of pulsed electric fields on controlling fermentation rate of brined Raphanus sativus

This study investigated the effects of pulsed electric fields (PEF) on the fermentation quality characteristics, morphology, and antioxidant activities of brined and fermented radish with different PEF strengths (1.5 kV/cm. 2.0 kV/cm). Electrical conductivity and Z-index showed that as the strength of PEF increased, the permeability of the cell membrane and the degree of disruption of the cell increased. The pretreatment with PEF accelerated the brining rate, thereby reducing the time required for brining by approximately PEF1.5 kV/cm (56.6%) and PEF2.0 kV/cm (70%) compared to Control. The growth rate of lactic acid bacteria viability was inhibited in the PEF group thus approximately 1–2 log CFU/ml lower than Control. The cellular structure maintenance of radish was improved in the PEF group than in the control group. Altogether, these findings suggest that PEF could effectively increase the storage period (2–5 days) for controlling the excessive growth of lactic acid bacteria which induce overripening during the fermentation of vegetables. Industrial relevanceA fermented food produced by lactic acid bacteria (LAB) is kimchi, a traditional Korean food that is consumed worldwide; however, excessive growth of LAB can reduce the quality of kimchi. PEF technology can be used to control LAB in kimchi to produce a superior product without the addition of antimicrobial agents.

Viability of bacteria associated with root caries after Nd:YAG laser application in combination with various antimicrobial agents: An in vitro study.

The neodymium-doped yttrium aluminum garnet (Nd:YAG) laser has various therapeutic applications in dentistry, including the treatment of dentin hypersensitivity and the bacterial reduction therapy in periodontology. The addition of antimicrobial agents may enhance the impact of the laser on bacterial viability. This in vitro study aimed to assess the effect of Nd:YAG laser application in combination with various chemical antimicrobial agents, including hydrogen peroxide (H2O2), sodium hypochlorite (NaOCl), chlorhexidine (CHX), and sodium fluoride (NaF), on the viability of bacteria implicated in the etiology of root caries. Three oral bacterial species were examined: Streptococcus mutans (S. mutans); Streptococcus sanguinis (S. sanguinis); and Enterococcus faecalis (E. faecalis). The bacteria were grown in broth at 37°C, and then treated with the chemical agents and/or irradiated with an Nd:YAG laser for 30 s. Each treatment modality was repeated 3 times: group 1 - no treatment; group 2 - 0.5% H2O2; group 3 - 0.5% NaOCl; group 4 - 0.12% CHX; group 5 - 2% NaF; group 6 - Nd:YAG laser irradiation; group 7 - laser and 0.5% H2O2; group 8 - laser and 0.5% NaOCl; group 9 - laser and 0.12% CHX; and group 10 - laser and 2% NaF. The viability of the bacteria was determined by plating them, counting viable colonies, converting the data into colony-forming units (CFUs)/mL, and transforming them into the log form. Statistical analysis was performed using the two-tailed paired t test. Irradiation with an Nd:YAG laser alone did not show a statistically significant effect against any of the bacterial species. The only effective antimicrobial used alone was CHX for S. mutans. Chlorhexidine with Nd:YAG resulted in a greater reduction in S. mutans and E. faecalis than either treatment alone. Meanwhile, H2O2 with Nd:YAG also showed an enhanced S. mutans reduction. Treatment with 0.5% NaOCl in conjunction with Nd:YAG brought the most significant reduction in viability for all bacteria in comparison with other treatment modalities. The Nd:YAG laser combined with 0.5% NaOCl resulted in the most substantial reduction in bacterial survival as compared to the antimicrobials or the Nd:YAG laser used alone.

Analysis of the Effect of Various Potential Antimicrobial Agents on the Quality of the Unpasteurized Carrot Juice.

Short shelf-life and poor microbial quality of minimally processed foods of plant origin pose a serious problem for the food industry. Novel techniques of minimal treatment combined with disinfection are being researched, and, for fresh juice, the addition of antimicrobial agents appears to be a promising route. In this research, fresh, nonfiltered, unpasteurized carrot juice was mixed with four potential antimicrobials (bourbon vanilla extract, peppermint extract, cannabidiol oil, and grapefruit extract). All four variants and the reference pure carrot juice were analyzed for metapopulational changes, microbial changes, and physicochemical changes. The potential antimicrobials used in the research have improved the overall microbial quality of carrot juice across 4 days of storage. However, it is important to notice that each of the four agents had a different spectrum of effectiveness towards the groups identified in the microflora of carrot juice. Additionally, the antimicrobials have increased the diversity of the carrot juice microbiome but did not prevent the occurrence of pathogenic bacteria. In conclusion, the use of antimicrobial agents such as essential oils or their derivatives may be a promising way of improving the microbial quality and prolonging the shelf-life of minimally processed foods, such as fresh juices, but the technique requires further research.

A novel multi-gradient PASS nanofibrous membranes with outstanding particulate matter removal efficiency and excellent antimicrobial property

Air pollution, especially tiny pollutant particles and harmful microorganisms, has become a serious environmental issue, bringing great damage to human body. Air filtration has been a widely used and effective method for air purification. However, the addition of antimicrobial agents usually leads to the agglomeration and the toxicity of the filter material. Here, a versatile poly (aryl sulfide sulfone)/graphene oxide@silver (PASS/GO@Ag) air filtration membrane was fabricated by in-situ reduction and electrospinning approach, resulting in high filtration efficiency and excellent biocompatibility. The results showed that GO@Ag antimicrobial agent was successfully synthetized. The Ag nanoparticles (NPs) on the GO surface not only increased the antimicrobial property but also reduced the agglomeration of the antimicrobial agent. Meanwhile, GO@Ag was wrapped on the surface of the PASS nanofibers by ultrasonication to form a rough surface to further improve the filtration efficiency. The as-prepared PASS/GO@Ag membrane exhibited high air filtration performance (99.63 ± 0.34 %, 79.17 ± 1.07 Pa). Besides, it also showed excellent antimicrobial properties and good biocompatibility. The antibacterial rates of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were 99.57 ± 1.04 % and 97.93 ± 1.31 %, respectively. More importantly, the PASS/GO@Ag membrane could endow long-term use for one month, with the antibacterial rates of E. coli and S. aureus of 96.52 ± 1.20 % and 94.48 ± 1.13 %, respectively. Therefore, the developed membrane will have great potential for personal air filtration.

Effect of the Antimicrobial Agents Peppermint Essential Oil and Silver Nanoparticles on Bone Cement Properties.

The main problems directly linked with the use of PMMA bone cements in orthopedic surgery are the improper mechanical bond between cement and bone and the absence of antimicrobial properties. Recently, more research has been devoted to new bone cement with antimicrobial properties using mainly antibiotics or other innovative materials with antimicrobial properties. In this paper, we developed modified PMMA bone cement with antimicrobial properties proposing some experimental antimicrobial agents consisting of silver nanoparticles incorporated in ceramic glass and hydroxyapatite impregnated with peppermint oil. The impact of the addition of antimicrobial agents on the structure, mechanical properties, and biocompatibility of new PMMA bone cements was quantified. It has been shown that the addition of antimicrobial agents improves the flexural strength of the traditional PMMA bone cement, while the yield strength values show a decrease, most likely because this agent acts as a discontinuity inside the material rather than as a reinforcing agent. In the case of all samples, the addition of antimicrobial agents had no significant influence on the thermal stability. The new PMMA bone cement showed good biocompatibility and the possibility of osteoblast proliferation (MTT test) along with a low level of cytotoxicity (LDH test).

Additives Imparting Antimicrobial Properties to Acrylic Bone Cements.

PMMA bone cements are mainly used to fix implanted prostheses and are introduced as a fluid mixture, which hardens over time. The problem of infected prosthesis could be solved due to the development of some new antibacterial bone cements. In this paper, we show the results obtained to develop four different modified PMMA bone cements by using antimicrobial additives, such as gentamicin, peppermint oil incorporated in hydroxyapatite, and silver nanoparticles incorporated in a ceramic glass matrix (2 and 4%). The structure and morphology of the modified bone cements were investigated by SEM and EDS. We perform experimental measurements on wettability, hydration degree, and degradation degree after immersion in simulated body fluid. The cytotoxicity was evaluated by MTT assay using the human MG-63 cell line. Antimicrobial properties were checked against standard strains Staphylococcus aureus, Pseudomonas aeruginosa, and Candida albicans. The addition of antimicrobial agents did not significantly affect the hydration and degradation degree. In terms of biocompatibility assessed by the MTT test, all experimental PMMA bone cements are biocompatible. The performance of bone cements with peppermint essential oil and silver nanoparticles against these two pathogens suggests that these antibacterial additives look promising to be used in clinical practice against bacterial infection.

Wound healing and antibacterial activities of water-soluble chitosan nanoparticles and excretion/secretion as a natural combination from medicinal maggots, Lucilia cuprina

Wounds management takes a high interest in the medical field and the addition of antimicrobial agents in an assortment of wound dressings leads to delay the wound healing. This study aimed at preparing natural combination between excretion/secretion (ES) and water-soluble chitosan nanoparticles (from Lucilia cuprina maggots) and investigating its antibacterial and wound healing activities. ES of maggots was collected, and the water-soluble chitosan nanoparticles (WSCNPs) were prepared and characterized. Antibacterial activities of combinations were evaluated against Staphylococcus aureus, Bacillus subtilis, Escherichia coli, and Proteus vulgaris. ES-WSC-2 combination that contains 50% ES and 1% WSCNPs showed highest antibacterial activity against all tested bacteria compared to the other combinations. In vitro, the ES-WSC-2 combination was used to study the wound healing activity by scratch assay. The synergism between ES and WSCNPs (in ES-WSC-2 combination) accelerated the wound healing rate which suggests the use of this combination as an effective natural antibacterial and wound healing agent.

High‐pressure processing of shalgam with respect to quality characteristics, microbial inactivation, and shelflife extension

High hydrostatic pressure (HHP) processing of traditional fermented turnip juice (shalgam) was studied with respect to quality attributes, microbial inactivation, and shelflife extension. According to Box–Behnken design, shalgam samples were processed using 3–15 min, 4–40°C, and 200–500 MPa. The optimum processing conditions involved 34.23°C, 15 min, and 500 MPa for the color intensity and tone of 3.43 and 0.69 and the numbers of viable total mold and yeast, Lactococcus lactis subsp. cremoris, and Lactobacillus paracasei of 3.09, 2.51, and 2.68 log cfu/ml, respectively. Shalgam samples processed under the optimum conditions were stored at 4 and 22°C for 90 days. The control samples at 4 and 22°C were spoiled at 60 and 45th days, respectively. The storage time rather than the HHP processing affected physical properties, organic acids, phenolic compounds, and anthocyanins of shalgam. The treatment samples had significantly lower microbial growth during the storage time. Practical applications Due to the deteriorated color, bioactive, and sensory properties, the traditional heat processing of shalgam with the addition of antimicrobial agents (such as sodium benzoate) to extend its shelflife is not desirable by consumers. Alternative processing technologies are needed to extend its shelflife with no significant changes in its important properties. Its HHP treatment appeared as a practical option that preserved its quality parameters and extended its shelflife.

Sputter-Deposited Ag Nanoparticles on Electrospun PCL Scaffolds: Morphology, Wettability and Antibacterial Activity

Porous scaffolds made of biocompatible and environmental-friendly polymer fibers with diameters in the nano/micro range can find applications in a wide variety of sectors, spanning from the biomedical field to textiles and so on. Their development has received a boost in the last decades thanks to advances in the production methods, such as the electrospinning technique. Conferring antimicrobial properties to these fibrous structures is a primary requirement for many of their applications, but the addition of antimicrobial agents by wet methods can present a series of drawbacks. In this work, strong antibacterial action is successfully provided to electrospun polycaprolactone (PCL) scaffolds by silver (Ag) addition through a simple and flexible way, namely the sputtering deposition of silver onto the PCL fibers. SEM-EDS analyses demonstrate that the polymer fibers get coated by Ag nanoparticles without undergoing any alteration of their morphological integrity upon the deposition process. The influence on wettability is evaluated with polar (water) and non-polar (diiodomethane) liquids, evidencing that this coating method allows preserving the hydrophobic character of the PCL polymer. Excellent antibacterial action (reduction > 99.995% in 4 h) is demonstrated against Escherichia coli. The easy fabrication of these PCL-Ag mats can be applicable to the production of biomedical devices, bioremediation and antifouling systems in filtration, personal protective equipment (PPE), food packaging materials, etc.

Et ve et ürünlerinin üretimi ve saklanmasında antimikrobiyal ambalajlama sistemlerinin kullanımı

Many microbiological, enzymatic, physicochemical, and biochemical changes occur during the production and storage of fresh and processed meat products, which tend to deteriorate more easily by their nature. Nevertheless, consumers mainly prefer cost-effective foods that have a longer shelf life and minimally modified natural properties, can be easily prepared, and in which fewer additives are used. For these reasons, the food packaging industry has turned towards developing new applications with different functions that are not found in traditional packaging methods, such as antimicrobial packaging systems, especially for the protection and improvement of food quality and safety. In this type of packaging, in addition to improving food safety and quality, the shelf life of the product is extended by slowing down the growth rate of microorganisms. Thus, the existing growth of microorganisms during the transportation and storage of the product is also prevented. Therefore, the preservatives taken into the human body with foods are reduced, and the negative effects on health are also avoided. In these systems, the application of antimicrobial food packaging components to the packaging material can be performed by the addition of antimicrobial agents into the polymer, coating polymer surfaces with antimicrobial agents, immobilizing antimicrobial agents on the polymer, and using polymers with antimicrobial properties. In this review, antimicrobial packaging and application methods were generally explained, and innovative packaging systems and their use in meat and meat products were evaluated.

PCL/β‐AgVO3 nanocomposites obtained by solvent casting as potential antimicrobial biomaterials

AbstractThe adhesion of microorganisms on biomaterials can impair its effective application. The addition of antimicrobial agents is a promising alternative to overcome this limitation. In this work, films of polycaprolactone (PCL) and nanostructured β‐AgVO3 (SV) were produced by solvent casting with 0.1, 0.5, and 1.0 wt% of SV. The effect of SV on the structure of PCL was investigate using Fourier transform infrared spectroscopy (FTIR), X‐ray diffraction (XRD), Raman spectroscopy, differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). The antimicrobial activity of the films against Staphylococcus aureus and Escherichia coli was evaluated by the agar diffusion method and by direct contact test. FTIR confirmed the presence of SV into the PCL films, with chemical interaction between them. SEM showed that SV nanorods were well dispersed and with good interfacial adhesion with PCL. XRD diffraction and Raman spectroscopy showed that the presence of SV increased the number of nucleation sites, reducing the size of crystallites and increasing the amorphous domains in the PCL matrix, consequently reducing crystallinity. This behavior was confirmed by DSC, which showed a reduction in the crystallinity with increasing SV content. Films with 1 wt% of SV showed antimicrobial activity against Staphylococcus aureus in direct contact test.

Effect of natural ingredients addition as antimicrobial agents in Dioscoreahispida Dennst starch-based biofilm

The addition of antimicrobial agents in bioplastic food packaging aims to extend the food storage period and prevent the growth of pathogenic microbes. The use of antimicrobial agents from natural ingredient can make the biofilms safer to use. In this study, biofilms were made by adding natural antimicrobial agents from turmeric extract with the composition of starch 1.2% v/v total weight, 0.4% chitosan and variation of turmeric extract concentrations. 1.5% glycerol were added as a plasticizing. The best biofilms obtained by adding 0.375% of the extract with tensile strength and elongation values were 18.1 kgf/mm2 and 30.24%. The edible films can inhibit the growth of Escherichia coli bacteria which can be seen from the formation of clear zones around edible films on antimicrobial activity assay by agar diffusion method. Application of the edible film as food coating delayed the decay of coated food.

Antimicrobial efficacy of silver, zinc oxide, and titanium dioxide nanoparticles incorporated in orthodontic bonding agent

Background: One of the most important complications of fixed orthodontic treatment is formation of white spots, which are initial carious lesions. Addition of antimicrobial agents into orthodontic adhesive material might be wise solution for prevention of white spots formation. The aim of this study was to evaluate the antibacterial properties of orthodontic adhesive primer against S. Mutans after adding the three different types of nanoparticles (Ag, ZnO, or TiO2). Materials and methods: Discs were prepared using empty insulin syringe approximately 2 mm×2 mm rounded in shape specimens (40 discs) were divided into four groups (ten discs for each group): The first group was the control (made from primer only), the second group (10 discs made from primer and incorporation of Ag NPs), the third group (10 discs made from primer and incorporation of ZnO NPs), and the fourth group (10 discs made from primer and incorporation of TiO2 NPs). The antibacterial properties of orthodontic bonding agent after incorporation of (Ag, ZnO, or TiO2) nanoparticles were evaluated by disc diffusion test and viable count of mutans streptococci. Results: The results of this study showed that there were high significant differences between the all groups using ANOVA F-test, and the colony forming unit were 99×10³, 39.6×10³, 19.4×10³, 6.6×10³ CFU/mL respectively. Conclusion: The incorporation of these nanoparticles (Ag, ZnO, or TiO2) into Transbond ™ XT adhesive primer helps to enhance the antibacterial properties of primer against the S. mutans.

PROPERTIES OF SOY PROTEIN ISOLATE ANTIMICROBIAL FILMS AND ITS APPLICATION IN PRESERVATION OF MEAT

Recently, increasing interest to improve food safety and extend their shelf-life has led to the development and testing of the edible films with antimicrobial properties. The soy protein isolate (SPI) antimicrobial films were made with Nisin (N), sodium lactate (NaL), EDTA (E) and their optical combination (C). The C film showed a significant (p<0.05) antimicrobial effect on three food pathogens, E.coli, Salmonella and Bacillus cereus, which inhibitory zone is 32mm, 33.33mm and 32.33mm, respectively. The addition of N and NaL to SPI film reduced its mechanical properties, that is, the tensile strength (TS) was reduced from 10.8716MPa to 8.1405MPa (N1) and 3.2715MPa (NaL3) and the elongation at break (E) was increased from 3.03% to 4.73% (N3, N4) and 11.21 % (NaL4). While the addition of EDTA and combination increased TS from 10.8716MPa to 17.0600MPa (E4) and reduced E from 3.03% to 2.36% (E1). The water vapor permeability (WVP), oxygen permeability (OP) and total color difference (ΔE) of films had changed with the addition of antimicrobial agents. The FTIR analysis showed no specific interaction between active groups of Nisin with functional group of control film. However, the intensity of peaks in the spectrum of NaL and EDTA increased, indicating interactions between NaL, EDTA and SPI.The application experiments showed the total bacterial count and TVB-N value of sample wrapped by ordinary wraps, SPI film and SPI antimicrobial film were incresed as storage time extended. On the 6th day, the sample wrapped by SPI film has been metamorphism, which total bacterial count and TVB-N value were 8.922 lg cfu/g and 21.340 mg/100g. On the 9th day, the sample wrapped by ordinary wraps has been metamorphism, which total bacterial count and TVB-N value were 7.866 lg cfu/g and 21.150 mg/100g. And the sample wrapped by SPI antimicrobial film had been metamorphism on the 12th day, indicating that the SPI antimicrobial film had a bacteriostatic preservation effect on the meat antibacterial preservation and extend the shelf life to 3-6 days compared with SPI film and ordinary wraps. The SPI antimicrobial film broadens the application of SPI film.

Modification of Honeybee Silk by the Addition of Antimicrobial Agents.

Honeybee silk proteins can be produced at high levels in recombinant systems, fabricated into materials, and are tolerant of amino acid modifications: properties that make them exciting templates for designing new functional materials. Here, we explore the properties of materials either made from silk-antimicrobial peptide (AMP) fusion proteins or silk containing entrapped AMPs or silver nanoparticles. Inclusion of AMP within the silk protein sequence did not affect our ability to express the proteins or process them into films. When AMP-silk proteins and Escherichia coli cells were coincubated in solution, a reduction in cell numbers was observed after degradation of the chimeric protein to release a truncated version of the AMP. In films, the AMP was retained in the silk with leaching rates of <1% per day. Films containing silver nanoparticles were antimicrobial, with the silk preventing aggregation of nanoparticles and slowing the rate of dissolution of the particles.

Selective media for detection and quantification of Brazilian Ralstonia solanacearum isolates in soil

ABSTRACT The efficacy of five selective media described in the literature for the detection of Ralstonia solanacearum in soil was evaluated using isolates from different regions of Brazil. The selective media were evaluated regarding their sensitivity, target-pathogen repression index, capacity for suppressing contaminating microorganisms and recovery rate of the pathogen in soil. No bacterial growth was observed at the concentrations tested for FSM and SM-1 media. Some isolates grew on the PCCG medium with the addition of antimicrobial agents, but only at concentrations of 106 cfu/mL. For the SM and SMSA-E media, adequate sensitivity for the detection of R. solanacearum in soil was observed, enabling detection at a concentration of approximately 103 cfu/gram of soil. SMSA-E (Selective Medium South Africa - Elphinstone) was found to be the most effective in suppressing the growth of contaminating microorganisms, resulting in the lowest rate of repression of R. solanacearum and the highest recovery rate of the bacterium in the soil.

Antimicrobial Property of Hydrocolloid Impression Material Incorporated with Silver Nanoparticles AgainstStaphylococcusAureus

Dental impressions can easily become contaminated with patient’s blood and saliva which are capable of transmitting infectious diseases to dental personnel. The addition of antimicrobial agents into impression materials could be effective in reducing the chances of cross-infection. Silver nanoparticles have been applied in dentistry as a potent antimicrobial agent. This study aims to evaluate the in vitro antimicrobial efficacy of silver nanoparticles incorporated to irreversible hydrocolloid impression material against Staphylococcus aureus . Silver nanoparticles (AgZrPO 4 , National Direct Network Company, Thailand) at concentrations of 0.25%, 0.50%, 1.00% and 1.50% w/w were added to powder of impression materials (Kromopan, Lascod, Ilaty). Impression material samples were prepared on sterile plate in accordance with manufacturer’s instruction. After setting, a 100 microliter of S. aureus ATCC6538 suspension (10 6 cells/mL) were inoculated on the surface of the impression sample and left for 10 minutes. The amount of S. aureus on the surface was quantified using imprint technique on Mannitol Salt agar. Impression materials incorporated with AgZrPO 4 showed antimicrobial property against S. aureus (up to 95% reduction) compared with control (impression material without AgZrPO 4 ). Even though the mechanism of antimicrobial action was not clearly understood, AgZrPO 4 incorporated to impression material was demonstrated to possess an inhibitory effect against pathogenic bacteria. Further studies are needed to investigate physical properties of the material and the clinical usage.

Evaluation of the antibacterial activity of a conventional orthodontic composite containing silver/hydroxyapatite nanoparticles.

BackgroundOne of the most important complications of fixed orthodontic treatment is the formation of white spots which are initial carious lesions. Addition of antimicrobial agents into orthodontic adhesives might be a wise solution for prevention of white spot formation. The aim of this study was to evaluate the antibacterial properties of a conventional orthodontic adhesive containing three different concentrations of silver/hydroxyapatite nanoparticles.MethodsOne hundred and sixty-two Transbond XT composite discs containing 0, 1, 5, and 10 % silver/hydroxyapatite nanoparticles were prepared and sterilized. Antibacterial properties of these composite groups against Streptococcus mutans, Lactobacillus acidophilus, and Streptococcus sanguinis were investigated using three different antimicrobial tests. Disk agar diffusion test was performed to assess the diffusion of antibacterial agent on brain heart infusion agar plate by measuring bacterial growth inhibition zones. Biofilm inhibition test showed the antibacterial capacity of composite discs against resistant bacterial biofilms. Antimicrobial activity of eluted components from composite discs was investigated by comparing the viable counts of bacteria after 3, 15, and 30 days.ResultsComposite discs containing 5 and 10 % silver/hydroxyapatite nanoparticles were capable of producing growth inhibition zones for all bacterial types. Results of biofilm inhibition test showed that all of the study groups reduced viable bacterial count in comparison to the control group. Antimicrobial activity of eluted components from composite discs was immensely diverse based on the bacterial type and the concentration of nanoparticles.ConclusionsTransbond XT composite discs containing 5 and 10 % silver/hydroxyapatite nanoparticles produce bacterial growth inhibition zones and show antibacterial properties against biofilms.

Effect of the Antimicrobial Agents Addition on the Stability of Part-Baked Bread during Refrigerated Storage and on the Sensory Quality of Full-Baked Bread

Part-baked bread (PBB) is a product which offers advantages to producers and consumers. The lower cost of refrigeration in comparison with freezing makes it an interesting option to preserve the PBB. The main problem of PBB stored in refrigeration is the mold occurrence on its surface. The addition of an antimicrobial agent in the formulation of PBB capable to delay the proliferation of mold would help to extend its useful life. The aim of this study was to determine the effect of potassium sorbate in comparison with calcium propionate on the number of microorganisms of PBB stored in refrigeration, as well as on the sensory quality of full-baked bread obtained from PBB. From the tests performed it was observed that there were no molds on the surface of PBB with antimicrobial agents during 28 days of storage at 5ºC, while molds were on control PBB at 15 days of storage. It was also found that calcium propionate (0.16% flour basis) was more effective than potassium sorbate (0.16% flour basis) on delaying microorganisms growing. Addition of antimicrobial agents did not affect significantly the sensory attributes of bread obtained from PBB. However, the addition of propionate caused a decrease on the specific volume of bread.

BROWNING INHIBITION AND MICROBIAL CONTROL IN FRESH-CUT PERSIMMON (DIOSPYROS KAKI 'ROJO BRILLANTE') BY APPLE PECTIN-BASED EDIBLE COATINGS

‘Rojo Brillante’ persimmons can be commercialized as a fresh-cut commodity after removing natural fruit astringency by applying high levels of CO2. However, the shelf life of minimally-processed fruit is rather limited due to enzymatic browning and microbial growth. The aim of this study was to develop new edible coatings based on apple pectin with a combination of antioxidants and antimicrobial agents. Treatments included one of the following antimicrobials, i.e., potassium sorbate (PS) at 0.2 or 0.4%, sodium benzoate (SB) at 0.4%, or nisin (NI) at 500 IU/ml, added to 1% apple pectin coatings containing 1% citric acid and 1% calcium chloride (CaCl2) as antioxidants. Persimmon slices were dipped in the coatings, the aqueous antioxidant solution or water (control), and were packed under normal atmosphere and stored at 5°C for 9 d. Color, polyphenoloxidase (PPO) activity, visual quality, overall flavor and microbial growth were measured after 2, 5, 7 and 9 days of storage. Coated samples and those dipped in the antioxidant aqueous solution presented lower a* and higher b* values than the control samples, indicating browning inhibition. These results correlated with the lower PPO activity of treated samples compared to the control samples. The persimmon slices treated with coatings containing PS and SB reached the limit of marketability after 7 days of storage. Addition of antimicrobial agents to apple pectin coatings slightly affected the initial overall fruit flavor. After 2 days of storage, off-flavors disappeared and samples were ranked above the limit of acceptability by the judges. The antimicrobial coatings inhibited the growth of mesophilic aerobic bacteria, and those containing SB and NI were the most effective. No growth of molds, yeasts and psychrophilic aerobic bacteria during storage was monitored.