Effects of Pseudomonas chlororaphis and gaseous chlorine dioxide on the survival of Salmonella enterica on tomatoes

Control of Salmonella enterica on tomatoes is important for food safety. The aim of this research was to evaluate the survival of Salmonella enterica serovars Montevideo (SM) and Typhimurium (ST) on tomatoes exposed to gaseous chlorine dioxide and Pseudomonas chlororaphis (Pc). Pc was applied to stem scars of tomatoes prior to inoculations with SM and ST. Tomatoes were treated with gaseous ClO₂ at 0.4 mg L^?1 for 2 and 4 h (90% R.H. 13 °C), respectively. At 4 h of ClO₂ treatment, SM and ST populations were reduced to 0.82 and <0.30 log CFU g^?1, respectively. Tomatoes treated with SM and ST had 5.42 and 5.37 log CFU g^?1 of Salmonella. Tomatoes treated with Pc + Salmonella count was 2.59 (treated) and 5.83 log CFU g^?1 (control). Salmonella survival was similar at 2 and 4 h of ClO₂ treatment. Application of ClO₂ and Pc may reduce contamination of tomatoes by Salmonella serovars.     

Shelf life and quality of probiotic yogurt produced with Lactobacillus acidophilus and Gobdin

This study evaluated the effect of dry white mulberry and walnut paste (Gobdin, a traditional Turkish food) in probiotic yogurt on the survival of Lactobacillus acidophilus and yogurt properties. Six different yogurts were produced with 0%, 5% and 10% Gobdin using Lactobacillus bulgaricus + Streptococcus thermophilus and with 0%, 5% and 10% Gobdin using L. bulgaricus + S. thermophilus + L. acidophilus. The physical, chemical, microbiological and sensorial properties of the yogurts were evaluated based on storage at 4 ± 1 °C. Probiotic shelf life and the most suitable combinations were determined. The highest L. acidophilus count (8.65 log cfu g^?1) was found in the 5% Gobdin‐supplemented yogurt on the 7th day of storage, while the lowest count (8.11 log cfu g^?1) was found in the probiotic control yogurt on the 21st day. Although the L. acidophilus counts in the probiotic yogurts declined during storage, all values found throughout the 21‐day storage period were >8 log cfu g^?1. This is above the level necessary to provide the desired therapeutic effect in probiotic products (10⁶–10⁷ cfu g^?1). The highest overall acceptability score was obtained on the first day from the yogurt with 5% Gobdin. However, all yogurt samples had general acceptability scores between 7 and 8 points from a 9‐point maximum. Thus, this study determined that a new functional yogurt can be produced using L. acidophilus with 5% Gobdin.     

Comparison of vacuum impregnation and soaking techniques for addition of the probiotic Lactobacillus acidophilus to minimally processed melon

This study aimed to evaluate the vacuum impregnation (VI) and soaking methods in the addition of Lactobacillus acidophilusLA‐3 to minimally processed melon (MPM). The melons were washed, sanitised in chlorine solution (200 mg L^?1), peeled and cutted into cubes. Lactobacillus acidophilusLA‐3 (1.4 × 10¹⁰ CFU g^?1) were added to the MPM through both techniques. The L. acidophilusLA‐3 count in MPM was similar to those commonly found in dairy products having probiotic claim, but VI was more efficient than soaking in maintaining the viability (8.61 and 7.98 Log CFU g^?1, respectively). The pH, acidity and soluble solids were not affected by probiotic culture and the incorporation technique; however, the VI affected the firmness of fruit. The MPM was within Brazilian standards for their microbiological characteristics. MPM may be used as a carrier of probiotic bacteria, being one more alternative for individuals who consume probiotic products.     

Bacterial inactivation and quality changes of fresh‐cut avocados as affected by intense light pulses of specific spectra

Intense light pulses (ILP) treatments have good prospects for becoming an alternative to traditional thermal methods for decontamination of food surfaces. The aim of this work was to evaluate which ranges of the light spectrum are responsible for bacterial inactivation and their effect on the quality of fresh‐cut avocado. Results show that the effectiveness of ILP treatment decreases when the ultraviolet (UV) spectral region is blocked (particularly UV‐C). ILP treatments without UV‐C light (305–1100 nm) and an overall fluence of 10.68 J cm^?2 caused reductions of 2.47 and 1.35 log CFU g^?1 in the initial counts of inoculated Escherichia coli and Listeria innocua, respectively, in comparison with those treated using only VIS–NIR light (0.83 and 0.68 log CFU g^?1, respectively). Treatments applying light of a wavelength between 305 and 1100 nm had a more pronounced impact on colour, texture and headspace gas composition than treatments that did not contain UV light (400–1100 nm).     

Effect of encapsulated Lactobacillus plantarum as probiotic on dry-sausages during chilled storage

The impact of free and encapsulated Lactobacillus plantarum addition on the physicochemical and microbiological properties during chilled storage (60 days) of dry-fermented sausages have been studied. Control (C) treatment was performed without probiotic incorporation, and the reformulation was comprised of L. plantarum as free cells (F) in alginate spheres (EA), in water-in-oil simple emulsion (ESM) and in water-in-oil-in-water double emulsion (EDM). After 60 days of storage, lower (P < 0.05) lipid oxidation was observed in F and EA (0.602–0.625 mg MDA kg⁻¹) while it was higher (P < 0.05) in EDM (1.949 mg MDA kg⁻¹). Treatments C and ESM presented intermediate TBARS levels compared to other treatments at the end of storage. All dry-fermented sausages presented high levels of lactic acid bacteria during the whole chilled storage (8.06–9.29 log CFU g⁻¹ at day 0 and 8.02–9.35 log CFU g⁻¹); however, EA treatment presented the highest L. plantarum viability even at 60 days of storage (8.34 log CFU g⁻¹). Therefore, the strategy of L. plantarum inoculation in alginate spheres seems to be the best strategy for the delivery of probiotics during chilled storage of dry-fermented sausages.     

Development and quality characteristics of functional Kulfi fortified with microencapsulated betalains

Fruit and vegetable waste valorisation has opened opportunities for the utilisation of food waste for extraction and development of valuable functional foods. Therefore, the study was designed to develop a functional Kulfi fortified with encapsulated betalains extracted from red beetroot (Beta vulgaris L.) pomace. Moreover, fortified functional Kulfi samples were studied for physico-chemical, antioxidant, microbiological and sensory analyses. Fortified functional Kulfi reported the higher antioxidant activity (64.88% and 75.27%) with reduced melting rate (1.84 mL min⁻¹ and 2.08 mL min⁻¹) and microbial profile (3.77 log CFU g⁻¹ and 3.14 log CFU g⁻¹) compared with control. Sensory analysis showed a no significant (P > 0.05) impact on the overall acceptability of functional Kulfi (7.25) compared with the commercial Kulfi (7.20), which was further confirmed by a bi-plot of principal component analysis. Overall, the encapsulated betalains improved the quality characteristics of functional Kulfi and could be used for the development of frozen dairy products.     

Effect of different levels of fat and inulin on the microbial growth and metabolites in probiotic yogurt containing nonviable bacteria

Effects of different levels of fat and inulin on bacterial cell counts, degree of proteolysis and concentrations of organic acids in the yogurt containing inactivated cells of probiotic strains Bifidobacterium animalis and Lactobacillus acidophilus were investigated. Results showed that both L. acidophilus and B. animalis grew well in the yogurt samples reaching cell counts higher than 10⁶ CFU mL^?1 at the final pH of 4.5. Inulin at the concentration of 1% had no significant effects on the production of organic acids and cell counts of L. acidophilus, but promoted the growth of B. animalis with a reduction in the degree of proteolysis. Generally, different fat levels showed significant effects on the production of organic acids and nonsignificant effects on the cell counts of probiotic bacteria and degree of proteolysis. In case of lactic acid, the ratio of L‐ (+)to D‐ (?) isomer ranged from 50/50 to 80/20 in yogurt samples.     

Viability of Lactobacillus acidophilus in rice bran‐enriched stirred yoghurt and the physicochemical and sensory characteristics of product during refrigerated storage

This study was aimed at investigating the fortification of probiotic yoghurt with rice bran to increase nutritional properties of the product. The different levels of rice bran (0.3%, 0.6%, 0.9% and 1.2%) were incorporated into milk. The yoghurt samples were produced after pasteurisation, addition of starter culture and 1% Lactobacillus acidophilus suspension (6 × 10⁸ CFU mL^?1) and incubation. During sample storage in refrigerator, the viability of L. acidophilus, viscosity and physicochemical and sensory properties of product were investigated. Rice bran significantly increased the viability of L. acidophilus (P < 0.05). In addition, all probiotic yoghurts incorporating rice bran indicated higher viscosity and acidity and lower pH and syneresis compared to plain yoghurts. Furthermore, increments in rice bran incorporation levels resulted in a reduction in consumers' sample preferences. In general, the addition of rice bran at a suitable level could increase L. acidophilus viability and improve quality attributes of yoghurt.     

Antilisterial effect of two bioprotective cultures in a model system of Iberian chorizo fermentation

This study reports the different effects of two bioprotective cultures on the growth of different Listeria monocytogenes strains by a rapid assay simulating the first stage of Iberian chorizo fermentation. Ground pork with or without protective cultures was inoculated with L. monocytogenes and incubated under two different conditions simulating the traditional, slow fermentation temperature (7 °C, 1 day) and a high, fast fermentation temperature (20 °C, 1 day), followed in both cases by storage at 7 °C for 13 days. Both bioprotective cultures reduced the growth of L. monocytogenes by at least 2 log CFU g^?1 at the end of both incubation periods compared with a noninoculated culture control lot. The best results were obtained with the strain Lactobacillus sakei CTC494, which exerted a bactericidal effect on L. monocytogenes under both conditions assayed, achieving a 5.4‐log reduction after 14 days compared with the control when the initial temperature was 20 °C.     

Effect of partial replacement of potassium lactate and sodium diacetate by natural green tea and grape seed extracts and postpackaging thermal treatment on the growth of Listeria monocytogenes in hotdog model system

Low‐ (5%) and high‐fat (20%) chicken and turkey hotdogs were formulated in three groups: no antimicrobials (control), chemical preservatives (potassium lactate and sodium diacetate) alone and partial replacement of chemical preservatives by green tea (GTE) and grape seed extracts (GSE), surface inoculated (c. 10³ CFU g^?1) with Listeria monocytogenes, treated with or without heat treatment (65 °C for 104 s) to determine the growth of L. monocytogenes until spoilage (28 days). Maximum growth inhibitions (c. 2.0 CFU g^?1) were observed in the treatments having chemical preservatives and plant extracts regardless of the meat and fat type. Furthermore, plant extracts along with chemical preservatives demonstrated additional inhibitory effect on the growth of L. monocytogenes survivors in chicken hotdog samples followed by postpackaging heat treatment. Results demonstrated that natural GTE and GSE can partially replace the chemical preservatives and further enhance the antilisterial activities when combined with heat treatment.     

The effect of co-encapsulation of Lactobacillus rhamnosus GG ATCC 53103 with inulin on alginate/chitosan matrix: the viability in fermented soy blend and simulated digestive system

This research verified the ability of Lactobacillus rhamnosus encapsulated with inulin to tolerate the simulated digestive system and their viability in a soy blend. Probiotic encapsulated in alginate-chitosan matrix without inulin presented a better encapsulation efficiency (80.92%) than encapsulation with inulin (57.39%). On the 28th day, the count of probiotics decreased by 3.42 and 1.99 logarithmic cycles of free and encapsulated cells without inulin, respectively. In contrast, the microorganisms encapsulated with inulin showed an increase of 1.26 logs CFU g⁻¹. During gastrointestinal simulation, cell counts decreased by 0.78, 1.55 and 1.95 CFU g⁻¹ logs for encapsulated cells without inulin, free and encapsulated with inulin, respectively. Sensory panellists liked the fermented soy blend with encapsulated lactobacilli, and this result shows the possibility to create new probiotic foods of plant origin. Therefore, the alginate/chitosan matrix can be considered adequate for the encapsulation of L. rhamnosus. The inulin reduces the encapsulation efficiency and increases the cell loss in gastrointestinal simulation. Considering cellular losses, the best option for preparing a fermented soy blend is to use L. rhamnosus encapsulated without inulin.     

Microencapsulation of probiotic cells by means of rennet-gelation of milk proteins

Probiotic cells were microencapsulated in milk protein matrices by means of an enzymatic induced gelation with rennet. Water insoluble, spherical capsules with a volume-based median of 68 ± 5 μm were obtained from a novel developed emulsifying and subsequent internal gelation process. A high encapsulation yield was found due to the encapsulation procedure for Lactobacillus paracasei ssp. paracasei F19 and Bifidobacterium lactis Bb12. After incubation at low pH-values, microencapsulation yielded higher survival rates compared to non-encapsulated probiotic cells. The viable cell numbers of encapsulated Lactobacillus paracasei and Bifidobacterium lactis were 0.8 and 2.8 log units CFU g⁻¹ higher compared to free cells after 90 min incubation at pH 2.5. The improved survival of encapsulated cells can probably be explained by a higher local pH-value within the protein matrix of the capsules caused by the protein buffering capacity, protecting the cells during incubation under simulated gastric conditions at low pH. The study indicates that rennet-induced gelation of skim-milk concentrates for the microencapsulation of probiotic cells can be a suitable alternative to current available technologies, mainly based on ionotrophic gelation of plant-polymer solutions.     

Microbial inactivation and quality improvement of tomatoes treated by package film with allyl isothiocyanate vapour

In‐package sanitisation was developed using polylactic acid (PLA) films with allyl isothiocyanate (AIT) vapour. Tomatoes were artificially inoculated with Escherichia coli, Geotrichum candidum and Fusarium oxysporum and stored in clamshell boxes with the film fixed to the underside of the lid. The changes in bacterial and fungal populations and the quality of tomatoes during storage at 4 and 10 °C were evaluated. The results revealed that the film treatment (4 × 8 cm² film in 1 L box) reduced the populations of inoculated bacteria and fungi on tomatoes by 2–3 log CFU g^?1, and then significantly (P < 0.05) inhibited their growth during the 21‐day storage period at both temperatures. Tomatoes subject to film treatment had fewer changes in quality (colour, firmness, contents of total soluble solid, titratable acids and vitamin C) than the control samples during storage. The antimicrobial PLA film can be used for in‐package sanitisation to extend the shelf‐life of packaged tomatoes or similar perishable vegetables.     

Application of cold oxygen plasma for the reduction of Cladosporium cladosporioides and Penicillium citrinum on the surface of dried filefish (Stephanolepis cirrhifer) fillets

This study was conducted to investigate the effects of cold oxygen plasma (COP) on the reductions of Penicillium citrinum and Cladosporium cladosporioides on the surface of dried filefish fillets (Stephanolepis cirrhifer). The counts were significantly (P < 0.05) reduced with the increase in the treatment time (3–20 min) of COP on the fillets. However, no significant (P > 0.05) differences were observed in the counts between 3 and 5 min of COP. The average decrease in the counts of C. cladosporioides and P. citrinum caused by 3–20 min of COP was 0.91 and 1.04 log₁₀ CFU g^?1, respectively. A reduction of >1‐log₁₀ CFU g^?1 was observed on the fillets treated with COP for >10 min. Decimal reduction time (d_R) by Weibull model was 9.32 and 7.42 min of COP for C. cladosporioides and P. citrinum, respectively. The fillets exposed to 20 min of COP displayed increased thiobarbituric acid reactive substance (TBARS) and decreased overall sensory acceptance. However, the fillets treated with 10 min of COP received satisfactory TBARS and consumer acceptance. Therefore, a 10‐min COP could be effective in reducing >90% and inactivating of the mould without causing any deleterious changes to the physicochemical and sensory qualities of the fillet.     

Anti‐inflammatory and cytotoxic effects of ginseng extract bioconverted by Leuconostoc mesenteroides KCCM 12010P isolated from kimchi

A bioconversion technique using microorganisms has been applied to ginseng to increase content of bioactive ginsenoside and biofunctionality such as anticancer, anti‐obesity and antioxidant activities. The objective of this study was to screen lactic acid bacteria for bioconversion of ginsenosides and to evaluate anti‐inflammatory and cytotoxic effects of bioconverted ginseng extract. Strains isolated from kimchi were screened for their β‐glucosidase activities using esculin agar. Selected strain was identified based on 16S rRNA sequencing and carbohydrate fermentation. During ginseng fermentation, viable cell number and pH were determined. Bioconverted ginsenosides were analysed by HPLC. Anti‐inflammatory effects were evaluated using RAW 264.7 cells, and cytotoxic effects were determined by MTT assay. Among 166 isolates screened, Leuconostoc mesenteroides was selected for ginseng bioconversion, as it showed a higher β‐glucosidase activity and viable cell number than any of the other tested strains. After fermentation for 2 days, viable cell number was 8.8 log CFU mL^?1 and final pH was 4.8. Ginsenoside Rb₂ was bioconverted into ginsenoside Rg₃ (Rb₂ → Rd → Rg₃) by L. mesenteroides. The nitric oxide contents of 2‐day‐fermented extract decreased by as much as 25%, compared to a non‐fermented extract. The cell viabilities of HepG2, HT‐29, HeLa and LoVo treated with fermented ginseng extract also decreased by 49.7%, 20.2%, 21.0% and 8.7%, respectively, compared to those of control cells treated with non‐fermented extract. Ginseng extract bioconverted by L. mesenteroides showed anti‐inflammatory and anticancer effects. Therefore, bioconverted ginseng extract might have applications in the pharmaceutical and/or functional food industry.     

Effects of electron beam irradiation on microbial inactivation and quality of kimchi paste during storage

The effects of electron beam irradiation on microbial inactivation and quality of noninoculated and inoculated (Listeria monocytogenes) kimchi pastes were examined. Kimchi paste samples were irradiated at doses of 2, 4, 6, 8 and 10 kGy and stored for 21 days at 4 °C. Irradiation (10 kGy) reduced the populations of total aerobic bacteria, lactic acid bacteria, and yeast and moulds in the samples by 1.72, 2.24 and 0.86 log CFU g^?1, respectively, compared to the control. In particular, coliforms were not detected at 8 and 10 kGy, and the population of L. monocytogenes in inoculated samples was significantly decreased by 2.67 log CFU g^?1. Electron beam irradiation delayed the changes in O₂ and CO₂ concentrations, pH, acidity and reducing sugar content observed in kimchi paste during storage. These results suggest that electron beam irradiation can be used to improve the microbiological safety and shelf life of kimchi paste.     

A new approach to modelling the shelf life of Gilthead seabream (Sparus aurata)

A total of 217 Gilthead seabreams were subdivided in four groups, according to four different storage conditions. All fish were evaluated by both Quality Index Method (QIM) and microbiological analysis, sampling skin, gills and flesh, separately. A QIM score predictive system was set by modelling the growth of microflora of skin, gills and flesh and coupling these predictions to each related partial QIM score (QIM_Skin, QIM_Gills, QIM_Flesh). The expression of QIM score as a function of bacterial behaviour was carried out by the employment of two coefficients. The predicted mean bacterial concentrations corresponding to the QIM score at 14 days were always near to Log 8 CFU g^?1 in the case of ‘S’ (skin) and ‘G’ (gills) series. Moreover, predicted QIM scores were in a good agreement with observed data, reproducing the observed mean time of rejection as well as the bacterial spoilage level (Log 8 CFU g^?1), for all kinds of storage condition.     

Shelf life of alginate beads containing lactobacilli and bifidobacteria: characterisation of microspheres containing Lactobacillus delbrueckii subsp. bulgaricus

Capsules, containing different microorganisms (Lactobacillus plantarum, L. casei, L. delbrueckii subsp. bulgaricus, L. delbrueckii subsp. delbrueckii, L. reuteri, L. rhamnosus, Bifidobacterium breve and B. animalis subsp. lactis), were produced through a simple extrusion protocol and dipped in a CaCl₂ solution (0.5% or 8%). Beads were characterised, to assess the encapsulation yield (EY) and the shelf life at 4 °C (defined as the time to retain inside a cell count of 6 log CFU g^?1); then, L. delbrueckii subsp. bulgaricus was used as target for system optimisation, through the study of the kinetic of cell release, as a function of the concentration of CaCl₂ solution, agitation (150 rpm) and recycling. The EY was 50% or higher, and the shelf life was at least 30 days. Concerning beads containing L. delbrueckii subsp. bulgaricus, the release of cells from capsules followed a biphasic (diauxic) trend and the microsphere could be used successfully for two times, as only after third reuse, the amount of release cells decreased.     

Quality of fresh‐cut purple‐fleshed sweet potatoes after X‐ray irradiation treatment and refrigerated storage

The effect of X‐ray irradiation on the quality of fresh‐cut, refrigerated purple‐fleshed sweet potato (PFSP) cubes was investigated. Packaged sweet potato cubes were treated with 0, 250, 500, 750 or 1000 Gy X‐ray irradiation and stored at 4 ± 1 °C for 14 days. After 14 days, total aerobic bacteria counts were 4.1 and 3.2 log₁₀ CFU g^?1, and mould–yeast counts were 3.3 and 3.0 log₁₀ CFU g^?1 in 750 and 1000 Gy treated samples, respectively. Doses up to 1000 Gy did not affect the firmness, moisture content and anthocyanin content of PFSP cubes throughout storage. PFSP cubes' flesh colour did not change during the first week of storage, but lightness (L*) increased after 14 days. Also, irradiation doses at 750 and 1000 Gy decreased saturation (C*) significantly, producing duller flesh colour than controls. Results indicate that X‐ray irradiation treatment at doses up to 1000 Gy can reduce microbial populations while maintaining the physical quality and anthocyanin content of PFSP cubes up to 14 days of storage.     

Reduction of Listeria monocytogenes in cold‐smoked salmon by bacteriophage P100, nisin and lauric arginate,singly or in combinations

Three GRAS antimicrobials including, lauric arginate (LAE), bacteriophage P100 (phage P100) and bacteriocin nisin, were evaluated either singly or in combinations for the reduction of initial load of Listeria monocytogenes in cold‐smoked salmon (CSS). The stability of phage P100 in the presence of LAE (200 ppm) and nisin (500 ppm) or at 10× and 100× of these concentrations was determined at 4 °C or 30 °C for 24 h in a broth model. Phage P100 was found to be highly stable in the presence of these antimicrobial agents as plaque‐forming units (PFU) did not vary between control and antimicrobial‐treated phage. The survival of L. monocytogenes in the presence of phage P100, nisin and LAE showed remarkable reduction within 24 h both at 4 °C or 30 °C in broth. Treatment of CSS containing 3.5 log CFU cm^?2 L. monocytogenes with phage P100 (10⁸ PFU mL^?1), nisin (500 ppm) and LAE (200 ppm) showed strong listericidal action and reduced the L. monocytogenes by 2–3 log CFU cm^?2 after 24 h. Among the combined treatments, phage P100 + LAE or nisin + LAE exhibited the most listericidal action in which L. monocytogenes cells were reduced to undetectable level within 24 h in CSS.