Production of snack bar enriched with paraprobiotics grown in banana peel medium, nutritional, sensory and quality parameters.

Introduction: Objective: this research aims to develop a product with high sensory and nutritional quality to make paraprobiotics developed in banana peel consumable within the scope of waste evaluation. Methods: Lactobacillus plantarum and Lactobacillus casei probiotics were developed here by using banana peels as a medium, and paraprobiotics were obtained from these strains by the pasteurization method at 80 °C for 30 minutes. Two types of bars, with and without paraprobiotics, were produced, and the nutritional and sensory quality characteristics of the bars were examined. Results: bars with and without paraprobiotics showed similar properties in terms of energy, protein, carbohydrate, saturated fat, Ca, Mg, Zn, Fe, Na, and total sugar values and sensory criteria, but showed significantly different levels in terms of total fat, potassium, total fiber, total phenolic substance and antiradical activity values. Conclusion: bars with and without paraprobiotics are in the category of "protein added, protein source, or protein-containing", "high fiber", "low sodium" products.

Introducción: Objetivo: esta investigación tiene como objetivo desarrollar un producto con alta calidad sensorial y nutricional para hacer consumibles los paraprobióticos desarrollados a partir de la cáscara de plátano en el ámbito de la evaluación de residuos. Métodos: en este estudio, se desarrollaron probióticos Lactobacillus plantarum y Lactobacillus casei utilizando la cáscara de plátano como medio, y se obtuvieron paraprobióticos a partir de estas cepas mediante el método de pasteurización a 80 °C durante 30 minutos. Se produjeron dos tipos de barras, con y sin paraprobióticos, y se examinaron las características de calidad nutricional y sensorial de las barras. Resultados: las barras con y sin paraprobióticos mostraron propiedades similares en cuanto a energía, proteínas, carbohidratos, grasas saturadas, calcio, magnesio, zinc, hierro, sodio y valores totales de azúcar, así como criterios sensoriales, pero presentaron niveles significativamente diferentes en términos de grasa total, potasio, fibra total, sustancias fenólicas totales y valores de actividad antirradical. Conclusión: las barras con y sin paraprobióticos se encuentran en la categoría de productos "con agregado de proteínas, fuente de proteínas o con contenido de proteínas", "alto contenido de fibra" y "bajo contenido de sodio".

Purification and characterization of a Metschnikowia pulcherrima killer toxin with antagonistic activity against pathogenic microorganisms.

Yeasts can produce toxins in protein or glycoprotein structures that can act as an inhibitor on some bacteria and yeast species. The effects of those toxins on the growth of pathogenic and food spoilage microorganisms are subject to various studies. Metschnikowia pulcherrima was determined to be a killer toxin-producing yeast that was tested against three selected microorganisms, namely Escherichia coli Type-I, Micrococcus luteus and Candida albicans. The killer toxin only showed inhibitory activity against M. luteus. Different pH (5-6-7-8), temperature (20-25-30-35 °C) and carbon source (glucose-glycerol-ethanol-acetate) combinations were applied to stimulate the growth and toxin production of the killer yeast. The greatest increase among the different combinations was obtained at 20 °C and pH 7 when glycerol was used as the main carbon source. It was then also tested against other pathogen indicators or pathogens under these conditions. The killer toxin was partially purified by ethanol precipitation and showed inhibitory activity against M. luteus (36 mm). According to the protein profile obtained by SDS-PAGE, the molecular weight of the inhibitor toxin was measured about 7.4 kDa. The molecular weight with amino acid sequence of the killer toxin was 10.3 kDa and determined by MALDI-TOF mass spectrometry.

A natural approach, the use of killer toxin produced by Metschnikowia pulcherrima in fresh ground beef patties for shelf life extention.

A novel killer toxin produced by yeast Metschnikowia pulcherrima was purified and added into ready to cook meatballs to enhance their microbial safety and extension of their shelf life. The agent was added into ready to cook meatballs at two different concentrations (1%-K1 and 2%-K2). The results of those two groups were compared to the control group (K0) lacking the killer toxin. Physical, chemical and microbiological analyses were carried out in meat dough and all analyses were repeated at two day intervals during 10 day-storage at +4 °C. Addition of inhibitor compound in meat dough decreased the numbers of total aerobic mesophillic bacteria, yeast and molds and lactic acid bacteria. Staphylococci/Micrococci, coliform bacteria and total psychrotrophic bacterial counts of the samples were determined as well. Results showed that all indicators of microbial deterioration were found to be higher in K1 group than K2 group, revealing that there was an inverse correlation between the concentration of killer toxin and the number of microorganisms causing spoilage. In addition to 1 log decrease in the number of microorganisms in toxin added groups, the high TBARS values of the control group also showed the effectiveness of the toxin. Toxic effect analysis results showed that the killer toxin had no toxic effect on L929 mouse fibroblast cells after 24h exposure.

Determination of competition and adhesion abilities of lactic acid bacteria against gut pathogens in a whole-tissue model.

In an intestinal system with a balanced microbial diversity, lactic acid bacteria (LAB) are the key element which prevents the colonization and invasion of gut pathogens. Adhesion ability is important for the colonization and competition abilities of LAB. The aim of this study was to determine the adhesion and competition abilities of LAB by using a whole-tissue model. Indigenous strains were isolated from spontaneously fermented foods like cheese and pickles. The aggregation and competition abilities of the isolates were determined, as well as their resistance to gastrointestinal conditions. Four Lactobacillus strains and one Weissella strain were found to be highly competitive against three major gut pathogens, namely Clostridium difficile, Listeria monocytogenes and Salmonella Enteritidis. Tested strains decreased the number of pathogens to below their disease-causing levels. According to the results, the numbers of C. difficile and L. monocytogenes bacteria decreased by an average of 3 log, and their adhesion rates decreased by approximately 50%. However, the number of S. Enteritidis bacteria was decreased by only 1 log compared with its initial number. We thought that the weak effect on Salmonella was due to its possession of many virulence factors. The results showed that natural isolates from sources other than human specimens like the Weissella strain in this study were quite competent when compared with the human isolates in terms of their adhesion to intestines and resistance to gastrointestinal tract conditions. It was also revealed that a whole-tissue model with all-natural layers can be successfully used in adhesion and competition tests.

The importance of the S-layer on the adhesion and aggregation ability of Lactic acid bacteria.

S-layer proteins in Lactic acid bacteria are not the only cell surface structures used for aggregation, but also plays significant role for intestinal tissue adhesion along with some other functional elements. In addition, it was determined that the properties of S-layer proteins differs not only between species but also the strains which belong to same species. In this work, presence and some functions of S-layer in lactic acid bacteria were determined, its effect on resistance to gastrointestinal enzymes, aggregation and adhesion ability were investigated as well. For this purpose S-layers of microorganisms were removed by 5 M LiCl treatment and size of the proteins were determined by SDS-PAGE analysis. The removal of S-layer proteins caused a change in the resistance of microorganisms to GIS enzymes. After the S-layer removal, two strains considerably lost their resistance to GIS enzymes. The strains mostly lost their aggregation ability in the absence of S-layer. The results showed that S-layer proteins are not the only structures involved in aggregation processes but, is a major mediator in Lactobacilli. Removal of S-layer had no effect on adhesion ability of W. cibaria DA28, the effect on L. casei DA4, L. coryniformis DA263 and L. plantarum DA140 was moderate, but the effect was high on L. plantarum DA100. The study showed that S-layer proteins play limited protection against GIS enzymes. In addition, absence of S-layer adversely affected aggregation and adhesion ability of strains.

Adhesion mechanisms of lactic acid bacteria: conventional and novel approaches for testing.

Adhesion ability is a primary criterion for the selection of probiotic microorganisms. Lactic acid bacteria contribute the majority of microorganisms with probiotic properties. They have several important mechanisms for intestinal epithelial cell adhesion. In order to adhere to the intestinal cells, they generally use various structures such as flagella, pili, S layer proteins, lipoteichoic acid, exopolysaccharides and mucus binding proteins. Various in vitro experiments were designed or study models were developed to reveal the mechanisms they utilize for binding to the intestinal cells, yet, the mechanisms for their adhesion are not fully explained. The major disadvantage of conventional models is the lack of layers forming the intestinal mucosa. Besides, these models omit the presence of natural microbiota, digestive conditions and the presence of a food matrix. Because of the disadvantages of existing models, natural tissues or novel applications like 3D organ cultures, which are better able to mimic in vivo conditions, are preferred.

Effect of probiotics on aspirin-induced gastric mucosal lesions.

BACKGROUND/AIMS: We aimed to investigate the role of a probiotic mixture, including 13 different bacteria, in the prevention of aspirin-induced gastric mucosal injury. METHODS: Forty rats were allocated into 4 groups: normal control, aspirin, probiotic control, and probiotic plus aspirin. Normal control and aspirin groups received 0.2 ml of skim milk by daily gavage for 14 days. Probiotic control and probiotic plus aspirin groups were administered 0.2 ml/day of probiotic mixture (1.3 x 10(10) cfu/ml) suspended in skim milk by daily gavage for 14 days. On day 15, gastric lesions were induced by administration of aspirin (200 mg/kg) in the aspirin and probiotic plus aspirin groups. Normal control and probiotic control groups were given saline. RESULTS: Pretreatment with probiotic mixture reduced aspirin-induced gastric damage scores (4.50 ± 0.43 and 2.60 ± 0.40, p<0.01) and exerted tendency of downregulation of proinflammatory cytokines elicited by aspirin (p>0.05). We also found that the probiotic mixture increased sIgA production approximately 7.5-fold in the stomach, and significantly reduced the malondialdehyde (MDA) increase in the gastric mucosa elicited by aspirin (p<0.001). Additionally, pretreatment with the probiotic mixture alleviated aspirin-induced reduction of mast cell count in the gastric mucosa. CONCLUSIONS: Probiotic mixture pretreatment attenuates the aspirin-induced gastric lesions by reducing the lipid peroxidation, enhancing mucosal sIgA production, and stabilizing mucosal mast cell degranulation into the gastric mucosa.

Preventive effect of probiotics and α-tocopherol on ethanol-induced gastric mucosal injury in rats.

The protective effect of a probiotic mixture of 13 different bacteria and α-tocopherol on 98% ethanol-induced gastric mucosal injury was evaluated. Levels of gastric mucosal pro- and anti-inflammatory cytokines, malondialdehyde, and secretory immunglobulin A were measured. Rats were allocated into four groups: control, ethanol, probiotic, and α-tocopherol. The control and ethanol groups received skim milk for 14 days. Probiotic and α-tocopherol groups were administered probiotic mixture suspended in skim milk and 100 mg/kg α-tocopherol, respectively, by daily gavage for 14 days. On Day 15, gastric lesions were induced by administration of ethanol 98% (1 mL) to all rats except those in the control group. Probiotic, but not α-tocopherol, seemed to inhibit ethanol-induced gastric mucosal tumor necrosis factor-α, interferon-γ, and interleukin-2 production (P > .05). Ethanol caused the elevation of mucosal interleukin-4 level (compared to the control, P < .05). Probiotic pretreatment significantly suppressed the ethanol-induced increase of gastric mucosal interleukin-4 levels. Pretreatment with either probiotic or α-tocopherol inhibited the ethanol-induced increase of mucosal malondialdehyde concentration (P < .01 and P < .05, respectively). Probiotic pretreatment enhanced the gastric mucosal secretory immunoglobulin A concentration (P < .001). In conclusion, probiotic mixture and α-tocopherol reduced ethanol-induced gastric mucosal lipid peroxidation, suggesting that they may be beneficial for gastric lesions induced by lower ethanol concentration.

Viability of human-derived probiotic lactobacilli in ice cream produced with sucrose and aspartame.

A mixture of human-derived probiotic strains of Lactobacillus acidophilus, L. agilis and L. rhamnosus was used as a probiotic culture in ice cream manufacture. Viability and survival of these probiotic cultures were investigated in two different ice cream formulations. Ice cream with sucrose and ice cream with aspartame were prepared and each of these was divided into two subgroups: one with direct addition of the probiotic culture and one with milk fermented by the same probiotic culture. Ice cream samples were stored at -20 degrees C for 6 months and the survival rate of cultures were determined monthly. Probiotic cultures underwent tests for resistance to bile salts, antibiotics, acidic conditions; they were found to be highly resistant to such challenges. Chemical analysis of ice cream samples, such as determination of acidity, pH and solid matter, was also performed. The probiotic cultures remained unchanged in ice cream stored for up to 6 months regardless of the sweeteners used. Using probiotic cultures in ice cream mixes did not alter the characteristics of the product.

Evaluation of increased incubation temperature and cefixime-tellurite treatment for the isolation of Escherichia coli O157:H7 from minced beef.

To improve enrichment and isolation of Escherichia coli O157:H7, this study evaluated increased incubation temperature and cefixime-tellurite (CT) on five strains of each of the following bacteria, E. coli, Hafnia alvei, Enterobacter spp., Citrobacter freundii and E. coli O157:H7, and two strains of E. coli O157:nH7. These were grown in pure culture in LST broth with varying cefixime-tellurite concentrations. A range of incubation temperatures from 37 to 46 degrees C was investigated for the inhibition of cohabitant microorganisms. Minced beef, spiked with E. coli O157:H7 and cohabitant microorganisms was investigated. Increased incubation temperature (42 degrees C) and treatment with half of the prescribed amount of cefixime-tellurite by BAM for SMAC agar in enrichment step were the most effective in selectively growing E. coli O157:H7. The results show that E. coli O157:H7 is more resistant to these two conditions than the other cohabitant bacteria.

Effect of reuterin produced by Lactobacillus reuteri on the surface of sausages to inhibit the growth of Listeria monocytogenes and Salmonella spp.

Reuterin is a bacteriocin produced by some strains of Lactobacillus reuteri. The strain used in this study was isolated from raw milk from a dairy farm nearby Ankara. Beef sausage is a long years produced bratwurst style meat product in Turkey, as well as in some other countries in the Mediterranean region. Sausages are produced by raw meat; sometimes lactic starter cultures are added or spontaneous fermentation is employed. The production and storage conditions of the product promotes the growth of Listeria monocytogenes and Salmonella spp. Although nitrate is added as an antimicrobial substance against many pathogens, sometimes however nitrate application is not preventive enough on the surface because of the natural film around the sausages. Since most of the contaminations take place at post production steps, pathogenic growth is more effective on the surface of the sausages in refrigerated conditions. In this study, reuterin was applied to the surface of the sausages in order to prevent the growth of these two pathogens along with nitrate used as an additive in the product. Reuterin has inhibited the growth of L. monocytogenes considerably but not of Salmonella spp. on the surface of the sausages.