Faten Kachouri

Enhancement of polyphenols in olive oil by contact with fermented olive mill wastewater by Lactobacillus plantarum

Abstract The effect of olive mill wastewater (OMW) phenolic compounds with low and high molecular weight depolymerisation by Lactobacillus plantarum on the transport of phenolics from OMW to olive oil was studied. Incubation of olive oil samples with fermented OMW by L. plantarum caused polyphenols to decrease in OMW and increase in oil with multiple biological effects. The lower total phenolic content in fermented OMW of 845 mg/l in comparison to OMW control with 1247 mg/l resulted from the depolymerization of phenolic compounds of high molecular weight by L. plantarum. Fermentation with L. plantarum induced reductive depolymerisation of phenolic compounds of OMW which are more soluble in olive oil. The total simple polyphenols content of olive oil mixed with OMW and fermented by L. plantarum was higher (703 mg/l) than an olive oil control mixed with OMW (112 mg/l). Simple polyphenols content was increased in olive oil when L. plantarum was added to OMW, especially for oleuropein, p-hydroxyphenylacetic, vanillic and ferulic acids and tyrosol.

Volatile Constituents and Antimicrobial Activity of Lavandula stoechas L. Oil from Tunisia

Abstract An oil obtained from the dried leaves of Lavandula stoechas L. in 0.77% yield was analyzed by capillary GC and GC/MS. Fenchone (68.2%) and camphor (11.2%) were the main components of the 28 identifed molecules. This oil has been tested for antimicrobial activity against six bacteria, and two fungi. The results showed that this oil was active against all of the tested strains; Staphylococcus aureus was the more sensitive strain.

Removal of Aflatoxin B1 and Inhibition of Aspergillus flavus Growth by the Use of Lactobacillus plantarum on Olives

Olives can be contaminated with a wide variety of molds (Aspergillus and/or Penicillium) that can be occurring naturally on fresh and processed olives and could support mycotoxin production. The aim of this work was to investigate aflatoxin B1 (AFB1) production by fungi and its bioaccumulation in olives during storage and to study the impact of the application of Lactobacillus plantarum on the inhibition of mold development and production of AFB1. Two different treatments were applied: (i) olives with natural microflora and (ii) olives inoculated with Aspergillus flavus after elimination of natural microflora. AFB1 has been extracted from olives and quantitated by high-performance liquid chromatography using a fluorescence detector. Results showed the absence of this metabolite in the olives for the season 2008 to 2009. In 2009 to 2010, AFB1 was detected at the level of 11 μg/kg. The application of L. plantarum during the storage of olives favors the reduction of the level of AFB1 to 5.9 μg/kg correlated with a decrease in the amount of molds (86.3%). The images obtained by environmental scanning electron microscopy showed that L. plantarum was able to adhere to the olive surface and probably produce a biofilm that inhibits the multiplication of yeast and fungi by oxygen competition. Results showed an increase of antioxidant activity and amount of total phenolic compounds of olives, respectively, by 24 and 8.6%. In many olives contaminated with A. flavus, AFB1 was present at an initial level of 5.15 μg/kg and increased to 6.55 μg/kg after 8 days of storage. The biological detoxification of AFB1 in olives by L. plantarum is confirmed by the reduction of the level of AFB1 to 2.12 μg/kg on day 0 and its absence after 4 days of storage.

Microflora distribution and assessment of microbiological quality milk from Tunisian collection centres

Eighty samples of raw milk, collected from eight Tunisian centres, were characterised. All these samples contained approximately 10 cfu/ml of mesophilic aerobic bacteria (MAB), lactic acid bacteria (LAB), yeasts and coliforms dominated the microflora of these samples. They varied from 10 to 10 cfu/ml. More than 70% of the analysed samples contained 10 cfu/ml of Pseudomonas. The content of contaminating microflora like Staphylococcus, coliforms and mesophilic and thermophilic Bacillus ranged from 10 to 10 cfu/ml. However, mesophilic and thermophilic Clostridium were absent in all samples. This study could allow establishing the microflora distribution, revealing the non conformity of these eighty samples with standards, and pointing out eventual microbiological standards values of raw collected milk by comparison with standards.

Chemical Composition and Antioxidant Activity of Myrtus communis L. Floral Buds Essential Oil

Abstract The essential oil of Mytrus communis L. floral buds from Tunisia was analyzed by GC and GC/MS. Thirty-seven compounds were identified, representing 98.7% of the total oil. The major constituents were described as α-pinene (48.9%) and 1,8-cineole (15.3%). The antioxidant activity of the obtained essential oil was investigated by means of β-carotene bleaching (BCB) test and free radical scavenging assay using 2,2-diphenyl-1-picrylhydrazyl radical (DPPH). Results showed that Myrtus communis L. floral buds essential oil has a significant antioxidant effect when tested by each method respectively. The strong antioxidant activity of the studied oil can be attributed to the high content in hydrocarbon monoterpenes and oxygenated monoterpenes.

Kinetic analysis and mathematical modeling of growth parameters of Lactobacillus plantarum in protein-rich isolates from tomato seed.

The aim of the present study was to evaluate the applicability of using protein-rich isolates from tomato seed as a sole source of nutrition for the growth of lactic acid bacteria. Unstructured mathematical and logistic models were proposed to describe growth, pH drop, lactic acid production and nutriment consumption by Lactobacillus plantarum in whole and defatted isolates in order to compare their suitability for the production of a fermented beverage. These media have considerable good quantities of nutriment that allowed the growth of L. plantarum, after which the cell numbers begin to decline. The maximum biomass was observed in defatted isolate (1.42 g L−1) followed by the whole isolate (1.24 g L−1). The lactic acid increased by about 5.5 and 6.5 times respectively in whole and defatted protein isolates. However, significant nutriment consumption occurred during the growth phase as well as stationary phase. A reduction of 61.90% and 95.88% in sugar content, as well as 21.91% and 16.93% reduction in protein content were observed respectively in whole and defatted isolates. In most cases, the proposed models adequately describe the biochemical changes taking place during fermentation and are a promising approach for the formulation of tomato seed-based functional foods.

Production of bioactive peptides from tomato seed isolate by Lactobacillus plantarum fermentation and enhancement of antioxidant activity

ABSTRACT Tomato seed contains proteins of high nutritional value and nutraceutical properties, which can be recovered for application as food additives. In this study, we investigated the use of a Lactobacillus plantarum strain to obtain high-added-value peptides from the fermentation process using tomato seed meal extract as the substrate. Potentially tomato seed meal extract have antioxidant activity which is correlated to the amino acid structures, compositions and sequences. After 24 h of fermentation, the radical scavenging activity of the isolated extract was increased by 87%. The increase of antioxidant activity is potentially attributed to the production of different bioactive peptides bio transformed during fermentation. L. plantarum growth on tomato seed meal extract as substrate reduced content of crude and soluble proteins by 18.44% and 68.99%, respectively, after 24 h of fermentation. Gel filtration chromatography showed a depolymerization of high molecular weight of polymers. HPLC analysis showed a significant decrease in the concentration of total amino acids, especially glutamic acid and aspartic acid. FTIR results showed that the fermentation favors the production of new amides and aromatic compounds. The production of protease by L. plantarum was investigated and results showed that highest activity (401.45 U/ml) were obtained after 20 h of fermentation. Results confirmed that L. plantarum could degrade and convert tomato seed proteins into bioactive peptides that contributed positively to the improvement of antioxidant activity of the protein isolate.