Clarification of pomegranate juice by ultrafiltration: study of juice quality and of the fouling mechanism

Introduction. Ultrafiltration (UF) is a single-unit operation for the clarification and fining of fruit juices. The purpose of the UF is to remove suspended solids as well as haze-inducing and turbidity-causing substances to obtain a clear juice during storage. Specifically, the polymerization of phenolic compounds and their interaction with other components (e.g., proteins) could cause a haze complex and turbidity in fruit juices, which can foul the ultrafiltration membrane. Materials and methods. Fresh pomegranate juice was clarified by the ultrafiltration process on a laboratory scale. In experimental tests performed according to the total recycle and the batch concentration mode, the effects of transmembrane pressure (TMP) and enzyme pre-treatment on permeation flux and quality of juice were studied. Results. With the total recycle mode, the effect of TMP on the color and clarity of clarified pomegranate juice was significant. The initial color of the raw pomegranate juice was reduced from 74% to 33% and the clarity decreased from 77% to 42% by UF when the TMP increased from (1 to 3.6) bar. Total phenolic rejection decreased from 45% to 21% when the TMP rose from (1 to 2) bar and remained constant above this value. With the batch concentration mode at TMP = 2 bar and velocity 1 m·s–1, the enzymatic treatment (5 U·mL–1, 300 min, T = 20 °C) of pomegranate juice provided the highest permeate flux, a decrease in total phenolics of 50% and an increased clarity of 30%. Fouling of the UF membrane during pomegranate juice processing is mainly due to the retention of polyphenols and/or proteins; thus, several blocking mechanisms were studied, using a recently developed membrane-fouling model. Analysis revealed that the membrane separation process was controlled by the gel layer mechanism of raw pomegranate juice and complete pore blocking mechanism with enzymatic pre-treatment

Alpha-amylase gene of thermophilic Streptomyces sp. TO1: nucleotide sequence, transcriptional and amino acid sequence analysis

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Antioxidant and antimicrobial activities of solvent extract obtained from rocket (Eruca sativa L.) flowers

International audienceBackground and aim: Eruca sativa or most commonly known as rocket is a worldwide herbaceous plant usually used for salad preparations due to its astringent properties. The health benefits of its leaves and seeds were widely investigated, however no study has been conducted on its flowers demonstrating these benefits. The aim of this work is to investigate the phytochemical properties of solvent extract from rocket flowers. Method: Rocket flowers were collected at their blooming day and solvent extracts were prepared meaning hydrodistillation. Non-polar compounds were extracted using hexane and the efficiency of the obtained extract was evaluated using antibacterial and antioxidant activities. The antibacterial activities were tested against 11 pathogenic strains, whereas the antioxidant activities were tested through DPPH free radical scavenging activity, total antioxidant capacity and β-carotene bleaching test. Results: The antibacterial activities showed good growth inhibition compared to positive controls. The diameter of the inhibition zones reached a maximum of 16.7 ± 0.1 mm when tested against Salmonella typhimurium using 14 mg extract. The results obtained for the antioxidant activities showed more than 90% DPPH free radical inhibition, 315 μg AAE/ml for 71 mg/ml extract and more than 70% inhibition using β-carotene bleaching assay. Conclusion: The obtained phytochemical properties demonstrated the health benefit features of rocket flowers and their potential uses as feedstock of bioactive molecules

Application of Asymetrical and Hoke Designs for Optimization of Laccase Production by the White-Rot Fungus Fomes fomentarius in Solid-State Fermentation

Statistical approaches were employed for the optimization of different cultural parameters for the production of laccase by the white rot fungus Fomes fomentarius MUCL 35117 in wheat bran-based solid medium. first, screening of production parameters was performed using an asymmetrical design 2533//16, and the variables with statistically significant effects on laccase production were identified. Second, inoculum size, CaCl2 concentration, CuSO4 concentration, and incubation time were selected for further optimization studies using a Hoke design. The application of the response surface methodology allows us to determine a set of optimal conditions (CaCl2, 5.5 mg/gs, CuSO4, 2.5 mg/gs, inoculum size, 3 fungal discs (6 mm Ø), and 13 days of static cultivation). Experiments carried out under these conditions led to a laccase production yield of 150 U/g dry substrate

Date Seeds as a Natural Source of Dietary Fibers to Improve Texture and Sensory Properties of Wheat Bread

International audienceThe aim of this work was to investigate the effect of date seed water-soluble polysaccharides (DSP) and hemicellulose (DSH) as dietary fiber sources in enhancing the wheat bread’s quality. DSP and DSH were extracted from the three date seed varieties Deglet Nour, Ghars Souf, and Allig. The extraction yields ranged from 3.8% to 6.14% and from 13.29% to 18.8%, for DSP and DSH, respectively. DSP and DSH showed interesting functional properties and were incorporated at 0.5% and 0.75% (w/w) in wheat flour with low bread-making quality (FLBM). The results showed that the addition of 0.75% DSH significantly improved the alveograph profile of the dough, and in a more efficient way than that of DSP. Furthermore, bread evaluation revealed that the addition of DSH considerably improved the volume (by 24.22%) and the texture profile of bread (decrease of the hardness and chewiness by 41.54% and 33.81%, respectively), compared to control bread (prepared with FLBM). A sensory analysis showed that the better overall acceptability was found for bread supplemented with DSH. Results in this work demonstrate that hemicellulose fraction extracted from date seeds (DSH) and added with a level of 0.75% to FLBM represents the component that improved bread quality the best

Date Seeds as a Natural Source of Dietary Fibers to Improve Texture and Sensory Properties of Wheat Bread

The aim of this work was to investigate the effect of date seed water-soluble polysaccharides (DSP) and hemicellulose (DSH) as dietary fiber sources in enhancing the wheat bread’s quality. DSP and DSH were extracted from the three date seed varieties Deglet Nour, Ghars Souf, and Allig. The extraction yields ranged from 3.8% to 6.14% and from 13.29% to 18.8%, for DSP and DSH, respectively. DSP and DSH showed interesting functional properties and were incorporated at 0.5% and 0.75% (w/w) in wheat flour with low bread-making quality (FLBM). The results showed that the addition of 0.75% DSH significantly improved the alveograph profile of the dough, and in a more efficient way than that of DSP. Furthermore, bread evaluation revealed that the addition of DSH considerably improved the volume (by 24.22%) and the texture profile of bread (decrease of the hardness and chewiness by 41.54% and 33.81%, respectively), compared to control bread (prepared with FLBM). A sensory analysis showed that the better overall acceptability was found for bread supplemented with DSH. Results in this work demonstrate that hemicellulose fraction extracted from date seeds (DSH) and added with a level of 0.75% to FLBM represents the component that improved bread quality the best

Functional characterization of Penicillium occitanis Pol6 and Penicillium funiculosum GH11 xylanases

Xylanases are hemicellulolytic enzymes, which are responsible for the degradation of heteroxylans constituting the lignocellulosic plant cell wall. Xylanases from the GH11 family are considered as true xylanases because of their high substrate specificity. In order to study in depth a crucial difference in the thumb region between two closely related xylanases from Penicillium in terms of kinetic parameters and inhibition sensitivity, the GH11 xylanases from Penicillium occitanis Pol6 (PoXyn3) and from Penicillium funiculosum (PfXynC) were heterologously expressed in Pichia pastoris. The PoXyn3 and PfXynC cDNAs encoding mature xylanases were cloned into pGAPZ alpha A vectors and integrated into the genome of P. pastoris X-33 under the control of the glyceraldehyde 3-phosphate dehydrogenase constitutive promoter. PfXynC was expressed as a His-tagged recombinant protein and purified from the supernatant homogeneity by a one-step purification protocol using immobilized metal affinity chromatography. The recombinant PoXyn3 was purified using a single anion-exchange chromatography. The purified recombinant enzymes were optimally active at 45 degrees C and pH 4.0 for PoXyn3 and 40 degrees C and pH 3.0 for PfXynC. The measured kinetic parameters (k(cat) and V-max) showed that PfXynC was five times more active than PoXyn3 irrespective of the substrate whereas the apparent affinity (K-m) was similar. The recombinant enzymes showed distinct sensitivity to the Triticum aestivum xylanase inhibitor TAXI-I

Solvent extract from Opuntia stricta fruit peels: Chemical composition and Biological activities

International audienceBackground and aim: Opuntia stricta is belonging to the Cactaceae family. Its fruit is composed of around 69% peels, 21% pulp and 10% seeds. Extracting bioactive compounds from the peels; the major part usually discarded, helps to reduce the cost and environmental concerns associated with their disposal. Many studies have been interested in extracting dyes and phenolics from O. stricta peels, showing their antioxidant properties, but no work was devoted to extract and characterize the non-polar compounds meaning hydrodistillation. Method: O. stricta fruits were collected at ripening, the peels, pulps and seeds were manually separated. Peels were then blended, hydrodistilled, and the non-polar compounds were extracted and identified using gas chromatography–mass spectrometry. Afterwards, the antioxidant and antibacterial activities of the extracted molecules were investigated. Results: The extracted non-polar compounds from O. stricta fruit peels were mainly terpene alcohols. The major components were trans-linalool oxide, cis-linalyl oxide and linalool with 38.3%, 29.6% and 23.4%, respectively. The antioxidant activities showed high inhibition of the DPPH free radicals with 84% at 50 mg/ml, higher reducing power than that of ascorbic acid, and high total antioxidant activity with 309 ± 37 μg ascorbic acid equivalent at 25 mg/ml. The antibacterial activities showed high growth inhibition against Staphylococcus aureus and partial inhibition against Enterococcus faecalis. Conclusion: Non-polar compounds extracted meaning hydrodistillation from O. stricta fruit peels exhibit high antioxidant activities and inhibit the growth of S. aureus. They represent thus a promising way for the valorization of this by-product