M.A. Ayadi

Blue-green algae (Arthrospira platensis) as an ingredient in pasta: free radical scavenging activity, sensory and cooking characteristics evaluation.

The effects of semolina enrichment with blue-green algae (Arthrospira platensis) at three different levels (1, 2 and 3 g/100 g of semolina) on the colour, cooking properties, firmness, free radical scavenging activity and sensory characteristics of pasta are reported. Microalgae addition resulted in higher swelling index and lower cooking loss than the control sample. A significant increase in pasta firmness was evidenced with an increase of added microalgae due to structural reinforcement. In addition to colouring, the use of A. platensis (2 g/100 g of semolina) can enhance the sensory quality and nutraceutical potential as evaluated by free radical scavenging activity of pasta.

Proteomic profiling of camel and cow milk proteins under heat treatment.

Cow and camel milk proteins before and after heat treatment at 80°C for 60min were identified using LC/MS and LC-MS/MS following monodimensional electrophoresis. The database used for the identification of camel and cow proteins was set from http://www.uniprot.org/. The obtained results showed that, after heating, camel milk at 80°C for 60min, camel α-lactalbumin (α-la) and peptidoglycan recognition protein (PGRP) were not detected while camel serum albumin (CSA) was significantly diminished. When heating cow milk at 80°C for 60min, α-lactalbumin (α-la) and β-lactoglobulin (β-lg) were not significantly detected. Moreover, 19 protein bands from SDS-PAGE were analyzed and a total of 45 different proteins were identified by LC-MS/MS. Casein fractions were kept intact under a heat treatment of 80°C during 60min of both camel and cow milks. Camel and bovine whey proteins were affected by a heat treatment of 80°C for 60min.

Optimised amylases extraction from oat seeds and its impact on bread properties.

Statistical approaches were employed for the optimisation of the extraction of amylolytic activity from oat (Avena sativa) seeds. The application of the response surface methodology allows us to determine a set of optimal conditions (ratio seed weight/buffer volume 0.1, germination days 10 days, temperature 20 °C and pH 5.6). Experiments carried out under these conditions led to amylase production yield of 91 U/g. Its maximal activity was in the pH 5.6 and at 55 °C. Study of the incorporation of the optimised oat extract into the bread formulation revealed an improvement of the sensory quality and the textural properties of fresh and stored bread. Three-dimensional elaborations of Confocal Laser Scanning Microscopy (CLSM) images were performed on crumb of the different breads to evaluate the influence of amylase activity on microstructure. The result showed improved baking characteristics as well as overall microscopic and macroscopic appearance.

Foaming and adsorption behavior of bovine and camel proteins mixed layers at the air/water interface

The aim of this work was to examine foaming and interfacial behavior of three milk protein mixtures, bovine α-lactalbumin-β-casein (M1), camel α-lactalbumin-β-casein (M2) and β-lactoglobulin-β-casein (M3), alone and in binary mixtures, at the air/water interface in order to better understand the foaming properties of bovine and camel milks. Different mixture ratios (100:0; 75:25; 50:50; 25:75; 0:100) were used during foaming tests and interfacial protein interactions were studied with a pendant drop tensiometer. Experimental results evidenced that the greatest foam was obtained with a higher β-casein amount in all camel and bovine mixtures. Good correlation was observed with the adsorption and the interfacial rheological properties of camel and bovine protein mixtures. The proteins adsorbed layers are mainly affected by the presence of β-casein molecules, which are probably the most abundant protein at interface and the most efficient in reducing the interfacial properties. In contrast of, the globular proteins, α-lactalbumin and β-lactoglobulin that are involved in the protein layer composition, but could not compact well at the interface to ensure foams creation and stabilization because of their rigid molecular structure.

Yield and composition of pectin extracted from Tunisian pomegranate peel.

A central composite design was employed to determine the influence of extraction conditions on production yield and chemical composition of pectin from pomegranate peels. Response surface methodology (RSM) was used to quantify the integral effect of the three processing parameters (extraction duration, temperature and pH) on yield. A second-order polynomial model was developed for predicting the yield of pomegranate peels pectin based on the composite design. Yields ranged from 6.4 to 11.0±0.2%. Optimal temperature, duration and pH value of the extraction were 86°C, 80min and 1.7, respectively. The uronic acid and the total neutral sugar content of the extracted pectins ranged from 377 to 755mg/g and from 161 to 326mg/g, respectively. Moreover, the degree of methylation varied with the extraction conditions and the extracted pectins were low methylated. On high pressure size exclusion chromatography (HPSEC), the elution pattern of the acid-extracted pectins showed that severe conditions were associated with lower hydrodynamic volume.

The foaming properties of camel and bovine whey: The impact of pH and heat treatment

The effect of heat treatment (70°C or 90°C for 30min) on the foaming and interfacial properties of acid and sweet whey obtained from bovine and camel fresh milk was examined. The maximum foamability and foam stability were observed for acid whey when compared to sweet whey for both milks, with higher values for the camel whey. This behavior for acid whey was explained by the proximity of the pI of whey protein (4.9-5.2), where proteins were found to carry the lowest negative charge as confirmed by the zeta potential measurements. Interfacial properties of acid camel whey and acid bovine whey were preserved at air water interface even after a heat treatment at 90°C. These results confirmed the pronounced foaming and interfacial properties of acid camel whey, even if acid and sweet bovine whey exhibited the highest viscoelastic modulus after heating.

Effect of substituted gelling agents from pomegranate peel on colour, textural and sensory properties of pomegranate jam

A series of pomegranate jams were prepared from a Tunisian ecotype (Tounsi) with different amounts of sugar (10, 20 and 30%) and low-methoxylated pectin (0.2, 0.7 and 1.2%). The most appreciated formulation was that contaning 30% sugars and 0.2% pectin. Then, commercial pectin was substituted by other gelling agents (pomegranate peel powders dried at 50°C vs lyophilized, pectin and fibre extracted from pomegranate peel) for the preparation of pomegranate peel-based jams. The elaborated jams were evaluated for physichochemical, colour, texture and sensory characteristics. Results revealed that the jam (JPP2) elaborated with 0.2% pectin extracted from pomegranate peel exhibited similar overall acceptability to that prepared with commercial pectin. However, it was more acceptable than other pomegranate peel-based jams, which was related to a better appreciation of sweetness and colour. According to the colour and texture measurements, this sample (JPP2) was more reddish and less firm than other samples.

The effect of pH and heat treatments on the foaming properties of purified α-lactalbumin from camel milk

The effect of pH (4.3 or 6.5) and heat treatment (70°C or 90°C for 30min) on the foaming and interfacial properties of α-lactalbumin extracted from camel milk were studied. The increased temperature treatment changed the foaming properties of camel α-lactalbumin solution and its ability to unfold at the air-water interface. At neutral pH, heat treatment was found to improve foamability, whereas at acid pH (4.3) this property decreased. Foams were more stable after a heat treatment at pH 4.3 than at 6.5, due to higher levels of protein aggregation at low pH. Heat treatment at 90°C for 30min affected the physicochemical properties of the camel α-lactalbumin by increasing free thiol group concentration at pH 6.5. Heat treatment also caused changes in α-lactalbumins surface charge. These results also confirm the pronounced aggregation of heated camel α-lactalbumin solution at acid pH.

Physicochemical properties of water-soluble polysaccharides from black cumin seeds

In the present work, water-soluble polysaccharides were isolated from black cumin seeds. Polysaccharides were characterized by their carbohydrate composition, molecular weight, thermal stability and by FTIR, NMR spectroscopy and X-ray diffraction. The surface, the functional and the antioxidant properties of black cumin water-soluble polysaccharides (BCWSP) were also investigated. BCWSP consisted mainly of galacturonic acid (30.20%), glucuronic acid (17.66%) and neutral sugar (22.99%). BCWSP was composed of high peak molecular weight. The FTIR spectrum obtained for BCWSP showed two most important absorptions, at 1659 and 1085 cm-1, which corresponded to COO- of uronic acids and pyranose form, respectively. NMR spectroscopy data suggested that the BCWSP is probably a rhamnogalacturonan backbone with galactan and arabinan side chains. X-ray pattern revealed the semi-crystalline behavior of BCWSP. WHC and OHC of BCWSP were relatively high and varied with temperatures. The polysaccharide zeta potential was greatly affected by pH. Results indicated that the decrease of surface tension has influenced foaming and emulsifying capacities. The DPPH radical scavenging activity of the BCWSP was 63.25% at 1 mg/mL. The BCWSP displayed moderate reductive, β carotene bleaching and chelating abilities. Overall, our results suggested that BCWSP could be used as alternative additives in food and non-food products.