Characterization of pectins extracted from pomegranate peel and their gelling properties.

The composition of pomegranate peel, the main by-product during pomegranate processing, and some of the characteristics of the water-soluble pectins were investigated. Four tunisian pomegranate peels were subjected to hot aqueous extractions (86°C, 80min, 20mM nitric acid). Pomegranate peels yielded between 6.8% and 10.1% pectins. The extracted pectins were low methylated and were characterized by the predominance of homogalacturonan regions. Principal component analysis applied on FT-IR spectral data in the region between 4000 and 650cm(-1) differentiated the samples according to their degree of methylation. At pH 3, in the presence of 0.7% pectin, all solutions showed a rapid gel formation with G'>G″. With decreasing temperature from 90°C to 10°C, G' increased to reach a plateau at 10°C. The variation in the pectin gel formation between varieties was attributed to difference in pectin characteristics particularly the hydrodynamic volume and the neutral sugar content.

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.

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.

Volatile and lipid analyses by gas chromatography/mass spectrometry and nutraceutical potential of edible wild Malva aegyptiaca L. (Malvaceae).

Volatile and lipid chemical compositions, and nutritional and antioxidant properties of Malva aegyptiaca, an edible wild plant largely distributed in North Africa, were investigated. Forty-nine compounds of volatiles were identified showing large qualitative and quantitative differences during three phenological stages. The flowering stage was characterized by the presence of a high number of terpenic compounds, among them dillapiole was found to be the major one (55.15%). The nutrient composition of leaves and fruits was investigated in the present work. Fruits' lipidic fraction was characterized by its high level of linoleic acid (n-6) (36.17%). Interestingly, leaves' lipidic fraction was characterized by its very high content of camphor (43.69%) and by its relatively high content of linoleinic acid (n-3) (14.69%). Furthermore, our results showed that the phenolic contents varied from 352 to 404 mg gallic acid equivalent/g ethanolic and acetonic extracts, respectively. These extracts revealed interesting antioxidant activities including free radical scavenging activity (EC(50) = 0.38-0.57 mg/ml) and reducing power (EC(50) = 0.12-0.18 mg/ml).