Effects of Processing on the Compositions and Physicochemical Properties of Fibre Concentrate from Cooked Fruit Pomaces

in Food and Bioprocess Technology (in press)

This study examined the influence of applied tech- nologies namely desugaring, grinding, and bleaching on the compositions (cellulose, hemicelluloses, lignins, and pectins), physicochemical properties ... [more ▼]

This study examined the influence of applied tech- nologies namely desugaring, grinding, and bleaching on the compositions (cellulose, hemicelluloses, lignins, and pectins), physicochemical properties (water-holding capacity (WHC), swelling capacity (SWC), oil-holding capacity (OHC)) and the colour of dietary fibre (DF) during the production of fibre concentrates from unusual cooked apple and pear pomaces. Thermogravimetric analysis (TGA) and optical microscopy were also performed to monitor process-induced modifica- tion. All the processing conditions affected the compositions and physicochemical properties of DF. The bleaching treat- ment induced the greatest changes on DF producing yellow cellulose-rich fibre concentrates with improved WHC from 3.2 to 10.0 g/g and improved SWC from 4.0 to 8.8 ml/g. Otherwise, reduction of the particle size influenced hydration properties and colours of DF. WHC and SWC tended to increase with the particle size whereas smaller granulometric size increased the lightness of fibres. Desugaring increased the DF content in both pomaces by 1.2-fold with slight modifica- tion of apple insoluble dietary fibre ratio. Fibre concentrates had improved WHC and SWC up to 1.4-fold. All processes had no significant effect (p < 0.05) on OHC of DF except with ultrafine apple fibre concentrates. Results showed that pro- cessing had overall positive effects on DF contents and hy- dration properties of pomaces from cooked fruits. Bleached fibre concentrates from apple pomace had the highest WHC (10.0 g/g) whereas that of pear had the highest fibre content (89.9 %). Fibres from cooked fruit pomaces may therefore be used as textural ingredients or functional foods. [less ▲]

Effect of New Synthetic PEGylated Ferulic Acids in Comparison to Ferulic Acid and Commercial Surfactants on the Properties of Wheat Flour Dough and Bread

in Journal of the Science of Food and Agriculture (in press)

BACKGROUND: Ferulic acid esterified with poly(ethylene glycol) with three different average molecular weights (200, 400 and 1000 g/mol) was studied in breadmaking. The effects of these antioxidants on the ... [more ▼]

BACKGROUND: Ferulic acid esterified with poly(ethylene glycol) with three different average molecular weights (200, 400 and 1000 g/mol) was studied in breadmaking. The effects of these antioxidants on the properties of wheat flour dough and bread were analyzed and compared with those obtained with ferulic acid and two commercial surfactants, diacetyl tartaric acid ester of mono- and diglycerides and sodium stearoyl lactylate. Farinographic and alveographic methods as well as weight, volume and bread firmness measurements were used for this purpose. <br /> <br />RESULTS: Such as ferulic acid, when the PEGylated derivatives were implemented in the dough (5000 ppm), it accelerated its breakdown and decreased its rheological properties. However, it allowed to avoid the important diminution of loaf volume observed when dough supplemented with ferulic acid was baked. That decrease in volume was related to the inhibition of the yeast (Saccharomyces cerevisae) by the unesterified ferulic acid. Moreover, two of the PEGylated ferulic acids even contributed to an increase of loaf volumes (5-6%) and demonstrated crumb softener properties. <br /> <br />CONCLUSION: The addition of ferulic acid in wheat flour dough caused the inhibition of the yeast, which resulted in decreased bread volume. That effect could be avoid by the esterification of ferulic acid with poly(ethylene glycol). [less ▲]

Comment évaluer la texture des aliments?

in Science culinaire (in press)

Rapport scientifique et technique du projet HYDRASANTE (annee 3)

Report (2013)

Effects of extraction solvents on phenolic contents and antioxidant activities of Tunisian date varieties (Phoenix dactylifera L.)

in Industrial Crops & Products (2013), 45

Second-grade dates (Phoenix dactylifera L.), with hard texture, from six Tunisian cultivars were analysed for their composition and antioxidant activities. Results showed predominance of total sugars and ... [more ▼]

Second-grade dates (Phoenix dactylifera L.), with hard texture, from six Tunisian cultivars were analysed for their composition and antioxidant activities. Results showed predominance of total sugars and a relatively low content of protein, fat andash. On the other hand, optimisation of extraction of antioxidant was carried using five different solvents. The highest level of phenolic compounds for all dates varieties was found in the 70% acetone extract. This level ranged from 199.43 to 576.48 mg of GAE/100 g fresh weight. However, extraction into 50% methanol gave the highest antioxidant activity from 89.55 to 109.67 mg equivalents of ascorbic acid/g fresh weight. For both two olvents, Bejo exhibited the highest phenolic content and total antioxidant activity, while Baydh El Hamam presented the owest. A positive linear correlation between total antioxidant activity and phenolic contents was observed (R2 = 0.83; R2 = 74 for acetone/H2O and methanol/H2O, respectively). The antioxidant activity of acetone/H2O and methanol/H2O extracts was carried using DPPH radical-scavenging activity and reducing power. These results showed that dates had strongly scavenging activity on DPPH reaching 90.12% in methanol/H2O from Deglet Nour. Whereas, acetone/H2O showed the best reducing power which Bejo was significantly higher than the other varieties. This study demonstrates the potential antioxidant activity with Tunisian date, that we can use these natural extracts as food additives in replacement of synthetic compounds. [less ▲]

Effect of extraction conditions on the yied and purity of ulvan extracted from Ulva lactuca

in Food Hydrocolloids (2013)

A study of the influence of extraction conditions (pH: 1.5 and 2; temperature: 80 °C and 90 °C; extraction time: 1-3 h), on the yield, chemical composition and purity of the sulphated cell wall ... [more ▼]

A study of the influence of extraction conditions (pH: 1.5 and 2; temperature: 80 °C and 90 °C; extraction time: 1-3 h), on the yield, chemical composition and purity of the sulphated cell wall polysaccharides ulvan, extracted from the green seaweed Ulva lactuca and precipitated by alcohol is carried out. The alcohol precipitate yields varied from 21.68% to 32.67% (%dw/dw) depending on the pH. At pH 2, the alcohol precipitate yields and the uronic acid recovery from extract juice are higher than those obtained at pH 1.5. Other compounds than ulvan such as cellulose, hemicellulose, proteins and ash are solubilized from the cell walls of Ulva lactuca at both pH, and they are precipitated with alcohol. The alcohol precipitate obtained from different extraction conditions has high uronic acid (20.37%-23.60%) and neutral sugar content (20.09%-29.12%), especially when the conditions (pH, temperature) are drastic. It contains rhamnose (13.35%-15.59%), glucose (2.90%-10.97%), and xylose (2.36%-2.73%). A decrease in the molecular weight of ulvan was observed at acid pH, and for long extraction times. The presence of proteins (1.94%-2.32%) and inorganic material (33.36%-47.15%) in alcohol precipitate prove the lower purity of ulvan extracted and shows that ulvan precipitation with ethanol is not specific. © 2012 Elsevier Ltd. [less ▲]

Influence of monopalmitin on the isothermal crystallization mechanism of palm oil

in Food Research International (2013), 51(1), 344-353

Influence of steam explosion on physico-chemical properties and hydrolysis rate of pure cellulose fibers

in Bioresource Technology (2012), 121(221-227),

The aim of the present study is to compare the effect of different steam explosion treatments on physicochemical properties and hydrolysis rate of a pure bleached cellulose. The results showed that ... [more ▼]

The aim of the present study is to compare the effect of different steam explosion treatments on physicochemical properties and hydrolysis rate of a pure bleached cellulose. The results showed that moderate steam explosion treatments (severity factor below 5.2) did not improve the enzymatic hydrolysis rate of the cellulose fibers. The characterization of the obtained samples showed an increase of the cellulose accessibility coupled with an increase of the overall crystallinity of the substrate. In these conditions, the higher accessibility is counterbalanced by the increased crystallinity. Indeed, a greater proportion of the substrat is accessible by only a fraction of the enzymatic complex (exo-glucanases) activities. When the severity factor reached 5.2, a decrease of the cellulose enzymatic hydrolysis rate was observed. In this case, TGA analysis showed an increase of the char level at the end of the pyrolysis which traduced an important thermal degradation of the samples. The thermal degradation of cellulose lead to an important change in substrate composition, which induced a decrease of the cellulose ratio available for hydrolysis and caused a decrease of the hydrolysis yields. [less ▲]

An emulsion whippable at room-temperature

Patent (2012)

he present invention relates to an oil-in-water emulsion for whipped cream and to a whipped cream obtained by whipping the emulsion. In particular, the present invention relates to a stabilized whippable ... [more ▼]

he present invention relates to an oil-in-water emulsion for whipped cream and to a whipped cream obtained by whipping the emulsion. In particular, the present invention relates to a stabilized whippable oil-in-water emulsion upon increasing the trilaurin triglyceride content of its oily phase, and to the stabilized cream obtained by whipping the emulsion. The present invention further relates to the methods for obtaining this emulsion and this cream, and to the uses of an oil-in-water emulsion according to the invention or of the stabilized cream according to the invention. [less ▲]

Effect of heat treatment of rennet skim milk induced coagulation on the rheological properties and molecular structure determined by synchronous fluorescence spectroscopy and turbiscan

in Food Chemistry (2012), 135(3), 1809-1817

Heat treatment applied to milk induces denaturation of whey proteins, leading to a complex mixture of whey protein and whey protein coated casein micelles. The present paper investigates the effects of ... [more ▼]

Heat treatment applied to milk induces denaturation of whey proteins, leading to a complex mixture of whey protein and whey protein coated casein micelles. The present paper investigates the effects of heat treatment (60 and 80 °C during 20 min) and rennet-induced coagulation temperature (30 and 40 °C) determined by rheology, synchronous fluorescence spectroscopy (SFS) and turbiscan measurements. The gelation times determined by rheology and SFS increased with the increase of heat treatment applied to milk. The rise in temperature induced a decrease in the maximum curd firming rate and an increase in the viscosity of the investigated milk samples. The principal component analysis (PCA) applied, sepa- rately, to the SF and turbiscan spectra showed a clear discrimination between: (i) raw milks and heated milks; and (ii) milks renneted at 30 °C from those renneted at 40 °C. The results showed the ability of SFS as a rapid and non-destructive technique for the: (i) monitoring network structure and molecular inter- action during the coagulation process; and (ii) determination of gelation time of rennet-induced coagu- lation of studied milk samples. [less ▲]