Imad Toufeili

Effect of glass transition and cross-linking on rheological properties of gluten: Development of a preliminary state diagram

ABSTRACT The glass transition temperature of gluten at different moisture levels was determined by differential scanning calorimetry and mechanical spectrometry. The dynamic moduli (G′ and G″) of gluten with 10–40% moisture were measured as a function of temperature by pressure rheometry. At 10% moisture, gluten exhibited entangled polymer flow at 92–140°C and networking reactions at higher temperatures. At higher moisture levels, gluten experienced structured flow before networking cross-linking reactions. The onset temperature of the reaction zone was 120°C in 20% moisture gluten and 93°C at moisture levels of 30–40%. Softening of the vitrified network occurred at 184, 181, and 170°C in 20, 30, and 40% moisture gluten, respectively. A preliminary state diagram of gluten as a function of moisture and temperature was developed.

The effect of substitution of sodium chloride with potassium chloride on the physicochemical, microbiological, and sensory properties of Halloumi cheese.

This study investigated the effect of salt reduction and partial replacement with KCl on the microbiological and sensory characteristics of fresh and matured Halloumi cheese. Halloumi samples were matured for 8 wk and moisture, fat, protein, pH, lactic acid, sodium, and potassium contents determined. Instrumental textural characteristics of the samples were measured using a texture analyzer. Microbiological analyses included counts of total bacteria, lactic acid bacteria, yeasts and molds, total coliforms, and psychrophilic bacteria. Descriptive sensory analysis was carried out by a 9-member panel, and acceptability testing was conducted with 72 panelists. Salt treatment had a significant effect on the pH, sodium, and potassium contents of the cheeses, whereas age by salt treatment interaction had a significant effect on the pH, lactic acid, and potassium contents of the samples. No major trends could be discerned from the texture profile analysis. All tested microorganisms increased with storage but in general did not differ between treatments and were, in certain instances, lower than levels reported in the literature for other cheeses. Descriptive analysis revealed a significant difference between salt treatments for bitterness, crumbliness, and moistness, whereas age of cheese was significant for saltiness and squeakiness. Salt treatment had no significant effect on any of the acceptability variables for all Halloumi samples.

The characterization of the physicochemical and sensory properties of full-fat, reduced-fat, and low-fat ovine and bovine Halloumi

Halloumi cheese is a popular cheese in Lebanon and the Middle East. Today, health-conscious consumers are demanding lower fat foods with sensory properties that are comparable to their full-fat counterparts. The objectives of this work were to characterize the physicochemical and sensory properties of bovine and ovine Halloumi of different fat levels and to provide a baseline sensory profile for Halloumi cheese. Full-fat, reduced-fat, and low-fat samples were produced from ovine and bovine milks in 2 batches resulting in a total of 12 batches. The fat, protein, moisture, ash, pH, sodium, and calcium levels were determined and the instrumental textural characteristics of the samples were measured using a texture analyzer. Eleven trained panelists used quantitative descriptive analysis to profile the sensory attributes of the samples and an acceptability test was conducted with 84 panelists. The type of milk (ovine vs. bovine) significantly affected the moisture and protein contents, whereas fat level had a significant effect on moisture, fat, protein, and ash contents. Instrumental texture analysis revealed that the type of milk significantly affected adhesiveness, chewiness, and hardness, whereas the fat level affected chewiness, hardness, adhesiveness, and cohesiveness. The sensory results of the trained panelists revealed that the ovine cheese was more yellow and harder than bovine cheese, whereas bovine cheese was squeakier. Low-fat and reduced-fat cheeses were also more yellow and harder than full-fat cheese, and full-fat cheese was more moist with no significant differences between the low-fat and reduced-fat varieties. Type of milk and fat level did not have any significant effect on fermented flavor, whey flavor, or saltiness. Bovine cheese received significantly higher scores on overall acceptability, texture acceptability, and significantly lower scores on the food action rating scale. Full-fat cheese obtained the highest score on overall acceptability, and texture acceptability decreased significantly with decreasing fat levels.

Substitution of wheat starch with non-wheat starches and cross-linked waxy barley starch affects sensory properties and staling of Arabic bread

Substitution of starch from barley, corn, oat, potato, rice or sorghum for prime wheat starch in the formulation of Arabic bread resulted in breads with significantly (P < 0.05) different textural attributes from regular wheat bread except for barley starch. Substitution of waxy barley starch (957 g kg−1 amylopectin) for wheat starch (279 g kg−1 amylopectin) resulted in bread that was not significantly different from regular wheat bread when assessed in the fresh state. However, upon aging, the waxy barley starch-containing bread staled at a significantly (P < 0.05) faster rate than regular wheat bread. Breads made with waxy barley starch cross-linked with 50, 200 or 500 ppm phosphorus oxychloride showed higher enthalpy of melting (ΔH) upon aging and staled faster than the bread formulated with waxy barley starch. These findings suggest that amylopectin retrogradation is one of the determinants of Arabic bread staling and that cross-linking promotes recrystallisation of amylopectin, possibly by keeping the polymer chains in close proximity. The rate of staling in breads formulated with cross-linked waxy barley starch decreased with increasing levels of cross-linking, possibly owing to restrictions in the degree of starch swelling. © 1999 Society of Chemical Industry

Some nutritional and sensory properties of bulgur and whole wheatmeal kishk (a fermented milk-wheat mixture)

Changes in phytic acid, phytase activity and HCl-extractability of Ca, Fe, Mg and Zn during fermentation of kishk formulated from bulgur (cracked and bran-free parboiled wheat) or whole wheatmeal were monitored. Phytic acid and phytase activity decreased and the proportions of HCl-extractable Ca, Fe, Mg and Zn increased as fermentation progressed. The whole wheatmeal kishk contained lower (p < 0.05) amounts of phytic acid and its Ca, Fe, Mg and Zn were more (p < 0.05) amenable to extraction by 0.03 N HCl than bulgur kishk. The soup prepared from whole wheatmeal kishk was significantly (p < 0.05) more yellowish in colour, more sour, less gritty, less cohesive and contained more bran particles than the bulgur-based formulation. Both formulations were liked to a similar degree. These findings suggest that substitution of whole wheatmeal for bulgur in the formulation of kishk enhances the availability of Ca, Fe, Mg and Zn without undue effects on the acceptability of the final product.

Ripening changes and sensory properties of bovine, caprine and ovine shankleesh

Abstract Bovine, caprine and ovine defatted-yoghurt-derived coagula were fermented to shankleesh at 6 °C and 85% RH. Over 70 days of ripening, residual lactose decreased and levels of water-soluble nitrogen, total volatile acids, total volatile bases, free fatty acids and pH showed marked increases. Sensory properties of the final products were related to compositional variations and the progress of biochemical changes during ripening. Caprine coagula developed into highly acceptable products exhibiting well-balanced sensory profiles. The bovine and ovine samples were downgraded due to a combination of inferior flavour and texture attributes. Quality shankleesh was identified as a fermented defatted-yoghurt product possessing moderate pungency and mustiness, a perceptible bitter note and a moderately cohesive, adhesive, dry and hard texture.

The characterization of the physicochemical and sensory properties of full-fat, reduced-fat and low-fat bovine, caprine, and ovine Greek yogurt (Labneh)

Concentrated/Greek yogurt or Labneh is a semisolid food produced from yogurt by eliminating part of its water and water-soluble compounds. Todays world is geared toward the production of lower fat foods without compromising the texture and flavor of these products. The objective of this study was to characterize the physicochemical and sensory properties of bovine, caprine, and ovine Labneh with different fat levels. Bovine, caprine, and ovine milks were used to produce two batches of full-fat (∼10%), reduced-fat (∼5%), and low-fat (<1%) concentrated yogurt samples. Chemical analyses of fat, moisture, protein, ash, syneresis, acidity, pH, sodium, magnesium, and calcium contents were conducted. Instrumental texture analysis using the back extrusion method was applied. Quantitative descriptive sensory analysis was used to profile samples by 11 trained panelists and the acceptability of samples was assessed by 47 panelists. Type of milk significantly affected (P < 0.001) all chemical attributes except moisture and nitrogen-free extract, and fat level significantly impacted moisture, fat, protein, ash, acidity, and magnesium contents of Labneh. Type of milk significantly affected apparent modulus, hardness, hardness work done, and adhesive force, whereas fat level significantly affected hardness. Type of milk significantly affected the sensory attributes of syneresis, compactness, goaty odor and flavor, rate of flow, color, shininess, bitter flavor, denseness, melting rate, and spreadability, whereas fat level affected only color, denseness, and melting rate. Type of milk had a significant effect on overall acceptability and acceptability of flavor and texture.

Synthesis and taste properties of maltose and maltitol analogues

Abstract The hypothesis that intramolecular hydrogen bonding is responsible for the sweetness of maltitol is tested by the synthesis of maltitol analogues which differ in configuration at C″ 3 and C′ 4 and sensory evaluation of the products. 3- Allo -maltitol and galacto maltitol were synthesised by treating suitably protected methanesulphonylated derivatives of benzyl β-maltoside with sodium benzoate followed by removal of the blocking groups and subsequent reduction with sodium borohydride. Sensory evaluation of maltose, maltitol and their analogues revealed that the non-reducing end is involved in the generation of the sweet response and that intramolecular hydrogen bonding governs the accession of this class of polyol sweeteners to the receptor site on the tongue.

Developing a Carob‐Based Milk Beverage Using Different Varieties of Carob Pods and Two Roasting Treatments and Assessing Their Effect on Quality Characteristics

BACKGROUND This work aimed at formulating a carob-based milk beverage and assessing its chemical and sensory properties. Six varieties of carob pods, each processed into roasted and unroasted powders, were used to develop 12 prototypes of the beverage. Chemical and physico-chemical analyses (moisture, ash, fibre, protein, sugars, total-phenolics, total-antioxidants, water activity and colour) and sensory tests were conducted. RESULTS The variety of carob pod had a significant effect on all chemical variables in carob powders (P < 0.01), except for sugars, and when incorporated in the beverage, on moisture, total phenolics, total antioxidant activity and colour parameters (L, a, b; P-values < 0.001). Roasting treatment significantly increased fibre, total phenolics, total antioxidant activity (P-values < 0.001), fructose, glucose (P-values < 0.05), and a-value levels (P < 0.01), significantly lowered moisture (P < 0.05), water activity, L- and b-values (P-values < 0.001) in carob powders; and significantly increased the beverages total phenolics, a-value (P-values < 0.001) and total antioxidant activity (P < 0.01). Roasting treatment significantly increased the beverages acceptability ratings. Beverages formulated with roasted carob powder had higher ratings for level of residue, colour, caramel odour, mocha odour and flavour, roasted coffee odour and flavour, viscosity mouthfeel and bitter aftertaste. Principal component analysis was conducted; PC1 and PC2 separated attributes according to roasting treatment and variety of carob pods, respectively. CONCLUSION The use of Akkari roasted and Baladi Ikleem el Kharoob roasted to formulate a carob-based milk beverage is recommended.

Glass Transition Behavior and Rheological Properties of Surfactants and Gluten-Surfactant Mixtures

ABSTRACT Diacetyltartaric acid esters of monoglycerides (DATEM) and sodium stearoyl lactylate (SSL) displayed thermal events corresponding to glass transition temperature (Tg) and melting of crystalline domains, while monoglycerides (MG) exhibited an endothermic peak corresponding to melting of crystalline structures when heated in a differential scanning calorimeter. The plasticizing effect of water on Tg of gluten exhibited little apparent change in the presence of DATEM, MG, or SSL (glutensurfactant 10:1), in the moisture range of 6.5–21.3% as shown by mechanical spectrometry and differential scanning calorimetry. Glutensurfactant mixtures showed higher G′ and apart from gluten-SSL, which displayed higher tan δ (G″/G′) at ≤2.51 rad/sec, lower tan δ values than gluten in the frequency range of 0.1–100 rad/sec. DATEM and SSL softened the gluten network before cross-linking reactions, while MG shifted the onset of cross-linking reactions to higher temperatures at moisture contents of 30–40%. Complete vitr...