Hanna Khouryieh

Effects of xanthan–locust bean gum mixtures on the physicochemical properties and oxidative stability of whey protein stabilised oil-in-water emulsions

The effects of xanthan gum (XG)-locust bean gum (LBG) mixtures (0.05, 0.1, 0.15, 0.2 and 0.5 wt%) on the physicochemical properties of whey protein isolate (WPI) stabilised oil-in-water (O/W) emulsions containing 20% v/v menhaden oil was investigated. At higher concentrations, the apparent viscosity of the emulsions containing XG/LBG mixtures was significantly higher (p<0.05) than the emulsions containing either XG or LBG alone. Locust bean gum showed the greatest phase separation, followed by XG. Microstructure images showed depletion flocculation at lower biopolymer concentrations, and thus led to an increase in creaming instability and apparent viscosity of the emulsions. Addition of 0.15, 0.2 and 0.5 wt% XG/LBG mixtures greatly decreased the creaming of the emulsions. The rate of lipid oxidation for 8-week storage was significantly lower (p<0.05) in emulsions containing XG/LBG mixtures than in emulsions containing either of the biopolymer alone.

Physical and sensory characteristics of cookies prepared with flaxseed flour.

BACKGROUND Flaxseed has many health benefits and is considered a functional food ingredient. Flaxseed flour (0-18%) was used to partially replace wheat flour in cookies and its effects on the physical and sensory characteristics of the cookies were investigated. A correlation analysis was conducted between the instrumental and sensory data. RESULTS The cookie dough stickiness significantly (P < 0.05) decreased in relation to higher percentages of flaxseed flour. The 18% flaxseed cookies had the firmest texture, darkest color and lowest water activity. The 18% flaxseed cookies had the greatest spread ratio. However, this resulted in cookies of unacceptable quality properties. In consumer acceptance tests, cookies made with 6% and 12% flaxseed flour had the highest rating among all sensory attributes, while the 18% flaxseed cookies had the lowest sensory scores. The flavor attribute was most highly correlated with the overall acceptability (r = 0.90). CONCLUSION Results indicated that flaxseed flour can be incorporated in cookies as a partial replacement up to 12% of wheat flour without negatively affecting the physical and sensory quality. The correlation results suggest that the flaxseed flavor attributes best predict consumer preference for overall acceptability, though texture and color attributes also contribute.

Effect of xanthan/enzyme-modified guar gum mixtures on the stability of whey protein isolate stabilized fish oil-in-water emulsions.

The effect of xanthan gum (XG) and enzyme-modified guar (EMG) gum mixtures on the physicochemical properties and oxidative stability of 2wt% whey protein isolate (WPI) stabilized oil-in-water (O/W) emulsions containing 20%v/v fish oil was investigated. EMG was obtained by hydrolyzing native guar gum using α-galactosidase enzyme. At higher gum concentrations (0.2 and 0.3wt%), the viscosity of the emulsions containing XG/EMG gum mixtures was significantly higher (P<0.05) of all emulsions. Increasing concentrations (0-0.3wt%) of XG/EMG gum mixtures did not affect the droplet size of emulsions. Microstructure images revealed decreased flocculation at higher concentrations. Primary and secondary lipid oxidation measurements indicated a slower rate of oxidation in emulsions containing XG/EMG gum mixtures, compared to XG, guar (GG), and XG/GG gum mixtures. These results indicate that XG/EMG gum mixtures can be used in O/W emulsions to increase physical and oxidative stabilities of polyunsaturated fatty acids in foods.

Effect of sorghum flour composition and particle size on quality properties of gluten-free bread

White, food-grade sorghum was milled to flour of varying extraction rates (60%, 80%, and 100%) and pin-milled at different speeds (no pin-milling, low-speed, and high-speed) to create flours of both variable composition and particle size. Flours were characterized for flour composition, total starch content, particle size distribution, color, damaged starch, and water absorption. Bread was characterized for specific volume, crumb structure properties, and crumb firmness. Significant differences were found (P < 0.05) in the composition of sorghum flours of varying extraction rate, most notably for fiber and total starch contents. Flour particle size and starch damage were significantly impacted by extraction rate and speed of pin-milling. Water absorption increased significantly with increasing extraction rate and pin-milling speed. Breads produced from 60% extraction flour had significantly higher specific volumes, better crumb properties, and lower crumb firmness when compared with all other extractions and flour types. The specific volume of bread slices ranged from 2.01 mL/g (100% extraction, no pin-milling) to 2.54 mL/g (60% extraction, low-speed pin-milling), whereas the firmness ranged from 553.28 g (60% extraction, high-speed pin-milling) to 1096.26 g (commercial flour, no pin-milling). The bread characteristics were significantly impacted by flour properties, specifically particle size, starch damage, and fiber content (P < 0.05).

Creaming and oxidative stability of fish oil-in-water emulsions stabilized by whey protein-xanthan-locust bean complexes: Impact of pH

The impact of pH on the physicochemical properties of 10% menhaden oil-in-water (O/W) emulsions containing 2% whey protein isolate (WPI) and 0.1% xanthan (XG)-locust bean gum (LBG) mixtures was investigated. The O/W emulsions containing 0.1% XG-LBG mixtures were compared to emulsions with 0.1% XG and 0.1% LBG. The results indicated that stability is dependent on pH and biopolymer type. At both pH 3 and 5, emulsions containing either XG or XG-LBG mixtures had large particle sizes, viscosity, droplet aggregation, and creaming index, resulting in poor physical stability which can be related to the adsorbed protein-polysaccharide interactions. At pH7, the XG-LBG emulsions showed the greatest resistance to phase separation and resulted in stable emulsions. Lipid oxidation measurements also indicated that XG-LBG mixtures can be used to form stable emulsions at pH 3 and pH 7. These results have significant implications for the development of novel structures containing lipid phases susceptible to lipid oxidation.

Effect of flaxseed flour incorporation on the physical properties and consumer acceptability of cereal bars

Extensive research has revealed numerous nutritional and health benefits of flaxseed due primarily to its nutrients content. The objective of this study was to evaluate the effect of flaxseed flour addition on the physical and sensory characteristics of cereal bars. Four formulations of the flaxseed cereal bars were prepared by partially replacing oats with flaxseed flour added at levels of 0 (control), 6%, 12% and 18%. There were no significant differences (p > 0.05) in water activity, moisture and firmness values between the flaxseed bars and control. Flaxseed addition significantly (p < 0.05) decreased lightness and increased redness of the bars. There were no significant differences (p > 0.05) between the 12% flax cereal bars and the control with respect to sensory attributes and overall acceptability. The overall acceptability for both 12% flax bars and the control was in between ‘like moderately’ and ‘like slightly’ on the 9-point hedonic scale. The overall acceptability was most highly correlated with flavor acceptability for both control (r = 0.80) and 12% flax (r = 0.82) cereal bars. Flaxseed bars provided 12% dietary fiber of the daily recommended value. These results indicated that flaxseed flour incorporation up to 12% substantially enhanced the nutritional qualities of the cereal bars without affecting their sensory and quality properties.

Evaluation of sorghum flour functionality and quality characteristics of gluten-free bread and cake as influenced by ozone treatment

Commercially milled food-grade sorghum flour was subjected to ozone at the rate of 0.06 L/min for 15, 30, and 45 min. The pH of ozone-treated flour decreased as exposure time increased. The L* (lightness) values of sorghum flour significantly increased (p < 0.05), while the b* (yellowness) values significantly decreased as ozone exposure time increased. Peak viscosity significantly increased as time of ozonation increased from 0 to 45 min. Results showed that gluten-free cake volume significantly increased as ozonation time increased. Additionally, longer ozonation exposure times increased cells per slice area, lightness, and slice brightness values in gluten-free cakes while reducing crumb firmness. Despite improving lightness and slice brightness values, ozonation did not significantly increase the specific volume of gluten-free batter-based bread. While ozonation improved the volume and texture in cakes, it did not have the same positive effects on gluten-free bread. Bread made from ozonated sorghum flour had an open ragged structure with equivalent volume to the control flour. In both applications, the increased brightness and lightness values due to ozone exposure is recommended to increase the acceptability of sorghum products.