Mayonnaise is a mixture of egg yolk, vinegar, water, spices and 70-80% oil forming a semi-solid oil-in-water emulsion. When preparing a low-fat mayonnaise with an increased water content, thickening agents are required for increased viscosity and emulsion stability. The hydrocolloids xanthan gum and guar gum are sometimes used for this purpose and they act synergistically creating a viscosity increase. However, guar gum has poor acid stability, and because mayonnaise is an acidic product guar gum will eventually start to degrade causing a viscosity decrease and subsequent emulsion separation. Despite this fact, guar gum and xanthan gum are extensively used in mayonnaises today. The aim of this degree project was to explore how the synergy between guar gum and xanthan gum influences the viscosity of a low fat mayonnaise and whether high acidity will have an impact on the viscosity over a 4-week period. This was to examine if and if so, how a mayonnaise recipe can be modified to maintain a cost efficient product with the desired rheological properties in times of hydrocolloid price fluctuations. The study was conducted by preparing 15 mayonnaises with 50% fat, either at pH 3,5; 4 or 5 and a total of 0,6 % hydrocolloids with varying proportions of guar gum and xanthan gum. The mayonnaise samples were studied by measurements of viscosity, color changes and a visual comparison of their mayonnaise-like flow-properties compared to Hellmann’s Real Mayonnaise used as reference. The viscosity of the mayonnaises increased with increasing ratio of guar gum. On the other side, there were greater viscosity losses in mayonnaises with increasing ratio of guar gum 4 weeks after preparation compared to 4 days, with no apparent signs of correlation between higher acidity and hydrocolloid degradation. Mayonnaises with 20% xanthan gum and 80% guar gum had the texture most similar to the reference. In these low-fat mayonnaises, the use of more xanthan gum led to an undesired “slimy” texture and a lower viscosity – an important aspect if adjusting a low-fat mayonnaise recipe by increasing the ratio of xanthan gum. Because a commercial mayonnaise sometimes is consumed several months after manufacturing, that time frame is most likely required in order to fully measure how much the high acidity in mayonnaise will affect its viscosity. This project has shown a pattern where viscosity in the assessed mayonnaises starts to decrease a few weeks after preparation. However to find out exactly to what extent and how this would affect the overall product, and ultimately: if guar gum/xanthan gum combinations are suitable for long-term mayonnaise applications, further studies are required. / Viskositet och syrastabilitet i majonnäs med låg fetthalt och olika proportioner av xantan och guarkärnmjöl Majonnäs är en blandning av äggula, vinäger, vatten, kryddor och 70-80% olja som bildar en semi-solid olja-i-vatten-emulsion. För att tillverka en lågfettsmajonnäs med högre vatteninnehåll behöver förtjockningsmedel tillsättas för viskositet och emulsionsstabilitet. Hydrokolloiderna xantangummi och guarkärnmjöl används ibland i detta syfte och de utövar en synergi som ger ökad viskositet. Dock har guarkärnmjöl dålig syrastabilitet och eftersom majonnäs är en sur produkt kommer guarkärnmjölet efter ett tag att brytas ned vilket leder till en viskositetsminskning och emulsionsseparation. Trots detta används guarkärnmjöl och xantangummi i stor utsträckning i majonnäser idag. Syftet med examensarbetet var att undersöka hur synergin mellan guarkärnmjöl och xantangummi påverkar viskositeten i en lågfettsmajonnäs och huruvida en hög syrahalt kommer att påverka viskositeten under en 4-veckorsperiod. Detta för att se om och i så fall hur ett majonnäsrecept kan modifieras för att erhålla en kostnadseffektiv produkt om priset på hydrokolloider växlar. För arbetet bereddes 15 majonnäser med 50% fetthalt, antingen med pH 3,5; 4 eller 5 och totalt 0,6% hydrokolloider med olika proportioner av guarkärnmjöl och xantangummi. Majonnäserna undersöktes genom mätning av viskositet, färgförändringar och en visuell jämförelse av deras majonnäsliknande flytegenskaper i förhållande till Hellmann’s Real Mayonnaise som användes som referens. Viskositeten i majonnäserna ökade med ökande halt guarkärnmjöl. Å andra sidan minskade viskositeten i högre grad med ökande halt guarkärnmjöl 4 veckor efter tillverkning jämfört med 4 dagar, men inga tydliga samband mellan högre syrahalt och nedbrytning av hydrokolloider syntes. Majonnäser med en blandning av 20% xantangummi och 80% guarkärnmjöl hade den konsistens som var mest lik referensen. I dessa försök med lågfettsmajonnäser ledde användandet av högre halt xantangummi till en oönskad ”slimig” textur och en lägre viskositet – en viktig aspekt om ett recept på lågfettsmajonnäs ska modifieras genom att öka halten xantangummi. Eftersom en kommersiell majonnäs ibland konsumeras flera månader efter tillverkning så är det troligtvis den tidsramen som krävs för att helt kunna mäta hur mycket den höga syrahalten i majonnäs kommer att påverka dess viskositet. Detta projekt har påvisat ett mönster där viskositeten i de analyserade majonnäserna börjar minska några veckor efter tillverkningen. Men för att få reda på exakt i vilken utsträckning och hur detta skulle påverka produkten i sin helhet, och i slutändan: om kombinationen med guarkärnmjöl och xantangummi är lämplig för majonnäser med lång hållbarhet krävs ytterligare studier.

This study examined the effects of guar gum and xanthan gum on flax supplemented breads through objective and sensory testing. Breads containing flaxseed and gums were found to have a significantly (p<0.05) higher water activity than the control bread. Control bread was also found to have a higher (p<0.05) volume while flax breads containing guar gum had a significant (p<0.05) decrease in volume. Control bread and bread containing guar gum were significantly (p<0.05) harder in crumb texture. Breads with flax and xanthan gum displayed a significant (p<0.05) amount of springiness. While there was no significant (p>0.05) difference in peroxide values among bread samples, control bread had a lower (p<0.05) anisidine value indicating a decrease in hydroperoxide breakdown. While not significant (p>0.05), bread containing xanthan gum had a lower anisidine value than the other treatments. Sensory analysis found bread with both gums to be moister (p<0.05) and have a strong (p<0.05) yeasty aroma and fresher flavor. Control bread was found to have the least (p<0.05) yeasty aroma and taste significantly (p<0.05) less bitter but more stale. / Master of Science

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Consumer's demand for more natural and high quality food products products, presenting health benefits, has increased over the years. Besides the nutritional aspects, an appealing appearance and texture is also required. Cloudiness or opacity (cloudy appearance) is an important citrus drinks property (orange, lime, lemon, etc.), since it gives natural fruit juice appeal. This property can be achieved through addition of clouding agents, which also help in uniform distribution of flavors throughout the liquid beverage. A common problem in the beverage industry is producing cloud or flavor emulsions that remain stable over the desired shelf life. Beverage cloud emulsions are oil-in-water emulsions to provide cloudiness and are prepared in a concentrated form, but diluted prior to the consumption. / Optical and rheological properties of beverage cloud emulsions as a function of water-phase and oil-phase concentrations were investigated. The specific gravity of phases, particle size distribution and creaming stability of prepared emulsions in diluted forms were evaluated. The rate of cloud emulsion creaming by determining the rheology of water phase, difference in specific gravities of the phases and droplet properties of the emulsion in presence and absence of weighting agents (sucrose acetate isobutyrate and brominated vegetable oil) or/and xanthan gum was studied. Flow and dynamic rheological properties of single-phases and emulsions containing modified starch and arabic gum as surface active hydrocolloids as well as xanthan and tragacanth as stabilizers gums were investigated. Finally, stability of cloud emulsions in orange juice drink was examined. / Oil-phase concentration had a significant effect (P < 0.05) on increasing the opacity of emulsion. Raise in viscosity of emulsions was more pronounced as oil concentration increased and shear thinning behavior of oil added emulsions was associated with droplet flocculation. Creaming in acidified sugar solution of 11°Bx and pH 3 was observed when the oil-phase specific gravity decreased and sedimentation occurred at the lower viscosity of water phase. Addition of xanthan gum into the water phase decreased the flow behavior index (n) form 0.88 down to 0.31 and increased elastic modulus (G') over 20 times at elevated frequency (o = 50 rad/s) and perk up the stability of the emulsion. / The xanthan gum added emulsion indicated smaller average particle size and demonstrated 14 and 5 times slower separation compared to the emulsions without or with the addition of weighting agents respectively. Starch-xanthan stabilized emulsion and associated water phase at 1.5:1 surface active gum to oil ratio demonstrated viscoelastic behavior (G' ≥ G") with lower droplets coalescence and creaming rates, 0.013 nm/day and 0.02 percent backscattering/day respectively. Conversely, arabic-xanthan stabilized emulsion at 1:1 gum to oil ratio showed the highest rate of droplets coalescence at 0.057 rim/day and greater degree of creaming at 0.61 percent transmission/day. While creaming were associated with arabic gum stabilized emulsions, after 3 month storage, modified starch illustrated appropriate shelf stability with no sign of creaming in orange juice drink.

Thesis (Ph.D.)--Auburn University, 2005. / Abstract. Vita. Includes bibliographic references (ℓ. 135-169)

Sapote gum polysaccharide was examined for homogeneity by ion-exchange chromatography on diethylaminoethyl (DEAE)-cellulose and by fractional precipitation of its propionate derivative. The polysaccharide showed essential homogeneity and was therefore suitable for structural analysis. The polysaccharide showed a low negative specific rotation and contained residues of L-arabinose, D-xylose, D-glucuronic and 4-O-methyl-D-glucuronic acids. A new method was developed for the simultaneous estimation of 4-O-methyl-D-glucuronic acid and other uronic acids by gas-liquid chromatography. Uronic acids in polysaccharides may be reduced by reaction with lithium borohydride in tetrahydrofuran. After hydrolysis and reduction of the monosaccharides the acetylated alditols may be separated by gas-liquid chromatography on a column of butanediol succinate. The method permits the simultaneous estimation of 4-O-methyl-D-glucuronic acid, D-glucuronic acid and D-galacturonic acids. It was found by this method that L-arabinose, D-xylose, D-glucuronic and 4-O-methyl-D-glucuronic acids were present in the ratio of 1:2.8:0.48:0.52. An examination of the O-methyl-derivative of the gum yielded 2,3,5- (+++) and 2,3,4- (+)- tri-O-methyl-L-arabinose, 2,3,4- (+)- tri-O-, 2,3- (+)- di-O-, 3-0- (+++)-methyl-D-xylose, 3,4- (++)- di-O-methyl-D-glucuronic and 2,3,4— (++)- tri-O-methyl-D-glucuronic acid. The methylation data indicates the high degree of branching in the polysaccharide. The presence of 3,4-di-O-methyl-D-glucuronic acid also indicates that a part of the total uronic acids is branched at C-2. Autohydrolysis of the gum yielded a series of oligouronic acids and a lesser branched polysaccharide. The polysaccharide after methylation, reduction and hydrolysis afforded 2,3,4-tri-O-methyl, 2,3-di-0-methyl, 3-O-methyl-D-xylose and 2,3,4~tri-O-methyl-D-glucose in a molar ratio of 2: 1.3: 1: 2 indicating that the degraded polysaccharide has a xylose backbone. Sapote gum polysaccharide after successive periodate oxidation, borohydride reduction and mild acid hydrolysis yielded a series of homologous glycosides, (xylosyl) n=1,2,3 glycerol, which were fully identified by methylation and periodate oxidation. The occurrence of these glycosides signifies a random branching in the polysaccharide. Periodate oxidation and subsequent complete acid hydrolysis of the carboxyl reduced polysaccharide afforded ethylene glycol, glycerol, 2-O-methyl-D-erythritol, D-xylose and 4-O-methyl-D-glucose whose molar ratios were determined by gas-liquid chromatography (g.l.c.). The presence of 4-O-methyl-D-glucose indicates that a major part.of 4-O- methyl-D-glucuronic acid is branched at C-2 (a conclusion supported by the methylation data) and 2-O-methyl-D-erythritol arises from a minor part of 4-O-methyl-D-glucuronic acid with no substituent at C-2. Partial acetolysis of the carboxyl-reduced polysaccharide afforded a new series of oligosaccharides [formula omitted] and [formula omitted]. The results confirm the presence of the oligouronic acids in the polysaccharide. A new method for the selective cleavage of glycosiduronic acids, Hofmann. degradation, was applied to sapote gum in order to study the resulting degraded polysaccharide and to find out the nature of the substituent on 4-O-methyl-D-glucuronic acid. The degraded polysaccharide after methylation and hydrolysis afforded 2,3,4-tri-O-methyl-, 2,3-di-O-methyl-, and mono-O-methyl-D-xylose in a molar ratio of 3: 11: 2. An oligosaccharide originally attached at C-2 of 4-O-methyl-D-glucuronic acid was isolated. Digestion of the polysaccharide with arabinofuranosidase yielded free arabinose indicating that a major part of the terminal non-reducing arabinose units are in the furanose form and linked with xylose in [symbol omitted] configuration. Some enzymes with known ‘xylanase’ activity did not degrade the gum because of the high degree of branching of the polysaccharide. The structural evidence suggests that sapote gum polysaccharide possesses a highly branched xylan framework to which are attached L-arabinose units, D-glucuronic acid and 4-O-methyl-D-glucuronic acid containing side chains. / Science, Faculty of / Chemistry, Department of / Graduate

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