Preparation Of Fat Substitutes And Their Applications:Manipulating Aggregation Of Oil Droplets In Emulsions Through Flaxseed Gum And Modified Cassava Starch

Fat is an essential ingredient in our daily diet and it plays an important role in determining the physical and chemical properties and sensory characteristics of foods,especially some emulsion-based foods such as margarine,sauces,spreads or some dairy beverages.However,many scientific studies have shown that excessive fat intake can be detrimental to health.The purpose of this article is to prepare fat substitutes.First,whey protein isolate(WPI)and whey protein concentrate(WPC)as the research object,mainly investigated the effect of heat pretreatment(90°C,5 min)on the physical stability of oil-in-water emulsions during storage.Then,using the above emulsions as the matrix,the effects of flaxseed gum,modified cassava starch and different environmental pH values on the aggregation of oil droplet in the whole mixed system were studied,and the best fat substitute was selected.Finally,the feasibility of substituting oil in mayonnaise was explored to provide the theoretical basis for the further development of low-fat products with good texture characteristics.The specific results showed as follows:(1)The effect of preheated treatment(90°C,5 min)on the physical stability of rapeseed oil-in-water emulsion during of prepared by using WPI and WPC as stabilizer were investigated.The changes trend of ζ-potential,particle size,flocculation index,creaming index,rheological property and the partition coefficient of protein in the emulsion during the whole storage period(0d to 14 d)were measured.The results showed that the pre-heated whey protein isolate(H-WPI)and whey protein concentrate(H-WPC)could significantly reduce the physical stability of the emulsion during during the whole storage period compared with the unheated WPI and WPC,especially the lower ζ-potential(p < 0.05),and higher particle size,flocculation index,creaming index and viscosity(p < 0.05).Furthermore,the preheat-treated could significantly increase the distribution of the protein on the surface of the emulsion membrane(p < 0.05).The results indicated that the thermal pretreatment significantly reduced the physical stability of the whole emulsion during storage.(2)Using the emulsions prepared with WPI,WPC,H-WPI,and H-WPC as matrixs,the effects of flaxseed gum(0-0.02%,w/v),modified cassava starch(0-6%,w/v)and the different pH values(pH 3.0,5.0 and 7.0)in a mixed system on the aggregation of oil droplets were investigated.The results showed that,at pH 3.0,with the increasing of flaxseed gum concentration,theζ-potential of the mixed system decreased,and the particle size and apparent viscosity increasedsignificantly(p < 0.05),indicating that the addition of anionic flaxseed gum promotes the aggregation of oil droplets.However,a large number of visible aggregates were formed when addition of 0.02%(w/v)flaxseed gum,thereby exerting a negative influence on the sensory quality.At pH 5.0,similar results were also observed,but the particle size,apparent viscosity was larger than that of at pH 3.0(p < 0.05).At pH 7.0,the particle size and apparent viscosity of the mixed system did not change significantly with the increase of flaxseed gum concentration(p > 0.05).(3)Under the conditions of any pH value,addition of cassava modified starch(0-6%,w/v)could significantly increase the particle size,apparent viscosity and short-term storage stability of the mixed system(p < 0.05),and significantly reduced the L* value of the mixing system(p <0.05).Finally,with H-WPI as emulsifier,and 3%(w/v)cassava modified starch,under the condition of pH 3,the mixed system prepared by heating(90°C,5 min),which has the best rheological and sensory properties(p < 0.05).In summary,manipulating aggregation of oil droplets in emulsions through flaxseed gum and modified cassava starch can help to develop low calorie fat substitute with similar texture and appearance of high-fat products.(4)With mayonnaise as the research object,by partial replacement of the 10%,20%,30%,40% and 50% respectively,full fat mayonnaise as control.The result showed that with the increasing of substitution ratio,the L*-value of the mayonnaise sample increased significantly(p <0.05),the b*-value decreased significantly(p < 0.05),and the particle size,apparent viscosity,storage modulus(G’),and loss modulus(G’’)decreased significantly(p < 0.05).At the same time,addition of fat substitutes also had a significant effect on emulsion stability(p < 0.05),negatively affecting sensory evaluation.Based on the above results,the optimal substitution ratio was determined to be 10%.