توصيفگر ها :
استئارين شترمرغ , استئارين دنبه گوسفندي , اولئوفوم , بهينه سازي , سيستمهاي مخلوط , رئولوژي
چكيده انگليسي :
An oleofoam, or “oil foam”, is a non-aqueous foam in which air bubbles are dispersed in a continuous oil phase containing crystalline particles of structuring agents. This innovative aerated system is valuable for the design of healthier lipid-based food products with low-fat content and enhanced textural properties. However, the options of structuring agents for stabilizing non-aqueous foams are limited due to the low surface tension in the oil phase. In Iran, there is a large capacity to produce animal fat, although a small amount is used in the food industry. Utilizing stearin fractions of sheep tail and ostrich fats as slaughterhouse by-products seems to be a promising option for structuring oil. Therefore, fats were extracted by the wet rendering method and subjected to a two-stage dry fractionation, and their fatty acid composition and physicochemical properties were measured in the first part of the study. The gas chromatography showed that oleic acid, palmitic acid, and stearic acid were the main fatty acids in sheep tail fat, and oleic acid, palmitic acid, palmitoleic acid, and linoleic acid were dominant in the fatty acid profile of ostrich fat. After fractionation, an increase in the saturation level of stearin and soft stearin in both fats improved the melting point. In the second part of the study, the stearin fraction of sheep tail (STS) and ostrich (OSS) fats at 35 wt% was utilized to structure various oils (canola, sesame, sunflower, and flaxseed oils). STS-based oleogels showed βʹ needle-like crystals, longer gelling time and firmer structure as well as higher storage modulus (Gʹ) and lower oil loss (<11%) compared to OSS-based, containing bigger rosette-like β crystals. Moreover, oils with higher unsaturation levels and iodine values resulted in lower viscosity, accelerated crystallization rate, improved firmness, and enhanced oil retention. Hence, a combination of STS and flaxseed oil resulted in a gel with appropriate characteristics for food application. In the third part, the oleofoam formulation was optimized by adjusting the proportions of STS (15-35 wt%), glycerol monostearate (GMS; 0-10 wt%), and sorbitan monostearate (SMS; 0-10 wt%) using an optimal mixture design. The best three formulations giving oleogels with maximum oil binding capacity and intermediate hardness, and oleofoams incorporating high air content and forming stable foams resulted those containing 27 %(w/w) STS and 8 % of GMS or/and SMS. These systems were selected for further analysis and compared to a control sample based on STS. The mixed oleogels based on STS and surface-active agents exhibited two crystallization peaks, with GMS and SMS as primary nuclei that induced subsequent crystallization, forming more crystals, as observed through polarized light microscopy. Van der Waals forces and hydrogen bonding in mixed systems led to more GʹLVR and yield point compared to the control. After whipping, the oleofoam containing STS and GMS displayed smaller air bubbles (30.42 µm) that were uniformly dispersed within the oil continuous network, demonstrating significant stability against heating up to 50 ℃ (97%). Over time, STS-GMS-based oleofoam maintained ultrastability, confirming its structural integrity, and was subsequently selected for use in compound chocolate production. In the last part, cocoa butter substitute (CBS) was partially replaced by oleofoam at 25%, 50%, and 75 % in the compound chocolate formulation. Replacing the cocoa butter substitute with oleofoam in the formulation reduced the saturated fatty acid content, density, and energy of the compound chocolate (p < 0.05); however, it enhanced the loss tangent compared to the control sample. Also, the oil loss of the samples containing 25% and 50% replacement was not significantly different from the control sample after 45 days’ storage.
