Production Of Trans-free Bakery Shortening By Enzymatic Interesterification

Shortening is a widely used solid fat in baking industry, it introduces a crisp or softeningeffect to bakery products. Shortening production often involves the use of hydrogenated oils.However, partial hydrogenation of fats is usually accompanied by the formation of trans-fattyacid(TFA) which is harmful to human health.Therefore, enzymatic interestification(IE) as agreen and efficient process gradually become widely used in all kinds of special fats productionsince no trans-fatty acids will be produced in the reaction process. In this research, immobilizedcommercial lipase Lipozyme RM IM was used as catalyst. Three extensive and economical oilsincluding palm stearin(PS), fully hydrogenated palm oil(FHPO) and soybean oil(SO) wereinterestified to produce zero trans-fatty acids bakery shrotening.First, oil blends of PS, FHPO and SO with different mass ratios were interestified. Incomparision to a popular commercial bakery shortening(Pilot), Interestified blend IE-C (PS:FHPO: SO=70:15:15) showing a similar SFC curve was selected to be the ideal shorteningformulation. Further, Single factor optimazation of main factors on enzymatic interestificationincluding reaction time, reaction temperature and enzyme dosage were done by monitoring thechange of SFC curve and slip melting point (SMP). The optimum reactions were reaction time6h, reaction temperature60℃, enzyme dosage4%(w/w oil) with stirring speed of350r/min.Secondly, conventional oil properties (SMP, acid value, peroxide value and moisture), fattyacid profiles (FFA profiles), solid fat content (SFC), thermal behaviors and crytal morphologywere done to evaluate the differences between physical blend (PB-C) and interestified blend(IE-C). Study found that before/after interestification, the acid value, peroxide value as well asmoisture were in line with industrial standards. FFA profiles between PB-C ans IE-C was almostthe same because rearrangement and radomization of fatty chain would not change total FFAprofile during interesterification. IE-C mainly contained palmitic acid (49.44%), oleic acid(30.44%) and linoleic acid (11.82%) with a total unsaturated fatty acids of43%, zero TFA wasdetected. A commercial butter lebaling5.5%natural TFA was used as a control to verify thereliability of the detection process. Differential scanning calorimetry (DSC) curve showed thatmelting and crystallization behavior between PB-C and IE-C changed significantly. Afterinteresterification, with the formation of new triglycerides species, high melting triglycerides markedly reduced, endothermic melting peak shifted to a lower temperature, indicating a lowermelting point, which was consistent with SMP change. Change of DSC curve showed a relativemild and wide range of plastic. X-ray diffraction (XRD) suggested polymorphic form of PB-Cis mixed and complex while β’ form is predominant in IE-C. Crystal microstructures of blendwere measured by polarized light microscope (PLM). Coarse and leaf-like crystals wereobserved in PB-C while spherical and pin cushion shaped crystals were observed in IE-C andCS, respectively, which indicated β polymorphic crystal formation tendency in PB-C and β’tendency in IE-C and CS.Furthermore, β’ form was found to be stable in IE-C under7weeks oftemperature-fluctuated storage experiment.Finally, the emulsifying properties of each emulsifier and blend of emulsifiers that werewidely used in bakery such as lecithin, diacetyl tartaric acid ester of mono-glycerides (DATEM)and Sodium stearoyl-2-lactylate (SSL) were studied by the performance of aeration and waterabsorption. IE-C met most of the commercial bakery shortening requirments with optimumemulsifier formulation listed as follow:0.2%lecithin and0.1%SSL(w/w). In addition, biscuitbaked experiments were conducted. Sensory and physical properties of biscuit showed that thebaking performance of IE-C was comparable to the commercial available shortening CS.