Enzymatic Catalyzed Synthesis Of Low-Calorie Salatrim

Excessive consumption of oil would cause high blood fat, atherosclerosis, cancer and other diseases. The effect should not be underestimated and great attentions are paid to the development of low-calorie fat. As one of the main materials for the preparation of chocolate and other confectionery product, cocoa butter (CB) brings to product good test and quality, but it also brings the problem of high energy inevitably. Salatrim composed of butyric acid and stearic acid has low calorie and similar characteristics with CB and CB analygue, it can be considered as a kind of low-calorie CB analogue. A kind of low-calorie structured lipids-Salatrim was obtained by interesterification of tributyrin (TB) and methyl stearate (St-ME) in solvent-free System. The technology of the interesterification was studied and the reaction product was purified. The melting properties, crystallization behavior and other physicochemical properties of Salatrim were compared with CB and CB analogue to afford guide to the application of Salatrim.Salatrim was obtained by interesterification of tributyrin (TB) and methyl stearate (St-ME), catalyzed by a commercially immobilized 1,3-specific lipase, Lipozyme RM IM from Rhizomucor miehei in solvent-free System. After comparing three reactors, the rotary evaporator under low pressure was chosen as the proper reactor for our study. We investigated the influences of substrate molar ratio, enzyme amount, reaction temperature and reaction time on the conversion of St-ME and the content of LLL-TAG. The condition optimization of the process was conducted by using the response surface methodology(RSM). The optimal conditions for highest conversion of St-ME and lowest content LLL-TAG were determined to be a reaction time 6.52 h, a substrate molar ratio (St-ME: TB) 1.77:1 and an enzyme amount 10.34% at a reaction temperature 65 oC, and under which conditions, the actually measured conversion of St-ME and content of LLL-TAG were 78.47%, 4.89% respectively, in good agreement with the predicted value.After short-range molecular distillation of the reaction product, one kind of low-calorie CB analogue-Salatrim was obtained. By comparing the physical properties of Salatrim,CB,cocoa butter equivalent (CBE), cocoa butter replacer (CBR) and cocoa butter substitutes (CBS), we found that they had close melting point with that of Salatrim is 37.2 oC. Salatrim also have similar SFC curve with them, which suggested that Salatrim have excellent mouthfeel. The hardness of it is between that of CB and CBR and close to that of CBE. Through analysising and comparing, we could see that polymorph tendency for Salatrim was less and their crystal form was allβ' and stable. Both of Salatrim and CBS gradually grow to Spherulites. The former's nucleation and aggregation was faster than the latter, but its size of crystal was smaller. CBR had fine granular crystals. The intermolecular connection of Salatrim was relatively weak, so its space density was lower than CBR and CBS. Isothermal crystallization kinetics results showed that the impact of temperature on Salatrim's crystal nucleation and growth was little, almost without induction period and the crystallization rate was higher than that of CBR and CBS. The non-isothermal crystallization characteristic of Salatrim was the same with that of CBR. Both of them showed two peaks on DSC diagrams at different cooling rates, while CBS had always been a single peak. The cooling rate changed from 1°C/min to 20°C/min, however the n values of them changed little, indicating that the cooling rate had little effect on their nucleation and growth types. Crystallization rate of CBS, Salatrim (peak I) and CBR (peak II) decreased with the decreasing cooling rate, and the decreasing was significant at 1 oC/min. In general, under non-isothermal conditions, the three fats'crystal formation mechanism and crystallization rate were similar.Compatibility studies between the CB and CB analogue was carried out and conclusions were drawn from the iso-temperature curves andΔSFC-T curves analysis. That was the compatibility of Salatrim with CB or CB analogies was very limited. Just like CBS, Salatrim was suitable for replacing CB completely in chocolate, chocolate coating and other confectionery product, under which circumstance, high-fat cocoa pulp should be replaced by low-fat cocoa powder.