| Hydrogenated palm kernel oil(HPKO)as cocoa butter substitute was used for this study to investigate the effects of sucrose(Su), and their alternatives, such as isomaltulose(Is), xylitol(Xy), D-mannitol(D-Ma), lactitol(La) and maltitol(Ma) on the crystallization behavior of fat. For the final product of chocolate, the melting property and their storage stability of chocolate was also studied.The effects of sugars on the crystallization behavior of HPKO were observed as following:(1) Solid fat content(SFC) of HPKO were increased by added sugar. Lactitol accelerated the crystallization rate, followed by isomaltulose, sucrose, maltitol, D-mannitol and xylitol. If the sugars have the similar molecular structure, the smaller density of powdered sugars with the same adding amounts could provide more crystallization sites for crystallization of HPKO.(2) In general, after adding sugars, the products density was increased, which led to the increase of hardness. When the amounts of sugars increased from 30% to 40%, the hardness of samples were increased. Further increasing sugar, i.e. 50% sugars did not show the increase of the hardness. On the contrary, the hardness of adding 50% lactitol was less than adding 40% lactitol which may be due to the small density of lactitol.(3) After adding sugars, the onset temperature and melting enthalpy of HPKO were increased which indicated that sugars promoted the crystallization of HPKO.(4) The products viscosity increased with the amounts of sugars increased. The viscosity did not conform to crystallization rate which may related to crystal form or the hydroscopicity of sugars.(5) The crystallization properties, rheology and hardness of samples with Is and Ma were similar to Su. So, Is and Ma may acted as sucrose substitutes.Su, Is and Ma were added into chocolates(Su100, Su:Is 75:25, Su:Is 50:50, Su:Is 25:75, Is100, Su:Ma 75:25, Su:Is 50:50, Su:Is 25:75 and Ma100) at different ratio.(1) The sensory properties of chocolates did not have significant difference.(2) The viscosity and yield stress of chocolate paste with maltitol were bigger than the paste with isomaltulose which may be caused by the open loop structure of maltitol.(3) The microstructure of pastes with sucrose and isomaltulose were more compact which led to increased hardness.(4) The liquid oil migration rate for chocolate made from sugar, isomaltulose and maltitol were slower and their hardness were bigger than the other samples at storage temperature of 35℃. It indicated better heat resistant, which were related to microstructure of products and the molecular structure of sugars.Finally, the 9 chocolates were storaged at fluctuant and constant temperature seprately.(1) At the fluctuant storage temperature from 22 to 32℃ with 12 hr for one circle and the humidity controlled at 60%, chocolates(Su100, Su:Ma 75:25, Su:Ma 50:50, Su:Is 75:25) formed granular crystals after 8 weeks which indicated sucrose and maltitol were more sensitive to the humidity. Fresh chocolate formed β′ crystals, but turned to α, β′ and β crystals with time( polymorphism conversion). The offset temperature of chocolate surface was higher than the central indicated the separation of components in chocolate.(2) Except for Ma100, chocolates were slight bloom at constant temperature storage(25℃) after 8 weeks, but the chocolates still stayed at β′ crystal form. After 12 weeks, all the samples bloomed and formed mixed crystal form of β′ and β. But the offset temperature of chocolate surface was lower than central which induced by oil migration. In conclusion, Ma100 did not form granular crystals during fluctuant temperature storage and bloomed later than other samples during constant temperature storage. Therefore, Ma100 may act as one of the sucrose substitutes for chocolate. |
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