Preparation Of Mango Kernel Fat-based Heat Stable Chocolate Fats And Their Bloom Resistance

Fats and oils are the most important ingredients of chocolates,which are responsible for their structural integrity and quality.Cocoa butter?CB?is the primary fat in typical chocolates.However,the global development of chocolate has been currently hampered as CB has met a series of problems,especially softening properties and fat bloom in tropic/subtropical areas?or in summer time?.Also,the huge market demand of chocolates results in a shortage of CB resource and its rise in price.It is,therefore,necessary to manufacture chocolates with high thermal and bloom stabilities using a suitable cocoa butter alternative,i.e.,cocoa butter improver?CBI?,who is still solid at hot weather while CB is completely melted at this temperature.In the present study,mango?Mangifera indica L.?kernel,a new resource from the byproduct of the second largest produced tropical fruit,was exploited by extracting its fat and followed by appropriating processes to produce CBI.Heat stable chocolate fats were then made by mixing CBI and CB,and their positive effects in relation to thermal and bloom stabilities on dark chocolates were further analyzed and evaluated.First of all,mango kernel fats?MKFs?from 15 mango varieties cultivated in China were extracted using hexane.Their characteristics,e.g.,iodine values,slip melting points,compositions of lipid,fatty acid,triacylglycerol and micronutrients?mainly including tocopherol,sterol and squalene?and oxidative stabilities,were systematically analyzed to ascertain their differences in compositions and properties.MKF contained 30.0%-55.4%of StOSt?St,stearic acid;O,oleic acid;as known as 1,3-distearoyl-2-oleoyl-glycerol?,which indicated that this fat is an ideal CBI-source.However,17.7%-47.4%of polyunsaturated fatty acid-triacylglycerols such as StOO,POO?P,palmitic acid?and OOO,1.8%-4.2%of diacylglycerols and 1.9%-6.6%of free fatty acids were found in MKFs,which will result in negative effects on fat crystallization,thus suggesting further refining and fractionation were needed to remove these interfering components and to make the fat meet edible standards.Hierarchical cluster analysis was then carried out to select suitable mangoes based on the abovementioned indices.It is concluded that Huangpi,Biantao,Yuexi,Chiin Hwang and Ivory were the preferred varieties with abundant resources which could be used in industrial production of CBIs.Then,solvent fractionation was carried out to prepare CBI with less amounts of polyunsaturated fatty acid-triacylglycerols and diacylglycerols.However,traditional solvents are characterized as low selectivity?e.g.,hexane?or limited regulations?e.g.,acetone?.Selection of different solvents for fractionation is worthy of reconsideration in the present study.The MKF third stearin,as an ideal CBI,was successfully prepared by developing three-stage fractionation using a novel solvent,2-methylpentane.Multiple variance and linear regression model analyses showed a significant correlation between slip melting point change of the third stearin and polarity?Log P?of the used fractionation solvent.As supposed,interfering components like diacylglycerols?from 4.0%to 0.8%?,and StOO,POO and OOO?from 34.8%to 9.7%?in the third stearin decreased significantly after fractionation,while levels of StOSt and sn-2 oleic acid increased from 44.7%to 69.2%and from 81.5%to 89.1%,respectively.The yield of the third stearin for this fractionation technique was 47%-51%.The third stearin showed excellent thermal stabilities in terms of slip melting point,solid fat content and melting/crystallization behaviors compared to CB.It is,therefore,recommended as an ideal CBI.In addition,acceptable compatibility was obtained from binary mixtures with 10%-30%CBI in CB at room temperature.However,no significant improvement on heat stabilities were observed in final chocolate products manufactured from these chocolate fats.Next,more than 30%CBI in CB might lead to poor compatibility and low bloom stabilities.That is,the application in the manufacture of chocolates was limited due to unsatisfactory eutectic effects,which resulted from the crystallization difference of the two initial fats.POP is theoretically suggested to be mixed with the MKF third stearin?CBI?and CB to improve compatibility of the fat mixture.Hard palm-mid fraction?a high-quality POP-rich fat?,the third stearin from MKF and CB were then mixed to produce hard chocolate fats by using physical blending and enzymatic interesterification.Optimal physical-blending fat prepared from 10%hard palm-mid fraction,55%the third stearin and 35%CB showed accepted compatibility.It contained 60.9%StOSt,21.1%POSt and 9.5%POP.However,the compatibility was reduced with more addition of POP-rich fats,but it could be improved by enzymatic interesterification.Optimal interesterified fat was then enzymatically synthesized from 20%hard palm-mid fraction,60%the third stearin and 20%CB.It shared similar triacylglycerol composition to physical-blending fat:55.7%-59.0%StOSt,23.4%-23.8%POSt and 8.2%-11.1%POP.Both physical-blending fat and interesterified fat exhibited significantly higher thermal stabilities in comparison to CB,and they could melt completely at body temperature?about 37??.Furthermore,?₂ type was found in the stabilized fats,which was similar to that of CB.However,crystals of physical-blending fat and interesterified fat tended to become plate-like crystals at room temperature,whereas CB showed spherulitic growth.The plate-like property might enhance the densities of chocolate structures,improving tempering efficiency and preventing fat bloom.Finally,MKF-based dark chocolates were prepared using the two hard chocolate fats?physical-blending fat and interesterified fat?and improved tempering technique,to extend their application in chocolate products.Two MKF-based chocolates and CB-chocolate?the control?were made in this term.Both MKF-based chocolates showed higher thermal stabilities compared to the control,CB-chocolate,based on the analyses of shape retention index,hardness,and melting behavior.In particular,MKF-based chocolates became runny at 37?,and therefore could avoid leaving waxiness in the mouth,but CB-chocolate completely lost its shape at 32?.Bloom tests showed that CB-chocolate was covered with white-round-shaped stripe at around 5th day,while only slight bloom was observed in the two MKF-based chocolates at about 60th day,indicating that bloom stabilities were significantly improved?55 days-delay?by introducing the MKF third stearin.The improvements were attributed to the MKF-based chocolate fats based on the analyses of microstructures,triacylglycerol compositions and crystalline types.More specifically,high StOSt levels,optimized triacylglycerol compositions and plate-like growth of both MKF-based chocolate fats contributed to enhancing the densities of chocolate structures,which could prevent bloom from fat meltdown at hot temperature,and further recrystallization and polymorphic transformation at room temperature.In conclusion,MKF is an excellent natural fat in the manufacture of CBI as well as heat stable chocolate fats by new solvent fractionation,physical blending or enzymatic interesterification.The prepared fats significantly improved the heat and bloom stabilities of final dark chocolates by improved tempering process,which are suitable for the future use in hot weather-regions.