Influence of lecithin and PGPR in the microstructuration process of dark chocolates

Author(s)

Valter Luís Zuliani Stroppa

• Document type: Master's Dissertation
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Faculdade de Engenharia Química
• Defense date: 2011-11-07

Examining board members

Theo Guenter Kieckbusch; Lireny Aparecida Guaraldo Gonçalves; Priscilla Efraim

• Advisor: Valdecir Luccas; Theo Guenter Kieckbusch

Abstract

Chocolates are confectionary products composed by a lipid phase based mainly on cocoa butter that contains cocoa mass, sugar, emulsifiers and eventually milk solids and aromas. Physical characteristics of chocolates like gloss, hardness, melting at mouth temperature and thermal stability result from the crystalline structuration accomplished by the fat phase. The triacylglycerols in cocoa butter can be organized in up to six different polymorphs but only two of them are stable and therefore yield better quality products. The addition of emulsifiers to chocolates intends to improve the rheological behavior during processing by the reduction of the interfacial tension between the fat phase and the solid particles. The emulsifiers promote the coating of the solid particles by an oily layer, lubricating the interfaces that then can serve as active elements for nucleation. This work examines the effects of the addition of the two most used emulsifiers in chocolate, namely soy lecithin and PGPR (polyglycerol polyricinolate) in the crystalline structuration of chocolates. Chocolates with different contents of the two emulsifiers were produced, following a 22 complete factorial rotational design. The lecithin level varied from 0.08 to 0.92% and the PRPG content from 0.02 to 0.58%. The influence of the additives was characterized by rheometry (determination of the flowing parameters), nuclear magnetic resonance (monitoring the crystallization kinetics), Temperindex (pre-crystallization level quantification), and snap test (structural resistance). The values of Casson's plastic viscosity of the chocolates, measured at 40ºC, varied from 1.4 to 5.9 Pa.s while the yield value ranged between zero to 34 Pa. The kinetic parameters evaluated from crystallization isotherms at 15ºC modeled by the Avrami equation resulted in the exponent n varying from 2.598 to 2.956 and k parameters between 5.15 10-5 min-n and 2.85 10-5 min-n when the different amount of emulsifiers were used. These effects are associated to the ability of lecithin to enlarge the crystal volume and to the nucleating potential of PGPR (AU)

• FAPESP's process: 09/04925-3 - Study of the Influence of Emulsifiers on the Microestruturation of Dark Chocolatte.
• Grantee: Valter Luís Zuliani Stroppa
• Support Opportunities: Scholarships in Brazil - Master