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Future of Cocoa Butter Research
20 Future of Cocoa Butter Research Nissim Garti1 and Neil R. Widlak2 1
Casali Institute of Applied Chemistry, The Hebrew University of Jerusalem, Jerusalem, Israel, and 2ADM Cocoa Division, Archer Daniels Midland Company, Milwaukee, Wisconsin, USA
Introduction Commercial Perspective Chocolate and confection are the largest commercial applications for cocoa butter. Expansion of global markets of both cocoa butter and compound coatings will have a strong influence on the future research of cocoa butter and other confectionery fats. Chocolate made with cocoa butter, established the “gold standard” for delivering what consumers desire from cacao. Government standards of identity for chocolates (dark, milk, white….) established in mature market countries regulate the composition of chocolate products to maintain a minimum standard of quality. While the market opportunities in mature confectionery markets (Europe and North America) may differ from market opportunities in developing confectionery markets (China, India, Korea, Russia, South America, as examples), both markets share similar technical challenges. Overcoming barriers to market growth due to technical gaps, and not the gaps themselves, will differentiate research priorities between the two markets.
Research Perspective Cocoa butter is a key ingredient in chocolate. Its chemical and physical structure, along with its crystallization behavior during manufacturing, in the presence of a complex mixture of the other ingredients, sensitive and exact narrow ranges for optimum cooling and storage, provide a great number of opportunities that impact product quality and conditions that produce substandard products that fail to meet minimum acceptable quality standards. Cocoa butter is a complex mixture of triglycerides that precipitate together in a very harmonic way into as many as six polymorphic structures, depending on the temperatures and physical conditions that are applied. Almost any possible parameter 497
498
N. Garti and N.R. Widlak
and variation in the process have been examined extensively by hundreds of laboratories around the world for generations. Research efforts were made to clarify and to better understand the characteristics of the suspension of the solids (sugars, cocoa solids, and coca butter particles) in the molten liquid continuous phase during the process. Hundreds of samples have been analyzed from every possible stage of the crystallization process and within the solid matrix upon cooling (supersaturation, nucleation, growth, and post-crystallization and aging). Many techniques were applied including melting behavior, microscopic observations, solid fat content (SFC), Infrared molecular vibrations, NMR, etc . In spite of all these efforts, many open questions remain unsolved and many are still in their infancy stage. The controversy on the total mechanism of the fat and chocolate behavior remains part of the scientists’ work, there are still quite obscure issues that need additional extensive research work. In this short chapter, we will stress some of the major issues and technical gaps to be filled through future research. In many of the studies, scientists deal with confectionary blends of fats together with cocoa butter—or even without it—and these mixtures behave quite differently. Therefore, it is often difficult to deduce much from these studies on the behavior of cocoa butter in pure chocolate. In addition, milk chocolate is quite different in composition from dark chocolate, and the existence of milk solids and milk fat greatly influence the behavior of cocoa butter during the crystallization process. Moreover, today’s compositions of chocolate enriched with cocoa solids dictate quite different cocoa butter behavior in the suspension and in the process of its crystallization. Any additional component in the chocolate filling has strong influence on the crystallization process and even more effect during the storage and aging stages. All these complex connections are still quite unclear. Additionally, the push for more healthy food products with reduced sugar levels and minimal saturated fatty acid levels concern most of the population in the modern society, Efforts to replace those ingredients at least in part by other ingredients (e.g., sweeteners, oils) greatly affect cocoa butter crystal behavior. Thus, any generalization and prediction of the behavior of cocoa butter in these complex environments is challenging. Yet a better understanding of the basics on simple chocolate will be very helpful in guiding development of technologies that will facilitate selecting the proper blend of compositions and processes conditions. Our specific recommendations for future research are concentrated on the behavior of cocoa butter in dark chocolate.
Future Work Recommendations Chocolate is delightful food that imparts joy and pleasure. To maintain chocolate’s delightful properties, it is essential to optimize its texture, mouth feel, mechanical
Future of Cocoa Butter Research
499
properties, organoleptic properties, etc. The product must be perfectly understood, balanced, and controlled through every stage of production and distribution. Chocolate and ‘chocolate-like’ products (coatings, fillings, etc) exhibit several major problems during shelf life, such as, fat and/or sugar bloom, textural changes, graininess associated with moisture intake, loss of gloss, oxidative instability, and more. Bloom is the most important phenomenon that needs better understanding and control. In the past, it was concluded fat bloom is related to solid-solid mediated polymorphic transitions of form V to form VI cocoa butter. Efforts were made to identify, characterize, and control this complex polymorphism. Various ways were suggested to crystallize the proper polymorph as a means to prevent, or retard, cocoa butter’s transformation to the most stable but undesirable form VI. Form VI was believed to be the primary contributor to graininess and bloom. Several physical controls and many emulsifiers were suggested and shown to achieve this aim. After years of extensive studies, and using new advance analytical and physical methods, it is now clear that the polymorphic transitions are the consequence of the bloom phenomena and not the cause for chocolate bloom. It seems clear that fat composition (internal composition of SOS, POP vs. SSO and PPO), types of ingredients (sugar, lecithin, etc), and size and shape of the particles, play a significant role in the nucleation and growth stage of the cocoa butter crystals during the cooling. Lack of understanding and control of these variables and the impact of cooling parameters can lead to suboptimal crystallization of the cocoa butter. Uncontrolled nucleation (too slow) and nonuniform crystal growth will lead to nonhomogeneous network structures with an increase of voids that help facilitate migration of liquid oil fractions to the surface of the chocolate. These fractions recrystallize forming an unappealing gray (or white) grainy layer of solid fat (bloom) on the surface of the chocolate. It seems the bloom can occur on chocolate in the preferred form V. Although formation of form V cocoa butter is generally an indication chocolate was produced under ideal conditions (optimum number of crystals, shape, melt profile, etc), it is not a guarantee the proper microstructure or homogeneous network structures were achieved. It is now postulated that chocolate with no (or minimum) bloom can be manufactured even with polymorph VI cocoa butter provided temperatures during conching and tempering are tightly controlled. Much work remains to prove this new hypothesis and working model. It is our hope that with the use of new and advanced techniques it will be possible, in the future, to verify these concepts and to make chocolate without any bloom (or with minimum bloom). The controversy between those that relate chocolate to polymorphism transformations and those that claim that it is the outcome of uncontrolled crystallization protocol still must be solved. Bloom occurs in many forms and many causes. The number of possible mechanisms are limited only by our imagination.
500
N. Garti and N.R. Widlak
Another very important future task is to control the texture of the chocolate to optimize the properties of cocoa butter blends in fillings and coatings composed of cocoa butter and other compounded fats. Texture and organoleptics are strongly dictated by the growth stage of the fat crystals. Crystallization rules and parameters must be applied to improve crystals network formation exhibited in texture of the final products. This is very important for small manufacturers that utilize a significant portion of rework in their compounded chocolates, coatings, and fillings. It is important to be able to change the crystallization conditions that can tolerate additional melting and resolidification. Maintaining consistent flow properties after melting and resolidification will require, in most cases, addition of small amounts of additives. Many of the “chocolate-like” products for confectionary applications are based on complex mixtures of cocoa butter and other fats such as milk fat, CBS, CBE, and/or palm kernel and hydrogenated palm kernel fats. These binary, tertiary (and greater) blends can form at certain compositions (ratios), under specific conditions, eutectic systems with unique properties (lower melting and slower crystallization behavior), and different physical characteristics (mechanical properties). And some blends may be totally incompatible, forming separated phases with unpredictable and inconsistent crystallization behaviors and subsequent physical properties. It is essential to work on understanding the structure correlations of fat mixtures to the eutectic formation and to distinguish them from diluted solid mixtures. Based on these properties it will be easier to design fats to meet specific properties. It is well documented that lecithin and other emulsifiers play a very significant role in determining the rheology properties of molten chocolate and in controlling other aspects such as nucleation rates. Lecithin is known to control and reduce plastic Cason viscosity and yield stress by coating sugar particles. The correlations between crystal sugar particles size, amount of sugar, and cocoa butter and the ratio between them is documented, but other properties related to blends of fats and internal fat compositions remain to be illustrated. It is essential to design more sophisticated experiments to correlate the structure of lecithin to its activity and to better understand why excess lecithin is increasing yield stress. Synergism between lecithin and other emulsifiers is also important in controlling physical properties of the chocolate. Very little significant work was carried out in understanding the difference in the activity (yields stress and plastic viscosity) of PGPR, Sorbian esters, YN, and lecithin. Very little is known on the uniqueness of each emulsifier in relation to the nucleation and growth rates (crystals shape and size). Even less is known on possible synergism or antagonism of these emulsifiers. New sources of lecithin from sunflower, canola, and corn have been recently introduced to replace soy lecithin. It is important to study and understand the prerequisites of the headgroups and tails of the lecithins to their activity in adsorption on sugar particles,
Future of Cocoa Butter Research
501
cocoa powder particles, and in the continuous bulk. So these new sources of lecithin can be optimized for commercial purposes. The search for other additives (monoglyceride lactate and monoglyceride citrate) that provide gloss, mechanical properties, and other rheological properties are in progress and will have to be further studied. It seems that better quality and healthier chocolate can be manufactured by incorporation of nutritional additives into the chocolate matrix of the cocoa butter. Vitamins, nutraceuticals, etc., can be now introduced into the chocolate without causing any severe taste and organoleptic alternations. The use of novel natural carriers will facilitate such improvements. And finally, chocolate is very sensitive to moisture, oxidation reactions, flavor loss, etc. Work must be done to guide manufactures on ways to minimize these phenomena. In conclusion, although much is known about cocoa butter and chocolate we have still long way to go until this complex yet simple product will be fully understood and optimized.
Casali Institute of Applied Chemistry, The Hebrew University of Jerusalem, Jerusalem, Israel, and 2ADM Cocoa Division, Archer Daniels Midland Company, Milwaukee, Wisconsin, USA
Introduction Commercial Perspective Chocolate and confection are the largest commercial applications for cocoa butter. Expansion of global markets of both cocoa butter and compound coatings will have a strong influence on the future research of cocoa butter and other confectionery fats. Chocolate made with cocoa butter, established the “gold standard” for delivering what consumers desire from cacao. Government standards of identity for chocolates (dark, milk, white….) established in mature market countries regulate the composition of chocolate products to maintain a minimum standard of quality. While the market opportunities in mature confectionery markets (Europe and North America) may differ from market opportunities in developing confectionery markets (China, India, Korea, Russia, South America, as examples), both markets share similar technical challenges. Overcoming barriers to market growth due to technical gaps, and not the gaps themselves, will differentiate research priorities between the two markets.
Research Perspective Cocoa butter is a key ingredient in chocolate. Its chemical and physical structure, along with its crystallization behavior during manufacturing, in the presence of a complex mixture of the other ingredients, sensitive and exact narrow ranges for optimum cooling and storage, provide a great number of opportunities that impact product quality and conditions that produce substandard products that fail to meet minimum acceptable quality standards. Cocoa butter is a complex mixture of triglycerides that precipitate together in a very harmonic way into as many as six polymorphic structures, depending on the temperatures and physical conditions that are applied. Almost any possible parameter 497
498
N. Garti and N.R. Widlak
and variation in the process have been examined extensively by hundreds of laboratories around the world for generations. Research efforts were made to clarify and to better understand the characteristics of the suspension of the solids (sugars, cocoa solids, and coca butter particles) in the molten liquid continuous phase during the process. Hundreds of samples have been analyzed from every possible stage of the crystallization process and within the solid matrix upon cooling (supersaturation, nucleation, growth, and post-crystallization and aging). Many techniques were applied including melting behavior, microscopic observations, solid fat content (SFC), Infrared molecular vibrations, NMR, etc . In spite of all these efforts, many open questions remain unsolved and many are still in their infancy stage. The controversy on the total mechanism of the fat and chocolate behavior remains part of the scientists’ work, there are still quite obscure issues that need additional extensive research work. In this short chapter, we will stress some of the major issues and technical gaps to be filled through future research. In many of the studies, scientists deal with confectionary blends of fats together with cocoa butter—or even without it—and these mixtures behave quite differently. Therefore, it is often difficult to deduce much from these studies on the behavior of cocoa butter in pure chocolate. In addition, milk chocolate is quite different in composition from dark chocolate, and the existence of milk solids and milk fat greatly influence the behavior of cocoa butter during the crystallization process. Moreover, today’s compositions of chocolate enriched with cocoa solids dictate quite different cocoa butter behavior in the suspension and in the process of its crystallization. Any additional component in the chocolate filling has strong influence on the crystallization process and even more effect during the storage and aging stages. All these complex connections are still quite unclear. Additionally, the push for more healthy food products with reduced sugar levels and minimal saturated fatty acid levels concern most of the population in the modern society, Efforts to replace those ingredients at least in part by other ingredients (e.g., sweeteners, oils) greatly affect cocoa butter crystal behavior. Thus, any generalization and prediction of the behavior of cocoa butter in these complex environments is challenging. Yet a better understanding of the basics on simple chocolate will be very helpful in guiding development of technologies that will facilitate selecting the proper blend of compositions and processes conditions. Our specific recommendations for future research are concentrated on the behavior of cocoa butter in dark chocolate.
Future Work Recommendations Chocolate is delightful food that imparts joy and pleasure. To maintain chocolate’s delightful properties, it is essential to optimize its texture, mouth feel, mechanical
Future of Cocoa Butter Research
499
properties, organoleptic properties, etc. The product must be perfectly understood, balanced, and controlled through every stage of production and distribution. Chocolate and ‘chocolate-like’ products (coatings, fillings, etc) exhibit several major problems during shelf life, such as, fat and/or sugar bloom, textural changes, graininess associated with moisture intake, loss of gloss, oxidative instability, and more. Bloom is the most important phenomenon that needs better understanding and control. In the past, it was concluded fat bloom is related to solid-solid mediated polymorphic transitions of form V to form VI cocoa butter. Efforts were made to identify, characterize, and control this complex polymorphism. Various ways were suggested to crystallize the proper polymorph as a means to prevent, or retard, cocoa butter’s transformation to the most stable but undesirable form VI. Form VI was believed to be the primary contributor to graininess and bloom. Several physical controls and many emulsifiers were suggested and shown to achieve this aim. After years of extensive studies, and using new advance analytical and physical methods, it is now clear that the polymorphic transitions are the consequence of the bloom phenomena and not the cause for chocolate bloom. It seems clear that fat composition (internal composition of SOS, POP vs. SSO and PPO), types of ingredients (sugar, lecithin, etc), and size and shape of the particles, play a significant role in the nucleation and growth stage of the cocoa butter crystals during the cooling. Lack of understanding and control of these variables and the impact of cooling parameters can lead to suboptimal crystallization of the cocoa butter. Uncontrolled nucleation (too slow) and nonuniform crystal growth will lead to nonhomogeneous network structures with an increase of voids that help facilitate migration of liquid oil fractions to the surface of the chocolate. These fractions recrystallize forming an unappealing gray (or white) grainy layer of solid fat (bloom) on the surface of the chocolate. It seems the bloom can occur on chocolate in the preferred form V. Although formation of form V cocoa butter is generally an indication chocolate was produced under ideal conditions (optimum number of crystals, shape, melt profile, etc), it is not a guarantee the proper microstructure or homogeneous network structures were achieved. It is now postulated that chocolate with no (or minimum) bloom can be manufactured even with polymorph VI cocoa butter provided temperatures during conching and tempering are tightly controlled. Much work remains to prove this new hypothesis and working model. It is our hope that with the use of new and advanced techniques it will be possible, in the future, to verify these concepts and to make chocolate without any bloom (or with minimum bloom). The controversy between those that relate chocolate to polymorphism transformations and those that claim that it is the outcome of uncontrolled crystallization protocol still must be solved. Bloom occurs in many forms and many causes. The number of possible mechanisms are limited only by our imagination.
500
N. Garti and N.R. Widlak
Another very important future task is to control the texture of the chocolate to optimize the properties of cocoa butter blends in fillings and coatings composed of cocoa butter and other compounded fats. Texture and organoleptics are strongly dictated by the growth stage of the fat crystals. Crystallization rules and parameters must be applied to improve crystals network formation exhibited in texture of the final products. This is very important for small manufacturers that utilize a significant portion of rework in their compounded chocolates, coatings, and fillings. It is important to be able to change the crystallization conditions that can tolerate additional melting and resolidification. Maintaining consistent flow properties after melting and resolidification will require, in most cases, addition of small amounts of additives. Many of the “chocolate-like” products for confectionary applications are based on complex mixtures of cocoa butter and other fats such as milk fat, CBS, CBE, and/or palm kernel and hydrogenated palm kernel fats. These binary, tertiary (and greater) blends can form at certain compositions (ratios), under specific conditions, eutectic systems with unique properties (lower melting and slower crystallization behavior), and different physical characteristics (mechanical properties). And some blends may be totally incompatible, forming separated phases with unpredictable and inconsistent crystallization behaviors and subsequent physical properties. It is essential to work on understanding the structure correlations of fat mixtures to the eutectic formation and to distinguish them from diluted solid mixtures. Based on these properties it will be easier to design fats to meet specific properties. It is well documented that lecithin and other emulsifiers play a very significant role in determining the rheology properties of molten chocolate and in controlling other aspects such as nucleation rates. Lecithin is known to control and reduce plastic Cason viscosity and yield stress by coating sugar particles. The correlations between crystal sugar particles size, amount of sugar, and cocoa butter and the ratio between them is documented, but other properties related to blends of fats and internal fat compositions remain to be illustrated. It is essential to design more sophisticated experiments to correlate the structure of lecithin to its activity and to better understand why excess lecithin is increasing yield stress. Synergism between lecithin and other emulsifiers is also important in controlling physical properties of the chocolate. Very little significant work was carried out in understanding the difference in the activity (yields stress and plastic viscosity) of PGPR, Sorbian esters, YN, and lecithin. Very little is known on the uniqueness of each emulsifier in relation to the nucleation and growth rates (crystals shape and size). Even less is known on possible synergism or antagonism of these emulsifiers. New sources of lecithin from sunflower, canola, and corn have been recently introduced to replace soy lecithin. It is important to study and understand the prerequisites of the headgroups and tails of the lecithins to their activity in adsorption on sugar particles,
Future of Cocoa Butter Research
501
cocoa powder particles, and in the continuous bulk. So these new sources of lecithin can be optimized for commercial purposes. The search for other additives (monoglyceride lactate and monoglyceride citrate) that provide gloss, mechanical properties, and other rheological properties are in progress and will have to be further studied. It seems that better quality and healthier chocolate can be manufactured by incorporation of nutritional additives into the chocolate matrix of the cocoa butter. Vitamins, nutraceuticals, etc., can be now introduced into the chocolate without causing any severe taste and organoleptic alternations. The use of novel natural carriers will facilitate such improvements. And finally, chocolate is very sensitive to moisture, oxidation reactions, flavor loss, etc. Work must be done to guide manufactures on ways to minimize these phenomena. In conclusion, although much is known about cocoa butter and chocolate we have still long way to go until this complex yet simple product will be fully understood and optimized.