Colloid and surface phenomena aspects of Chocolate Chin Kok Ooi Teck Yu Sia Anshu Verma Shushan Munshi CE 457/527

Introduction Chocolates has a wide variety and found in common places Has to meet consumer need Types of chocolates Good for health

Marketing Designing chocolates Energy Size Price Efficiency Legal requirements Advertisement

Components and Compositions The ingredients of chocolate Cocoa, cocoa butter, milk and sugar Additional ingredients Lecithin(emulsifier) and flavoring agents

Cocoa and Cocoa butter Both are obtained from the seeds of ‘Theobroma Cocoa’. ‘Cocoa beans’ grow in pods.

Cocoa and Cocoa butter General compositions of cocoa bean CompositionPer centCompositionPer cent Moisture Cocoa Red Fat Ash Albuminoids Astringent matters Cellulose Cane sugar Alkaloids Starch

Cocoa and Cocoa butter Alkaloids Theobromine and caffeine Theobromine – 3,7-dimethyl-xanthine Caffeine – 1,3,7-trimethyl-xanthine ‘Cocoa red’– is formed during the drying of the beans by the action of enzymes on the glucosides.

Cocoa and Cocoa butter Special characteristics of cocoa butter: The melting point of cocoa butter is between 32°C and 36°C. In spite of low melting point, cocoa butter is hard and brittle at normal room temperature. Help to prevent ‘fat bloom’

Milk Compositions of cow milk ComponentContent (% w/w) Water87.3 Proteins (caseins & whey proteins)3.3 Fat3.9 Lactose4.6 Minerals0.65 Others (vitamins, organic acids, etc)0.32

Milk Compositions of lipids in milk Component Content (% of total fat) Triglycerides96-99 Diglycerides Monoglycerides Free fatty acids Phospholipids Sterols Cerebosides

Sugar Sucrose Combination of ‘glucose’ and ‘fructose’ Sugar bloom

Chocolate manufacturing process Chocolate -coated goods Chocolate manufacture Press Cake Breaking Grinding Sifting Cocoa Powder Enrobing Plain or Milk Chocolate Fermented and Dried Beans Cleaning Roasting Breaking and Winnowing NibShellNib-Shell Mixtures Germ Separation Germ-free Nib Milling Cacoa-Mass (Chocolate liquor ) Cocoa manufacture AlkalizationAddition of Sugar, Flavor, Milk etc. and Cocoa Butter Removal of excess moisture Mixing Fat Pressing Cocoa Butter Refining Conching Tempering Molding

Major function of these processes 1. Fermenting and drying Removal of adhering pulp Removal of moisture 2. Roasting Critical for flavor development 3. Winnowing Removal of seed coat Size selection of nibs 4. Milling Release of fat from cells

Major function of these processes 5. Cocoa manufacture Production of additional fat (cocoa butter) 6. Refining Grinding of sugar particles 7. Conching Reduction in viscosity 8. Tempering Pre-crystallization process

Chocolate flow properties Chocolate exhibits non-Newtonian properties For Newtonian fluid: For Bingham fluid: 123 D oo  Different types of rheogram: (1) Newtonian; (2) Bingham; (3) pseudoplastic (e.g. chocolate)

Steiner’s model for chocolate - adapted from Casson’s model for printer’s ink where r, R are the inner and outer radius of the cylinder respectively,  is the angular velocity, D N is the shear rate at the inner cylinder.  CA = (1/slope) 2 = (1/K 1 ) 2 = plastic viscosity according to Casson;  CA = (b/2) 2 =K 0 2 = yield value according to Casson

b=2K 0 Casson rheogram according to OICC

Factors affecting the flow properties of chocolate Fat content: Influence of fat content on Casson parameters of two milk chocolates with 0.25% lecithin.(1) Fine chocolate with 5.7% particles > 20  m; (2) moderaltely coarse chocolate with 16% particles > 20  m.

Lecithin and other emulsifiers: immediate reduction in viscosity Moisture content: increases viscosity Particle size distribution: Influence of fineness on Casson parameters of two milk chocolates with 0.25% lecithin. (1) 30% fat; (2) 32% fat

Temper: increases viscosity Thixotropy: decreases viscosity Vibration: decreases viscosity Temperature: Influence of temperature on Casson parameters of two milk chocolates. (1) 34% fat, without lecithin; (2) 30% fat, 0.15% lecithin

Surface- active substances in chocolate manufacturing Lecithin is the chief surfactant used The other surfactants are: ammonium phosphatides (YN) polyglycerol polyricinoleate (PGPR) The chief function are: reduce viscosity Reduce thickening due to moisture and temperature Modify the setting behavior of fat phase Flow characteristics of plain chocolate with added surface-active lipids Addition Casson plastic viscosity (poise) Casson yield value (dynes/cm 2 ) 0.3% soy lecithin 0.3% YN 0.3% sucrose dipalmitite 0.3% PGPR 0.8% PGPR

Influence of soya lecithin addition on Casson parameters of two dark chocolates. (1) 33.5% fat, 1.1% water; (2) 39.5% fat, 0.8% water Viscosity reduction of dark chocolate by soya lecithin and by synthetic active lipids. Apparent viscosity determined at shear rate 15 s -1 and 50 o C; initial apparent viscosity before addition: 19.5 Pa s or 195 poises. (1) Soya lecithin; (2) phospholipid YN; (3) sucrose dipalmitate; (4) polyglyceryl polyricinoleate, PGPR

Mechanism of viscosity reduction by lecithin 1. a monomolecular film is formed on the surface of the non-fatty particles by surfactant molecules. 2. reduction in internal friction by promoting the coating of sugar and cocoa solids by fatty medium. 3. increase in the amount of ‘free’ cocoa butter in the dispersion medium by displacement from the surface of solids. 4. prevention of agglomeration of sugar particles and cocoa particles by break down of any lattice-type structure between them. 5. absorption of moisture

Effect of lecithin on the stability of emulsions Lecithin molecule at interface between water and oil oil-in- water water- in-oil Types of emulsions Oil CreamingSedimentatio n CoalescenceSeparatio n Creaming of emulsions: four phases

Chocolate – an emulsion of hydrophilic sugar and lipophilic cocoa particles in a continuous fat medium Molecular structure of main phospholipids found in lecithin Phospholipid structure at the interface of an emulsion

PACKAGING AND STORAGE METHOD OF WRAPPING: MOLDED CHOCOLATE BLOCKS. CHOCOLATE COUNTLINES. BOXED CHOCOLATE. TWRIST WRAPPING. MATERIAL FOR PACKAGING: ALUMINUM FOIL. REGENERATED CELLULOSE FILM (RCF). PLASTIC FILM.

MOLDED CHOCOLATE BLOCK Protection against dirt, moisture and taint. It is more economical. Wide surface for labeling.

CHOCOLATE COUNTLINES Normally wrap in “pillow pack” By heavy-backed foil, waxed paper or glassine. Protection against moisture vapor and taint.

BOXED CHOCOLATE Usually, a thin layer of greaseproof film includes at the inner fitment. It prevents crushing of sweetness and cushioning. Protect against handling dirt.

TWRIST WRAPPING In “double end fantail” form. By aluminum foil, backed and unbacked plain sliver, colored and printed film. Protection against dirt and taint.

ALUMINUM FOIL Best barrier for water vapor and gas transmission. Thickness range from 7-12  m for pure aluminum. Combination with special alloy for extra strength. Thickness range 7-8  m.

REGENERATED CELLULOSE FLIM (RCF) Packaging in flexible form. Usually coated or giving other treatments. Protection against moisture vapor and taint. PVDC for extra protection such as electrostatics. An advantage for tear strip product.

PLASTIC FILM Three different forms: polyethylene, polyvinyl chloride and polyester. Available in film or coating purposes. Protection against moisture, gas and ultraviolet.