Appendix I Special Methods of Analysis There are many publications available on food analysis and some of these give details of methods that can be applied to confectionery. All chocolate and confectionery manufacturers should be acquainted with The International Office of Cocoa and Chocolate (IOCC), 172, Avenue de Cortenbergh, 1040 Bruxelles, Belgium; and The International Sugar Confectionery Manufacturers' Association (ISCMA), 194, rue de Rivoli, 75001 Paris, France. Both of these organizations convene a general assembly every five years and monitor all aspects of the industry. The IOCC publishes "official" methods of analysis that are regu­ larly updated and accepted internationally as reference methods. Periodic bulletins are also published that describe the activities of these organizations. Analytical methods special to the industry are described in some manufacturers' brochures. Trade journals frequently contain articles concerning the application of these methods and the significance of the results obtained. Analytical procedures were mentioned when necessary in earlier chapters. Some of the following methods are repeated from the second edition of this book with updated insertions where considered necessary. PARTICLE-SIZE DETERMINATION The particle size of cocoa, chocolate, and confectionery products is a fundamental property. It has importance both organoleptically and in manufacturing processes. In chocolate, the smoothness on the palate is related to the absence of coarse particles of sugar and cocoa material. Fondant creme is similar. In cocoa powder, the fineness of particles is related to suspension in a liquid, for example, milk and water. Particle size distribution-that is, the proportion of particles of different sizes-is important economically. 825 826 CHOCOLATE, COCOA, AND CONFECTIONERY In chocolate, the use of cocoa butter to obtain a given fluidity is linked with the proportion of very fine particles. Because of greater total surface area, these require more cocoa butter to "wet" them. Particle Variation The type of particle in the various chocolate and confectionery products varies considerably in appearance, shape and size. In cocoa liquor, the particles, when examined under the micros­ cope, are irregular but without sharp edges, and range in color from a transparent light brown through reddish brown to opaque dark brown. In dark chocolate, the cocoa particles are similar but less con­ spicuous because of the presence of sugar. The sugar crystals are readily visible as clear plates usually of irregular shape because they have been shattered during the grinding process. Milk chocolate contains cocoa particles, sugar crystals, and milk solids particles, but if milk chocolate is made from crumb, only one type of particle is visible. These are aggregates of milk solids, sugar, and cocoa liquor that have been formed during the crumb process by the final crystallization and drying processes, and these con­ glomerates are broken down in the chocolate-refining process but not separated into their constituent particles. These aggregates are a light-brown color and in some of them sugar crystals and cocoa particles can be seen cemented together. In the manufacture of milk crumb, it is important to ensure that, at the crystallizing stage, the sugar crystals formed are small and in the microscopic examination the aggregates are separated by the use of chemical mounting liquid so that the sugar crystals can be measured independently. In a milk chocolate made from milk powder, the milk powder particles are clearly visible as separate, pale-yellow, irregular shapes. In fondant creme the visible particles are sugar crystals only and as most of these have grown out of a syrup without much hindrance they are mainly cubic and present a very regular appearance under the microscope. There is a difference between a freshly prepared "base" fondant and a fondant that has been remelted and cast into molding starch. The latter has a proportion of large crystals due to growth at the remelting and casting stage with a background of small crystals as present in the "base fondant." Large crystals may also be present in "base" fondant due to bad beating or cooling during manufacture, and this is discussed under "Fondant Manufacture." The size distribution APPENDIX. I: SPECIAL METHODS OF ANALYSIS 827 TABLE A.1. PARTICLE SIZE OF CONFECTIONERY PRODUCTS Base product Manufactued product Particle size Cocoa liquor Cocoa particle Superfine cocoa or 100 11m 0.0040 in. size chocolate manufacture Drinking cocoas 200 11m 0.0080 in. Chocolate-dark Cocoa particle Fine eating chocolate or 30-50 11m 0.0012-0.0020 in. size high-quality covering Average covering chocolate 75-100 11m 0.0030-0.0040 in. Sugar crystal Fine eating chocolate or 25-35 11m 0.0010-0.0014 in. size high-quality covering Average covering chocolate 50 11m 0.0020 in. Chocolate-milk Crumb aggregate Fine eating chocolate 35 11m 0.0014 in. size Average covering chocolate 50 11m 0.0020 in. Fondant creme "Base" fondant from machine 10-15 11m 0.0004-0.0006 in. Fondant after casting 25-30 11m 0.0010-0.0012 in. (assortments ) of the sugar crystals in fondant has an important bearing on smoothness on the palate. An approximate guide to the particle sizes that may be expected in these products is shown in Table A.1. The figures are "averages of the larger particles." It must be understood that these figures cannot be compared with micrometer readings (see later). Methods of Determination Methods of particle size determination may be summarized: 1. Micrometer and modifications. 2. Microscope, including computer scanning. 3. Wet sieving, using either water or petroleum solvent. 4. Sedimentation. 5. Electronic counting, Coulter counter, laser beam. Micrometer Over the years, the standard engineer's micrometer has been used more than any other instrument for determining the fineness of chocolate paste from the refining rolls. 828 CHOCOLATE, COCOA, AND CONFECTIONERY The method utilizes a small amount of the refiner paste mixed with an equal amount of a liquid oil. One drop of the mixture is applied to the lower face of the micrometer jaws and the jaws closed, using the spring-loaded control, until movement ceases. The value is read on the micrometer scale. It is a "figure" only and does not represent the size of any particles or take their shape into account. Isolated large sugar crystals are most likely crushed. The result, in the hands of a skilled person, is meaningful but really represents the thickness of a layer of particles compressed between the jaws of the micrometer using a standard force. The weakness of the instrument is in the variability of micrometers, the people using them, the size of the sample, and the fact that there is no precise information about the actual size of the particles or the proportion of the different sizes. An improvement of recent years is the electronic micrometer in which the jaws are larger in area and are closed under precise pressure. The reading is digital but the figure obtained is in the same category. The value of the micrometer method as a means of monitoring the refining process led to research on how its value might be improved. Metriscope This apparatus was devised by Lockwood (1958) of the Cadbury Research Laboratories, and is an ingenious mechanical device for measuring the efficiency of chocolate or liquor grinding. The method is really a refinement of the micrometer method and uses a much larger sample for test. Further details of the apparatus are avail­ able from: Confectionery Division Research Laboratories, Cadbury/Schweppes Ltd., Bournville, Birmingham, England. The principle of the method is the support of a tapered steel "stopper" in a socket by a film of the chocolate or liquor to be measured for fineness. The stopper and socket have a taper of exactly one in ten and the trapped film of cocoa and sugar particles causes the stopper to be raised twenty times the thickness of the film by reason of the taper slope. The protrusion of the stopper is measured accurately by micrometer and this can be related to the average size of the larger particles in the chocolate or liquor. The Metriscope is fully automatic and will give several repeat readings in a short space of time. The machine uses a 10z (28.4 g) sample dispersed in 5 oz of lecithinated cocoa butter and this gives a APPENDIX I: SPECIAL METHODS OF ANALYSIS 829 Sock~t Chocolate Fig. A.1 . Principle of the Metriscope much more representative result than that obtained from the very small sample taken from micrometer assessment. Figure A1 is a diagram of the stopper and socket and Figs. A2 and A3 are illustrations of the machine in use in a number of factories. Fig. A.2. Metriscope--Front Fig. A.3. Metriscope--Rear 830 CHOCOLATE, COCOA, AND CONFECTIONERY Method of Determination Materials rwrmally tested. Paste from refiners, chocolate from conche, finished chocolate, liquor. Apparatus required. Metriscope, electric Vibro-mixer, 5-fl-oz mea­ sure (for cocoa butter), l-oz dispenser (for refiner paste), stainless­ steel container (approx 10 fl oz capacity), palate knife, oven at 45°C (113°F). Cocoa Butter for Dispersion This is cocoa butter in which is dissolved 0.25 percent of soya lecithin. Preparation of Sample for Testing One ounce of refiner paste is measured out using the "dispenser" and the plug of chocolate placed on the perforated disk of the Vibro-mixer and mixed for 1 min with 5 fl oz of the cocoa butter containing 0.25 percent lecithin. The sample is then ready for immediate test. The other materials tested are usually weighted into small beakers, mixed with a small amount of the 5 fl oz cocoa butter using the palate knife, and then transferred to the stainless-steel container for mixing. Operation of the Metriscope The instrument heater is switched on for 2 hr before using the Metriscope to ensure that the instrument will operate on liquid cocoa butter.