The hand-book of household scienceA popular account of heat, light, air, aliment, and cleansing, in their scientific principles and domestic . cavi-ties of which are seen small dropsof the aromatic volatile oil of cof-fee. This appearance is shown in(Fig. 104). If now we place afragment or section of roasted cof-fee under a magnifier, it will beobserved that these drops of oilin the cells are no longer visible(Fig. 105). They have, in part,been dissipated by the heat, andin part, become more generally dif-fused throughout the mass of theseed; a portion being driven to thesurface.
The hand-book of household scienceA popular account of heat, light, air, aliment, and cleansing, in their scientific principles and domestic . cavi-ties of which are seen small dropsof the aromatic volatile oil of cof-fee. This appearance is shown in(Fig. 104). If now we place afragment or section of roasted cof-fee under a magnifier, it will beobserved that these drops of oilin the cells are no longer visible(Fig. 105). They have, in part,been dissipated by the heat, andin part, become more generally dif-fused throughout the mass of theseed; a portion being driven to thesurface. It is obvious, that roastingproduces certain chemical changesin coffee, which alter its flavor andtaste, and bring out the peculiarand highly esteemed aroma forwhich this beverage is distinguish-ed. Johnston states that the peculiar aromatic principle which givesflavor to coffee, exists in extremely minute quantity, (one part in fiftythousand,) and is generated in the roasting process. The heat also Appearance of unroasted coffee-berriesmagnified, showin? tlie size and form oftlie cells, and the drops of oil contained intheir cavities. Fi&. Appearance of roasted coffee berries. 206 COMMON B£VJ£IiAG£S. sets a portion of tbe cafein free from its combination with tannicacid, and ovapoi-ates it. The temperature is sufficiently high to de-compose the sugar, and change it to brown, burnt sugar, or darkens in color during roasting, swells much in bulk, andloses a considerable portion of its weight, by evaporation of its waterand loss of other constituents. Coffee roasted to a reddish brown,loses in weight, 16 per cent., and gains in bulk, 30 per cent. To achestnut hrown, it loses 20 per cent, in weight, and gains 50 inbulk. To a dark Irotcn, it loses 25 per cent, of weight, and gains50 in bulk. 563. nints concerning the Boasting Processi—The roasting of coffeeis an operation of considerable nicety; more, perhaps, dependingupon it than upon tlie variety of th
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Keywords: ., bookcentury1800, bookdecade1860, booksubjectfood, booksubjecthome
