Foods : their origin, composition and manufacture / by William Tibbles.

  • Tibbles, William, 1859-1928.
Date:
1912
Catalogue details

Licence: In copyright

Credit: Foods : their origin, composition and manufacture / by William Tibbles. Source: Wellcome Collection.

Provider: This material has been provided by The University of Leeds Library. The original may be consulted at The University of Leeds Library.

    53/972 page 41
    in the urine, and, according to Fischer, the organism protects itself against the poisonous action of camphor and chloral by this mode of deahng with them. ^ Levulose, Fructose, or fruit-sugar, like dextrose, is widely dis- tributed throughout the vegetable kuagdom, frequently in company with it, especially m fruit and honey. When pure, levulose forms shining needles or crystals of the rhombic system, but it crystalhzes with difficulty. It is soluble in water and boiling alcohol, but is barely soluble in cold alchool. It ferments with yeast, and yields alcohol, but more slowly than dextrose. It gives the same reactions as dextrose, but does not reduce Fehling's solution to quite the same extent. Levulose may be dried in a vacuum at 50° C. without change ; it then has the composition C^U^p^. It is levo-gyrate. The specific rotatory power of a 20 per cent, solution is - 71 4° at a temperature of 20° C. Alcohol reduces the rotatory power of levulose, just as it slightly augments that of dextrose. Levulose forms a compound or alcoholate with alcohol—CgHj^iOg(C2H5). Levulose is formed by the action of enzymes or acids upon various carbohydrates—e.g., cane-sugar (saccharose), inulin, rafftnose, etc. ; the process is called inversion, and is the result of hydrolytic cleavage. The sugar in fruit is usually a combination of dextrose and levulose, and is called invert-sugar ; it is uncrystallizable-, and forms granular masses in dried fruit; consists of 4 parts of levulose and 3 parts of hydrated dextrose, some of which arise by inversion of saccharose. It is levo-rotatory. A mixture of equal parts of levulose and dextrose does not give the same optical properties as invert-sugar, while a mixture of 2 parts of levulose and i part of hydrated dextrose form a crystalline compound.^ Sorbinose is a ketose; crystalline, levo-gyrate; convertible into sorbite by reduction. It is the sugar in the fruit of the service-tree and mountain-ash, and appears to arise from the hydrolysis of a glucoside, or, according to Freund, from the oxidation of a gelatinous substance in service fruit.^ Agavose is a sugar from Agave Americanus. It is very sweet; reduces Fehling's solution five-eighths as strongly as dextrose. It yields no mucic acid on oxidation. After inversion it is levo- rotatory. Mannose, or Seminose, does not occur free in Nature, but is in combination with other carbohydrates. It is fermentable with yeast, and is dextro-gyrate. It is obtained by the hydrolysis of carbohydrates, especially in the shavings of ivory-nut, and by the oxidation of mannite. Mannite (CgH^^OJ occurs naturally in many vegetable substances, notably m manna, of which it forms 30 to 60 per cent. It also occurs in celery, roots of Scorzonem hispanica, and numerous other ] Bunge's Organic Chemistry, p. 113. Winter, Moniteuv Scientifique, February, 1888. Chemical News, 1891, ii. 260.
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