A text-book of the science and art of bread-making : including the chemistry and analytic and practical testing of wheat, flour, and other materials employed in baking / by William Jago.

  • William Jago
Date:
1895
Catalogue details

Licence: Public Domain Mark

Credit: A text-book of the science and art of bread-making : including the chemistry and analytic and practical testing of wheat, flour, and other materials employed in baking / by William Jago. Source: Wellcome Collection.

    101/740 page 69
    129. Organic Constituents : Fatty Matters.—of tlie mune- vous organic bodies found in wheat, fat has not l)een chosen as the first to 1)0 described because of its importance as a <;rain con.stituent, but because it has the simplest composition of tlie ori^anic bodies ])i'esent, and tlierefore may fitly serve as an introduction to tlie chemistry of the more comi)licated compounds to follow. All grains contain more or le.ss fat ; rice has tlie least (piantity, viz. 01 per cent.; maize and oats have respectively 4'7 and 4’() per cent. ; wheat occupies a medium position with a percentage' of l-J to l b. The fat of wheat is not eejually dis- .seminate'd through the grain, but is almost entirely contained in the germ and husk or bran. An analysis by Church gives the cpiantity of fat in “fine wheat flour” as O'S; it is, however, doubtful if this analysis were made since the time when the ])roblem of degerming flour has received so much attention from the miller. It has been already exjilained that the fats arc* salts of certain acids, with glycerin as a base. They are characterised bj' their unctuous nature and by leaving a greasy stain on jiaper or linen. Fats are in¬ soluble in water, and from their low s])ecific gravity float on the surface •of that liijuid. On the other hand, all fatty bodies dissolve readily in either ether or light jietroleum spirit. As food stuffs, the fats occupy a high ])osition ; in tables giving the relative nutritive value of difierent articles of food, fat heads the list. If this were tlie only point to b() considered, the presence of fats in wheat and flour would be highly advantagi'ous. They have, unfortunately, one great di’awback, and that is that they become rancid on standing. This effect is paiticularly noticeable in flour imperfectly freed fi'om germ. The rancidity is due to slow oxidation of certain constituents of the fat; this change may liroceed sutHciently far to seriously affect the flavour of the Hour, with¬ out the fat as a whole being very greatly changed. The fat of wheat is of a light yellow colour, melts at a low temperature, and gradually <lai'kens in colour on being kept. This change ju’oceeds rapidly in the fat when maintained at a temperature of 70 or 80° C. Konig states that the fat of rye, a grain very similar to wheat, has the following composition : — (dycerin, ... ... ... l-HO iier cent. Oleic acid, ... ... ... 90-60 ,, Palmitic and stearic acids, ... 8-10 ,, According to Konig, therefore, the fat of rye* consists largely of free fatty acids, tlu' glycerin present being insuHicient to iK'utralise but a .snudl proportion of the acids pres(*nt. Recently, Sti'llwaag made an analysis of the fat of barl(*y as <‘xtracted by ether with the following i-esults ;— Kret'fatty acids. 13(;-J Neuti-al fats. 77-78 Lecithin, 4-91 Cholesterin, ... 6-08 An e.xamination of wheat fat has i-eca'iitly bs'en made in the authors laboratory, the r(*sults of which ar(‘ as follows; A samjile of perfectly
    digitised image 1
    digitised image 2
    digitised image 3