Invert sugar preparation

Colour Reactions.—These are used for the detection of commercial invert sugar and are based on the colorations given by certain substances with methylfurfural and hydroxymethylfurfural, which occur in commercial invert sugar as decomposition products formed from the levulose during the inversion of saccharose by acids. Invert sugar prepared with invertase or by other special methods does not contain these decomposition products and consequently does not give the colour reactions. The most reliable of the latter are as follows ... 

Mention should also be made of glutamic acid and invert sugar which are used in foodstuffs and demand the use of hydrochloric acid-resistant material in manufacture, and of the essential flavouring oils which should preferably be stored and prepared in stainless steel and aluminium equipment. 

With products prepared with addition of sugar, determinations of the saccharose and other sugars, i.e. of the lactose and of the invert sugar which may be formed by the inversion of the saccharose, are carried out by the following methods. 

As a rule milks which have been well prepared contain either no invert sugar Or but very little. 

In polarimetric determinations, the mutarotation must always be taken into account, this being greatest in glucose and less marked in levulose, invert sugar, maltose and lactose. Solutions of these sugars do not assume constant rotations until they have been prepared about 24 hours or kept at a high temperature for a short time. 

In presence of invert sugar, 50 c.c. of the solution prepared as above are subjected to inversion in the usual way and polarised, the saccharose being calculated by Clerget s formula (see later Raw Sugar). 

Determination of the Sugars.—The principal sugar present is saccharose, but invert sugar is also found—mostly due to inversion of the saccharose during the preparation of the fruits—as well as glucose, which is added directly. The method of determination is as follows ... 

To ascertain the quantity of sugar (saccharose) used in the preparation of the preserved fruit, from the total sugar (invert sugar x 0 95 plus saccharose) contained in the sample must be deducted the natural sugar (also calculated as saccharose) due to the quantity of fruit in the sample. For this purpose it is, of course, necessary to know the saccharine contents of different fruits, so that an analysis of fruit of the same quality preserved in water in the same conditions as in the syrup must be made. 

Detection and Determination of Dextrin.—Dextrin occurs especially in products containing commercial glucose and its presence is demonstrated by the high dextro-rotation (see Crystallised Fruit, Determination of the Sugars, c). To determine it, 100 c.c. of the inverted solution, prepared as for the determination of the sugars (see 1), are treated as indicated on p. 142 (section 4) to transform the dextrin into glucose,... 

Ordinary glucose yields in addition to fructose and mannose a new ketose, pseudofructose, which has not yet been obtained in a pure state, and another substance, which is reducing but not fermentable, having the properties of a ketose and for whieh we suggest the name glutose. This substance can easily be prepared by the action of lead hydroxide on commercial fructose.. .. It can also be prepared by using invert sugar and lime. 

Comments an equimolecular mixture of dextrose and fructose prepared by the hydrolysis of sucrose with a suitable mineral acid such as hydrochloric acid. Invert sugar may be used as a stabilizing agent to help prevent crystallization of sucrose syrups and graining in confectionery. A 10% aqueous solution is also used in parenteral nutrition. 

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