This Standard sets out a polarimetric method for determining the sucrose content of sweetened condensed milk of normal composition which has been prepared from whole, partially skimmed or skimmed milk and sucrose only, and which contains no altered sucrose.

NOTE: It has been found by investigation that sucrose is generally present in an unchanged condition in fr eshly manufactured product, but that it is sometimes part ly alt ered during storage, and that the altered sucrose is present, in cases that have been examined, not as invert sugar but as a mixture of glucose, fructose and laevan.

The presence of the laevan interferes with the polarimetr ic and other procedures usually applied to the determination of sucrose.

If the presence of alt ered sucrose is suspected because of the age of the product, it may be detected with a modif ied Barfoed reagent (copper acetate and acetic acid) using specified test condit ions under which there is no reduction of the copper by sucrose, and the effect of the lactose is negli gible, whilst the eff ects of glucose and fructose remain at a high level. The Barfoed process wil l detect as lit tle as 0.1 percent of the invert sugars, glucose and fructose.

If no significant sucrose alteration is detected, the method described below for determining sucrose should be used. If the alteration is significant, the method described in The Analyst* is recommended for the determination of the original sucrose content of the sample.

* MILK PRODUCTS SUBCOMMITTEE TO THE STANDING COMMITTEE ON UNIFORMITY OF ANALYTICAL METHODS, Milk Products Report No 3, ‘The Analysis of Sweetened Condensed Milk In Which The Sucrose Has Altered During Storage', The Analyst, 1932, Vol. 57, pp 630-652.