The available carbohydrate of fruits

IT is now generally recognised that determinations of available carbohydrate in fruits and vegetables are of much more value for dietetic purposes than those of total carbohydrate, whether the latter have been determined by acid hydrolysis or calculated by difference.Figures for the available carbohydrate of the fruits and vegetables commonly eaten in this country were given by McCance and Lawrence [1929].An acid hydrolysis was used, followed by a determination of "total" reducing power.Realising, however, that this reduction was partly due to the products from easily hydrolysable pentosans and other non-fermentable sugars, McCance and Lawrence determined these constituents separately and deducted their reducing value from that of the total sugar.The remainder they considered to be available carbohydrate.Their figures in some instances are too low because the strong acid employed and the prolonged time of boiling led to a destruction of a consider- able proportion of the fructose.They mentioned that something of this -ort was taking place, but considered that for practical purposes the error could be neglected.A study of the available carbohydrates of fresh fruits has now been made by the most reliable methods which can be obtained.Sucrose, fructosr;, glucose and starch have each been determined separately.Since these are generally con- sidered to be the only fruit carbohydrates which are absorbed ag sugars from the gut, their sum constitutes the available carbohydrate of the fruit.Small amounts of maltose may be present in starchy fruits such as the banana.If this is the case, the error so introduced must be insignificant, since determinations of glucose and fructose by two independent methods have been found to agree.From the nature of the methods employed this would not have been the case if appreciable amounts of maltose had been present (vide infra).Fresh, raw fruits only have been used, and all determinations have been carried out on the e1ible portion. METHODS.Preparation of the fruit.Almost all the fruit has been obtained from the Amalgamated Fruiterers and the Army and Navy Stores.Each variety of English and foreign fruit came from at least four, and usually from six, different sources and was known therefore to have been grown under various soil and