This section is from the book "Experimental Cookery From The Chemical And Physical Standpoint", by Belle Lowe. Also available from Amazon: Experimental cookery.
Brittles are much harder than caramels or taffies and are cooked to high temperatures. At the temperatures to which they are cooked carameli-zation of the sugar may take place, and this as well as added substances tends to prevent crystallization. If caramelization is very extensive, a number of decomposition products of sugar may develop, among which are some acid substances. The greater the amount of caramelization the stronger the flavor developed. Soda is often added to brittles. It not only neutralizes the acidity developed and lessens the bitter flavor but owing to gas formed gives a porous texture to the brittle.