I found this baking tip for cutting down on sugar when stewing sour fruit in my Mum’s old High School Cookery Book written by Grace Bradshaw. Grace was a graduate of the Calder Training College of Domestic Science in Liverpool and formerly HM Inspector for the Ministry of Education, and House Craft Mistress of Manchester High School for girls. The book was written for secondary schools and training colleges and was used as a textbook at Dungannon Royal School, the school my Mum attended as a teenager.
Back then the school was called Dungannon High School for Girls. It later amagamated with the adjacent boys school, Dungannon Royal. Mum says that before the schools amalgamated, the boys and girls used to come and talk to each other over the fence.
Stewed Fruit Tip
Bicarbonate of soda added to sour fruits, for example damsons or rhubarb, neutralises the acid and thus diminishes the amount of sugar required. For each 450 g / 1 lb of fruit, slowly stir in half a level teaspoonful of bicarbonate of soda towards the end of the cooking and before adding the sugar.