The influence of thermal processing of fruit and vegetables on their glycaemic index and glycaemic load

Abstract

Diabetes is a metabolic disease caused, among others, by malnutrition. Therefore, more attention is paid to products containing carbohydrates, as they increase the blood glucose concentration. In order to prevent type 2 diabetes and obesity, it is recommended to consume food with a low glycaemic index (GI) and glycaemic load (GL). The GI value of foodstuffs is influenced by their composition, as well as physicochemical and biochemical changes occurring in raw materials during technological processes. The aim of the study was to determine the influence of technological processing on the glycaemic index and glycaemic load values of selected vegetables and fruit. The research was conducted on cruciferous vegetables, carrots, potatoes and apples. The raw materials underwent pretreatment, which included washing, peeling, shredding and thermal processing. In order to determine the glycaemic index, clinical trials were conducted on 20 healthy people of both sexes, aged 20-60 years, normal weight (BMI 18-24.5). The content of dietary fibre and its fractions was also measured in the products. The thermal treatment influenced the GI and GL values of the food products and content of dietary fibre. The highest GI and GL values were measured in the boiled and baked products, whereas the GI and GL values of the steamed foodstuffs were slightly lower. The results let us conclude that adequate handling of raw materials, i.e. appropriate thermal processing, may limit the development of type 2 diabetes. Diabetic patients are advised to use steaming as the preferable method of thermal processing of foodstuffs.