1700022 (1 of 11)
DOI 10.1002/star.201700022
Starch/Stärke 2018, 70, 1700022
REVIEW
Glycaemic index of wheat bread Barbara Borczak 1, Marek Sikora 2, Elz_ bieta Sikora 1, Anna Dobosz 2 and Joanna Kapusta-Duch 1 1 2
Faculty of Food Technology, Department of Human Nutrition, University of Agriculture in Krakow, Krakow, Poland Faculty of Food Technology, Department of Carbohydrate Technology, University of Agriculture in Krakow, Krakow, Poland
Here, the concept and critical reviews concerning the glycaemic index are presented and the influence on human health with regard to the diets of various glycaemic indices are thoroughly reviewed. It is stated that wheat bread is regarded as high glycaemic index food, with some solutions having been proposed in order to reduce this indicator in three research areas: (i) the raw materials, (ii) the milling process, and (iii) bread-making along with the post-baking processes. Regarding the use of raw materials, future trends in bakery production might include the application of some plants that are rich in antioxidants, along with some selected, edible byproducts. Jet milling – with high air pressure – was proposed as a modification of the traditional method. With regard to bread-making, together with the post-baking process, it has been proposed that the kneading time should be reduced, along with extended fermentation, sourdough fermentation, reduced yeast quantity, decreasing bread volume, post-baking processes with the application of freezing and frozen storage before final baking, and a combination of sourdough or dietary fibre with the freezing and frozen storage before final baking. Growing consumer demands have led to the search for more innovative ingredients. In this context, further studies on the impact of newly designed breads on the glycaemic index are required.
Received: February 1, 2017 Revised: June 1, 2017 Accepted: July 17, 2017
Keywords: Glycaemic index / Glycaemic response / Reduction / Wheat bread
1
The concept of the glycaemic index (GI)
In 1981, Jenkins et al. [1, 2] introduced a method of classifying different carbohydrate foods in the diet based on their impact on postprandial glycaemia. Previously, it was believed that non-digestible carbohydrates should be consumed by people suffering from type 2 diabetes, mainly due to the low and time extended glycemic response (GR hereafter). These carbohydrates also used to be recommended for healthy subjects as they were beneficial in preventing hyper secretion of insulin and hypoglycemia between meals. Complex polysaccharides, such as starch, were considered to be non-digestible while monosaccharides
Correspondence: Dr. Barbara Borczak, Faculty of Food Technology, Department of Human Nutrition, University of Agriculture in Krakow, Krakow, Poland E-mail:
[email protected] Fax: þ48 126624812 Abbreviations: GI, glycemic index; GL, glycaemic load; GR, glycaemic response; RDS, rapidly digestible starch
ß 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
and disaccharides were quickly digested. In the course of further studies, it was demonstrated that factors related to a product other than the molecular weight of carbohydrates were also important determinants of the GR [3]. Summarising, the chemical structure of carbohydrates does not necessarily indicate their physiological effects [4]. Hence, different products containing the same quantity of carbohydrates were characterised by different glycaemic and insulinaemic responses [5].
2
Critical reviews of the GI concept
The indicator of GR, which is often referred to as the glycaemic index, has some limitations. Different authors have expressed arguments supporting its imperfections [3, 6, 7], particularly highlighting the fact that GI does not reflect the glycemic response whatsoever, and that the better predictor of GR is the glycaemic load (GL). This takes into account not only the amount of the carbohydrates eaten with the diet, but also their quality. Many authors have used the
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Starch/Stärke 2018, 70, 1700022
term GI inappropriately, and concluded that the GI of subjects may vary each day. In their Consensus, Augustin et al. [3] emphasised that ‘GI’ was not the same as GRand so should be clearly distinguished.
3 Impact of diets of various GI and GL on human health The World Health Organisation (WHO) encourages the reduction in the daily consumption of free sugars to less than 10% of the total energy intake although even further reduction of sugar consumption, below 5% per day, would be more beneficial for health. Mono- and disaccharides added to foods and drinks by food producers, along with those that are naturally present in honey, syrups and fruit juices, are regarded as free sugars. WHO recommendations are based on the analysis of scientific evidence which show that adults consuming lower amounts of sugars have a lower body weight while those consuming higher amounts have a higher body weight. This research also revealed that children drinking more sugarsweetened drinks are more susceptible to excessive weight gain – or even obesity – than those drinking less sugarsweetened drinks [8]. Thus, the question is whether a relationship exists between increased postprandial blood glucose, health and diseases. Evidence has shown that high insulin and blood glucose levels might evoke antioxidant stress in the organisms and increase the risk of diet-dependent diseases such as cardiovascular diseases, cancer and diabetes [9], especially, in the case of type 2 diabetes where the oxidative stress is very harmful. Nowadays, type 2 diabetes is considered an important problem because it represents, globally, 90% of all cases of diabetes and accounts for five major causes of death [10]. Taking into account the above one might assume that all the carbohydrate-rich food influence the postprandial glucose and insulin levels in the same way. It has been proposed that the diets of high GI promote considerable weight gain [3]. Among the products with high GI (>70%) there are white and wholemeal wheat breads, baked and boiled potatoes, jam, biscuits and sweets. In turn, in the groups of food products with moderate (55–70%) and low (
