Improving the health benefits of bread

4
B ecause bread has long been the staple food in temperate countries, this led to massive changes in diet, with coarse wholemeal or brown breads being almost completely replaced by white products in the UK by 1880. Although the science of nutrition was then in its infancy, concerns were nevertheless expressed about the impact of this change in diet on the nutrition and health of the population. Foremost among the critics of white bread in the UK were May Yates and Thomas Allinson. Allinson qualified as a doctor in 1879 and established a practice in London. He believed that diet was crucial for health, and particularly advocated the consumption of stone ground wholemeal wheat. He was frequently in dispute with orthodox medicine and was “struck off” (disqualified from practicing) in 1892, having been found guilty of “infamous conduct” (self- promotion). In the same year he purchased a stone mill and established a milling and baking company that continues to produce wholemeal bread to the present day. By contrast, May West was not trained as a scientist but became convinced of the benefits of wholemeal bread during a visit to Sicily. She founded the Bread Reform League in 1880 and spent 40 years campaigning for the use of high extraction (about 85 percent) flours. The late 19th Century also saw the introduction of improved “patent” breads, the most well known being “Hovis” which is enriched in wheat germ. Despite the compulsory production of high extraction and wholemeal breads in the UK during the two World Wars, white bread has remained the favourite for much of the British population, and in many other countries. Although those who promoted improved breads in the 19th Century recognised the importance of fibre and protein, the health benefits were not soundly established until the early 20th Century, with the discovery of vitamins and the recognition that these are depleted when the bran and germ are removed to produce white flour. Since then, many studies have been reported positive relationships between flour extraction rate and the contents of “beneficial” components in flour, including B vitamins, Vitamin E, minerals, fibre and “bioactive” phytochemicals, with the differences in concentrations of these components between wholemeal and white flour exceeding ten-fold in some cases. Wholegrain and health Recent interest in the relationship between wheat and health has been stimulated by the wholegrain movement, which can be dated from the approval granted by the US Food and Drugs Administration in 1999 that “Diets rich in whole grain foods and other plant foods and low in total fat, saturated fat, and cholesterol, may help reduce the risk of heart disease and certain cancers." This has stimulated interest from both industry and academics and the establishment of bodies to promote wholegrain consumption, such as the Whole Grains Council, Grains for Health Foundation and Healthgrain Forum. The role of vitamins and minerals in health is well established but recent attention has focussed on dietary fibre. There is strong scientific evidence that increased consumption of cereal fibre, Improving the health benefits of bread by Peter Shewry, Distinguished Research Fellow, Department of Plant Biology and Crop Science, Rothamsted Research, UK The development of roller milling in the 19th Century made white bread affordable to all social classes for the first time, leading to a love affair with white bread, which remains in many countries to the present day. 40 | November 2015 - Milling and Grain F

description

The development of roller milling in the 19th Century made white bread affordable to all social classes for the first time, leading to a love affair with white bread, which remains in many countries to the present day.

Transcript of Improving the health benefits of bread

Because bread has long been the staple food in temperate countries, this led to massive changes in diet, with coarse wholemeal or brown breads being almost completely replaced by white products in the UK by 1880. Although the science of nutrition was then in its infancy, concerns were nevertheless expressed about the

impact of this change in diet on the nutrition and health of the population. Foremost among the critics of white bread in the UK were May Yates and Thomas Allinson.

Allinson qualified as a doctor in 1879 and established a practice in London. He believed that diet was crucial for health, and particularly advocated the consumption of stone ground wholemeal wheat. He was frequently in dispute with orthodox medicine and was “struck off” (disqualified from practicing) in 1892, having been found guilty of “infamous conduct” (self-promotion). In the same year he purchased a stone mill and established a milling and baking company that continues to produce wholemeal bread to the present day.

By contrast, May West was not trained as a scientist but became convinced of the benefits of wholemeal bread during a visit to Sicily. She founded the Bread Reform League in 1880 and spent 40 years campaigning for the use of high extraction (about 85 percent) flours. The late 19th Century also saw the introduction

of improved “patent” breads, the most well known being “Hovis” which is enriched in wheat germ. Despite the compulsory production of high extraction and wholemeal breads in the UK during the two World Wars, white bread has remained the favourite for much of the British population, and in many other countries.

Although those who promoted improved breads in the 19th Century recognised the importance of fibre and protein, the health benefits were not soundly established until the early 20th Century, with the discovery of vitamins and the recognition that these are depleted when the bran and germ are removed to produce white flour. Since then, many studies have been reported positive relationships between flour extraction rate and the contents of “beneficial” components in flour, including B vitamins, Vitamin E, minerals, fibre and “bioactive” phytochemicals, with the differences in concentrations of these components between wholemeal and white flour exceeding ten-fold in some cases.

Wholegrain and healthRecent interest in the relationship between wheat and health

has been stimulated by the wholegrain movement, which can be dated from the approval granted by the US Food and Drugs Administration in 1999 that “Diets rich in whole grain foods and other plant foods and low in total fat, saturated fat, and cholesterol, may help reduce the risk of heart disease and certain cancers." This has stimulated interest from both industry and academics and the establishment of bodies to promote wholegrain consumption, such as the Whole Grains Council, Grains for Health Foundation and Healthgrain Forum.

The role of vitamins and minerals in health is well established but recent attention has focussed on dietary fibre. There is strong scientific evidence that increased consumption of cereal fibre,

Improving the health benefits of breadby Peter Shewry, Distinguished Research Fellow, Department of Plant Biology and Crop Science, Rothamsted Research, UK

The development of roller milling in the 19th Century made white bread affordable to all social classes for the first time, leading to a love affair with white bread, which remains in many countries to the present day.

40 | November 2015 - Milling and Grain

F

particularly in wholegrain, results in reduced risk of a range of chronic diseases including type two diabetes, stroke and some types of cancer (notably colorectal). The scientific evidence for the role of dietary fibre and other cereal carbohydrates in health has been reviewed in detail in a recent report from the

UK Scientific Advisory Committee on Nutrition. Although, the roles and benefits of “bioactive” phytochemicals remain to be established, few would dispute that increasing flour extraction rate could have a significant impact on the health of consumers.

Wheat grain structure and millingIn botanical terms the wheat grain is a single-seeded fruit, called

a caryopsis. It consists of three main parts, which have different functions and compositions. The central part of the grain is the endosperm, which accounts for about 90 percent of the total grain.

This is essentially a storage tissue, being packed with starch and protein, which are digested to support the growth of the seedling during germination. However, the outer layer of endosperm cells differ from the others, being rich in dietary fibre, protein, oil, B vitamins, minerals and phytochemicals. These outer aleurone cells account for about 6.5 percent of the grain. The embryo is relatively small, accounting for about 3 percent of the total grain, and develops into the seedling on germination.

It is similar in composition to the aleurone, except for a lower proportion of dietary fibre. Outside of the embryo and endosperm are the seed coat (testa) and the fruit coat (pericarp)) which provide protection to the grain (see figure). These outer layers are very rich in fibre and associated phenolic acids but not in other beneficial components. Conventional milling has been developed to separate the starch-rich cells of the central endosperm (called the starchy endosperm) from the outer layers, aleurone and germ, which are together recovered as bran.

The process is remarkably effective, with the yield of white flour approaching 80 percent of the total grain. However, as flour yield approaches and exceeds 80 percent there is increasing

starchy endosperm

germ

Aleurone

pe

rica

rp a

nd

te

sta

Milling and Grain - November 2015 | 41

F

“contamination” with bran tissues, particularly with the aleurone, which adheres tightly to the outer starch-rich cells (figure). Hence, the concentrations of beneficial components increase significantly as extraction rate rises.

Challenges to increasing flour extraction rate for bread making

Increasing the flour extraction rate poses challenges for food processing and for the consumer acceptability of the products. Increasing the content of bran in bread-making flour reduces the acceptability to consumers accustomed to consuming white bread, due to the grittiness associated with bran particles and to the colour and flavour (more wheaty and bitter with an aftertaste) associated with the presence of proanthocyanidin pigments in the testa of the “red” grained types of wheat which are largely used for bread making.

In theory, the latter problem is easy to eliminate as “white” grained wheats are available which lack the pigment and associated flavour. However, white wheats are highly susceptible to “pre-harvest sprouting” when subjected to cool and wet conditions at harvest, leading to loss of value as sprouted grain cannot be used for food processing. Hence, white wheats are not widely cultivated and the grain is too expensive to be used except for premium products. It has not been possible to separate the red colour from the resistance to sprouting by conventional plant breeding but work in progress on understanding the precise relationships between the two seemingly unrelated phenomena might allow the use of modern molecular tools to produce white wheats that are also resistant to sprouting.

It should also be noted that higher intrinsic processing quality is required for producing wholemeal and high extraction breads than for white bread. This is because processing quality is mainly determined by the gluten proteins, which are located exclusively

in the white flour. These proteins are therefore diluted by about 25 percent in wholemeal, and to a correspondingly lesser extent in high extraction flours. It is therefore necessary to use grain of higher protein content and/or protein quality, or to supplement low protein flour with “vital gluten” produced by the industrial separation of starch and gluten from flour.

New approaches to producing enhanced floursTwo recent multinational projects supported by the European

Union have focused on developing new technologies to improve the quality and acceptability of whole grain and high extraction rate bread.

One option, which was explored, is to eliminate the more unpalatable fibre-rich outer layers of the bran while retaining the inner bran, which includes the nutrient-rich aleurone layer. This cannot be achieved by simple abrasion (debranning) of whole grain because of the oval shape and the presence of a crease. The Health grain programme (2005-2010) therefore developed a process in which the grain was pearled twice, initially to remove the outer bran (approx three percent dry wt) and then the inner bran (up to 15 percent original dry wt). The first fraction was discarded while the second fraction, which was enriched in the aleurone layer, retained. Although the pearling removed most of the bran some remained in the crease region. The debranned grain was therefore milled and sieved using conventional procedures and the white flour recombined with an appropriate proportion of the second pearling fraction to give “Healthflour” which was enriched in beneficial components and had improved processing properties and higher acceptability.

Alternative approaches in the same project were to mechanically separate the aleurone layer using different types of mills to produce “aleurone powder” as an ingredient, and to finely grind the bran (micronisation) prior to fractionation by electrostatic separation. Miconisation also has the advantage that it increases the bioavailability of minerals, vitamins and phytochemicals. Following on from Health Grain, the Healthbread project (2012-2014) developed a range of concentrates from aleurone and wholegrain, which were successfully used by commercial partners using either long fermentation or sough dough systems.

There is no doubt that such new approaches can be used to produce bread which combines increased health benefits with good consumer acceptability. However, they will inevitably increase the cost of production, and current options are also more applicable to the low volume production of artisan breads than high volume factory production. Hence, their impact on the health of the whole population may be limited and cheaper and more widely applicable solutions should continue to be sought.

42 | November 2015 - Milling and Grain

F

CTB ADVERTISINGAd No. BR-2253F/201503

Brock Grain SystemsMilling and Grain

Brock Grain Systems

Storage | Handling | Conditioning | Structures

BROCK GRAIN SYSTEMSA Division of CTB, Inc.A Berkshire Hathaway Company

+1 574.658.4191 www.brockgrain.com [email protected]