The vast majority of bread is traditionally produced from wheat flour. Apart from its major constituent starch, wheat flour also contains many other types of substances of which the gluten, the non-starch polysaccharides as well as the lipids are the most important in terms of their impact on the processability of the raw material and in terms of the quality of the final products. We here provide the basics on the processability and quality determining wheat flour constituents and present common concepts on their fate during the breadmaking process as well as on approaches targeted to influence their functionality.

Wheat flour constituents: how they impact bread quality, and how to impact their functionality

Acid hydrolysis is an important chemical modification that can significantly change the structural and functional properties of starch without disrupting its granular morphology. A deep understanding of the effect of acid hydrolysis on starch structure and functionality is of great importance for starch scientific research and its industrial applications. During acid hydrolysis, amorphous regions are hydrolyzed preferentially, which enhances the crystallinity and double helical content of acid hydrolyzed starch. This review discusses current understanding of the effect of acid hydrolysis on starch structure and functionality. The effects of acid hydrolysis on amylose content, chain length distribution of amylopectin molecules, molecular and crystalline organization (including lamellar structure) and granular morphology are considered. Functional properties discussed include swelling power, gelatinization, retrogradation, pasting, gel texture, and in vitro enzyme digestibility. The paper also highlights some promising applications of acid hydrolyzed starch (starch nanocrystals) in the preparation of biodegradable nanocomposites, bio-hydrogen, and slowly digestible starch-based healthy foods.

Effect of acid hydrolysis on starch structure and functionality: a review.

Starch is a predominant component of wheat grain. It plays an important role in appearance, structure and quality of food products. Starch consists of two kinds of glucose polymers (amylose and amylopectin) with the ratio of amylose/amylopectin ranging between 25–28 and 72–75%, respectively. The isoforms of granule-bound starch synthase (GBSS) are responsible for the biosynthesis of amylose fraction, whereas amylopectin synthesis is more complicated with concerted activities of the soluble starch synthase together with branching and de-branching enzymes. Recently, waxy (amylose-free) and high-amylose wheats produced through the development of new physicochemical and biological techniques provide the unique starch functional properties. The starches of these wheats have the specific structures and unique characteristics that are believed to enhance the quality of food products. In this review, we will focus on recent advances in the studies of the characteristics of waxy and high-amylose wheat flours and starches and their application for food processing. In addition, we also propose further research ideas for clearer understanding of their characteristics and for their effective utilization.

Waxy and high-amylose wheat starches and flours—characteristics, functionality and application

The market for gluten-free products is increasing. Owing to better diagnostic methods, more and more people are identified to have coeliac diseases. Production of bakery products that do not harm these people is a big challenge for bakers and cereal scientists in the twenty-first century. The use of different cereals and flours makes it necessary to find possibilities to take over the task of gluten by other flour ingredients, by the addition of different components, by different flour and dough treatment or by changing the method of baking. The purpose of this review is to give an overview about the various possibilities to increase the baking quality of gluten-free bakery products, increasing their water-binding capacity, uniform the crumb structure and increase the final bread volume. All the listed methods and ingredients are already in single use helpful to increase the quality in gluten-free bread production.

Possibilities to increase the quality in gluten-free bread production: an overview

In the past years, research has been focused on biodegradable materials to replace petroleum based plastics for food packaging application. For this purpose, biopolymers are considered the most promising material because of their biodegradable nature and long shelf life properties like resistance to chemical or enzymatic reactions. Starch is renewable, cheap, and abundantly available biopolymer. However, the intermolecular forces and hydrogen bonds in starch resist it to be processed as a thermoplastic material. To overcome this issue, different plasticizers are used to have deformable thermoplastic material called thermoplastic starches (TPSs). A plasticizer enhances the flexibility, the process stability of starch below the degradation temperature. Plasticizer lowers the glass transition temperature (Tg).

TPS is very promising among the biobased materials available for the production of biodegradable plastic. TPS have some limitations; bad mechanical properties and water sensitivity. Starch absorbs water under higher relative humidity. This work will provide an outline about the research that has been done on TPS during last 15 years as biodegradable food packaging material.

Practical Applications
The basic role of food packaging material is to make it cost effective that satisfies industry requirements and consumer desires, and provide protection from three major classes of external influences: chemical, biological, and physical, e.g., such as exposure to gases, barrier to microorganisms, or from mechanical damage, respectively. These external influences may damage the quality of the food and shelf life. For this motive, starch has become the most preferred option among the verified classes of synthetic and natural materials. Retrogradation of starch chains in presence of water make it impossible to be use as packaging material. To overcome this issue, Starch has been plasticized with water and low molecular weight additive that can interact with its backbone by hydrogen bonding to produce thermoplastic starch (TPS). The objective of this review is to summarize numerous studies related to interaction of plasticizers and starch for the production of biodegradable TPS food packaging materials.

Thermoplastic Starch: A Possible Biodegradable Food Packaging Material—A Review

Modified starches have been investigated and developed for more than a century and have various applications in food, paper and textile industries. Recently, chemically modified starches such as esterified, etherified and/or cross-linked starches have been widely used for various prepared foods such as snack foods, breads and cakes to improve their quality. In breadmaking, starch is a major component and plays an important role in texture and quality of dough and bread. Therefore, modified starches, which were developed to decrease undesirable properties of native starches, also affect the properties of dough and quality of bread. The modified starches could be used to substitute up to 20% for wheat flour without deterioration of bread quality. However, vital gluten is also needed to blend with the substituted modified starches to improve loaf volume of bread. Generally, the substituted flours gelatinized more quickly and had higher peak viscosity than the wheat flour alone. The dough made from the substituted flours exhibit weaker and less stability than that made from the wheat flour. The breads substituted with hydroxypropylated starch were less firm and retained softness during storage longer than those with other modified starches or wheat flour alone. The acetylated starch also improved the firmness of bread crumb during storage, whereas cross-linked starches made the bread crumb harder because the chemical cross-linking retained the granular structure of starch in the gluten network resulting in increase in the firmness of bread crumb. However, cross-linked waxy starches retarded the firmness of bread crumb despite its high degree of cross-linking. Thus, the different kinds of chemically modified starches played the different roles in the texture and quality of doughs and breads. We propose that a suitable amount of modified starches should be useful for breadmaking to improve the functionality and quality of breads.

Recent advances in application of modified starches for breadmaking

The dough properties and baking qualities of a novel high-amylose wheat flour (HAWF) and a waxy wheat flour (WWF) (both Triticum aestivum L.) were investigated by comparing them with common wheat flours. HAWF and WWF had more dietary fiber than Chinese Spring flour (CSF), a nonwaxy wheat flour. Also, HAWF contained larger amounts of lipids and proteins than WWF and CSF. There were significant differences in the amylose and amylopectin contents among all samples tested. Farinograph data showed water absorptions of HAWF and WWF were significantly higher than that of CSF, and both flours showed poorer flour qualities than CSF. The dough of WWF was weaker and less stable than that of CSF, whereas HAWF produced a harder and more viscous dough than CSF. Differential scanning calorimetry data showed that starch in HAWF dough gelatinized at a lower temperature in the baking process than the starches in doughs of WWF and CSF. The starch in a WWF suspension had a larger enthalpy of gelatinization than thos...

Dough and Baking Properties of High-Amylose and Waxy Wheat Flours

Effect of various dextrin substitutions for wheat flour on dough properties and bread qualities

The effect of substitution of waxy-wheat flour (WWF) for common wheat flour, ‘Hermes’ on dough and baking properties was determined. Flours consisting of 20% WWF and 80% Hermes (20 WWF) and 40% WWF and 60% Hermes (40 WWF) were used. Two other mixed flours were prepared for comparison: one consisted of 20% Chinese spring flour (CSF) and 80% Hermes (20 CSF) and the other of 40% CSF and 60% Hermes (40 CSF). Breadcrumbs became softer with increasing WWF substitution, and harder with increasing CSF substitution. From cross sections of these breads from 20 WWF and 40 WWF, the partial substitution of WWF for Hermes was considered favorable for baking results. Especially, 40 WWF made larger loaves and improved glutinous texture, such as the chewing property or adhesiveness of breadcrumbs, as compared with Hermes alone. DSC data showed that WWF retarded the staling of breadcrumbs during storage and also accelerated the refreshing of breadcrumbs with softness and glutinous texture after reheating. Substitution of WWF decreased the setback of viscosity under the holding temperature and suppressed the gelation of starch under cooling, both of which improved the pasting property of starch. In addition, WWF appeared to suppress the formation of an insoluble network structure of starch during cooling, which improved the tolerance of gelatinized starch to the retrogradation. These results indicate that the partial substitution of WWF for common flour improved the softness and glutinous texture of breadcrumbs and retardation of staleness. Consequently, WWF might have applications in practical baking.

http://www.jstage.jst.go.jp/article/fstr/8/2/8_2_119/_pdf

Effect of substitution of waxy-wheat flour for common flour on dough and baking properties

The present investigation aims at understanding the role of chemically modified starch on the firmness of fresh or stale bread. Bread was prepared from wheat flour or substituted wheat flour that contained 18% chemically modified tapioca starch and 2% vital gluten. Hydroxypropylated tapioca starch (HTS), acetylated tapioca starch (ATS), phosphorylated cross-linked tapioca starch (PTS), and native tapioca starch (NTS) were tested. Bread prepared from the substituted flour with PTS showed a firmer texture on the day of baking compared with bread prepared from NTS, HTS, and ATS. PTS retained its granular structure in the gluten network after baking and seemed to play the role of filler particles in the gluten matrix, thereby increasing firmness of fresh bread crumb. Bread prepared from the substituted flour with HTS or ATS firmed at a lower rate and showed a lower endothermic melting enthalpy of amylopectin after three days of storage compared with NTS or PTS. These findings suggest that the staling...

Megumi Miyazaki

Papers

Recent advances in application of modified starches for breadmaking

Dough and Baking Properties of High-Amylose and Waxy Wheat Flours

Effect of various dextrin substitutions for wheat flour on dough properties and bread qualities

Effect of substitution of waxy-wheat flour for common flour on dough and baking properties

Starch retrogradation and firming of bread containing hydroxypropylated, acetylated, and phosphorylated cross-linked tapioca starches for wheat flour