Carbohydrate Chemistry for Food Scientists

James N. BeMiller

• Publisher: Woodhead Publishing and AACC International Press
• Year: 2018
• ISBN:
  9780128134382
• Edition: 3
• Topic: Tecnologia e ingegneria
• Subtopic: Scienze dell'alimentazione

Carbohydrate Chemistry for Food Scientists, Third Edition, is a complete update of the critically acclaimed authoritative carbohydrate reference for food scientists. The new edition is fully revised, expanded and redesigned as an easy-to-read resource for students and professionals who need to understand this specialized area. The new edition provides practical information on the specific uses of carbohydrates, the functionalities delivered by specific carbohydrates, and the process for choosing carbohydrate ingredients for specific product applications. Readers will learn basic and specific applications of food carbohydrate organic and physical chemistry through clearly explained presentations of mono-, oligo-, and polysaccharides and their chemistry.This new edition includes expanded sections on Maillard browning reaction, dietary fiber, fat mimetics, and polyols, in addition to discussions of physical properties, imparted functionalities, and actual applications. Carbohydrate Chemistry for Food Scientists serves as an invaluable resource on the chemistry of food carbohydrates for advanced undergraduate and graduate students, and a concise, user-friendly, applied reference book for food science professionals.

• Identifies structures and chemistry of all food carbohydrates – monosaccharides, oligosaccharides and polysaccharides
• Covers the behavior and functionality of carbohydrates within foods
• Extensive coverage of the structures, modifications, and properties of starches and individual hydrocolloids

1

Monosaccharides

Abstract

In addition to background information on carbohydrates in nature and in our food, this chapter describes monosaccharides related to foods that are open chain and pyranose and furanose ring structures, nomenclature of monosaccharides, isomerization of aldoses and ketoses, formation and hydrolysis of glycosides, and some functions of monosaccharides in foods.

Keywords

Aldose; Deoxy sugar; Dextrose; Fructose; Furanose ring; Glucose; Glycoside; Glycosidic bond; Hexose; Ketose; Monosaccharide; Pentose; Pyranose ring

Chapter Outline

1. Introduction
2. Structures and nomenclature
3. Isomerization
4. Ring forms
5. Glycosides
6. Other types of monosaccharides
   1. Some functions of monosaccharides in foods
7. Additional resources

Key information and skills that can be obtained from study of this chapter will enable you to:

• 1. Define and/or identify

chiral carbon atom	furanose ring
monosaccharide	anomeric carbon atom
saccharose group	anomers
dextrose	axial positions
aldose	equatorial positions
acyclic	glycoside
D sugar	glycosidic bond
L sugar	aglycon
ketose	deoxy sugar
pyranose ring	hygroscopic
Haworth projection	humectant

• 2. Identify and/or describe monosaccharides as to the kind of carbonyl group and number of carbon atoms (for example, aldotetrose, octulose, etc.).
• 3. Give Fischer and specific anomeric furanose and pyranose ring structures (Haworth projections) for the following: L-arabinose, D-xylose, D-galactose, D-glucose, D-mannose, D-fructose.
• 4. Make interconversions between names, acyclic structures, Haworth ring structures, and/or conformational ring structures of the sugars listed in objective 3.
• 5. Describe the chemical properties of hemiacetals and acetals.
• 6. Show the interrelationships of D-glucose, D-mannose, and D-fructose via isomerization.
• 7. Describe the conditions under which isomerization occurs.
• 8. When given the name of a glycoside of a sugar listed in objective 3 (for example, ethyl β-D-galactopyranoside), give its chemical structure and vice versa.
• 9. Describe the two general conditions under which hydrolysis of glycosides occurs.
• 10. Describe the relationship of carbohydrates to humectancy and water activity.

Introduction

Carbohydrates are present in all living cells. Energy reaching Earth in the form of sunlight is transformed by land and marine plants into sugars, which are used partly near the point of synthesis (that is, in a green growing shoot) for construction of various plant components and structures, and in part they are transported to other locations of the plant where they are used to make other components. These plant components supply food and energy to all other forms of life. Some of the initial photosynthetic carbohydrate material is converted into other organic compounds, such as proteins, fats, and lignin. Most of the remaining carbohydrate is converted into polymers of sugars (called polysaccharides, which constitute more than 90% of the dry matter of plants and at least three-fourths of the dry weight of all living organisms). It is estimated that as much as 10¹² tons of biomass are produced each year by photosynthesis.

Other than water, carbohydrates are the most common components of foods and the human diet (both as natural components and as added ingredients). Because milk contains carbohydrates (lactose and other oligosaccharides), carbohydrates are present in the very first food consumed by all mammals, including humans, and because they are constituents of all plant tissues, they are also present in the diets of almost all adult humans. They provide at least three-fourths of the caloric intake of humans on a worldwide basis. Starch, lactose, and sucrose are digested by normal humans, and they, along with D-glucose and D-fructose, are human energy sources. (Digestible carbohydrates, D-glucose, and D-fructose [along with proteins] contain about four calories per gram [dry weight], whereas fats and oils provide about nine calories per gram.)

Carbohydrates in foods are important, not only as energy sources but also as ingredients that impart texture and as dietary fiber that contributes to human health. Their use as food ingredients is large in terms of both quantities consumed and the variety of applications and products. Carbohydrate ingredients are abundant. They are inexpensive. They can be obtained from a variety of replenishable sources. They occur in diverse structures and degrees of polymerization. They are available in a large number of molecular sizes and shapes and in a variety of chemical and physical properties. They are amenable to both chemical and biochemical modifications (and in some cases physical and/or genetic modifications), and both modifications are employed to improve their properties and extend their use as food ingredients. They are nontoxic and, therefore, safe.

Naturally occurring and modified carbohydrates are used as ingredients in a wide variety of food products because of the wide range of functionalities they can impart. Therefore, much of the chemistry of carbohydrates is physical chemistry related to such properties as crispness, crystallization, emulsion and suspension stabilization, flow behavior, gel characteristics, gel formation, glass formation, glass transitions, humectancy, mouthfeel, water-holding capacity, and viscosity.¹ And carbohydrates are often used as ingredients because of the effects they have on other components of a formulation (the primary o...