Designing Functional Foods

Measuring and Controlling Food Structure Breakdown and Nutrient Absorption

D. Julian McClements, Eric A Decker

• Publisher: Woodhead Publishing
• Year: 2009
• Print ISBN: 9781845694326
• eBook ISBN: 9781845696603
• Topic: Technology & Engineering
• Subtopic: Food Science
• Index: Technology & Engineering

The breakdown of food structures in the gastrointestinal tract has a major impact on the sensory properties and nutritional quality of foods. Advances in understanding the relationship between food structure and the breakdown, digestion and transport of food components within the GI tract facilitate the successful design of health-promoting foods. This important collection reviews key issues in these areas.Opening chapters in Part one examine oral physiology and gut microbial ecology. Subsequent chapters focus on the digestion, absorption and physiological effects of significant food components, such as lipids, proteins and vitamins. Part two then reviews advances in methods to study food sensory perception, digestion and absorption, including in vitro simulation of the stomach and intestines and the use of stable isotopes to determine mineral bioavailability. The implications for the design of functional foods are considered in Part three. Controlling lipid bioavailability using emulsion-based delivery systems, designing foods to induce satiation and self-assembling structures in the GI tract are among the topics covered.With contributions from leading figures in industry and academia, Designing functional foods provides those developing health-promoting products with a broad overview of the wealth of current knowledge in this area and its present and future applications.- Reviews digestion and absorption of food components including oral physiology and gut microbial ecology- Evaluates advances in methods to study food sensory perception assessing criteria such as simulation of flavour released from foods- Investigates the implications for the design of functional foods including optimising the flavour of low-fat foods and controlling the release of glucose

Part I

Digestion and absorption of food components

1

Oral physiology, mastication and food perception

A. van der Bilt University Medical Center Utrecht, The Netherlands

Abstract

During chewing, food is reduced in size, while saliva moistens the food and binds the masticated food into a bolus that can be easily swallowed. Characteristics of the oral system, such as bite force, number of teeth and salivary flow, will influence the masticatory process. Properties of the food, such as hardness, moisture and fat content, will also have an influence on chewing. Numerous receptors in the mouth and nose respond to the ingested food and monitor the changes during chewing. This leads to perception of taste, odour and texture of the food. An overview of the neuromuscular control of chewing and swallowing is presented. Finally, the influence of age on oral physiology, food perception and nutrient intake is discussed.

Key words

oral physiology

mastication

food perception

neuromuscular control of chewing and swallowing

nutrient intake

1.1 Introduction

Chewing is the first step in the process of digestion and is meant to prepare the food for swallowing and further processing in the digestive system. In the mouth, the food is subjected to several mechanical and chemical processes. Taste and texture of the food are perceived and have their influence on the chewing process. The water in the saliva moistens the food particles, whereas the salivary mucins bind masticated food into a coherent and slippery bolus that can be easily swallowed.

In Section 1.2 oral factors determining the chewing result are introduced. The teeth are important in the masticatory system. They form the occlusal area where the food particles are fragmented. This fragmentation depends on the total occlusal area and thus on the number of teeth. Another important factor in mastication is the bite force. The bite force depends on muscle volume and jaw muscle activity. Furthermore, the production of sufficient saliva is indispensable for good chewing.

Section 1.3 deals with the influence of food characteristics on chewing. For instance, water and fat percentage and hardness of the food are known to influence the masticatory process. Food hardness is sensed during mastication and affects masticatory force, jaw muscle activity and movements of the lower jaw.

Food perception is discussed in Section 1.4. Numerous receptors in the oral cavity and nose respond to the initially ingested food and monitor the changes during processing. This leads to central perceptions of taste, odour, and texture of the food. Most sensations associated with food texture occur only when the food is manipulated, deformed or moved across the oral receptors.

In Section 1.5 an overview of the neuromuscular control of chewing and swallowing is presented. Mastication is a complex process, involving activities of various jaw muscles and the tongue. These activities result in patterns of rhythmic jaw movements, food manipulation and the crushing of food between the teeth. The movement of the jaw, and thus the coordination between the various chewing muscles, plays an important role in the fragmentation of the food.

In Section 1.6 the influence of age on oral physiology, food perception and nutrient intake is discussed. Oral physiological parameters such as jaw muscle force, dental state, salivary flow and composition, and oral sensitivity are influenced by age. The changed oral physiology may influence perception of taste, odour and texture of the food. As a result food choice may be altered, which could lead to inadequate nutrient intake. Future trends are discussed in Section 1.7.

1.2 Food processing in the mouth

All ingested solid foods, regardless of bite size and initial texture, are processed in a stereotyped way by humans (Hiiemae et al., 1978; Hiiemae, 2004; German et al., 2004). After ingestion, the food is transported from the front of the mouth to the occlusal surfaces of the post-canine teeth (Stage I transport); and then the food is processed by a series of masticatory cycles needed to comminute and soften the food (food processing stage). The number of processing cycles increases as foods become more difficult to chew. When food is ready to be swallowed, it is propelled posteriorly into the oropharynx (Stage II transport). Food accumulates in the oropharynx until it is finally swallowed (Pedersen et al., 2002). The initiation of swallowing, which is voluntary, has been thought to depend on separate thresholds for food particle size and for particle lubrication (Hutchings and Lillford, 1988). However, instead of this duality, it has also been suggested that swallowing is initiated when it is sensed that a batch of food particles is bound together under viscous forces so as to form a bolus (Prinz and Lucas, 1997).

1.2.1 Influence of oral physiology on chewing

Characteristics of the oral system, such as bite force, number of teeth and salivary flow rate, will influence the masticatory process, e.g. size reduction of food particles, salivation and mixing of food particles into a food bolus that can be swallowed. The number of chewing cycles needed to prepare food for swallowing (stage I transport until swallowing), defined here as swallowing threshold or moment of swallowing, is fairly constant within a subject for one type of food, whereas large variations in the number of chewing cycles until swallowing were observed among subjects (Lucas and Luke, 1986; Fontijn-Tekamp et al., 2004). For instance, the number of chewing cycles needed to swallow 9.1 cm³ of peanuts varied between 17 and 110 in a group of 87 dentate subjects (Engelen et al., 2005). Furthermore, the moment of swallowing appeared to be strongly correlated among various natural foods (Fontijn-Tekamp et al., 2004; Engelen et al., 2005). This means that subjects who used a small number of chewing cycles for one food consistently also used small numbers for all types of food. This implies that there are ‘slow’ and ‘fast’ swallowers (subjects who swallow any food after a relative low or high number of cycles, respectively). This is partly the result of the individual’s physiology, but possibly also of the social context.

Figure 1.1 illustrates the large variation in chewing behaviour among people. The jaw movement, rectified muscle activity, and muscle work (product of jaw gape and muscle activity) are shown for two healthy subjects (A and B). The subjects were instructed to chew and swallow a piece of bread (13 cm³). Subject A chewed 8 times on the bread and then swallowed it (upper three rows), whereas the second subject chewed the bread 34 times, thus more than four times longer, before he swallowed it (lower three rows). Figure 1.1 clearly illustrates that muscle work decreases while mastication proceeds and the food bolus is softened.

Fig. 1.1 Jaw movement (JM), rectified muscle activity (EMG) and muscle work (work) of two subjects chewing a piece of bread (13 cm³). EMG and work bursts occur while the jaw is closing. The work bursts decline while mastication proceeds and the food bolus is softened. The dashed lines indicate the moments before the food was swallowed. Subject B chewed the bread more than four times longer than subject A.

1.2.2 Masticatory performance and swallowing

Masticatory performance can be determined by quantifying the degree of fragmentation of an artificial test food (Optosil, a silicon rubber) after a fixed number of chewing cycles (van der Bilt et al., 1993). Subjects chew on cubes of Optosil with an edge size of 5.6 mm for 15 chewing strokes. The degree of fragmentation of the chewed food is determined by sieving the food through a stack of sieves. The amount of test food on each sieve is weighed and the median particle size of the chewed food particles is determined from the weight distribution of particle sizes. The degree of fragmentation of the c...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright page
• Contributor contact details
• Preface
• Part I: Digestion and absorption of food components
• Part II: Advances in research methods to study food sensory perception, digestion and adsorption
• Part III: Implications
• Index