Delivery and Controlled Release of Bioactives in Foods and Nutraceuticals

Nissim Garti

• Publisher: Woodhead Publishing
• Year: 2008
• Print ISBN: 9781845691455
• eBook ISBN: 9781845694210
• Topic: Technology & Engineering
• Subtopic: Food Science
• Index: Technology & Engineering

Active ingredients in foods must remain fully functional for as long as necessary and be transported and discharged appropriately to have the desired nutritional effect. Delivery and controlled release systems are an essential way to achieve these aims. This important book reviews how to optimise these systems to maximise the health-promoting properties of food products.Opening chapters review factors affecting nutrient bioavailability and methods to test delivery system efficacy. Part two addresses materials used and specific techniques for delivery and release. The benefits and drawbacks of structured lipids, micro- and nano-emulsions, food-protein-derived materials, complexes and conjugates of biopolymers, and starch as an encapsulation material for delivery of functional food ingredients, are all considered. Part three discusses the delivery and controlled release of particular nutraceuticals such as antioxidants and vitamins, folic acid, probiotics, fish oils and proteins. Part four covers regulatory issues and future trends in bioactives and nutraceuticals.Edited by a leading expert in the field, Delivery and controlled release of bioactives in foods and nutraceuticals is a valuable reference for those working in the food industry and particularly those developing nutraceuticals. - Reviews techniques to optimise the delivery and release of bioactives in food - Discusses the factors that affect nutrient bioavailability and methods to test delivery system efficacy - Addresses materials used and specific techniques for delivery and release

Part I

The effectiveness of controlled release and delivery systems

Outline

Chapter 1: Assessing the bioavailability of nutraceuticals

Chapter 2: Structure of the gastrointestinal mucus layer and implications for controlled release and delivery of functional food ingredients

Chapter 3: Testing the effectiveness of nutrient delivery systems

Chapter 4: Lyotropic liquid crystals as delivery vehicles for food ingredients

1

Assessing the bioavailability of nutraceuticals

R.M. Faulks and S. Southon, Institute of Food Research, UK

1.1 Introduction

A targeted delivery system, natural or engineered, for the efficient release of an active compound from a food, nutraceutical or pharmaceutical matrix, can provide a means of optimising both extent and rate of absorption of the compound into the body. Delivery systems may also have considerable benefit by protecting essential nutrients and other ‘bioactive’ food components during food processing and digestion. For example, it may prevent the loss of the component, or adverse interactions with inhibitors of absorption.

However, optimum absorption should not be confused with maximum absorption, as so often happens in the bioavailability field. The concept of ‘if a little does you good, more will be better’ has pervaded the nutraceutical market for many years. Even with the essential nutrients, getting ‘more’ into the body at a ‘faster’ rate does not necessarily equate to ‘improved’ function and ‘better’ health, in some instances quite the reverse is the case (Omenn et al., 1996). Different rates of delivery of the same load may have a profound effect on subsequent health outcome. For example, there are proven health benefits from ‘slow release’ carbohydrate foods; they do not overstimulate the secretion of insulin, cause unnecessary large excursions in blood glucose, or undesirable glycosylation of proteins. By analogy, the slower delivery of other food components may maximise health benefits by not overloading transport systems, or causing undesirable excursions in plasma and tissue concentration. Furthermore, the fact that some portion of nutrients escape absorption in the small intestine and are ‘lost’ to the colon should not automatically be interpreted negatively, since they may contribute positively to colon health through the maintenance of an appropriate microflora and the production of beneficial products of large bowel fermentation.

Achieving optimum (amount, rate and site) rather than maximum absorption via controlled or targeted delivery is particularly pertinent to the focus of this book and highlights the importance of understanding the bioavailability concept and measuring its components intelligently. The following sections examine the bioavailability concept and approaches to measuring its component parts.

1.1.1 The bioavailability concept

Each year there are approximately 200+ research publications with ‘bioavailability’ in the title. It is obvious from these publications that ‘bioavailability’ means different things to different people. Its most common usage by far is to describe absorption, or ‘being in a form’ that can be absorbed. For drugs and the correction of nutritional deficiencies in plants and animals, the endpoints are closely monitored and evaluated. Where there is a putative benefit to human health, the endpoints of greatest interest and utility, namely the metabolic consequences and impact on wellbeing, are unfortunately seldom monitored and evaluated adequately. Although changes in plasma concentration, nutrient retention/excretion etc., induced by interventions, may be simply measured, the failure to evaluate holistic health benefit in ‘healthy volunteers’ seriously undermines any subsequent dietary recommendations.

The term ‘bioavailability’ has arisen (1) from the nutritional concept that some nutrients in food are only partially ‘available’, e.g. lysine, niacin and iron, and (2) in the field of pharmacology where it is a useful working concept of the ‘rate and extent to which a drug reaches its site of action’.

Clearly bioavailability has a number of components, embracing absorption, distribution, metabolism, excretion (ADME), with subsequent biochemical and physiological effects. It is therefore a concept and as such has no numerical value or units; it cannot be increased or diminished, only changed. Nevertheless, as a concept, it has value in providing a framework for studying links between the administration of a compound, the metabolic and physiological consequences and impact on health.

The pharmacological concept is concerned with site-specific drug delivery in order to treat a disorder, where effective and timely treatment requires the drug to reach a site at a concentration for sufficient duration to elicit the desired effect. Within this concept consideration is given not only to absorption but to concentration and persistence in the body, metabolism, and whether the compound (or its effective metabolites) can actually reach the target organ or site and elicit a clearly defined and characterised response. This involves considerations of, for example, toxicity, hydrophobicity, solubility, molecular size and shape, affinity for target, membrane permeability, carriers and transport mechanisms. Some of these properties can be manipulated by the construction of analogues, or derivatives, to achieve the desired outcome, while minimising toxicity and loss of active component. Thus it is possible to make an injected drug more ‘bioavailable’ by improving the affinity of the target, or constructing a derivative drug with greater affinity for the target. This amounts to manipulating the way the drug is partitioned into the various body pools. The selection of drug candidates and their modification for delivery and efficacy is a very sophisticated process; in contrast, the foods we eat contain many components about which we know almost nothing and which do not lend themselves to modification as a way of manipulating ‘bioavailability’.

As with drugs, the concept of nutrient bioavailability should embrace all these key issues. Bioavailability should not be limited (as so often happens) to measurement of nutrient release from the food (or ingredient) matrix and subsequent absorption. However, a drug is generally a known synthetic construct for a specific purpose. Prior to bioavailability trials, the drug will not be present (or will be present at a very low concentration) in the tissues of human volunteers, giving a clear baseline. When the drug is administered, it and its metabolites can be seen clearly to appear and disappear from the plasma pool or other assayed tissue. This makes absorption and metabolic studies much simpler to perform and interpret. Additionally, a drug is normally consumed in tiny quantities and is less likely to affect satiety, consumption patterns and lifestyle, whereas foods need to be supplementary to (or replace items of) habitual diet. A drug is usually incorporated into a simple matrix with predictable ‘release’ characteristics. Unlike food components, a drug is not a compound to which the body is normally exposed from the cradle to the grave. It is, however, possible to treat food components like drugs and to feed the extracted component and/or package it in simple or complex characterised delivery systems. This does not really simplify measurement in a tissue already containing the same component and its metabolites that have been derived from the diet. Furthermore, the extrapolation from populations who derive health benefits from eatin...

Table of contents

• Cover image
• Title page
• Table of Contents
• Related titles
• Copyright
• Contributor contact details
• Preface
• Part I: The effectiveness of controlled release and delivery systems
• Part II: Materials and techniques for controlled release and delivery of nutrients
• Part III: Delivery and controlled release of particular nutraceuticals
• Index