Functional Foods and Beverages E-Book

• Herausgeber: John Wiley & Sons
• Kategorie: Fachliteratur
• Serie: Institute of Food Technologists Series
• Sprache: Englisch

Seitenzahl: 530

Veröffentlichungsjahr: 2018

Beschreibung

A much-needed guide to in vitro food functionality evaluation principles, processes, and state-of-the-art modeling There are more than a few books devoted to the assessment of food functionality but, until now, there were no comprehensive guides focusing on the increasingly important subject of in vitro food evaluation. With contributions from the world's foremost experts in the field, this book brings readers up to speed on the state-of-the-art in in vitro modeling, from its physiological bases to its conception, current uses, and future developments. Food functionality is a broad concept encompassing nutritional and health functionality, food safety and toxicology, as well as a broad range of visual and organoleptic properties of food. In vitro techniques bridge the gap between standard analytical techniques, including chemical and biochemical approaches and in vivo human testing, which remains the ultimate translational goal for evaluation of the functionality of food. Although it is a well- established field, in vitro food testing continues to evolve toward ever more accurate predictions of in vivo properties and outcomes. Both ethical and highly economical, these approaches allow for detailed mechanistic insights into food functionalities and, therefore, a better understanding of the interactions of food and human physiology. * Reviews the core concepts of food functionality and functionality evaluation methodologies * Provides an overview of the physiology of the gastrointestinal tract, including host-microbial interactions within it * Delves into the physiology of sensory perception of food, taste and texture as they relate to in vitro modeling * Explores the challenges of linking in vitro analysis of taste, aroma and flavor to their actual perception * Addresses in vitro models of the digestion and absorption of macronutrients, micronutrients, and phytonutrients * Describes in vitro evaluations of toxicants, allergens and other specific food hazards Functional Foods and Beverages is an indispensable working resource for food scientists as well as researchers working in government facilities dedicated to tracking food safety.

Leseprobe

The IFT Press series reflects the mission of the Institute of Food Technologists—to advance the science of food contributing to healthier people everywhere. Developed in partnership with Wiley‐Blackwell, IFT Press books serve as leading‐edge handbooks for industrial application and reference and as essential texts for academic programs. Crafted through rigorous peer review and meticulous research, IFT Press publications represent the latest, most significant resources available to food scientists and related agriculture professionals worldwide. Founded in 1939, the Institute of Food Technologists is a nonprofit scientific society with 22,000 individual members working in food science, food technology, and related professions in industry, academia, and government. IFT serves as a conduit for multidisciplinary science thought leadership, championing the use of sound science across the food value chain through knowledge sharing, education, and advocacy.

IFT Press Advisory Group

Casimir C. AkohChristopher J. DoonaFlorence FeeherryJung Hoon HanDavid McDadeRuth M. PatrickSyed S.H. RizviFereidoon ShahidiChristopher H. SommersYael VodovotzKaren Nachay

IFT Press Editorial Board

Malcolm C. BourneDietrich KnorrTheodore P. LabuzaThomas J. MontvilleS. Suzanne NielsenMartin R. OkosMichael W. ParizaBarbara J. PetersenDavid S. ReidSam SaguyHerbert StoneKenneth R. Swartzel

Functional Foods and Beverages

In vitro Assessment of Nutritional, Sensory, and Safety Properties

Edited by

Dr Nicolas Bordenave

Faculty of Health SciencesSchool of Nutrition SciencesUniversity of Ottawa, OttawaCanada

Dr Mario G. Ferruzzi

Department of Food, Bioprocessing and Nutrition SciencePlants for Human Health InstituteNorth Carolina State University, Raleigh, USA

This edition first published 2018

© 2018 John Wiley & Sons, Inc.

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Library of Congress Cataloging‐in‐Publication Data

Names: Bordenave, Nicolas, 1980–, editor. | Ferruzzi, Mario G., editor. | Institute of Food Technologists.Title: Functional foods and beverages : in vitro assessment of nutritional, sensory, and safety properties / edited by Dr. Nicolas Bordenave, Dr. Mario G. Ferruzzi.Description: First edition. | Hoboken, NJ, USA : Wiley, 2018. | Series: IFT Press series | Includes bibliographical references and index. |Identifiers: LCCN 2018015499 (print) | LCCN 2018016150 (ebook) | ISBN 9781118823156 (pdf) | ISBN 9781118823200 (epub) | ISBN 9781118733295 (hardback)Subjects: LCSH: Functional foods–Testing. | Nutrition–Evaluation. | Toxicity testing–In vitro. | BISAC: TECHNOLOGY & ENGINEERING / Food Science.Classification: LCC QP144.F85 (ebook) | LCC QP144.F85 F8636 2018 (print) | DDC 613.2–dc23LC record available at https://lccn.loc.gov/2018015499

Cover Design: WileyCover Image: © 279photo Studio/Shutterstock; © 9dream studio/Shutterstock; © Vadim Ginzburg/123RF

Titles in the IFT Press series

Accelerating New Food Product Design and Development (Jacqueline H. Beckley, Elizabeth J. Topp, M. Michele Foley, J.C. Huang, and Witoon Prinyawiwatkul)

Advances in Dairy Ingredients (Geoffrey W. Smithers and Mary Ann Augustin)

Bioactive Proteins and Peptides as Functional Foods and Nutraceuticals (Yoshinori Mine, Eunice Li‐Chan, and Bo Jiang)

Biofilms in the Food Environment (Hans P. Blaschek, Hua H. Wang, and Meredith E. Agle)

Calorimetry in Food Processing: Analysis and Design of Food Systems (Gönül Kaletunç)

Coffee: Emerging Health Effects and Disease Prevention (YiFang Chu)

Food Carbohydrate Chemistry (Ronald E. Wrolstad)

Food Irradiation Research and Technology (Christopher H. Sommers and Xuetong Fan)

High Pressure Processing of Foods (Christopher J. Doona and Florence E. Feeherry)

Hydrocolloids in Food Processing (Thomas R. Laaman)

Improving Import Food Safety (Wayne C. Ellefson, Lorna Zach, and Darryl Sullivan)

Innovative Food Processing Technologies: Advances in Multiphysics Simulation (Kai Knoerzer, Pablo Juliano, Peter Roupas, and Cornelis Versteeg)

Microbial Safety of Fresh Produce (Xuetong Fan, Brendan A. Niemira, Christopher J. Doona, Florence E. Feeherry, and Robert B. Gravani)

Microbiology and Technology of Fermented Foods (Robert W. Hutkins)

Multivariate and Probabilistic Analyses of Sensory Science Problems (Jean‐François Meullenet, Rui Xiong, and Christopher J. Findlay)

Natural Food Flavors and Colorants (Mathew Attokaran)

Nondestructive Testing of Food Quality (Joseph Irudayaraj and Christoph Reh)

Nondigestible Carbohydrates and Digestive Health (Teresa M. Paeschke and William R. Aimutis)

Nonthermal Processing Technologies for Food (Howard Q. Zhang, Gustavo V. Barbosa‐Ćanovas, V.M. Balasubramaniam, C. Patrick Dunne, Daniel F. Farkas, and James T.C. Yuan)

Nutraceuticals, Glycemic Health and Type 2 Diabetes (Vijai K. Pasupuleti and JamesW. Anderson)

Organic Meat Production and Processing (Steven C. Ricke, Michael G. Johnson, and Corliss A. O’Bryan)

Packaging for Nonthermal Processing of Food (Jung H. Han)

Preharvest and Postharvest Food Safety: Contemporary Issues and Future Directions (Ross C. Beier, Suresh D. Pillai, and Timothy D. Phillips, Editors; Richard L. Ziprin, Associate Editor)

Regulation of Functional Foods and Nutraceuticals: A Global Perspective (Clare M. Hasler)

Sensory and Consumer Research in Food Product Design and Development, second edition (Howard R. Moskowitz, Jacqueline H. Beckley, and Anna V.A. Resurreccion)

Sustainability in the Food Industry (Cheryl J. Baldwin)

Thermal Processing of Foods: Control and Automation (K.P. Sandeep)

Water Activity in Foods: Fundamentals and Applications (Gustavo V. Barbosa‐Ćanovas, Anthony J. Fontana Jr., Shelly J. Schmidt, and Theodore P. Labuza)

Whey Processing, Functionality and Health Benefits (Charles I. Onwulata and Peter J. Huth)

List of Contributors

Nicolas Bordenave, PhDFaculty of Health Sciences,School of Nutrition Sciences,University of Ottawa, Ottawa,Canada

Chureeporn Chitchumroonchokchai, PhDHuman Nutrition Program,Department of Human Sciences,The Ohio State University,Columbus, USA

Mark L. Failla, PhDHuman Nutrition Program,Department of Human Sciences,The Ohio State University,Columbus, USA

Mario G. Ferruzzi, PhDDepartment of Food,Bioprocessing and Nutrition Science,Plants for Human Health Institute,North Carolina State University,Raleigh, USA

Christopher Forsyth, PhDDepartment of Internal Medicine, Rush Medical College,Rush University,Chicago, USA

James Hollis, PhDDepartment of Food Science and Human Nutrition,Iowa State University,Ames, USA

Avinash Kant, PhDPepsiCo Intl, Beaumont Park R&D,Leicester, UK

Ali Keshavarzian, MDDepartment of Internal Medicine, Rush Medical College,Rush University,Chicago, USA

Rachel Levantovsky, PhDDepartment of Food Science and Commonwealth Honors College,University of Massachusetts,Amherst, USA

Rob Linforth, PhDFood Sciences, School of Biosciences,University of Nottingham,Nottingham, UK

Amy D. Mackey, PhDAbbott Nutrition,Abbott Laboratories,USA

Edwin K. McDonald IV, MDPritzker School of Medicine,The University of Chicago,Chicago, USA

Ossanna Nashalian, PhDFaculty of Health Sciences,School of Nutrition Sciences,University of Ottawa,Ottawa, Canada

Ezgi ÖzcanDepartment of Food Science,University of Massachusetts,Amherst, USA

Robin A. Ralston, PhDCenter for Advanced Functional Foods Research and Entrepreneurship,College of Food, Agricultural, and Environmental Sciences,The Ohio State University,Columbus, USA

Heather Rasmussen, PhD, RDDepartment of Clinical Nutrition, College of Health Sciences,Rush University,Chicago, USA

Steven J. Schwartz, PhDDepartment of Food Science and Technology,The Ohio State University,Columbus, USA

David A. Sela, PhDDepartment of Food Science,Center for Microbiome Research,University of Massachusetts,Amherst, USA

Christopher T. Simons, PhDDepartment of Food Science and Technology,The Ohio State University,Columbus, USA

Susan M. Tosh, PhDFaculty of Health Sciences,School of Nutrition Sciences,University of Ottawa,Ottawa, Canada

Ioannis Trantakis, PhDDepartment of Health Sciences and Technology,Swiss Federal Institute of Technology in Zurich,Zurich, Switzerland

Chibuike Udenigwe, PhDFaculty of Health Sciences,School of Nutrition Sciences,University of Ottawa,Ottawa,Canada

Amanda Wright, PhDHuman Health and Nutritional Sciences,University of Guelph,Guelph, Canada

Preface

Food functionality is a wide concept that encompasses nutritional/health functionality, food safety and toxicology, as well as broad aspects of visual and organoleptic properties of food. The evaluation of all these individual aspects have been widely covered in many books and review articles over the years. So, why have a book on in vitro systems for testing aspects food functionality?

As you will read in this book, in vitro techniques bridge the gap between standard analytical techniques (chemical and biochemical) and in vivo human testing, which remains the ultimate translational goal for evaluation of the functionality of food. Although well established, this domain is constantly evolving toward closer and higher throughput prediction of in vivo properties and outcomes. In vitro testing facilitates high throughput assessment of food properties in a cost‐effective manner without practical and ethical challenges of human testing. By establishing tight control of testing conditions, these approaches also allow for detailed mechanistic insights to be developed on food functionalities and therefore a better understanding of interactions between food and human physiology. Nevertheless, in vitro models, as with all model systems, have their own limitations. Research and development efforts are continuously progressing to refine these methods, their predictive power, and their applicability to diverse systems and conditions. In vitro testing of food functionality is therefore a field of its own and with this in mind, is deserving to be the main subject of its own text. The ambition of this book is to establish the current state‐of‐the‐art of in vitro models, from their physiological basis to their conception, their uses, and finally their future.

Chapter 1 reviews the concepts of functional foods and food functionalities, highlighting the necessity of evaluating such functionalities. In the next section (Chapters 2 and 3), Chapter 2 overviews the physiology of the gastrointestinal tract, presenting features that constitute the basis of in vitro models for evaluating food’s nutritional, toxicological and allergenic properties. Chapter 3 covers the physiology of sensory perception of food, taste and texture. In the final section (Chapters 4 to 9), Chapter 4 overviews the in vitro models of host–microbial interactions within the gastrointestinal tract as well as the gastrointestinal model themselves. Chapters 5 and 6 address the in vitro models for the digestion and absorption of macronutrients, micronutrients and phytonutrients. Chapters 7 and 8 address the in vitro evaluation of specific food hazards, namely toxicants and allergens. Finally, Chapter 9 presents the challenges of linking in vitro analysis of taste, aroma and flavor to their actual perception.

We hope that this book will be useful to food scientists, graduate students, professors and professionals, in academia, government research or food industry R&D, who are working hard to deliver safe products of increasingly high quality to consumers.

Nicolas BordenaveMario G. Ferruzzi

Acknowledgements

The editors are profoundly grateful to the contributing authors of this book. Their expertise and insights were critical to making this book a reality, and their patience and dedication through the delayed development of the project must be acknowledged. The editorial assistance and patience of David McDade, Athira Menon, Priya Subbrayal and the other staff members at John Wiley & Sons, are also gratefully acknowledged as well Carolyn Holleyman for her copy‐editing work.

1Overview of Functional Foods

Robin A. Ralston1, Amy D. Mackey2, Christopher T. Simons3 and Steven J. Schwartz3,*

1 Center for Advanced Functional Foods Research and Entrepreneurship, College of Food, Agricultural, and Environmental Sciences, The Ohio State University, Columbus, USA

2 Abbott Nutrition, Abbott Laboratories, USA

3 Department of Food Science and Technology, The Ohio State University, Columbus, USA

*Corresponding author.

1.1 Overview of Functional Foods

1.1.1 Foods and Nutrients are Linked to Health and Disease

The Centers for Disease Control and Prevention (CDC) indicates that a healthy lifestyle, including healthy foods, is one strategy to prevent chronic disease (CDC, 2012). Epidemiological studies have shown a diet rich in fruits and vegetables can reduce the risk of inflammatory and age‐related chronic diseases, including many cancers, cardiovascular disease, and inflammation (Barbaresko et al., 2013; Esposito and Giugliano, 2006; Heggie et al., 2003; Hu, 2003).

Foods, especially plant foods, contain non‐nutrient bioactive compounds that have potential to synergistically and positively impact health. The primary classes are phenolic compounds, carotenoids, alkaloids, nitrogen‐containing compounds, organosulfur compounds, and phytosterols (Liu, 2004, 2013a, 2013b). More than 5000 bioactive components have been identified in plant foods (Liu, 2004, 2013a), but it is thought that more than 25,000 bioactive components are actually present. Most of these components are metabolized to different compounds during and after digestion. Considering these 25,000 bioactives and all of their metabolites, it would be unrealistic to conclude there is a single compound which serves as a “silver bullet” for health promotion. Instead, it is the combination of many dietary compounds consumed from a variety of whole foods that likely confers the greatest health benefits (Liu, 2004). Undoubtedly, there is still much research required in order to fully understand the role of bioactive dietary compounds and their metabolites in human health.

1.1.2 Definition of Functional Foods

Defining functional foods can be difficult. There is no U.S. Food and Drug Administration (FDA) definition of functional foods, and all foods can be considered “functional” because all cause some physiological response. The Academy of Nutrition and Dietetics (AND) defines functional foods as “whole foods along with fortified, enriched, or enhanced foods that have a potentially beneficial effect on health when consumed as part of a varied diet on a regular basis at effective levels” (Crowe and Francis, 2013). Similarly, the Institute of Food Technologists (IFT) defines functional foods as “foods and food components that provide a health benefit beyond basic nutrition (for the intended population)” (IFT, 2005). Thus, functional foods can encompass fresh foods, such as tomatoes and broccoli, along with processed or cooked foods, such as tomato juice and broccoli soup. Functional foods also include foods that naturally contain non‐nutrient bioactive components, such as flax seeds, as well as foods fortified with bioactive components, such as various nutrition bars.

1.1.3 Functional Foods Market

As reviewed by E. Sloan, the Nutrition Business Journal (2013) reports that worldwide sales of functional foods were $118 billion in 2012. With an increase of 7% from 2011 to 2012, the United States is the largest market for functional foods (sales of $43.9 billion), followed by Japan ($22 billion), the United Kingdom ($8.1 billion), and Germany ($6.4 billion) (Sloan, 2014). Also reviewed by E. Sloan, the Multi‐Sponsor Surveys’ 2012 Gallup Study of Nutrient Knowledge and Consumption reports that 60% of adults in the U.S. consume functional foods or beverages at least occasionally (Sloan, 2014). These statistics confirm that not only is the study of functional foods valuable for consumer health, but also that there is interest by the food and nutrition industries to develop new products for consumers that truly improve health (Pricewaterhouse Coopers, 2009).

1.1.4 How Functional Foods are Studied

Large epidemiological studies are usually used to discover a potential association between a food or group of foods and a health condition. Due to wide variability in various characteristics of epidemiological cohorts (e.g. diet and other environmental exposures, race and other genetic factors), randomized, controlled, human clinical intervention studies are used to identify cause and effect relationships between a specific food and a health condition. These randomized controlled trials are considered the “gold standard”, mandatory to develop health claims, and usually required to develop dietary recommendations. While it is recognized that cellular or other in vitro models will never perfectly replicate the complex system of the human body, in vitro methods are an essential piece of the puzzle. They can be used to understand the identity and quantity of bioactive components in foods and their metabolites once the food is consumed. In addition, in vitro models are used to study mechanisms of action as well as absorption and metabolism. Because even small human clinical intervention studies are very expensive and time intensive, in vitro preclinical models are often used to validate epidemiological data, predict the outcome of a human or animal study, justify execution of human clinical trials, and predict human sensory perception of functional foods.

In vitro methodologies are typically used throughout a “crops to the clinic” approach to functional foods research, from growing the plant, producing a food product, analyzing the bioactive components, and predicting the bioavailability and biological activity of the bioactives, all with the goal of justifying use of the food in a human clinical study (Ferruzzi et al., 2012). These aspects are discussed below.

When growing a plant to be used as a functional ingredient in a food product, in vitro methodologies are used to understand genetic and molecular pathways which influence the levels of bioactive components in a plant. For example, genetic mapping techniques can be developed to identify plant varieties that contain higher levels of a specific bioactive component or a form of the bioactive component which is more biologically active or more bioavailable (Battino et al., 2009; Kuzina et al., 2011). In addition, growing conditions such as temperature, light, and soil nutrients can be modulated to optimize levels of a particular bioactive component (Bumgarner et al., 2012). Processing conditions, inclusion of other ingredients, and storage conditions can also impact the stability and biological activity of bioactive compounds, and thus can be monitored using in vitro analytical methods to identify and quantify bioactive compounds in food.

The techniques of high performance liquid chromatography (HPLC) in combination with photodiode array (PDA) and/or mass spectrometry (MS) are used for analysis of bioactive compounds in foods. PDA is sufficient to quantify compounds that are adequately detected with UV‐Vis absorption, while MS, based on a compound’s unique mass‐to‐charge ratio (m/z), is essential for compounds that require greater selectivity or are at lower concentrations and require greater sensitivity. Tandem MS (MS/MS) and accurate mass measurements provide further confidence in quantitation and identification, respectively. These methods are used to identify and quantify a range of bioactive compounds and their metabolites to help answer a variety of research questions. As above, analytical methods are essential to study the impact of different plant varieties, growing conditions, maturity levels, and plant disease on the type and amount of bioactive components in plants, and the impact of processing, storage, and the presence of other ingredients on the bioactive levels of a functional food product, ultimately predicting the potential health benefits. Bioactive identification and quantification is also critical when evaluating the stability and metabolism of a compound during simulated (in vitro) digestion and absorption, in addition to after consumption by animals or humans.

In vitro methods can be used to simulate the bioaccessibility and bioavailability of a functional food or a specific bioactive compound before advancing to a human clinical study. Bioactive components or their active metabolites must reach the target tissue in order to have a health benefit. Thus, bioactives must be released from the food, must remain stable during oral, gastric, and intestinal digestion, and must be delivered to the target tissue (Rein et al., 2013). Digestive stability and bioaccessibility can be predicted using cell‐free methods, while absorption and transport across cells can be investigated using Caco‐2 intestinal cell methods, saving valuable time and research funds. Many factors can influence stability, digestion, and absorption, such as the chemical properties of the bioactive component, the food source and its matrix, interaction with other components in the food, pH, and temperature (Failla et al., 2008; Rein et al., 2013). Newer multi‐compartmental models are also being developed that connect cultures of different cell types (e.g. intestine, liver, and adipose tissue) in order to study metabolism (Vinci et al., 2012).

Biological activity can also be predicted using in vitro models. Antioxidant activity is one of the most common in vitro screening assessments, but bioactive components have many synergistic mechanisms of action that go beyond antioxidant activity (Liu, 2004). Assessing multiple mechanisms provides a more complete picture of the potential biological activity of a bioactive or food. Therefore, the health benefits of a food or ingredient should not be based on a single antioxidant assay, and it is important that a multi‐faceted approach be taken before drawing conclusions. The appropriate in vitro model will be dependent on the disease or health condition that is being targeted. For example, when evaluating a food for its potential benefit in reducing risk of cardiovascular disease, in vitro markers might include models of platelet function (collagen‐induced platelet aggregation, TRAP‐induced P‐selectin expression as a marker of platelet activation) (Ostertag et al., 2011), inhibition of LDL carbamylation (Ghaffari and Shanaki, 2010), models of carotid injury (Sheu et al., 2013), oxidative stress‐induced cardiomyocyte injury (Li et al., 2013), and hemolysis assays (Li et al., 2013).

It is important to note the limitations of in vitro methods. It is impossible to replicate the conditions of the human body. For example, with in vitro experiments, there is no homeostasis, cell studies usually only include one type of cell grown in a monolayer, and experiments are usually optimized for maximum cell growth, all conditions which do not occur in the human body (Hartung and Daston, 2009). Thus, in vitro studies are only predictive of potential biological activity. In order to validate findings from in vitro experiments, animal and human clinical trials are required.

1.2 Functional Foods and their Regulatory Aspects

Around the world, most commercially available products consumed are categorized as food or drugs, with drugs intending to cure, prevent, treat, or mitigate disease, while food is generally consumed for taste, aroma, or nutritive value (Nutrilab v. Schweiker, 1983). Although functional foods may provide benefit beyond standard nutritive value, they must adhere to food regulations. The primary objective of regulatory authorities is to protect the public by ensuring food safety and preventing misleading or false product claims. Many countries do not have specific functional food regulations and often manage these through pre‐market evaluation of health benefit/disease risk reduction claims. Japan has one of the most developed regulatory frameworks for functional foods. In Japan, functional foods are officially recognized under a specific “food for specified health use (FOSHU)” which permits claims related to reduction of disease risk (Shimizu, 2012). Japanese regulatory authorities review these foods before they can be placed on the market. The application must include significant scientific evidence that demonstrates the benefit of the health claim, safety, and physical and chemical characterization.

The approach to establishing safety of a functional food does not differ from other foods. Similar to other regulatory bodies (such as the European Union and Canada), the US FDA has published guidance on the studies necessary to support the safety of a new food ingredient (Center for Food Safety and Applied Nutrition, 2007). This guidance helps develop data to demonstrate that a food ingredient is safe for the specific use at a specific use level, including for use as a functional food.

1.3 Nanotechnologies in Functional Foods

Nanotechnology is increasingly being used in functional food products. Nanotechnology is defined by the U.S. National Nanotechnology Initiative as “the understanding and control of matter at dimensions between approximately 1 and 100 nanometers (nm), where unique phenomena enable novel applications not feasible when working with bulk materials or even with single atoms or molecules” (U.S. National Nanotechnology Initiative, 2014). One application of nanotechnology in functional foods and nutraceuticals is to protect a functional ingredient from degradation during production, storage, or digestion (e.g. acidity of stomach) (Ranjan et al., 2014). For example, George Weston Foods (North Ryde, New South Wales, Australia) incorporates tuna fish oil into bread to enhance the bread’s health benefits, but to avoid off odors and flavors, the fish oil is encapsulated within nanoparticles and is released only in the acidic environment of the stomach rather than in the food product (Neethirajan and Jayas, 2011). Nanotechnology is also being used to control the release rate of a functional ingredient, improve bioavailability of a compound, or target delivery to a specific cell type or tissue (Ranjan et al., 2014). For instance, nanotechnology has been used to encapsulate probiotic bacteria to protect it from harsh stomach conditions, allowing controlled release of the bacteria in the neutral environment of the intestine (Neethirajan and Jayas, 2011). Several different types of delivery systems are being evaluated for use in food products, including:

Micelles:

Lipid‐soluble bioactives, e.g. limonene, lycopene, lutein, omega‐3 fatty acids, and essential oils, have very low bioavailability, limiting their use in functional foods (H. Chen, Weiss, and Shahidi,

2006

; McClements and Xiao,

2012

). Because of their polar head groups and nonpolar tail groups, micelles are being evaluated for encapsulation of nonpolar functional food components to allow incorporation into beverages (H. Chen

et al

.,

2006

). This strategy has been used in the pharmaceutical industry to more effectively deliver poorly water‐soluble drugs (McClements and Xiao,

2012

).

Liposomes and cubosomes

are bi‐ or tri‐phasic structures used to encapsulate water‐soluble compounds within a hydrophilic component and conversely, to encapsulate lipid‐soluble compounds within a lipophilic component. Liposomes and cubosomes are currently being used or evaluated for their ability to encapsulate the proteins lactoferrin and nisin Z to increase the shelf life of dairy products, encapsulate phosvitin (naturally found in egg yolk) to inhibit lipid oxidation in dairy products and ground pork, and encapsulate vitamin C to maintain its activity during long refrigerated storage (H. Chen

et al

.,

2006

). Cubosomes can be altered with pH and temperature changes, and can thus be used to control the release of functional compounds (H. Chen

et al

.,

2006

).

Nanoemulsions:

Because these emulsions are so fine, they are clear to the eye rather than opaque (B. Chen

et al

.,

2013

; H. Chen

et al

.,

2006

). Nanoemulsions are thermodynamically more stable than regular emulsions, and therefore do not separate over time (Ranjan

et al

.,

2014

). Because of these properties, nanoemulsions are commonly used in parenteral nutrition formulations (H. Chen

et al

.,

2006

), to add fat‐soluble bioactive components to clear beverages (B. Chen

et al

.,

2013

), and to obtain a creamy mouthfeel with limited lipid levels (H. Chen

et al

.,

2006

).

Biopolymeric nanoparticles

are nanopolymers that are linked to form solid particles. A variety of different types of compounds can be encapsulated with biopolymeric nanoparticles, and their use is becoming more popular in functional ingredients. Examples include chitosan (derived from crustacean shells) and the synthetic polymers polylactic acid, polyglycolic acid, and combinations of lactide, galactide, and caprolactone (H. Chen

et al

.,

2006

).

New tools also are incorporating biological and chemical ligands that can direct functional compounds within nanoparticles to a specific cell type (H. Chen et al., 2006). The ability to deliver a functional component to a targeted cell or tissue site increases effectiveness and efficiency, allows the compound to be incorporated into the product at lower levels, and therefore can result in fewer adverse effects. For example, if salt could be incorporated in such a way that it is directed only to taste buds that detect salt, the amount used in the food could be greatly decreased. In the future, there is potential to use nanotechnology to release a bioactive compound only in response to a specific biological trigger, such as a biochemical or genetic marker, leading to possibility of personalized nutrition (H. Chen et al., 2006). Use of nanotechnology in food applications is still in the early stages, and much research is needed to ensure safety, including how nanoparticles are absorbed in the gastrointestinal tract, where nanoparticles are distributed in human body, how long they remain, what concentration they reach, and if the nanoparticles affect unintended biological activity (McClements and Xiao, 2012; Ranjan et al., 2014). As with any new technology, consumers must be educated in order to maintain confidence in the technology and products using the it (Ranjan et al., 2014).

1.4 Sensory Functionalities of Foods

Consumers have expectations regarding the appearance, aroma, flavor, taste and texture of food products and, as such, these sensory properties are key drivers to product acceptance. As a consequence, food companies have traditionally invested heavily in the identification and optimization of important sensory attributes. Emerging evidence, however, suggests that consumers are becoming more savvy and are increasingly looking beyond the sensory attributes to other product characteristics that influence acceptance and choice (Ares, 2011; Wills et al., 2012). In this regard, interest in functional foods has recently burgeoned as consumers are seeking to improve health and wellness by incorporating functional ingredients into their diets. Unfortunately, many bioactive compounds have negative taste and flavor properties and require focused efforts to improve their palatability (Sun‐Waterhouse and Wadhwa, 2012). However, for many functional foods, the level of sacrifice that consumers are willing to make in taste and flavor in favor of functionality is unknown. Further research is needed to understand these tradeoffs and to determine their relative importance in different populations (e.g. healthy vs. diseased).

As with all food products, the sensory properties of functional foods should, as much as possible, be optimized to meet or surpass consumer expectations. Prior to executing expensive sensory and consumer testing, instrumental analyses can be completed to gain insight into various physical parameters of the product that influence sensory variables (Kilcast, 2013). Because the human senses are impacted by physiological and psychological factors, it is impossible to replicate human senses with an instrument, which can only provide a discrete measure of a specific property. However, instrumental analyses might be used to reduce the number of samples on which to conduct human sensory assessment. For each product, instrumental analyses should be verified with human sensory panels so that they can be used to predict future results. The superficial appearance and color of food are the first parameters of quality evaluated by consumers. Colorimetry can be used to measure factors contributing to the product’s appearance including the chromaticity and radiance, surface reflectance, transmittance and/or translucency (Clydesdale, 1978). Rheological assessments, infrared spectroscopy, water activity measurement and texture analysis can provide understanding of food properties related to perceived texture attributes including viscosity, tenderness, crunchiness, or chewiness, respectively (L. Chen and Opara, 2013; Tunick, 2011). Quantification of volatile and non‐volatile compounds enables the detection and identification of chemical species contributing to flavor, odor, and taste. These techniques are particularly important in understanding matrix interactions (e.g. sequestration of hydrophobic compounds into lipids) that impact flavor release and product perception as well as in the identification of taints or other compounds contributing unique sensations. Moreover, real‐time chemical analysis with techniques such as proton transfer reaction‐mass spectrometry or selected‐ion flow tube‐mass spectrometry enable correlating concentration of volatile flavor compounds in exhaled air to perception of flavor attributes.

In summary, functional foods have much potential to positively impact human health. Both consumers and the food and nutrition industries are eager to take advantage of these foods with health benefits beyond those imparted by traditional nutrients. A “big picture” crops to the clinic approach to studying functional foods is essential. In vitro methodologies are an important piece of this puzzle, and can be used to identify and quantify bioactive components in foods, identify potential mechanisms of action, and predict bioavailability and metabolism, and thus can be used to justify execution of a human clinical trial.

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2The In vivo Foundations for In vitro Testing of Functional Foods: The Gastrointestinal System

Edwin K. McDonald IV1, Heather Rasmussen2, Christopher Forsyth3 and Ali Keshavarzian3,*

1 Pritzker School of Medicine, The University of Chicago, Chicago, USA

2 Department of Clinical Nutrition, College of Health Sciences, Rush University, Chicago, USA

3 Department of Internal Medicine, Rush Medical College, Rush University, Chicago, USA

*Corresponding author.

2.1 Introduction

Despite lacking universally accepted definitions, there is substantial interest amongst consumers and researchers in using food to augment or optimize health, the concept underlying functional foods (Weaver, 2014; Milner, 1999). A significant reason for this underlying interest is a shift in nutritional research over the past 30 years from focusing on nutritional deficiencies to nutritional optimization. This shift is partly due to accumulating evidence linking poor diet to chronic non‐communicable diseases including diabetes, cardiovascular disease, and obesity along with an increasing prevalence of these conditions (Hasler et al., 2009; Cencic and Chingwaru, 2010). Further, recent advances in the “Omics” fields of metabolomics, nutrigenomics, proteomics, and microbiomics have created additional means by which functional foods can be studied. These fields highlight the possibility of progressing towards additional evidence‐based, optimized nutrition (Rist et al., 2006).

Despite considerable interest in functional foods, credible science‐based evidence linking functional foods to health benefits is lacking (Weaver, 2014). Although the FDA does not specifically define functional foods, the 1990 Nutrition Labeling and Education Act (NLEA) mandates a high standard of scientific evidence for obtaining FDA approval for health claims associated with foods (Williams, 2005). Randomized controlled trials, epidemiologic studies, and in vivo and in vitro studies are needed to identify functional foods and validate their associated health claims (Sohaimy, 2012; Weaver, 2014). Aside from identifying functional foods and their role in treatment of specific disease or for maintaining health, there is a need for mechanistic studies of functional foods. Fundamentally, mechanistic research of functional foods must answer several questions:

How are the bioactive components within a functional food processed by the gastrointestinal system?

What are the physiologic mechanisms and targets through which functional foods exert their beneficial effects?

What are biomarkers of exposure and response to components within functional foods?

What are appropriate doses of functional foods?

What are the safety considerations of functional foods? (Milner,

1999

).

Since functional foods require ingestion prior to conferring any health benefits, all functions of functional foods begin with the gastrointestinal tract. Additionally, the gastrointestinal environment extensively modifies many functional foods such that the bioactive compound of a functional food that reaches circulation differs from what was ingested (Foltz et al., 2010). As such, understanding the gastrointestinal tract and its underlying physiology is prerequisite for answering the questions above. In vitro modeling of the gastrointestinal tract can further elucidate answers to these aforementioned questions (Salminen et al., 1998; Pang et al., 2012).

2.2 Overview of the Structure of the Gastrointestinal Tract

Defined simply, the gastrointestinal tract (GIT) is a hollow, muscular tube consisting of the mouth, esophagus, stomach, small intestine, large intestine, and anus. It is 20–30 feet long in its entirety and has a substantial surface area due to its length and finger‐like projections extending from the inner intestinal lining known as villi. The wall of the GIT is largely composed of four layers: mucosa, submucosa, muscularis (or muscularis propia), and serosa (or adventitia). Each layer is comprised of specialized tissues with specific functions.

2.2.1 Mucosa

The mucosa is the innermost layer of the GIT. It is composed of the epithelium, lamina propria, and the muscularis propria (Ellen Kahn, 2010). The epithelium provides a physical barrier to the external environment as the mucosa contacts the gastrointestinal lumen, the inner cavity of the GIT. Epithelium is particularly relevant to functional foods since it is the primary site responsible for digesting and absorbing these foods. There are multiple cell types within the epithelium that vary throughout the regions of the GIT. Notably, intestinal epithelial cells (IECs) and secretory cells, such as enteroendocrine cells, are primarily responsible for digesting and absorbing foods. The epithelial cells are specialized for the absorption of nutrients and exchange of water and electrolytes, while the enteroendocrine cells such as cholecystokinin (CCK) and glucagon‐like‐peptide 1 (GLP‐1) secreting cells are responsible for promoting enzymatic breakdown of macronutrients and regulating satiety, respectively (Farré and Tack, 2013). Due to the predominance of hormone producing enteroendocrine cells within the epithelial layer, the GIT is the largest endocrine organ in the body (Chaudhri et al., 2006).

The lamina propria is the layer of connective tissue between the epithelium and the muscularis mucosa and supports the epithelial layer. It also contains immune cells such as plasma cells, macrophages, and lymphocytes (Shils and Shike, 2006). The muscularis mucosa is a thin layer of smooth muscle. Its contractions assist with the secretion of products contained in secretory cells within the epithelial layer (Ellen Kahn, 2010).

2.2.2 Submucosa

The submucosa is a layer of collagenous connective tissue situated between the muscularis mucosa and the muscularis propria and provides flexibility to the gastrointestinal tract. The submucosa contains blood and lymphatic vessels that recover absorbed nutrients that have traversed the epithelial layer. The submucosa also contains Meissner’s plexus, a nerve fiber plexus containing post‐ganglionic sympathetic and parasympathetic neurons. Additionally, scattered lymphoid nodules known as Mucosa Associated Lymphoid Tissue (MALT) are located in the submucosa (Shils and Shike, 2006).

2.2.3 Muscularis (or Muscularis Propria) and Serosa (or Adventitia)

The muscularis is primarily responsible for the motility of the GIT. It contains muscle organized in two layers, an inner circular layer and an outer longitudinal layer. The muscular layers of the GIT are composed of smooth muscle with the exception of skeletal muscle in the upper esophagus and external anal sphincter. Auerbach’s plexus, a nerve fiber plexus containing parasympathetic and sympathetic fibers, is localized between these two layers of smooth muscle (Shils and Shike, 2006). The serosa is the outermost layer of the GIT and is comprised of a thin layer of mesothelial cells. The adventitia is an outer layer of connective tissue. These outer layers contain nerves and blood vessels.

While all of these components of the GIT are critical to its function, a majority of the in vitro methods used to represent the GIT primarily model the mucosal layer, specifically the intestinal epithelial cells.

2.2.4 Additional Components of the Gastrointestinal Tract: Accessory Organs, Vasculature, Innervation, Gut‐Associated Lymphoid Tissue, and Microbiome