Nondestructive Testing of Food Quality

EDITORS Joseph Irudayaraj rChristoph Reh Nondestructive Testing of Food Quality Nondestructive Testing of Food Quality The IFT Press series reﬂects the mission of the Institute of Food Technologists – advancing the science and technology of food through the exchange of knowledge. 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.

IFT Book Communications Committee Dennis R. Heldman Joseph H. Hotchkiss Ruth M. Patrick Terri D. Boylston Marianne H. Gillette William C. Haines Mark Barrett Jasmine Kuan Karen Nachay

IFT Press Editorial Advisory Board Malcolm C. Bourne Fergus M. Clydesdale Dietrich Knorr Theodore P. Labuza Thomas J. Montville S. Suzanne Nielsen Martin R. Okos Michael W. Pariza Barbara J. Petersen David S. Reid Sam Saguy Herbert Stone Kenneth R. Swartzel Nondestructive Testing of Food Quality

EDITORS Joseph Irudayaraj rChristoph Reh Joseph Irudayaraj, PhD, is an associate professor of Agricultural and Biological Engineering at Purdue University, West Lafayette, IN. With over 15 years of research and teaching experience in biological and food engineering, Dr. Irudayaraj has been a faculty member at the University of Saskatchewan, Utah State University, and Penn State. His current role at Purdue is to develop micro and nanosensors for food, health, and environmental applications.

Christoph Reh, PhD, is a research scientist at Nestl´e Research Center, Lausanne, Switzerland working on scientiﬁc projects for innovative beverage concepts. Prior to his appointment he was involved for more than 10 years in process analytics including non-destructive testing for factory application and physico-chemical characterization of foods.

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First edition, 2008

Library of Congress Cataloging-in-Publication Data

Nondestructive testing of food quality / edited by Joseph Irudayaraj and Christoph Reh. – 1st ed. p. cm. – (IFT Press series) Includes bibliographical references. ISBN-13: 978-0-8138-2885-5 (alk. paper) ISBN-10: 0-8138-2885-6 (alk. paper) 1. Food–Quality. 2. Food industry and trade–Quality control. 3. Food adulteration and inspection. I. Irudayaraj, Joseph, 1961– II. Reh, Christoph. III. Series.

TP372.5.N66 2008 664.117–dc22 2007023792

The last digit is the print number: 987654321 Titles in the IFT Press series r Accelerating New Food Product Design and Development (Jacqueline H.P.Beckley, Elizabeth J. Topp, M. Michele Foley, J.C. Huang and Witoon Prinyawiwatkul) r Biofilms in the Food Environment (Hans P. Blaschek, Hua Wang, and Meredith E. Agle) r Calorimetry and Food Process Design (Gönül Kaletun¸c) r Food Ingredients for the Global Market (Yao-Wen Huang and Claire L. Kruger) r Food Irradiation Research and Technology (Christopher H. Sommers and Xuetong Fan) r Food Risk and Crisis Communication (Anthony O. Flood and Christine M. Bruhn) r Foodborne Pathogens in the Food Processing Environment: Sources, Detection and Control (Sadhana Ravishankar and Vijay K. Juneja) r High Pressure Processing of Foods (Christopher J. Doona, C. Patrick Dunne, and Florence E. Feeherry) r Hydrocolloids in Food Processing (Thomas R. Laaman) r Microbiology and Technology of Fermented Foods (Robert W. Hutkins) r Multivariate and Probabilistic Analyses of Sensory Science Problems (Jean-Francois Meullenet, Rui Xiong, and Chris Findlay r Nonthermal Processing Technologies for Food (Howard Q. Zhang, Gustavo V. Barbosa-Canovas, V.M. Balasubramaniam, Editors; C. Patrick Dunne, Daniel F. Farkas, James T.C. Yuan, Associate Editors) r Nutraceuticals, Glycemic Health and Diabetes (Vijai K. Pasupuleti and James W. Anderson) r Packaging for Nonthermal Processing of Food (J. H. Han) r Preharvest and Postharvest FoodSafety: Contemporary Issues and Future Directions (Ross C. Beier, Suresh D. Pillai, and Timothy D. Phillips, Editors; Richard L. Ziprin, Associate Editor) r Processing and Nutrition of Fats and Oils (Ernesto M. Hernandez, Monjur Hossen, and Afaf Kamal-Eldin) r Regulation of Functional Foods and Nutraceuticals: A Global Perspective (Clare M. Hasler) r Sensory and Consumer Research in FoodProduct Design and Development (Howard R. Moskowitz, Jacqueline H. Beckley, and Anna V.A.Resurreccion) r Thermal Processing of Foods: Control and Automation (K.P. Sandeep) r Water Activity in Foods: Fundamentals and Applications (Gustavo V. Barbosa- Canovas, Anthony J. Fontana Jr., Shelly J. Schmidt, and Theodore P. Labuza) r Whey Processing, Functionality and Health Benefits (Charles I. Onwulata and Peter J. Huth)

Contents

Contributors ix Preface xiii

Chapter 1. An Overview of Nondestructive Sensor Technology in Practice: The User’s View 1 Christoph Reh

Chapter 2. The Inﬂuence of Reference Methods on the Calibration of Indirect Methods 33 Heinz-Dieter Isengard

Chapter 3. Ultrasound: New Tools for Product Improvement 45 Ibrahim˙ G¨ulseren and John N. Coupland

Chapter 4. Use of Near Infrared Spectroscopy in the Food Industry 67 Andreas Niem¨oller and Dagmar Behmer

Chapter 5. Application of Mid-infrared Spectroscopy to Food Processing Systems 119 Colette C. Fagan and Colm P.O’Donnell

Chapter 6. Applications of Raman Spectroscopy for Food Quality Measurement 143 Ramazan Kizil and Joseph Irudayaraj

Chapter 7. Particle Sizing in the Food and Beverage Industry 165 Darrell Bancarz, Deborah Huck, Michael Kaszuba, David Pugh, and Stephen Ward-Smith

vii viii Contents

Chapter 8. Online Image Analysis of Particulate Materials 197 Peter Schirg

Chapter 9. Recent Advances in Nondestructive Testing with Nuclear Magnetic Resonance 211 Michael J. McCarthy and Young Jin Choi

Chapter 10. Electronic Nose Applications in the Food Industry 237 Parameswarakumar Mallikarjunan

Chapter 11. Biosensors: A Theoretical Approach to Understanding Practical Systems 283 Yegermal Atalay, Pieter Verboven, Steven Vermeir, and Jeroen Lammertyn

Chapter 12. Techniques Based on the Measurement of Electrical Permittivity 321 Malcolm Byars

Index 339 Contributors

Yegermal Atalay (11) Division Mechatronics, Biostatistics and Sensors, Department of Biosystems, Katholieke Universiteit Leuven, Willem de Croylaan 42, B-3001 Leuven, Belgium

Darrell Bancarz (7) Malvern Instruments Ltd., Grovewood Road, Enigma Business Park, Malvern, Worcestershire, WR14 1XZ, United Kingdom

Dagmar Behmer (4) Bruker Optik GmbH, Rudolf-Plank-Str. 27, 76275 Ettlingen, Germany

Malcolm Byars (12) Process Tomography Ltd., 86, Water Lane, Wilmslow, Cheshire, SK9 5BB, United Kingdom

Young Jin Choi (9) Department of Food Science and Biotechnology, San 56-1, Sillim-dong, Gwanak-gu, Seoul 151-742, Republic of Korea

John Coupland (3) Department of Food Science, 103 Borland Lab, The Pennsylvania State University, University Park, PA 16802, USA

Colette Fagan (5) Biosystems Engineering, UCD School of Agriculture, Food Science and Veterinary Medicine, Earlsfort Terrace, Dublin 2, Ireland

ix x Contributors

Ibrahim˙ G¨ulseren (3) Department of Food Science, 103 Borland Lab, The Pennsylvania State University, University Park, PA 16802, USA

Deborah Huck (7) Malvern Instruments Ltd., Grovewood Road, Enigma Business Park, Malvern, Worcestershire, WR14 1XZ, United Kingdom

Joseph Irudayaraj (6) 225 S. University Street, Purdue University, West Lafayette, IN 47907, USA

Heinz–Dieter Isengard (2) University of Hohenheim, Institute of Food Science and Biotechnology, Garbenstr. 25, D-Stuttgart, Germany

Michael Kaszuba (7) Malvern Instruments Ltd., Grovewood Road, Enigma Business Park, Malvern, Worcestershire, WR14 1XZ, United Kingdom

Ramazan Kizil (6) Istanbul Technical University, Chemical Engineering Department, Maslak, 34469 Istanbul, Turkey

Jeroen Lammertyn (11) Division Mechatronics, Biostatistics and Sensors, Department of Biosystems, Katholieke Universiteit Leuven, Willem de Croylaan 42, B-3001 Leuven, Belgium

Parameswarakumar Mallikarjunan (10) 312 Seitz Hall, Virginia Tech, Blacksburg, VA 24061, USA

Michael J. McCarthy (9) Department of Food Science and Technology, University of California– Davis, Davis, CA 95616-8598, USA

Andreas Niemoeller (4) Bruker Optik GmbH, Rudolf-Plank-Str. 27, 76275 Ettlingen, Germany Contributors xi

Colm O’Donnel (5) Biosystems Engineering, UCD School of Agriculture, Food Science and Veterinary Medicine, Earlsfort Terrace, Dublin 2, Ireland

David Pugh (7) Malvern Instruments Ltd., Grovewood Road, Enigma Business Park, Malvern, Worcestershire, WR14 1XZ, United Kingdom

Christoph Reh (1) Nestle research Center, Vers-Chez-les-Blanc, CH-1000 Lausanne, Switzerland

Peter Schirg (8) PS Prozesstechnik GmbH, Novartis Areal, K-970.1, CH-4002 Basel, Switzerland

Pieter Verboven (11) Division Mechatronics, Biostatistics and Sensors, Department of Biosystems, Katholieke Universiteit Leuven, Willem de Croylaan 42, B-3001 Leuven, Belgium

Steven Vermeir (11) Division Mechatronics, Biostatistics and Sensors, Department of Biosystems, Katholieke Universiteit Leuven, Willem de Croylaan 42, B-3001 Leuven, Belgium

Stephen Ward-Smith (7) Malvern Instruments Ltd., Grovewood Road, Enigma Business Park, Malvern, Worcestershire, WR14 1XZ, United Kingdom

Preface

During the last few years, nondestructive testing of food quality has drawn increasing attention by the food industry and research institutions. Based on the overwhelming need and the motivation provided by the success of the past Institute of Food Technologists (IFT) symposia on food quality testing and measurements, we brought together scientists and engineers from academia and industry to provide their perspectives on nondestructive testing methods. When preparing the book we realized the opportunity that nondestructive testing has provided to food science and food technology. On one hand, the food industry is now able to automate a large number of production control analyses, allowing the reduction of analytical costs, improving processes, and increasing product quality to meet the quality standards and regulations as well as customer satisfaction. Because of nondestructive testing methods, it is now possible to follow food products during processing without disturbing the product as a result of sampling requirements. The improvements were made possible by developments in related technology areas such as computing, optical devices, and miniaturization. The rapid development of CCD optical chips combined with a huge drop in price is a simple example that will attest to this fact. We hope that this book will help people become aware of the different technologies available and increase the impact of nondestructive testing of food in production and research. We leave the readers with the advice that a holistic approach considering process, product, people, and method will always give the best application for nondestructive testing. We are very thankful to all of our authors from academia and industry for giving us their precious time and providing us several interesting perspectives and valuable insights.

xiii

Nondestructive Testing of Food Quality

Chapter 1

An Overview of Nondestructive Sensor Technology in Practice: The User’s View

Christoph Reh

Introduction

This introductory chapter describes the area where nondestructive food testing is relevant and why it is considered to be an area of increased interest. This chapter should give an idea of the main drivers of this area of analytics and illustrate the limitations users will face when they will develop new applications. The requirements of a factory application are different from those of the use of nondestructive instrumentation in the ﬁeld, on the farm, in a warehouse, in the supermarket, in central laboratories, or even for speciﬁc research purposes. The underlying argument of this chapter is that the understanding of the operation of the applied sensor is important to validate the application. Often the simple use of nondestructive instruments lets the user believe that the analysis performed is relevant and valid. However, in reality, it might not be so.

Why Do We Need Nondestructive Testing to Increase Food Quality?

The success of nondestructive instrumentation in the food industry is driven by several considerations. Despite the often signiﬁcant invest- ment, more and more installations are beneﬁcial to the operator because of their good implementation. This can only be achieved when the target

1 2 Nondestructive Testing of Food Quality environment is well analyzed to fit the desired equipment in the optimum manner into plant operations. The planning phase is probably most important since the implications of people, instrumentation, methodol- ogy, required material, environment, and management are identified and translated into specifications. Success can be planned, and many diffi- culties can be avoided if the final installation is well understood from the start. The underlying drivers for using nondestructive instruments are either cost reduction or improved operations. During the evaluation phase, often only direct cost reductions and investments are considered. Because investments are often significant, the benefits are not always completely seen at the start of the project. The principal advantages of online applications are reduction of the analysis time, reduction of the cost of analysis, shortening of the release time, and, as a consequence, lowering of production costs. Additionally, operators can improve their process understanding, control of the process, and, as a consequence, the first time quality as a result of improved product consistency. Nondestructive testing equipment can be widely used throughout the food industry. The following areas are the most relevant:

1. Raw material control in the ﬁeld or at the factory reception 2. Process control either online or off-line after sampling 3. Rapid analysis of intermediate or ﬁnal products in the laboratory 4. Product development and storage testing 5. Research

Raw Material Raw material is of great importance for the food industry. To keep the stock in the warehouse, ingredients are often delivered just-in-time. This requires very rapid release procedures forcing companies to apply rapid nondestructive testing widely. Other drivers of this trend are the increased consumer demand for fresh products. This results in much of the industry shortening the chain between the farm and the consumer. Wherever time can be cut out of the supply chain, the consumer will beneﬁt. Another aspect is the relatively narrow speciﬁcations of raw materials required for more and more products. An integral part of nondestructive testing at raw material reception often ensures compliance An Overview of Nondestructive Sensor Technology in Practice 3

Figure 1.1. Online near infrared analyzer Corona to perform compositional analysis in food production (Carl Zeiss GmbH, Jena). with speciﬁcations set. The procedure leads in consequence to reduced product losses that are a result of more narrowly controlled speciﬁca- tions. In the longer term, an improvement of the consumer-perceived product quality is observed. Raw material control is therefore even extended into agricultural production. Ingredients can be oriented for their optimum use based on their on-site quality assessment.

Process Control Process control can be done either online or off-line. Under online analysis, we normally understand that no human sampling is involved in the measurement process. We further differentiate direct and bypass solutions. In a direct measurement, the instrument does not affect the process, and the product is directly placed in the process line, a storage tank, or a mixing operation. Figure 1.1 is a typical installation of an online analyzer in direct measurement showing a diode-array near infrared spectrometer type Corona from Carl Zeiss GmbH (Jena, Germany). A bypass instrument is placed in a bypass loop to which the product is diverted in order to perform the measurement. The product is then returned to the line after measurement. This is applied 4 Nondestructive Testing of Food Quality when the measurement instrument requires much defined measurement conditions, which cannot be achieved directly in the process. Exam- ples are requirements for a specific distance between a transmitter and receiver, the collection of sufficient product, or the compaction of the product. In some cases, the product is discarded, which is uncharacteris- tic of nondestructive testing. Nevertheless, these applications might still be very beneficial because they have significant advantages in terms of reduction of the use of chemicals, reduction of the influence of humans, and very short measurement times. The reduction or elimination of the use of chemicals is a strong driver for using indirect nondestructive techniques. To avoid any risk, chemicals are often banned in areas where they come into contact with the food. The alternative to online analysis is the measurement either off-line, at-line, or near-line. In all of these applications, a sampling procedure from the process line toward the instrument is required. The instrument can be either located next to the line, in a production laboratory, or in a central laboratory. The sampling procedure is in all cases a risk for the quality of the analytical result. Operator influence is considered to be a major source of error. Another influence can be the physical modifications a product undergoes before it is measured. On the other hand, it is often easier to install an off-line nondestructive installation because normally a standard instrument setup can be used.

Final Products The rapid analysis of intermediate or ﬁnal products in the laboratory is from a measurement point of view very similar to off-line analysis. The motivation for this type of application is to increase the efﬁciency of the analysis required for the release of these products. This is especially advantageous if a large number of samples need to be screened. Typical drivers are also cost reductions because of reduced cost of analysis and the reduction of chemicals used in the laboratory.

Product Development For product development and storage testing, nondestructive testing can be an advantage because of the ability to follow the properties of one single product over time. The majority of traditional analyses in the food An Overview of Nondestructive Sensor Technology in Practice 5 industry are based on destructive procedures, and it is not always certain that all products are exactly the same. By following a single product, the evolution can often be established more precisely.

Research The interest of research groups to apply nondestructive analysis is similar to the one mentioned for product development. The ability to follow one single product during a process or during its shelf life gives a huge advantage compared to traditional testing procedures. Even more, it gives the ability to follow changes, which could not be detected using traditional approaches. The development of the area of nondestructive analysis for food research is principally driven by the improved resolu- tion of sensors and the mathematical capabilities of today’s computers. In the case of food, this allows researchers to follow processes such as drying, cooking, baking, crystallization, homogenization, gelliﬁcation, or agglomeration.

Changes in the Food Industry and Consequences for the Use of Sensors

The food industry is undergoing a signiﬁcant process of consolidation. This typically results in an increase in the size of the production facility allowing the operator better use of the installation. It is obvious that real-time online analysis or rapid near-line analysis based on nondestructive techniques leads to clear beneﬁts for the operator. One of the observed trends is the increased automation of production. This allows an increased use of online instrumentation and especially of nondestructive instruments. The following list gives some of the advantages:

r Improved product quality r Less downtime between production cycles r Reduction of waste r Increase of capacity r Improved operational security r Better use of energy and resources r Shorter holding time of raw materials and ﬁnished products 6 Nondestructive Testing of Food Quality

A large number of production facilities are still labor intensive with a low level of automation. There is a strong tendency to reduce the human influence on the product by having more continuous or automated batch processes. This is only possible if the lot sizes are sufficiently big to generate an economical advantage. Another driver is the increased demand for traceability of the production. With an automated process and integrated sensors for measuring key attributes, the product quality at any point in time can be mapped. More and more, products receive a time coding, which often can be traced back to the data collected during production. On the other hand, not all product parameters can be measured auto- matically. Whereas the principal chemical composition and some physical product aspects can be measured by nondestructive instruments, the sensory characterization of the product still requires human testing. Despite massive efforts to develope electronic noses or electronic tongues, only very few applications are used industrially for product release. It is more common to use the available measurement capabilities to optimize the process and to keep the process conditions in an operating range where the required sensory parameters are delivered. The products are controlled for their key sensory aspects by a panel of experienced people for release purposes. This procedure is unlikely to be changed in the coming years because minor compo- nents or modifications can lead to significant changes in the product. It should be pointed out that contrary to the chemical and pharma- ceutical industries, food products are generally less defined regarding their chemical composition. The majority of the raw agricultural products have quite a wide specification. Additionally, not all processes in the food industry are understood in detail. This is especially true for all aspects related to aroma and taste of food because of the very complex chemistry occurring during processing. Additionally, if the product at the time of production is not yet in physical and chemical equilibrium, it does not provide the characteristics the consumer perceives.

What Are the Central Elements of Successful Use?

The successful use of nondestructive instrumentation relies on a com- plete understanding of the environment. The nondestructive technology An Overview of Nondestructive Sensor Technology in Practice 7 and its technical capabilities are only one piece. The following elements are of central importance:

1. Staff 2. Instrumentation 3. Method 4. Consumables 5. Place of installation 6. Management

Involving the Right Staff

Staff with adequate training is often key to installing a nondestructive testing instrumentation. This is normally not an issue for an academic application where the instrument is often a central part of the research. When used in an industrial environment, this issue becomes more critical. Often management considers nondestructive testing equipment easier to use and, therefore, assumes that normal factory staff should be easily able to install and operate the application. This assumption is especially incorrect for the period between the selection of the equipment and its installation. It might be true for the operational phase as long as the staff is well trained to perform the maintenance of the instrument. To develop correct specifications, to define adequate methods, and to find the correct location, a global understanding of the task is required. The most difficult applications are normally online applications because the process defines quite a number of parameters affecting the measurement. Often it is best to bring together a team covering production, engineering, quality assurance, and product development to correctly plan and install the equipment. After training of the operational staff, outside help will be required on an occasional basis.

Specifying the Instrumentation

The specification process is crucial for the success of any large invest- ment in analytical equipment, and this is especially true for nondestructive testing installations. As already mentioned, it would be 8 Nondestructive Testing of Food Quality preferable to run this process with a team of people with different expertise. The specification process is very well described by Bedson (1996). This paper gives guidance on how to perform equipment validation for any analytical instrument. In practice, it is very difficult to give general advice for the installation process covering a large number of different technologies because the critical points can vary from one technology to another. It is therefore extremely useful to consider the introduction of a nondestructive application as a process with a generic structure. Bedson (1996) developed guidance for the equipment qualification process, including the following four stages:

1. Design qualification 2. Installation qualification 3. Operational qualification 4. Performance qualification

Design Qualification Design qualification covers all tasks related to planning and selecting the application, including development of the specifications leading to selection of the supplier. The choice to develop an application should start from a clearly defined need for a certain measurement. The design qualification should lead to the development of instrument specifications, which will be the basis of the relationship with the instrument supplier. These specifications strongly depend on where the instrument will be deployed. For process control, an optimum performance within a relatively small range of variation of the targeted parameter might be targeted. For a research application, one will choose an instrument with high flexibility regarding its range of application. Apart from purely instrument-related specifications, one should also define the requirements related to staff, methods, installation, and consumables.

Installation Qualification The next step of the process is installation qualification covering all of the procedures related to installation of the equipment in its place of use. One of the most time-consuming exercises can be calibration, especially when process parameters are measured indirectly with techniques such An Overview of Nondestructive Sensor Technology in Practice 9 as near infrared spectroscopy, refractometry, microwave absorption, or similar techniques. To calibrate correctly the choice of a well-adapted reference method is often critical. Other issues in this context are reference laboratory performance, sampling procedures, and generation of a sample set covering the calibration range required. In a production environment, the variation in concentration of one naturally occurring ingredient can be quite small. Sometimes the range needs to be extended to develop a stable calibration. In other cases, physicochemical changes originating from the production process can affect either the reference analysis or the nondestructive technique. These are some of the problems which should be explored by the team during either installation or operational qualification.

Operational Qualification Operational qualification is required for the instrument to operate under defined conditions. This step is usually less critical when the two earlier steps have been performed well. It is obvious that a better specification of an application will lead to fewer surprises at this stage. It is important to accurately document all actions that have been performed. The better the documentation, the easier required actions can be identified.

Performance Qualification The final step of the described process is performance qualification where one has to demonstrate that the installation performs according to the specifications set at the beginning of the process. For process equipment, the focus of this validation process is assessment of the precision, accuracy, and robustness of the instrumental setup. It should be pointed out that the qualification process does not stop after the four qualification steps have been completed. Instruments will have to undergo requalification after any significant change such as:

r Change of place of installation r Modiﬁcation of the instrument or the operating software r Replacement of parts r Maintenance r Modiﬁcation of product or process 10 Nondestructive Testing of Food Quality

The degree of this requalification is strongly dependent on the type of equipment and the gravity of the change. Based on experience, during the qualification process, a protocol should be established for the most common changes. Changes related to the equipment often can be esti- mated based on validation studies. This can be best illustrated for the place of installation. Presentation of the food product to the equipment is often the most critical parameter for the overall performance of the equipment. During installation and calibration, aspects such as the distance of the sensor to the product, aperture of a measurement window, or angle of measurement are often assessed and documented. These data are very helpful to define the critical parameters for requalification. In the case of maintenance, repair, or upgrade, requalification is mainly targeted toward assessing the equal functioning of the new com- ponent. For most of these changes, the equipment supplier normally pro- vides a testing procedure. It is important to ensure the presence of these tests during design qualification because it limits the time required for requalification. Because measurement equipment is normally maintained by the quality assurance department, changes in the product or process are often overlooked or their influence on the measurement is underestimated. Compositional changes due to recipe adaptations or even natural varia- tions of raw materials can cause differences in the results. Other sources of difference can be changing operating conditions of ovens, mixers, homogenizers, and other processing devices. The effect of homogenization of milk on the measurement of fat and solid-non-fat (SNF) by mid-infrared spectroscopy is widely known and studied. This example will be discussed in more detail later in this chapter. For the reliable composition analysis of powders by near infrared spectroscopy, particle size is a critical parameter. Particle size distributions of powders often vary as a result of the operating conditions of mills, spray dryers, or agglom- erators. This influence can be limited either by including the variation of the particle size in the calibration model or by better controlling the operating conditions of the process unit. In reality, an approach taking both factors into account will probably be chosen. This illustrates that due to the introduction of nondestructive measurement, variation of the process and, as a consequence, of the product, can be detected and fixed. This leads then to an improved definition of the product and production with higher consistency. An Overview of Nondestructive Sensor Technology in Practice 11

Deﬁning the Method

Definition of the method is complementary to instrument specification and focuses more on the operational aspects of the application. This work should be done just after a first decision has been determined on what technology will be applied for the testing procedure. It might be that the required method procedures are part of the final decision of what technology will be applied. Defining the method is the outcome of the equipment qualification process mentioned under instrument specification. It is very important to translate all of the knowledge collected into an actionable method. The individual steps need to be well defined and documented to ensure long-term application by the operator. Operator training must include generating alertness to the critical points of any nondestructive testing application.

Ensuring the Supply of Consumables

The permanent availability of consumables is probably the easiest point to achieve. The importance of this point is the operational availability of nondestructive testing instrumentation. Especially in the case of online applications, an outage can lead to signiﬁcant losses in production. This point is especially relevant in countries or regions where after-sales support from the supplier is limited or slow. Apart from a service guar- antee from the equipment supplier, it is often advantageous to perform some of the maintenance in-house with your own staff. In this context, the availability of all consumables required for the normal operation of the application should be kept in stock. This could even include equipment parts in order to be able to perform any repairs that have a higher risk of happening. Training of the operator for these tasks needs to be additionally considered.

Identifying the Place of Installation

The place of installation refers to technical and operational parameters. The technical parameters are driven by the technology used for the 12 Nondestructive Testing of Food Quality nondestructive testing procedure. Almost all technologies have technical limitations in order to achieve an optimal result. These limitations will be covered in more detail in the chapters on major technologies used in the food industry. At this point it should be mentioned that in the case of nondestructive testing, normally the measurement setup should be adapted to the product and, in the case of production control, to the process line. Therefore, nondestructive instruments are often used after sample preparation. Sample preparation is applied when the outcome of the testing procedure can be improved by optimizing sample presentation to the equipment. It might be, therefore, important to decide if sample preparation might lead to a better result. To clarify the technical impact of the place of installation on the quality of the measurement, thorough knowledge of both aspects is required. Sample presentation of the measurement technology needs to be adapted to produce reliable and actionable results. The instrument setup needs to base its result on a representative sample. Parameters such as sample volume or measurement time are very important in this context. The operational aspects are most often more important than the technical aspects because the economical advantage is principally driven by optimization of the operation. It is of key importance to measure or control in order to be able to correct. But it is of limited use to measure a parameter that can no longer be changed when the result of the testing procedure comes available. There might be an advantage to automating a testing procedure used for product release. Nevertheless the gain in determining a process parameter, which can be used for process control, will lead to important savings for the operator.

Getting Management Support

Management support is the ultimate requirement for successful installation of nondestructive instruments. Automated analysis of product quality control often requires a change in mind-set. It goes along with significant changes on the production floor and in the factory laboratory. This affects the day-to-day work of the staff involved in the specific area and can completely change the way product quality is approached. As a consequence of improved product quality monitoring, more proactive intervention in the production process will be required,