Instrumental Assessment of Food Sensory Quality

A Practical Guide

David Kilcast

• Publisher: Woodhead Publishing
• Year: 2013
• Print ISBN:
  9780857094391
• eBook ISBN:
  9780857098856
• Topic: Technology & Engineering
• Subtopic: Food Science
• Index: Technology & Engineering

Instrumental measurements of the sensory quality of food and drink are of growing importance in both complementing data provided by sensory panels and in providing valuable data in situations in which the use of human subjects is not feasible. Instrumental assessment of food sensory quality reviews the range and use of instrumental methods for measuring sensory quality.After an introductory chapter, part one goes on to explore the principles and practice of the assessment and analysis of food appearance, flavour, texture and viscosity. Part two reviews advances in methods for instrumental assessment of food sensory quality and includes chapters on food colour measurement using computer vision, gas chromatography-olfactometry (GC-O), electronic noses and tongues for in vivo food flavour measurement, and non-destructive methods for food texture assessment. Further chapters highlight in-mouth measurement of food quality and emerging flavour analysis methods for food authentication. Finally, chapters in part three focus on the instrumental assessment of the sensory quality of particular foods and beverages including meat, poultry and fish, baked goods, dry crisp products, dairy products, and fruit and vegetables. The instrumental assessment of the sensory quality of wine, beer, and juices is also discussed.Instrumental assessment of food sensory quality is a comprehensive technical resource for quality managers and research and development personnel in the food industry and researchers in academia interested in instrumental food quality measurement. - Reviews the range and use of instrumental methods for measuring sensory quality - Explores the principles and practice of the assessment and analysis of food appearance, flavour, texture and viscosity - Reviews advances in methods for instrumental assessment of food sensory quality

1

Measurement of the sensory quality of food: an introduction

D. Kilcast, Food and Beverage Sensory Quality, UK

Abstract:

This chapter presents an overview of the nature of the sensory data that are generated by different types of quantitative sensory test procedures, the available types of instrumental measurements and principles, and analysis and statistical validation of instrumental data. The focus is primarily on methods that can be applied within quality control functions, but more advanced methods suitable for the investigation of instrumental–sensory relationships are also covered in outline.

Key words

human senses

sensory test procedures

instrumental–sensory correlations

statistical analysis

data validation

1.1 Introduction: food quality and consumer choice

Consumers fortunate enough to live in prosperous societies have the choice of an enormous and ever-increasing range of foods, and manufacturers find themselves in an intensely competitive situation. In less well-developed societies, hunger will be the constant driving force, and our diet will be determined by availability of any food that satisfies our basic nutritional needs. It is increasingly clear that if we are to understand what drives consumer choice of food, no single factor can be considered in isolation from other factors. For some years, psychology researchers have been developing models to understand consumer behaviour (e.g. Shepherd & Sparks, 1994). Although there are many circumstances under which non-sensory factors such as price, advertising and nutritional image can have strong effects, delivering the sensory characteristics of foods is required by consumers central to continued purchase of foods.

The importance of a holistic approach is also becoming more clear when the components of sensory perception are considered. During the sequences of actions that constitute food consumption we perceive a whole range of different characteristics relating to the appearance, flavour and texture of the food. Traditionally, it has been common industrial practice to consider these characteristics individually when analysing and designing food sensory quality, and this can be seen in the development of sensory methods that are specific to certain characteristics, for example the Flavour Profile Method and the Texture Profile Method (details of both methods can be found in Lawless & Heymann, 1998). Current sensory measurement systems, however, are increasingly focused on assessing all sensory factors that are likely to be important to perceived quality, and on understanding how these interact at both physiological and psychological levels.

Numerous sensory methods have consequently been developed to assess various aspects of sensory quality for both research and quality control (QC) purposes. The relevance of these sensory quality measurements (made by trained panels) to likely consumer response should ideally also have been established by carrying out appropriate correlation studies. The information secured by such research is vital in maximising product success, but can be out of reach of smaller companies operating on limited budgets, and there is a danger of falling prey to the temptation of extrapolating too far from a limited number of non-validated quality measurements. Similar considerations can also lead to the uncritical use of instrumental measurements that are assumed to be relevant to sensory quality.

The main uses of instrumental measurement are found in QC functions, for reasons given in the following section, and the remainder of this chapter will focus primarily on such uses. This is not to diminish the need for researchers to be aware of the value of instrumental–sensory quality relationships, particularly in the investigation of how factors such as product composition, product structure, processing and storage relate to sensory perception and consumer liking. However, the increasingly large numbers of such investigative techniques that can be used for this purpose are outside the scope of this chapter.

This chapter presents an overview of (i) the nature of the sensory data that are generated by different types of sensory test procedures, (ii) the types of instrumental measurements that are available and (iii) the analysis and statistical validation of instrumental data. The content of this overview is not intended to be exhaustive; more relevant accounts are presented in the subsequent chapters contributed by individual experts.

1.2 The role of instrumental measurement

The development of applied sensory techniques for evaluating the quality of consumer goods has been most extensive in the food and beverages industry, reflecting the intimate contact that users have with the finished product. In contrast, until relatively recently other manufacturers of consumer goods have relied almost exclusively on using various types of appropriate instrumental measurement methods to ensure that any important perceived sensory characteristics of the product are as intended. The extent of the use of instrumental methods in different industries therefore reflects the difficulties inherent in the availability of validated sensory techniques. Given the wide range of sensory techniques available to the food and beverage sector then, why is there such extensive usage of instrumental measurement methods in quality control functions, and why is there a growing demand for the development of new methods?

Many possible answers to these questions can be proposed, for example:

• Logistical difficulties (both time and cost) in setting up, operating and maintaining sensory panels, especially in small companies.

• Staff downsizing policies, giving rise to difficulties in securing adequate panellist numbers.

• The realisation that in order to maintain even a basic sensory QC system, resources in terms of facilities and panellist training require investment.

• Instability of results from sensory panels over long time periods.

• Possibility of contamination (accidental or malicious) of product by toxic chemicals, especially when investigating consumer complaint returns.

• The manufacturing business produces large numbers of small batches of different products, and key customers demand 100% batch testing.

• An unfounded expectation that there will be a simple and invariant 1:1 correlation between an instrumental parameter with a key sensory characteristic.

• Lack of appreciation of the power and relevance of formal testing procedures, and a failure to recognise that uncontrolled informal sampling procedures are not an adequate substitute.

• A naive faith in data that is generated by modern electronic instrumentation.

Lawless & Heymann (1998) have also pointed out that instrumental measurements should be used for evaluations that are repetitive, fatiguing and dangerous, and when decisions made with the data are not business critical – again, providing that a correlation can be established.

Irrespective of these concerns, consumer enjoyment of foods and beverages will be determined principally by a wide range of responses from the senses, and no instrument (or set of instruments) will be able to mimic these in the foreseeable future. However, the concerns listed above are not trivial, and although all companies must take all possible steps to employ sensory methods in QC, instrumental methods will continue to provide valuable quality input, provided that steps are taken to establish that the measurements relate to relevant sensory characteristics.

1.3 Sensory assessment of quality

1.3.1 The human senses

It is generally accepted that humans have five senses in operation, namely sight, smell, taste, touch and hearing, although warmth, cold, movement and pain may also be considered as senses of importance in a food context. Foods are complex mixtures of chemical compounds, arranged into structural units. The perception of the sensory characteristics of foods results from the stimulation of all our senses to some extent by the physicochemical properties of the foods. The sensory characteristics of food are generally grouped into three modalities – appearance, flavour and texture. These modalities are, however, not independent of one another. For example, colour, which is obviously an important appearance characteristic, can be shown to have an influence on flavour perception; consumers will assign higher scores for flavour intensity to darker foods than to lighter foods. The interaction between appearance and flavour is referred to as ‘visual flavour’. Similarly, textural characteristics such as viscosity can influence the perception of flavour, and some flavour characteristics, e.g. acidity, can affect textural characteristics. One means of defining flavour, texture and appearance is by taking into account the fact that each can be attributed to the stimulation of one or more senses. On this basis the International Standards Organisation (ISO, 1992) has proposed working definitions for flavour, texture and appearance, as given below.

Appearance: sensory characteristics of foods perceived largely by way of the visual sense. Input from other senses, especially smell, may contribute.

Flavour: the combination of taste and odour. Pain, heat, cold, tactile and visual sensations may also ...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Contributor contact details
• Woodhead Publishing Series in Food Science, Technology and Nutrition
• Foreword
• Preface
• Chapter 1: Measurement of the sensory quality of food: an introduction
• Part I: Principles and practice
• Part II: Advances in methods for instrumental assessment of food sensory quality
• Part III: Instrumental assessment of the sensory quality of particular foods and beverages
• Index