Vickie A. Vaclavik and Elizabeth W. Christian - Essentials of Food Science

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Part 1
Introduction to Food Components

Vickie A. Vaclavik and Elizabeth W. Christian Food Science Text Series Essentials of Food Science 4th ed. 2014 10.1007/978-1-4614-9138-5_1

Springer Science+Business Media New York 2014

1. Evaluation of Food Quality

Vickie A. Vaclavik 1 and Elizabeth W. Christian 2

(1)

The University of Texas Southwestern Medical Center, Dallas, Texas, USA

(2)

Department of Nutrition & Food Science, Texas Womens University, Denton, Texas, USA

Abstract

Food quality is an important concept because the food people choose depends largely on quality. Consumer preference is important to the food manufacturer, who wants to gain as wide a share of the market for the product as possible. Quality is difficult to define precisely, though it refers to the degree of excellence of a food and includes all the characteristics of a food that are significant and that make the food acceptable.

Introduction

Food quality is an important concept because the food people choose depends largely on quality. Consumer preference is important to the food manufacturer, who wants to gain as wide a share of the market for the product as possible. Quality is difficult to define precisely, though it refers to the degree of excellence of a food and includes all the characteristics of a food that are significant and that make the food acceptable.

Whereas certain attributes of a food, such as nutritional quality, can be measured by chemical analysis, food acceptability is not easy to measure as it is very subjective. In fact, consumers make subjective judgments using one or more of the five senses every time they select or eat any food. For example, potato chips, celery, and some cereals have a crunchy sound when they are eaten; the taste and smell of foods can be highly appealing or unacceptable; and the appearance and feel of a food are also important in determining its acceptability.

Food quality must be monitored on a regular day-to-day basis to ensure that a uniform product is produced and that it meets the required quality control standards. Companies must also monitor the quality of their products during storage while changing ingredients and developing new lines. Objective tests using laboratory equipment are useful for routine quality control, yet they cannot measure consumer preference. The only sure way to determine what a population thinks about any food is to ask them! This is done using sensory testing and asking panelists to taste a food and give their opinion on it. Both sensory and objective tests are important in evaluating food quality, and ideally, they should correlate with or complement each other.

However, some consumer attributes can be correlated to laboratory measurements. For instance, LAB color charts can serve to produce foods within the range of acceptability for consumers. The same is true for texture, which can be correlated to viscosity for flowable products or breaking strength for hard products (more details in the Texture section). Flavor is the hardest attribute to predict via analytical measurements.

Aspects of Food Quality

Food quality has both subjective and nonsubjective aspects. Appearance, texture, and flavor are largely subjective attributes, whereas nutritional and bacterial quality are not. The last two qualities can be measured objectively, either by chemical analysis, by measuring bacterial counts, or using other specific tests (Sahin and Sumnu ). They will only be mentioned briefly in this chapter, and the subjective qualities will be discussed in detail.

Appearance

The appearance of a food includes its size, shape, color, structure, transparency or turbidity, dullness or gloss, and degree of wholeness or damage. While selecting a food and judging its quality, a consumer takes these factors into account, as they are indeed an index of quality. For instance, the color of a fruit indicates how ripe it is, and color is also an indication of strength (as in tea or coffee), degree of cooking, freshness, or spoilage. Consumers expect foods to be of a certain color, and if they are not, it is judged to be a quality defect. The same is true for size , and one may choose large eggs over small ones, or large peaches over small ones, for example.

Structure is important in baked goods. For example, bread should have many small holes uniformly spread throughout, and not one large hole close to the top. Turbidity is important in beverages; for example, orange juice is supposed to be cloudy because it contains pulp, while white grape juice should be clear and without any sediment, which would indicate a quality defect.

Texture

Texture refers to those qualities of a food that can be felt with the fingers, tongue, palate, or teeth. Foods have different textures, such as crisp crackers or potato chips, crunchy celery, hard candy, tender steaks, chewy chocolate chip cookies, and creamy ice cream, to name but a few.

Texture is also an index of quality. The texture of a food can change as it is stored, for various reasons. If fruits or vegetables lose water during storage, they wilt or lose their turgor pressure, and a crisp apple becomes unacceptable and leathery on the outside. Bread can become hard and stale on storage. Products like ice cream can become gritty due to precipitation of lactose and growth of ice crystals if the freezer temperature is allowed to fluctuate, allowing thawing and refreezing.

Evaluation of texture involves measuring the response of a food when it is subjected to forces such as cutting, shearing, chewing, compressing, or stretching. Food texture depends on the rheological properties of the food (Bourne ). Rheology is defined as the science of deformation and flow of matter or, in other words, reaction of a food when a force is applied to it. Does it flow, bend, stretch, or break? From a sensory perspective, the texture of a food is evaluated when it is chewed. The teeth, tongue, and jaw exert a force on the food, and how easily it breaks or flows in the mouth determines whether it is perceived as hard, brittle, thick, runny, and so on. The term mouthfeel is a general term used to describe the textural properties of a food as perceived in the mouth.

Subjective measurement of texture gives an indirect evaluation of the rheological properties of a food. For example, a sensory panel might evaluate viscosity as the consistency or mouthfeel of a food. However, viscosity can be measured directly using a viscometer. Rheological properties are therefore discussed in more detail in section Objective Evaluation of this chapter.

Formulators typically turn to hydrocolloids first when trying to manipulate texture. It is important to remember that hydrocolloids vary significantly in their performance, price, ease of use and even impact on clean labeling (Berry )

Collectively known as texturants , some carbohydrate and proteins can impact the texture and mouthfeel of foods, while most likely contributing in a minor manner in terms of calories or flavor.

Research and Development (R&D) scientists now may use a blend of texturants in order to achieve the texture and mouthfeel desired in a specific food. Our approach is to get ample information on the ideal end product. In many cases it is important to retain information on other stabilizing systems in the product, as well as any ingredients that may have a synergistic reaction with the texturant. (Berry )

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