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L2 - Basic quality problems of food products.pptx
1. BASIC QUALITY PROBLEMS
OF FOOD PRODUCTS
CFD20002 : QUALITY ASSURANCE AND QUALITY CONTROL IN FOOD
INDUSTRIES
LECTURE 2
2. INTRODUCTION
• Quality of food is an extremely important aspect of human life and people
become more and more concerned about nutrition, food safety and
environmental issues that determine their acceptance of food products. Good
quality of food has not a constant definition but varies according to the food
category and to the consumers’ preferences.
• The consumers focuses on physical characteristics of the food products, as well
as abstract (intangible) food characteristics combined in four food quality
dimensions – health, taste, process and convenience, to examine their effects on
quality evaluation and purchase.
• Food quality can be described by but not limited to wholesomeness, freshness,
nutritional value, texture, smell, color, fragrance, and flavor. In addition to the
intrinsic characteristics of the product, food quality can be evaluated by the
brand, shopping environment, price, origin, production processes and so on.
3. INTRODUCTION
To understand the concept of quality of food products the following questions
can be addressed:
• How do consumers perceive quality? What constitutes quality? How can quality
perception be explained?
• To what extent physical characteristics of the product will affect the quality
evaluation and the purchase?
• To what extent other characteristics like brand, origin, price, will affect the
consumers’ quality evaluation and purchase?
• Is there a trade-off between perceived quality and price and what is it?
• Do quality expectations correspond to quality experiences?
• What roles play demographics and cultural characteristics of consumers in the
perception of quality?
4. TYPES OF FOOD QUALITY
• There are four different types of food quality (Grunert et al., 1996). These
are product-oriented quality, process-oriented quality, quality control, and
user-oriented quality.
• Product-oriented quality is measured by means of food product’s physical properties,
like fat percentage, muscle size of meat, sell content in milk, etc.
• Process-oriented quality is concerned with characteristics of the production process,
which are not necessary mirrored in physical characteristics of the product, like the
fulfillment of ecological and ethical production standards.
• Quality control refers to the extent to which product- and process-oriented quality
remains stable at pre-specified levels.
• Finally, user-oriented quality is the subjective quality perception of a user.
15. PHYSICAL ATTRIBUTES
• Physical attributes of food are related with the
appearance of food products, including:
• Color
• Shape
• Size
• Texture
• Etc.
Appearance
The first
impression
16. COLOR
Color is the one of the most important image
features because it contains the basic human vision.
Color significantly affects the consumer perception
of quality.
If the color is unacceptable, the other two major
quality factors,
flavor and texture, are not
likely to be judged at all.
17.
18.
19. COLOR
Color may be defined as the impact of the
wavelengths of light in the visual spectrum from
390-760 nm on the human retina.
The retinal cells may be sensitive to black and white
only or to red, green and blue (RGB) wavelengths of
light.
The correct interpretation by the brain in terms of
color depends on the adequacy of signals.
20. COLOR
• Light is the basic stimulus of colors, it is important to consider
the electromagnetic spectrum.
• Visible light forms only a small part of the electromagnetic
spectrum, with a spectral range from approximately 390 nm
(violet) to 750 nm (red).
• The sensitivity of the eye varies even within this narrow visible
range. Under conditions of moderate-to-strong illumination,
the eye is most sensitive to yellow-green light of about 550
nm.
21. FACTORS AFFECTING COLOR
Chemical composition
The appearance of a product as judged by its color
often be used to determine the pigment content of a
product, which in turn is often an index of quality.
Color measurement can be used to evaluate pigment
content (carotenoid, anthocyanin, chlorophyl, etc.)
Colorimetry and chromatography can be used to
measure the pigment content of food product.
22. FACTORS AFFECTING COLOR
Effect of lighting
The type of light falling on a object will affect the perception
of color.
For example, when green light is directed onto a white sheet
of paper, the paper will appear to be green.
But within fairly narrow ranges, the human brain will
compensate for small shifts in the color of the lighting
because the brain anticipates what the color should be.
23. FACTORS AFFECTING COLOR
In food products, it is possible to make products
look better or worse depending on the lighting.
Lighting in supermarkets is designed for the
ability to make product more favorable. But no
single lighting arrangement is optimum for every
food product. Example :
Cranberry juice under normal fluorescent tube
light with a high blue component will appear
almost black, while under warm fluorescent
lighting with a higher yellow-red component will
appear much redder.
24. FACTORS AFFECTING COLOR
Lighting to improve color appearance had been studied in
detail in the red meat industry.
It is possible to make cuts of red meat look much redder by
illuminating them with a pink light or by placing a reflector
painted red near the display case.
However, sometimes this method is considered as a fraud
because the consumer sees the actual color when product is
unpacked at home.
25. INTERACTION OF COLOR WITH OTHER
SENSES
Color seems to have significant effect on the perception of
sweetness, but only have little effect on the perception of
saltiness.
Many studies have shown that solutions colored dark red
will perceived to be sweeter than others of the same
sucrose concentration in lighter colors or distilled water.
26. COLOR SCALES
• There are three characteristics of light by which a
color may be specified: hue, saturation, and
brightness.
• Hue is an attribute associated with the dominant
wavelength in a mixture of light waves, i.e., it
represents the dominant color as perceived by an
observer.
• Saturation refers to relative purity or the amount of
white light mixed with a hue.
• Brightness is a subjective term, which embodies the
chromatic notion of intensity.
• Hue and saturation taken together are called
chromaticity.
• Therefore, a color may be characterized by
27. COLOR SCALES-CIE SYSTEM
• The basic colors however are only three: red, green and blue,
and other colors are derived by mixing these three.
• The Commission Internationale de l’Eclairage (CIE) defined a
system of describing the color of an object based on three
primary stimuli: red (700 nm), green (546.1 nm), and blue
(435.8 nm).
• The amounts of red, green, and blue needed to form any
given color are called the’ ‘tristimulus” values, X, Y, and Z,
respectively.
• A plot that represents all colours in x (red)-y (green)
coordinates is known as a chromaticity diagram
29. COLOR SCALES-CIE SYSTEM
• Sometimes, tristimulus systems of representation of colors
are not easily understood by the users in terms of object
color. Other color scales therefore were developed to
relate better to how we perceive color, simplify
understanding.
• A 3-dimensional rectangular L, a, b, color space was
evolved, in which at L (lightness) axis – 0 is black and 100
is white, a (red-green) axis – positive values are red;
negative values are green and zero is neutral, and b (blue-
yellow) – positive values are yellow; negative values are
blue and zero is neutral.
30. COLOR SCALES-CIE SYSTEM
• There are two popular L, a, b color scales in use today –
Hunter L, a, b, and CIE L∗, a∗, b∗.
• They are similar in organization, but will have different
numerical values.
• Hunter L, a, b and CIE L∗, a∗, b∗ scales are both
mathematically derived from X, Y, Z values.
• Hunter scale is over expanded in blue region of color
space, while CIE scale is over expanded in yellow region.
The current recommendation of CIE is to use L∗, a∗, b∗.
32. SIZE
Size is very important feature since it can
determine the loss of products during processing
and the final product yields.
Size can be measured in three dimensions such as
volume in the real world. However, it is usually
reduced to one or two dimensional measurements.
Size features include weight, volume, diameter,
area, surface area, perimeter, length, skeleton
length and width.
33. SIZE
• Some other measurements of size:
• Feret’s diameter: determined by the
distance of 2 pixels with the smallest and
the largest coordinates
• Major axis: the longest line that can be
drawn across food products, calculated by
measuring the distance between two
boundary pixels and by taking the longest
• Minor axis, which the longest line that can
be drawn through the object perpendicular
to the major axis.
34. SIZE
Area has become a very popular measurement for the
quality evaluation of fruit and vegetables such as the
determination of tomato ripeness.
Length measurements might also be used especially for
those long shape food products such as cucumber,
banana, which usually measured by skeleton length, mid-
line of the products.
Skeleton length
35. SIZE
• In meat industry, the calculation of surface
area and volume of ellipsoid meat joints can
be used to determine shrinkage during
processing.
• The measurement of area is also important in
meat --- the area of marbling/intramuscular
fat and the overall area to determine the
marbling score.
36. SIZE
• Size features can also be used for sorting of fish, and
many other products such as pizza, wheat grains.
37. SHAPE
• Shape is generally referred to the profile or
physical structure of objects geometrically.
• Conventional measurements of shape
called size dependents --- try to combine
different size parameters together to form
dimensionless expressions for shape
description.
38. SHAPE
•Some shape measurements applied to food
industries:
• Compactness: the ratio of area over the square
perimeter --- effective for perfect circle food products
• Elongation: the ratio of major axis over the minor axis
• Convexity: the ratio of convex perimeter over the
perimeter
• Roughness: the ratio of area over the square major axis
39. SHAPE
• However, those measurement are doubted. Are they
sufficient enough for describing the shape of food
products, especially those with the irregular shape, such
as broccoli, the whole body of fish, etc.
• Some size independent measurements are developed:
• Spatial moment
• Boundary encoding
• Fourier descriptor
40. TEXTURE
• Texture can be generally correlated to the sensory
properties of food products.
• Texture can also be used to determine chemical or
physical properties of food products --- contain more
information about chemical or physical properties than
color and size.
• Textural properties of food product will be change during
storage.
• The importance of texture in the overall acceptability of
foods varies widely, depending upon the type of food:
41. TEXTURE
• Critical:
Food in which texture is the dominant quality
characteristic, such as meat, potato chips,
cornflakes, etc.
• Important:
Food in which texture makes a significant but not
a dominant contribution to the overall quality, for
example most fruits, vegetables, cheeses, bread,
cereal based foods, candy, etc.
• Minor:
Food in which texture makes a negligible
contribution to the overall quality, for example
most beverages, thin soups, etc.
43. TEXTURE
• The textural properties of food are group of physical
characteristics that arise from the structural elements of
food, are sensed primarily by the feeling of touch, are
related to the deformation, disintegration, and flow of the
food under a force and are measured objectively by
function of mass, time and distance.
44. TEXTURE
• Relation between textural parameters and popular
nomenclature:
• Mechanical characteristics
Primary parameters Secondary parameters Popular terms
Hardness Soft – firm – hard
Cohesiveness Brittleness
Chewiness
Gumminess
Crumbly – crunchy – brittle
Tender – chewy – tough
Short – mealy – pasty – gummy
48. REFERENCES
• Bourne, M.C. (2002). Food Texture and Viscosity: Concept
and Measurement 2nd Ed. Academic Press. New York.
• Francis, F,J. (1995). Quality as influenced by color. Food
Quality and Preference 6 : 149-155.
• Zheng, C., Sun DW., and Zheng L. (2006). Recent
developments and applications of image features for food
quality evaluation and inspection – a review. Food Science
and Technology 17: 642-655.
49. EXERCISE
Describe the quality problems associated with banana on left
using the right figure as reference. Summarize your answer
based on the factors as discuss previously.
