Quality of foods may be defined as the composite of those characteristics that
differentiate individual units of product; these characteristics should have
significance in determining the degree of acceptability of that unit by the
buyer.
Some important characteristics of the food / food products are:
• Colour and gloss, viscosity and consistency, size and shape, texture and
flavour.
• Nutritive values (vitamins, minerals) – hidden attributes.
Quality is commonly thought of as degree of excellence. It may be considered
as a set of specifications, which are to be met within given tolerances or limits.
Quality Control may be defined as the maintenance of quality at levels and
tolerances acceptable to the buyer while minimizing cost for the vendor.
Food Quality Attributes
The quality attributes referred to as sensory may readily be classified in
accordance with the human senses by which they are perceived. The sensory
attributes namely, the senses of sight, touch, taste and smell.
accordance with the human senses by which they are perceived. The sensory
attributes namely, the senses of sight, touch, taste and smell.
Some of the important sensory quality attributes are described below:
Colour and gloss
Colour is an appearance property due to spectral distribution of light.
Glossiness, transparency, haziness, and turbidity are properties of materials
due to the differences in reflectance and transmittance of light.
Glossiness, transparency, haziness, and turbidity are properties of materials
due to the differences in reflectance and transmittance of light.
Physically, colour is a characteristic of light, measurable in terms of intensity
and wavelength. It arises from the presence of light in greater intensities at
some wavelengths than of others.
and wavelength. It arises from the presence of light in greater intensities at
some wavelengths than of others.
Light may be reflected, transmitted, absorbed, or refracted by the object being
illuminated. Spectrophotometers are used to measure colour of the products.
illuminated. Spectrophotometers are used to measure colour of the products.
Viscosity
Viscosity or consistency is an appearance property of great importance to food
products such as ketchup, creams, juices, pulp, jams, jellies, syrups, etc. The
measurement may be used to indicate the consistency of the products. It may
also be used as an index to the amount of ingredient in the product.
products such as ketchup, creams, juices, pulp, jams, jellies, syrups, etc. The
measurement may be used to indicate the consistency of the products. It may
also be used as an index to the amount of ingredient in the product.
Liquids flow as if they were composed of individual layers. The friction
resulting from the resistance to flow between the liquid layers is called
apparent viscosity. Brooke field or Ostwald viscometer is used to determine
the viscosity of the product.
resulting from the resistance to flow between the liquid layers is called
apparent viscosity. Brooke field or Ostwald viscometer is used to determine
the viscosity of the product.
Size and shape
Grading into various size and shape categories is usually one of the first steps
in food processing operations. This may be accomplished by hand or by means
of mechanical sorters, using screens, reels, slots, etc. Grading helps in
maintaining uniformity.
in food processing operations. This may be accomplished by hand or by means
of mechanical sorters, using screens, reels, slots, etc. Grading helps in
maintaining uniformity.
• Defects
Defects have been defined as “imperfections, due to the absence of
something necessary for perfection, or the presence of something that
distracts from perfection”.
something necessary for perfection, or the presence of something that
distracts from perfection”.
In grading foods for defects, tolerances may be established in terms of
maximum numbers of defective units allowable.
maximum numbers of defective units allowable.
Defects may be classified into:
1. Genetic – physiological,
2. Entomological,
3. Pathological,
4. Mechanical, and
5. Extraneous or foreign matter
Kinesthetics of texture
Kinesthetic characteristics deal with the sense of feel. They can be classified as
follows:
follows:
Finger feel:
• Firmness as encountered by the customer selecting a firm apple, measured
physically by compression.
physically by compression.
• Softness or yield quality as in selecting a peach, or plum measured
physically by compression.
physically by compression.
• Juiciness as in immature sweet corns where the thumbnail is used to test
the ease and amount of juice squeezed out of a kernel.
the ease and amount of juice squeezed out of a kernel.
Mouth feel:
• Chewiness, as sensed by the resistance of the product to compression
and shearing action of the teeth.
• Fibrousness as sensed by the presence of an inedible residue remaining in
the mouth after mastication, as well as resistance to cutting forces of the
teeth.
and shearing action of the teeth.
• Fibrousness as sensed by the presence of an inedible residue remaining in
the mouth after mastication, as well as resistance to cutting forces of the
teeth.
• Grittiness, as sensed by the presence of small grit particles, such as sand, or
stone cells.
stone cells.
• Mealiness, as sensed by the coating of starch or other material with
adhesive properties, over mouth tissues.
adhesive properties, over mouth tissues.
• Stickiness, as sensed by the mouth while chewing foods with adhesive
properties.
properties.
• Oiliness, as sensed in the mouth, caused by oily or soapy products.
The characteristics may be determined by tenderometers, texture meters,
puncture meters, succulo meters, fibro meters and pressure testers
puncture meters, succulo meters, fibro meters and pressure testers
Flavour
Flavour includes taste and odour/ aroma. Taste is a four-dimensional
phenomenon, consisting of sweet, sour, salt and bitter. Sweetness can be
measured by use of refractometers, sourness by pH meters, and saltiness by
flame photometer or by argentometric titration. Bitterness is not estimated but
compared to that of quinine sulfate. Odour/ aroma is determined by gas
chromatography.
phenomenon, consisting of sweet, sour, salt and bitter. Sweetness can be
measured by use of refractometers, sourness by pH meters, and saltiness by
flame photometer or by argentometric titration. Bitterness is not estimated but
compared to that of quinine sulfate. Odour/ aroma is determined by gas
chromatography.
Hidden characteristics
The hidden characteristics of quality are those, which the consumer cannot
evaluate with his senses, and yet are of real importance to his health and
economic welfare.
evaluate with his senses, and yet are of real importance to his health and
economic welfare.
Nutritive value is one of the hidden characteristics, which is
now considered by the consumer as an important attribute. Adulterants and
toxins are the other hidden characteristics. Toxins can be microbial toxins,
pesticide residues or heavy metals.
now considered by the consumer as an important attribute. Adulterants and
toxins are the other hidden characteristics. Toxins can be microbial toxins,
pesticide residues or heavy metals.