Food Evaluation

8/13/2019 Food Evaluation

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FOOD QUALITY-OBJECTIVES

Quality is rated consciously or sub consciously by all.

Customers expect products that are safe, of good

value, & of high sensory quality.

Food chosen on the basis of quality & likes & dislikes.

Satisfaction, for having paid the correct competitive

price for similar quality. Consumers look for food that is attractive in terms of

color, flavor, & texture, apart from other psychological

& social factors which they may associate with food.

Quality is the ultimate criterion of desirability of any

food product ---for which the customer is willing to pay

more in proportion to its presence & less because of

its absence. .


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OBJECTIVES

Quality monitoring is imperative in present times.

Universally accepted-----enables to realize appropriate price

both for the producer & seller. Attractiveness of food is clearly a quality.

When the mfgrs. & mfgrg. personnel know about various qualitycontrol requirements, final product of desired quality isobtained.

Any product released for marketing must conform with thestatutory standards.

Reproducibility is equally important.

Nutritional quality, shelf life & cost factor are other criteria which

may affect their selection. Knowing consumers preferences & perceptions of sensory

characteristics of food & beverage is vital to food mfgrs &caterers.

Without appropriate evaluation, there is high risk of marketfailure.


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IMPORTANCE OF EVALUATION TO

FOOD INDUSTRY

Helps in developing new products & maintainingquality in existing products.

How a consumer reacts to a particular food dictates

the quality to be produced.

Changes in menus to make food acceptable can beidentified.

Assists in determining shelf life of the product.

Helps understand how our product performs againstcompetitors products.

Helps to determine whether or not consumers can

detect differences between products due to recipe

modification.


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METHODS-

Easier to recognize quality than to define it.

Quality is some sort of mental summation of physical &chemical properties of food, involving many sensory factors.

However, their relation to palatability is not known ---hence besupplemented with chemical & physical tests.

SUBJECTIVE EVALUATION-

Carried out by a panel of individuals using a scoring system,based on various characteristics that can be judged using

human senses. Also called as- sensory, organoleptic, or psychometric

evaluation.

Distinctions among food-either differences or preferencesobtained by senses.

Difference testing is used to test the sensitivity of judges & todetermine whether inexpensive ingredient could replaceexpensive ingredient in the recipe.

The type of information that is required should be clear as thisdetermines the type of test that needs to be conducted.


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METHODS-ENVIRONMENT FOR CONDUCTING SENSORY

TESTS-

Separate sensory booths to be provided so thatjudges do not interact with each other, except whenpreparing profiles.

Controlled air & lighting, comfortable temperature,

non-smoking zone, provision of small sinks for spittingout samples or rinsing mouth to be observed.

SAMPLE PREPARATION & PRESENTATIONPROCESS

Samples should be of identical size, shape or portions.

Samples to be served at the customary servingtemperatures.

Sample plates should be marked with wax pencils.

PREFERENCE TESTS


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. PREFERENCE TESTS-

Useful in developing new foods & evaluating quality.

Provide information on selected characteristics & indicatepreference or acceptability of product.

Acceptance preference test Using single or two samples, it is found out whether a product

will be used by consumers & it also shows their preference forthe sample being tested.

One sample is used if a new product is introduced. Two

samples are offered if a food is modified. Hedonic scale relating to pleasant & unpleasant states is used

& ratings of preference or liking or disliking are measured.

Verbal hedonic scale consists of 9 point scale with phrasesfrom dislike extremely to like extremely.

Facial hedonic scale consists 5,7,or 9 faces depicting variousdegrees of pleasure & displeasure.

Disadvantage-

Hedonic scale indicates likes & dislikes for specificcharacteristics of food but not the change in intensity of those

characteristics.


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PREFERENCE TESTS-FACT [Food action] rating scale

More sensitive methodMade up of 9 point food action rating scale.

Codes used clearly indicate the action thepanelist would take regarding the food beingtested-say how often he/she will eat the food, &also indicates that it was never tried.

Two types of preference frequency scales are

used- one uses verbal categories & the otherone uses- quantitative categories.

These tests should supplement the hedonic

scale.


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2. DIFFERENCE TESTING- Determines whether the difference in two or more products can

be detected.

Results are more precise & reproducible.

A] DISCRIMINATION TESTS-

1] PAIRED COMPARISON-

From the two samples presented together, the difference in s

specific characteristic is judged & sample with greater level ofcharacteristic being measured is identified, e.g. sweeter pieceof cake & a standard cake.

50% chances of being right.

2] DUO TRIO TEST- From 2 control samples & one variable sample, one control

sample is presented first, followed by two other samples &asked to identify which of the 2 samples is different from thecontrol.

Chance of guessing correctly is 50%,


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DISCRIMINATION TESTS-3] TRIANGLE TEST-

3 samples [2similar + 1 different] are given togetherto identify the odd one, indicating its distinguishingfeatures.

Chances of guessing correctly are just 33%.

Sample presentation order- control, control,variable/control, variable, control/variable, control,variable/ variable, variable, control .

4] DILUTION TEST-

Quality of substituted ingredients [e.g. egg powder forfresh egg] is measured by presenting standardsample, followed by other samples which may or maynot contain the unknown at a definite level of dilution.

Poor quality product gets detected at lower dilution.


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DISCRIMINATION TESTS-5] TASTE THRESHOLD TEST-

It determines the lowest concentration of a substancethat can be detected.

Also indicates the lowest concentration of a substancerequired to be able to identify it.

6] RANK ORDER

A series of samples are ranked in increasing or

decreasing order of intensity for a specificcharacteristic e.g. in a product like pineapple souffl

for pineapple flavor. Does not measure the degree of difference.

Numerical values may be given to ranks; highest valueindicates the best product


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-Describe sensory attributes in exact words,

evaluator is asked to select the exact

description from the score card that matcheswith the sample.

Superior to preference tests as these detect

deviations between the samples.

Score card needs to be designed carefully

describing each characteristic over a range.

1] PROFILING-

Panel sits together & formulates a very detailed

word description, generally of flavor, which is a

standard for evaluating further products.


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- Food samples are individually evaluated using score

cards, having a series of descriptive terms or levels ofcharacteristics.

Numerical values or scores are assigned to eachdescriptive term, e.g. 1 to 6 for extremely dry toextremely juicy texture.

Evaluators to think of appropriate descriptive adjective

& take decision but not to decide on the basis ofscore. It is preferable not to mention numerical scoreson the score card given to them.

Score cards need to be designed for all recipes .

All products to be evaluated should be given codes inthe form of geometric shapes, colors, or randomlyselected 3 digit numbers. Avoid codes viz. 123 or

ABC-which suggest first choice.

Standard specifications for a standard high qualityproduct should be described.

OBJECTIVE METHODS


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OBJECTIVE METHODS Supplement the data obtained through sensory

evaluation to overcome human error,

sensory tests rely on panelists who may give highlyvariable results sometimes.

Personal health related problems or emotional upsets

may have major influence on their evaluation ability. Does not depend on human senses,

More reliable , less subject to error.

Results agree with sensory evaluation-if chosenappropriately.

Requires well maintained accurate testing devices.

CHEMICAL ANALYSIS


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CHEMICAL ANALYSIS Includes compositional analysis for establishing identity & quality as well as

conformity to the prescribed standards.

QUANTITATIVE ANALYSIS/ proximate analysis

Gives nutritional & biochemical information.

Nutrient analysis helps to mention the nutritive value per serving on thelabel.

For most foods analytical data is available,

Energy value of a food can be calculated easily.

Moisture affects stability of foods, making them susceptible for mouldgrowth, infestation, protein degradation & sprouting,

Ash is indicative of the mineral matter, Acidity,

Crude fibers are useful in determining the amount of shell in cocoa, hardwoody stalk in tea, chilies , & the amount of bran in ground cereals.

Proteins are determined by multiplying a factor 6.25 to the organic nitrogenas protein contains 16% Nitrogen.

Fat is measured by extracting it in ether, using the soxhlet extractionmethod.

Sugar concentration is measured using refractometer as degree brix.

Saltiness can be analyzed by flame photometry to measure sodium content.

ULTIMATE ANALYSIS

It means determination of a particular element or a compound.

ADDITIVES CONTAMINANTS &


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ADDITIVES, CONTAMINANTS &

MICROBIOLOGICAL QUALITY Checks safety.

Additives determined using different tests as per nature of the products.

Tests to determine purity & adulterants carried out separately. For testing contaminants chemical & instrumental tests available.

MICROBIOLOGICAL ANALYSIS

Important for quality assurance, food safety as well as conformity toprescribed standards.

Some of the methods used Direct microscopic count

Aerobic plate count of number of colonies of mesophilic aerobes per gram ofsample,

Coliform count as. E. coli is the best indicator of faecal organism,

Salmonella sp selected colonies are examined for their biochemical &

serological characteristics, Bacillus cereus blue colored colonies are examined,

Staphylococcus aureus black colonies with light colored margin & an outerclear zone are observed,

Clostridium botulinum & perfringens in anaerobic atmosphere,

Listeria monocytogenes for black colonies surrounded by black zone, & forsparkling blue colonies.


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ys ca exam na on Indicates the presence of extraneous organic & inorganic matter, weevil

grains, moldy & discolored units, along with moisture & volatile matter

Extraneous matter affects both sanitary quality & safety,

In case of water-soluble foods simple dissolution & filtration test is used.

In other cases proteins & starch are digested to enable separation of filththat is floated using organic solvents.

TESTS FOR VOLUME

SEED DISPLACEMENT TEST-

Test is conducted for volume of firm food products after the baked products

viz. cakes & bread are 24 hours old, using volumeter.

INDEX TO VOLUME

Indirect means of comparing volume,

Slice is taken from exactly the same portion on each sample.

Detailed outline is traced by a pointed pencil or by making an inkblot or aphotocopy of the slice.

Planimeter then used to trace the enter outline of a sample making sure thatall indentations and protrusions are recorded.

Final measurement on the planimeter represents the exact circumference ofthe slice.


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SPECIFIC GRAVITY TEST

This indicates the amount of air incorporated

into products for comparing the lightness of

products physically unsuited to volume

measurements.

Measure of the relative density of a food

sample in relation to that of water.

Measured by weighing a given volume of the

sample and then dividing that weight by the

same volume of water.

Low specific gravity and density indicates larger

amount of air incorporation and is associated

with good volume of the product.


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PRESS FLUIDS

Juiciness of foods measured

Measured by succulometer, a machine that applies pressure.

Amount of pressure applied and length of time applied for ismeasured.

Sample weighed both before and after pressure has beenapplied. Greater the weight loss, greater is the juiciness of the

sample.WETTABILITY

It is the ability of a food to absorb moisture during a controlledperiod of time (5 seconds).

High moisture retention means good wettability.DRYING OVEN

Food is gradually dried in an oven till its weight is constant.

Moisture content [%]= initial weightdried weight x 100

Initial weight

TEXTURE


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TEXTUREObjective methods should reflect the action of the mouth in

ingesting food,

action of tongue and jaw in moving food,

action of teeth in cutting, tearing shearing, grinding, andsqueezing food.

PENETROMETER

Measures tenderness of some foods, e.g., meat.

heavy cone action simulates the biting action of the teeth.

Force required to shear sample determines the texture.

Tenderness of gels and baked products may also be measured

TENSILE STRENGTH

force required to pull apart the meat sample, when fibers are

parallel to the force gives the strength of the muscle fiber.PUNCTURE TESTING

Firmness of fruits and vegetable tissues measured by theamount of force required to penetrate a sample to a specificdepth.

TEXTURE


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TEXTURESHORTOMETER

Baked product placed across two horizontal bars.

A single horizontal bar is brought down until it breaks the same and the force

is recorded. Values highly correlated with sensory values for tenderness.

COMPRESSIMETER

Firmness or softness of a cooked product measured by the force required tocompress a food sample to a predetermined amount.

Greater the force, firmer is the product.

SHEAR PRESS Measures the force required to cut through a baked product,

Compressibility ,extrusion, and textural characteristics of fruits andvegetables also measured.

PERCENT SAG

Measures tenderness of a gel. Greater the percent sag, more tender is the gel.

Percent sag = depth in containerdepth on plate x 100

Depth in container


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LINE SPREAD TEST

Foods such as white sauce, starch puddings, andbatters are is allowed to spread for 30 seconds to 2

minutes from a cylinder. Consistency is measured in distance (centimeter)

spread.

AMYLOGRAPH

Used for determining viscosity of starch pastes atcontrolled, selective temperatures.

FARINOGRAPH

Determines consistency of dough, & predicts quality of

the final product.VISCOMETER

Measures viscosity of liquids that flow.

JELMETER

Measures adequacy of the pectin content of fruit juices

APPEARANCE


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APPEARANCE

PHOTOGRAPH

These furnish a record of size if scales are included in the picture.

Grain of baked product is visible if lighting is carefully controlled.PHOTOCOPY

This furnishes the actual size and shape of a sliced or half baked product, &also indicates grain.

Sliced samples are arranged on a clear plastic.

INK PRINT METHOD

Refer to the Index to Volume method.

TEST FOR COLOUR

Color of the food sample is tested against a color sample to match.

Spectrophotometer and the Hunter color difference meter is commonly usedto identify food colors

TEST OF CELL STRUCTURE Cell structure of baked products can be measured by making photocopies of

cross sectional slices to reveal uniformity, size, and thickness of cell wallsthree dimensionally.

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Food Evaluation