judging of milk and milk products

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Sensory Evaluation UNIT 11 JUDGING OF MILK ANDMILK PRODUCTS

Structure

11.0 Objectives

11.1 Introduction

11.2 General Scoring and Grading Guide

11.3 Sensory Evaluation of Milk

11.4 Sensory Evaluation of Ghee

11.5 Sensory Evaluation of Table Butter

11.6 Sensory Evaluation of Ice cream

11.7 Sensory Evaluation of Cheddar Cheese

11.8 Sensory Evaluation of Khoa

11.9 Sensory Evaluation of Paneer

11.10 Sensory Evaluation of Dahi

11.11 Sensory Evaluation of Milk Powder

11.12 Let Us Sum Up

11.13 Key Words

11.14 Some Useful Books

11.15 Answers to Check Your Progress

11.0 OBJECTIVES

After reading this unit we should be able to:

l Draw representative samples of dairy products for judging;

l Recognize the samples with most desirable attributes;

l Identify the defects with intensity of different attributes of all range of dairyproducts; and

l Judge and grade various dairy products adopting appropriate sensory techniques.

11.1 INTRODUCTION

Dairy products have great significance in our diet. Each time we take our food,the dairy products, in one form or other, constitute the part of our menu. Theyare consumed not only for shake of nutritive value but also for rich aroma andpleasant taste. The palatability and eating quality of these products is judged/evaluated by sensory technique, which we have discussed in Unit 1. Also we havediscussed in Unit 2 that for the accurate evaluation of sensory quality of dairyproducts we need a trained or semi-trained panel. This panel should be familiar

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Judging of Milk andMilk Products

with the methods of sensory evaluation and produce reliable and accurate resultslike a calibrated instrument.

One of the prime objectives of milk processors and manufactures of dairy productsis to supply good quality products, which have high acceptability level amongconsumers. Therefore, all the products have to be judged prior to packaging oreven before dispatch to the consumers. This can only be meaningfully done if theevaluators know the proper method of judging of dairy products. In this unit weshall discuss the judging techniques of milk and those dairy products, which havecommercial significance in our country.

11.2 GENERAL SCORING AND GRADINGGUIDE

While judging a dairy product, the identification of a defect, if any, is importantbut equally important is to award correct scores for different attributes so that thedifference among the judges is minimum. Some of the defects are very serious,for example sour/high acid, rancid, oxidized and cowy flavour in fluid milk whereasothers like flat, weedy and cooked flavour are not very objectionable. The scoresare thus based on the nature of defect and its intensity. Finally grading of samplesis done on the basis of total score. A general scoring guide is given below (Table11.1) to help evaluators for consistent judging of dairy product.

Table 11.1 General Scoring Guide for Dairy Products

Quality of Grade Defect & Intensity Approximate ScoreDairy (% of theProducts Perfect Score

Excellent A No defect More than 90%

Good B Flavour: Flat, slight cooked/ More than 80%stale/ barny/ feed/ neutralized/ salty but less than 90%Texture: defects of only slightintensity

Fair C Flavour: Definite cooked/ barny/ More than 60% butneutralized/ feed/ flat. Slight rancid/ less than 80%oxidized/ metallic/ fishy/ yeasty/mouldy/ acidicTexture: Any texture defect ofdefinite intensity

Poor D Flavour: Any flavour defect of Less than 59%. Thethe higher intensity as given products areabove for grade C generallyTexture: Pronounced defect unacceptable at this

score

11.3 SENSORY EVALUATION OF MILK

Since milk is the raw material for all dairy products, its quality will ultimatelyinfluence the end products. Therefore, proper judging of milk, both raw andprocessed milks is very important and needs special care.

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Sensory Evaluation i. Desirable Attributes of Milk

Typically flavour of milk should be pleasantly sweet and possess neither a foretastenor an aftertaste. The natural richness in milk is due to presence of milk fat andthe sweetness due to milk sugar (lactose). The colour of cow milk is yellowishand of buffalo milk is white. The colour may vary depending on the extent ofmixing the two milks. There shall be no fat globules/particles on the surface.

ii. Score Card for Milk

A 25-point score card has been recommended by American Dairy ScienceAssociation (ADSA) and 100 points score card by BIS (Table 11.2).

Table 11.2 Score Cards for Milk

ADSA Score Card BIS Score Card

Attribute Perfect Score Attribute Perfect Score

Flavour 10 Odour 20

Sediment 3 Flavour 40

Package 5 Body (Consistency) 30

Bacteria 5 Colour & Appearance 10

Temperature 2

Total 25 100

Full perfect score is normally awarded when there is no defect in milk, and zeroscore for an unsalable product.

iii. Order of Examination and Scoring

i) Sediment: It should be performed first. The kind, amount and size of sedimentparticles should be carefully observed by visual observation and scored againsta chart of mental image.

A 3-point scale may be employed occasionally. The presence of any sediment inthe processed milk is serious and should receive a zero score. One possiblescoring system using a sediment disc could be:

No sediment 3

< 0.02 mg/disc 2

0.025 mg/disc 1

> 0.02 mg/disc 0

ii) Containers and closure: It should be carefully observed. Now-a-days milkis invariably packaged in polyethylene sachets. Hence, the evaluator must seethat the packaging is proper and there is no leakage/ pilferage from the pouches/containers. The containers should be examined for the extent of fullness (specifiedamount), cleanliness and printing.

iii) Flavour: Milk should be properly tempered between 13 and 18oC, preferably

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at 15.5oC. Samples should be served in clean, odourless glass or plastic bottles.For each evaluator, about 50 ml sample should be provided. Immediately afterremoving the lid, the panelist should smell the milk and simultaneously observefor the presence of cream plug or partially churned fat globules. Then mix thesample properly and take a generous sip, not less than 10 ml of milk, roll itaround the mouth and note the flavour and tectual sensation. Then expectoratethe sample. Sometimes, the aftertaste may be enhanced by drawing a breath offresh air very slowly through the nose. Slow agitation of milk leaves a thin film ofmilk on the inner surface of the bottle, which tends to evaporate thus readilygiving off the odour present. The BIS has recommended that milk sample shouldbe warmed to 45oC for evaluation of flavour and odour. Score of 30 has beenalotted to body, which means consistency (watery/curdy) as per the BIS.

iv) Temperature: Raw milk as well as pasteurized milk should be stored at7.2oC, but lower than 4.4oC is preferred. For pasteurized milk, if thetemperature is above 7.2oC, the sample may be scored zero. Full two pointsmay be given for a sample at or below 4.4oC.

v) Bacterial Count: The maximum permissible bacterial count in pasteurizedmilk in India is 30000/ml and coliform not more than 10/ml. A sample containinga higher count than this limit should get zero score out of five. The bacterialcount, however, cannot be done on every sample of raw milk for judgingpurpose. Hence, it is recommended to perform the bacterial count test aftera certain interval or in case of suspicion.

iv. Undesirable Attributes of Milk

The more common flavour defects of milk are: sour/high acid, flat, barny, feed,weed, bitter, cooked/burnt, rancid, oxidized, sunlight, cowy, salty, astringent andstale. The causes and method of simulation of these off flavour in milk for trainingpurpose have been discussed in Unit 2.

11.4 SENSORY EVALUATION OF GHEE

The judging of ghee is probably most ambiguous because of regional preferenceinvolved in it. Consumers in different regions of the country prefer different typeof flavour in ghee. In north India acidic and mild curdy ghee is preferred, in westdefinite curdy ghee, in south slightly to moderately cooked ghee and in easternregions slight curdy ghee is preferred. Therefore, the ghee evaluators shouldconsider these quality aspects and the area for which ghee is marketed. Despitethis regional preference, the most desirable attributes of ghee must be rememberedand judging should be done accordingly.

i. Desirable Characteristics

A good ghee sample is desired to have a pleasant, nutty and slightly cookedflavour. Ghee flavour is best described as a lack of oiliness or of blandness,sweetly rather than sharply acid. Any suggestion of rancidity is consideredobjectionable.

The body and texture of ghee plays an important role in its organoleptic evaluation.A good ghee sample should have well-developed granules dispersed fairly, thickly

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Sensory Evaluation and uniformly over the entire mass. Breakdown of granulation may result in thegreasy body, which lowers the ghee score.

A bright yellow colour caused by the presence of carotenoid pigments, is associatedwith cow ghee and constitutes a desirable criterion in areas where it is preferred.Buffalo ghee is white in colour. Sometimes, it may also have greenish tingedepending on the region and feeding schedule. Ghee from mixed milk has invariablystraw yellow colour. The colour of fats always appears deeper to the eyes whenmelted than when in solid form.

ii. Score Card for Ghee

The main attributes and weightage given to each are shown in tale 11.3.

Table 11.3 Score Card for Ghee (BIS)

Attribute Perfect Score

Flavour (aroma and taste) 50

Texture 30

Colour 10

Freedom from suspended impurities (ghee residue) 10

Total 100

iii. Technique of Sensory Evaluation of Ghee

i) Sampling: A representative sample should be drawn from the bulk or large lotin a clean and dry glass bottle. The bottle should have a cap/lid to close.

ii) Tempering of ghee: Whenever possible, the samples should be presented atroom temperature. However, the temperature of ghee can be varied dependingon the method of evaluation. Many panelists feel that odour, taste and residuecan be better detected when ghee is tempered to about 40oC.For textureevaluation ghee should be properly crystallized. The crystallization temperaturefor cow ghee ranges between 25-30oC and for buffalo ghee between 30-35oC.

iii) Rinsing medium: One per cent luke warm (40oC) saline water (NaCl) for oralrinsing the mouth in between the samples is very effective for fatty foods likeghee.

iv) Procedure: Sensory evaluation should always start with the visual observationsof the ghee sample. The colour of the melted samples should be judged first,followed by observation on suspended impurities (residue). Odour is perceivedimmediately after removing the lid and inhaling the smell. Subsequently a spoonfulof ghee is taken in mouth for taste and aroma. The body and texture should beevaluated at the end with the help of a spatula or glass rod.

iv Undesirable Attributes of Ghee

Colour defects: Two possible defects can be observed in ghee. i) too dark/brown due to high heating temperature during ghee making and ii) bleaching,which is due to excessive oxidation of ghee during storage.

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Flavour defects: The common flavour defects in ghee are: acidic, oxidized,rancid, curdy, smoky, burnt and bland or flat (lacking). The off flavours aresimulated in small lots of ghee as described below for familiarizing the judges.

i) Acidic ghee: Ripen cream to lactic acidity levels of 0.5, 1.0 and 1.5% andconvert directly into ghee or first convert into butter and then ghee.

ii) Curdy ghee: (a) Melt 500 g cooked butter at 80oC and leave it for 30 minutesfor pre-stratification and remove about 80% of the serum. Heat remaining partupto 100oC, store at room temperature, or (b) add about 5 g of curd (dahi) into100 g ghee and leave for 10-12 hrs at 40oC before evaluation.

iii) Smoky ghee: Put an empty glass beaker/container in inverted position on asmoke fire for sometime. Pour about 100 g normal melted ghee into the bottle.Close the bottle and turn it upside and down side three to five time.

iv) Burnt ghee: Raise the temperature of butter/ghee at last stage of ghee makingto about 130oC.v) Flat/lacking defects: Either take butter oil for evaluation orprepare ghee from butter under vacuum.

vi) Rancid and oxidized ghee: Methods of developing these defects are givenearlier in Unit 2.

Texture Defects: Greasy texture is a common defect in ghee and can be developedby overnight freezing (storage in refrigerator) of freshly prepared ghee followedby thawing. This practice may be repeated several times.

11.5 SENSORY EVALUATION OF TABLEBUTTER

i. Desirable Attributes of Table Butter

Butter package should be neat, clean and tidy in appearance and showing goodfinish. Salt must be uniformly distributed and properly dissolved. A uniform lightstraw colour throughout is most attractive and liked by the consumers. The bodyof good quality butter should be firm and showing a waxy, close knit texture. Itshould have smooth spreadability. A desirable flavour of butter is mild, sweet,clean and pleasant. It is so delicate that consumers always like to eat more.

ii Score Card of Butter

100 points score cards recommended by ADSA and BIS are given in table 11.4.

Table 11.4 Score card for table butter

Attribute Perfect ScoreADSA BIS

Flavour 45 50Body and Texture 30 30Colour 10 15Salt 10 Not prescribedPackage 5 5Total 100 100

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Sensory Evaluation iii. Scoring Technique for Butter

i) Tempering of butter: Butter should be tempered at 10oC for proper evaluationof its flavour and body and texture.

ii) Sampling: The sample of butter should be drawn with the help of a buttertrier from a larger block/lot. The trier should not be washed in warm waterbut should be wiped with a soft tissue or absorbent paper. Washing the trierin warm water results in a melted, greasy surface on the plug of butter taken.This obscures the true condition of the body and texture of butter and makesobservation of the colour difficult.

While taking the sample from a large lot, stand squarely in front of the sampleand observe the cleanliness and neatness of the package. Notice if thisappearance is carried throughout. Remove the wrapper and observe thesurface of butter. Get a mental picture of your observations. Then hold thebutter trier firmly in the hand, insert it diagonally near the centre of the butterturn it at 180o and withdraw the plug. In case of retail pack (100 g or less),a spatula may be used in place of a trier.

iii) Immediately after withdrawing the plug and before making any colourobservations, pass the butter plug slowly under the nose, inhale through thenose very slowly and notice the aroma present. Make a mental record of thisaroma.

iv) After observing the aroma, examine the colour for uniformity throughout.

v) Then examine the body and texture by pressing the ball of the thumb againstthe sides of the plug until it shows a break. Notice the presence or absenceof free moisture or beads of water and their clearness and also the nature ofbreak, that is, whether it is smooth or judged.

vi Break a piece, about three cms, from the plug of butter and put it into themouth. Chew it until it melts. Then roll the melted butter in the mouth until itcomes to body temperature. Meanwhile, feel the presence of “grit” which isun-dissolved salt between the teeth. Also critically feel the manner in whichthe butter melts. Notice the various sensations of taste and smell. Just beforeexpectorating the melted butter, roll it to the back roof of the mouth to detectthe palate flavours.

vii) Expectorate the sample, observe the aftertaste and notice whether or not theflavour persists. All the observations should be recorded in the score card.

iv. Undesirable Attributes

Colour: The main defects of table butter are: lack of uniformity, mottled, streaks,mold discolouration and bleached. Colour problem with butter are not very commonand serious.

Body and Texture: This attribute is of paramount importance from consumers’point of view particularly when butter is applied to bread, hence discussed inmore details here.

i) Crumbly or brittle: Such butter lacks cohesiveness and do not stick together

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but falls apart when broken or some pressure is applied. Crumbly butter haspoor spreadability.

ii) Gummy: Such butter sticks to the roof of the mouth and gives a gum likeimpression.

iii) Leaky: Butter that shows beads or droplets of moisture on the plug andon the back of trier is termed as leaky.

iv) Mealy or grainy: This defect can be detected by pressing the partly meltedbutter between the tongue and palate. Mealy butter lacks smoothness, henceit is a serious defect.

v) Sticky: Butter sticks on the trier or spoon.

vi) Weak: Melt quickly when exposed to room temperature.

vii) Greasy: Extremely smooth and quick melting when butter is taken intomouth are indication of greasy butter.

viii) Gritty: This defect is related to un-dissolved salt content in butter.

Flavour: The common flavour defect defects of table butter are: high acid,neutralizer, rancid, oxidized, fishy, yeasty, flat, fruity, briny and aged. The methodsof simulating these defects have been discussed earlier in Unit 2.

Check Your Progress - 1

1) Differentiate between aroma and flavour. Give the desirable attributes of milk.

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2) What do you understand by regional preferences of ghee? Give the characteristicsof good ghee. At what temperature ghee should be evaluated?

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3) Write the sequence of observations that should be followed for judging tablebutter.

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Sensory Evaluation 4) What are the common body and texture defects of table butter to which consumersare more concerned?

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11.6 SENSORY EVALUATION OF ICE CREAM

Ice cream is a highly popular frozen dairy product and liked by persons of all agegroup. Hence, several varieties of ice cream are available in market. Here we arediscussing the sensory evaluation of plain/vanilla ice cream.

i. Desirable Attributes of Ice Cream

a) Colour: The colour should be attractive, uniform, pleasing and typical of theflavour present in ice cream. Vanilla ice cream is invariably plain (no colour).The colour defects of ice cream are grey/dull; non-uniform, vivid and unnatural.

b) Package: The package or container should be neat, clean, attractive, full andprotective. The common package defects are: soiled, rusty, damaged, shrunkenice cream, ill shaped, etc.

c) Melting quality: Good quality ice cream should show little resistance towardsmelting when a dish is exposed to room temperature. During melting, the mixshould drain away as rapidly as it melts and form a smooth, uniform andhomogenous liquid in the dish. Any variation from this behaviour is due to somedefect and leads the consumers to be suspicious of its quality. Though theweightage to the melting quality is low (5 points), it is an important attribute onaccount of its correlation with the body and texture.

d) Body and Texture: The desired body in the ice cream is firm, has resistance,responds rapidly to dipping and melts down at ordinary temperature to a creamyconsistency. The desired texture should be fine, smooth, velvety and carries theappearance of creaminess throughout.

e) Flavour: Vanilla ice cream should be pleasantly sweet, having a creamy, delicatebouquet vanilla flavour that cleans up well, leaving only a very pleasant aftertaste.

ii. Score Card of Ice cream

The following score card based on 100 points is used for judging ice cream(Table 11.5)

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Table 11.5 Score Card for Ice Cream

Attributes Perfect Score

Flavour 45

Body and Texture 30

Bacteria 15

Colour and Package 5

Melting Quality 5

Total 100

In general practice, the item of bacteria is not done along with judging and theperfect score of 15 is allowed.

iii. Scoring Technique of Ice Cream

i) Tempering of ice cream: Ice cream starts melting immediately after removingfrom hardening room. Arrangement should, therefore, be made to hold the icecream at a uniformly low temperature so that its true body & texture characteristicscan be perceived. The temperature of judging, however, should not be so lowthat ice cream is intensely cold and very hard. Also, its evaluation at very lowtemperature temporary nimbs the taste senses that take long time for recoveryto normal condition. Generally, temperature in range of –15oC to –12.2oC issatisfactory for tempering the ice cream for sensory evaluation. To achieve, thisice cream should be taken out from the hardening room and placed in dispensingcabinet several hours prior to judging. In this way, ice cream tempers uniformly.

ii) Sampling: The retail package of ice cream should be served as such for judging.In case of a large lot or bulk, a regular ice cream dipper or scoop is used fordrawing the sample. The sample for melt down need not be large but must beuniform in size among the various lots of ice cream being judged. For this, acertain quantity of ice cream is kept in a clean petri-dish and melting qualitiesshould be observed from time to time during scoring. The samples from largelots can be placed in separate plates or all in one large service plate. For takinga sample into the mouth a metal spoon is better than a wooden spoon.

iii) The condition of ice cream starts changing immediately after taking it out ofthe cold store. Therefore, the judging and scoring of ice cream should be veryfast. The judges should record their observations as quickly as possible,particularly about the body and texture characteristics. The observations shouldbe made in the following sequence:

a) Examine the container for cleanliness, fullness, printing defects, etc.

b) Note the colour of ice cream for its intensity and uniformity.

c) While sampling with a dipper/scoop or spoon, note the way the productcuts and the feel of the dipper as its cutting edges pass through the frozenmass. Note particularly whether the ice cream tends to curl up or roll inserrated layers behind the dipper thus indicating excessive gumminess orstickiness. The feel of “dipping”, that is, the resistance offered, the evenness

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Sensory Evaluation of cutting, the presence of spiny particles and whether the ice cream is heavyand soggy, or light and fluffy, should be carefully observed.

d) Unless the ice cream has been melted and mix warmed, it is so cold thatfor all practical purposes any odoriferous substances present are practicallynon-volatile and, therefore, little or no aroma may be detected. During thejudging of ice cream, taste reactions (such as sweet, salty, sour or bitter)are perceived earlier than odour. Therefore, place a little sample directlyinto the mouth for warming and liquefying it. While manipulating the samplebetween the teeth and the palate, note the taste and odour sensations.The texture characteristics, such as gumminess, grittiness, coarseness,sandiness, etc. should also be felt simultaneously.

e) Note the melting qualities of ice cream. The judges should observe whetherthe ice cream has retained its form and appropriate size, even thoughsome free liquid may have oozed out, whether the melted liquid is creamycurdled, foamy, watery, and whether the tiny channels are formed as themelt drain flow down the sides of mass.

iv. Undesirable Attributes of Ice Cream

The defects related to colour and package have been given earlier and those ofmelting behaviour, body & texture and flavour are mentioned as below:

Melting quality: Does not melt or delayed melting, flaky or scummy, foamy orfrothy, wheying off or curdled and watery.

Body and texture: Crumbly (brittle/flaky/snowy), gummy (pasty/sticky), shrunken,soggy (heavy/doughy), weak, buttery/greasy, coarse (grainy/ icy/spiny), fluffy andsandy.

Off flavours: Cooked, sour, old ingredients, rancid, salty, inadequate or excessiveflavour, oxidized/tallowy, neutralizer, etc.

11.7 SENSORY EVALUATION OF CHEDDARCHEESE

i. Desirable Attributes of Cheddar Cheese

i) Colour: The colour of Cheddar cheese should be uniform throughout. Themost desired colour is very light straw for the natural colour cheese or deepstraw or yellow orange for the medium coloured cheese. The cheese should betranslucent, that is, it should appear as if one could actually see into the cheesefor a short distance.

ii) Finish and Appearance: Cheese with a desirable finish should show flat,parallel ends; square, even edges; an evenly-folded, neat, close fitting bandageor wrapper free from wrinkles; a clean, thin, uniform, close-adhering coating ofparaffin, showing no blisters or scales; and freedom from cracks, mold, rotspots, or soiled areas.

iii) Body and Texture: The desired body and texture of cheddar cheese is that

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which yields a full, solid, close-knit plug possessing smoothness, meatiness,waxiness and silkiness and which is entirely free from gas holes. Such cheeseslices well.

iv) Flavour: High quality American Cheddar Cheese has a characteristic cheddarflavour, described as clean, fine, nutty and pleasantly sweet.

ii. Score Card of Cheddar Cheese

The weightage given to different attributes is given in the score card (Table 11.6)

Table 11.6 Score card for Cheddar Cheese

Attributes Perfect score

Flavour 45

Body and Texture 30

Finish (Appearance and make-up) 15

Colour 10

Total 100

iii. Scoring Technique of Cheddar Cheese

i) Tempering Cheese: Cheese should be kept in a room at 10-15.5oC for asufficient of time to secure a uniform temperature throughout all parts of thecheese. A plug taken from warm cheese appears weak bodied while a plugfrom cold one will appear brittle or corky. Hence, to know the true characteristicsof cheese, tempering is must before scoring.

ii) Sampling: It is done with a cheese trier. The edges of a cheese trier aresharper than a butter trier. A trier that cuts a larger plug has an advantage overone of small diameter because it is much easier to detect the degree of opennessand the colour defects on the larger plug. Cheese trier is inserted in the middle ofthe cheese block, rotated at 180o and withdrawn. After drawing a plug of cheese,break the upper 2 cms and put in the hole again from where the plug was drawn.

iii) Sequence of observations

a) Aroma: Immediately after withdrawing the plug of cheese from the block passit slowly under the nose and inhale strongly to ascertain the aroma. Then examinethe remaining plug carefully. Make mental record of all these observations.

b) Colour: Note whether the colour is bright, clear or dull; whether it is uniform,free from mottles or light and dark portions, or it has seams or faded areassurrounding the mechanical holes.

c) Openness: Observe the nature and extent of openness in the cheese. Notewhether the holes are regular, angular, rounded, large, or small. Observe alsothe luster or shine of their inner surfaces and note if they are dry or wet.

d) Body and texture: Hold the ends of the plug by the fore-fingers and thethumbs of the two hands and bend the plug slowly into a semi-circle, observing

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Sensory Evaluation when it breaks and the nature of the break. Observe carefully whether the plugshows a resistance towards bending and finally breaks suddenly, or bends onehalf of one third and eventually tears apart slowly.

Take one of the broken pieces between the thumb and the fingers and work itup into a uniform mass, observing its resistance to the pressure of the thumb andthe fingers. Spread the mass thinly over the palm of the hand with the thumb andobserve whether the mass feels smooth, silky, waxy and fine or whether it issticky, pasty, mealy or crumbly. Reassemble the particles, compress them into aball, noting meanwhile the response of the cheese to its manipulation.

Also note the behaviour of cheese while biting, chewing, mastication and swallowing.

v) Flavour: Place the worked mass (ball) under the nose and observe the aroma.Compare this aroma with that noted when the sample was first removed fromthe cheese block. Place a small portion of the unworked plug into the mouth,chew it up to the semi-solid state, roll into the mouth, expectorate and note theflavour. Rinse the mouth occasionally with lukewarm saline water (1%), whichcleans the mouth satisfactorily to the previous cheese flavours.

iv. Undesirable Attributes of Cheddar Cheese

a) Colour: Some of the commonly found colour defects in cheese are: acid cut(bleached/faded); atypical colour specks (white or black, rust, etc.); mottledand seamy (uneven/wavy). White specks observed in highly ripened cheese arenot considered as a defect.

b) Finish and appearance: The judge may look of huffed, uneven size andedges of black, blistered/cracks, light spots, molds, rough and soiled surfacedefects as these may be correlated with some body and texture and flavourdefects in cheese.

c) Body defects: Corky (dry/hard), crumbly, curdy (rubbery), greasy, pasty,spongy, weak (soft) and short.

d) Texture defects: Mealy/grainy (gritty), gassy, sweet curd holes and open.

e) Flavour defects: High acid/sour, bitter, flat, moldy/yeasty, rancid, fruity, wheytaint, unclean, tallowy, etc.


1) What should be the desirable melting quality of the ice cream and why it isimportant?

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2) What are the sensory perceptions of gummy, soggy, sandy and fluffy defects inice cream?

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3) Write the method of sampling Cheddar cheese for sensory evaluation and whichobservations are made while sampling?

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4) How the body and texture of cheddar cheese is evaluated for sensory quality?

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11.8 SENSORY EVALUATION OF KHOA

i. Desirable Attributes of Khoa

a) Colour and Appearance: A good quality khoa, in general, should have uniformwhitish colour with perhaps a tinge of brown colour. Khoa made from cowmilk, however, has light yellow to deep yellow colour. The surface should beslightly oily/greasy i.e., showing the signs of little free fat. It should not have anyforeign matter.

b) Flavour: A typical mildly cooked flavour, similar to that perceived from boiledmilk, is most acceptable. The taste should be pleasantly sweet. Good qualityproduct shall not have any abnormal or objectionable flavour.

c) Body and Texture: The texture of khoa depends on its variety. In general auniform and slightly granular (equal to pinhead size) texture is most desirable.Pindi khoa is required for making burfi and peda in which homogenous texturewith very fine grains is required. Pindi khoa has smooth, compact andhomogenous texture. Dhap khoa has slightly loose texture with grains of biggersize than that of Pindi khoa. Danedar khoa is used for making kalakand andmilk cake in which presence of big grains with brown colour are considereddesirable attributes.

ii. Score Card of Khoa

A 100-point score card is more purposeful and objective, hence it is recommendedfor judging of khoa (Table 11.7)

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Sensory Evaluation Table 11.7 Score card for khoa


Flavour 45

Body and Texture 35

Colour and appearance 15

Package 05

Total 100

iii. Scoring Technique of Khoa

i) Tempering: Khoa should be kept at room temperature for judging purpose. Itis, however, desirable to have a constant temperature of about 30oC forconsistency in judging throughout the year.

ii) Sampling: A uniform sample weighing about 50 g for each judge is collectedfrom the bulk khoa. Alternatively, the judges may also use a cheese trier towithdraw the khoa sample.

iii) Sequence of observations:

a) The first step in judging khoa is the examination of packaging material, whichshould be neat and clean. The product should be properly protected.

b) Immediately after collecting a representative sample of khoa either by a knifeor cheese trier, bring it under the nose and inhale the odour of khoa andmake a mental memory of the same. Then observe the colour and appearance.Special attention should be paid to the detection of burnt particles, if any.

c) The texture of khoa is evaluated by observing the nature of plug forsmoothness, cohesiveness and whether it sticks to the trier. Pressing androlling a small piece of khoa in between the fore fingers and the thumb, notethe hardness, presence of free fat, etc. Spread a small mass of khoa on thepalm of your hand with the thumb and examine the uniformity, size andtoughness of the grains.

d) Take a sufficient quantity of khoa in the mouth. While rolling it about in themouth and chewing it in between the teeth, note the tactual and tastesensations.Expectorate the sample and note if any after-taste persists.

iv. Undesirable Attributes of Khoa

a) Colour and appearance defects: Too brown/dark, lack of uniformity,moist/ dry/ mouldy, surface, visible burnt/foreign particles.

b) Body and texture defects: Hard/dry, weak/loose, lack cohesiveness, grainy/gritty and sandy texture.

c) Flavour defects: Flat, smoky, burnt, sour/acidic, metallic, rancid, oxidized,stale, salty and neutralizer.

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Judging of Milk andMilk Products11.9 SENSORY EVALUATION OF PANEER

i. Desirable Attributes of Paneer

i) Colour and Appearance: Paneer should have uniform white colour withgreenish tinge if made from buffalo milk and slightly yellow colour if preparedfrom cow milk.

ii) Body and texture: The body of paneer should neither be too firm no too soft.It should retain its shape. The texture of good quality paneer should be compact,smooth, slight spongy and velvety. While masticating it should impart feeling offibrous texture with modest chewiness.

iii) Flavour: Paneer has a characteristic blend of the flavours of heated milk, curdand acid. It shall be pleasant, mildly acidic, slight sweet and nutty.

ii. Score Card of Paneer

The 100 points score card for paneer is exactly same as for khoa, presented intable 11.7 (Flavour 45; body and texture 35; colour and appearance 15 andpackage 5)

iii. Scoring Technique of Paneer

i) The optimum temperature of judging the paneer is about 15oC. It is highlyessential that temperature of all the samples should be same for uniformity inevaluation of body and texture.

ii) Like all other dairy products, start with the visual observation of the packagefor cleanliness, proper protection and absence of soiling material/whey etc.on the surface.

iii) Remove the package/wrapper and immediately inhale the smell and observethe surface. The spoilage of paneer during storage starts from surface dueto formation of bacterial slime (greenish/ yellowish coloration) and productionof putrid or acid smell. Also note the colour of product, presence of burntparticles or foreign particles in the paneer samples.

iv) Then with the help of a knife or a trier, collect a slice/plug of paneer fromthe larger block. This should also be brought under nose to inhale thesmell of interior portion. While cutting the sample particularly note theresistance offered, and whether the plug is intact or broken into pieces.Apply some pressure on the paneer block with the thumb and notewhether the compressed area returns back to its original form afterremoving pressure.

v) Take a sufficient piece of paneer in the mouth and while masticating notethe ease of biting by teeth and the taste quality and overall flavour. Thenexpectorate the sample

iv. Defects in Paneer

i) Colour: Dull, uneven colour due to surface evaporation, presence of burntparticles, mould growth, greasy surface due to bacterial slime.

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Sensory Evaluation ii) Body and texture: Dry/hard, rubbery, brittle, weak, sticky/ pasty, grainy/mealy, too open (lack compactness).

iii) Flavour: Sour, putrid, burnt, smoky, rancid, whey-like, musty, yeasty, bitter,feed/weed and foreign.

11.10 SENSORY EVALUATION OF DAHI

i. Desirable Characteristics and Defects of Dahi

i) Colour and appearance: The colour of dahi ranges from creamy yellow forcow to creamy white for buffalo dahi. It should be pleasing, attractive and uniformwithout showing any sign of browning and visible foreign matter. Dahi shouldhave smooth and glossy surface without appearance of any free whey on sidesor top. A cream or malai layer on the top is indication of wholesomeness andpurity, hence desirable.

ii) Flavour: A pleasant, sweetish aroma and a mild clean acid taste are lookedfor in dahi. It should be free from any off flavour. A good diacetyl flavour isalways desired in dahi. Skim milk dahi lacks the natural rich flavour and consideredas flat. Dahi shall not show any sign of bitterness, raw, yeasty, cheesy, sharp,and unclean off flavours.

iii) Body and texture: Good dahi is a weak gel like junket when made fromwhole milk. The body should be firm, homogenous and free from gas holes/bubbles. On cutting it should appear clean/sharp. The surface should be smooth,preferably with a creamy layer. Defects like grainy/lumpiness, ropy, shrunken,thin and wheying off should be absent in dahi.

iv) Acidity: Generally acidity in the range of 0.75 to 0.85%, as lactic acid isappropriate for good quality dahi. Excessive acidity imparts too much sourness/sharp/ astringent taste to the product, whereas low acidity in dahi is consideredas raw/bland.

ii. Score Card of Dahi

The following score card is suggested for sensory evaluation of dahi (Table 11.8)

Table 11.8 Score Card for dahi

Attributes Perfect Score

Flavour 45

Body and texture 30

Acidity 10

Colour and appearance 10

Container and closure 5

Total 100

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iii. Scoring Technique of Dahi

i) Temper dahi to about 10-15oC for proper judging.

ii) Note the condition of container/package for fullness, cleanliness and generalappearance.

iii) Remove the closure lid of the package and immediately observe the aromaby inhaling the product. Simultaneously, examine the appearance of dahi foruniformity of colour and presence of visible extraneous/foreign matter.

iv) Cut the curd by using a knife or spoon and observe for the firmness andevenness of cut. Also observe the interior of dahi mass for smoothness,presence of air/gas holes and free whey.

v) Place a spoonful of dahi in the mouth. Ascertain the taste and aroma ofproduct. While manipulating in mouth also note the tactual properties on thetongue and between teeth for grittiness/graininess..

vi) Note whether the acidity level is pleasant and typical to the product.

vi) Finally rinse your mouth with water.

11.11 SENSORY EVALUATION OF MILKPOWDERS

The sensory evaluation of milk powders assumes great significance in our country.Milk powders, particularly skim milk powder (SMP) is manufactured in largequantities at feeder balancing plants in the flush season and subsequently used inlean period in reconstituted form to maintain milk supply. Also it has become animportant export commodity. In this chapter we shall discuss the sensory evaluationof both, whole milk powder (WMP) and Skim Milk Powder SMP.

i. Desirable Attributes and Defects in Milk Powders

i) WMP: The flavour of dry whole milk should be clean, rich, sweet and pleasant.Frequently, dry milk may be unduly criticized as having a heated ‘or a ‘cooked’taste. This may be expected or even desired. The common flavour defects ofWMP are oxidized/tallowy, chalky, scorched, rancid and stale. The productshould be free flowing to some extent with absence of lumps. Presence of hardlumps is a serious defect in WMP. The colour of WMP depending on the sourceof fat varies from white to deep yellow. The defects such as scorched particles,browning or lack of uniformity should be absent.

ii) SMP: The flavour of good quality SMP, when reconstituted should be similarto that of fresh skim milk, that is, normally a flat taste because of practically nofat in it. Otherwise, the flavour is clean, sweet and pleasant and may have aslightly cooked or heated perception. The chief flavour defects of SMP arestale/storage, neutralizer and scorched. SMP prepared by spray process is veryfine in particle size and free flowing. The product pours readily somewhat likethat of corn meal. Cake formation is the most frequently occurring defect relatedto texture of SMP. Sometime the defect is so serious that the product looks ashard as a rock. The colour of SMP should be uniform and showing complete

58

Sensory Evaluation absence of scorched particles and browning. The product should have a creamywhite or light yellow colour.

iii. Score Card of Milk Powders

The weightage given to different attributes of milk powders is shown in table 11.9.

Table 11.9 Score card for milk powders


Package 5

Appearance of dry product 15

Flavour of dry product 20

Appearance of reconstituted milk 15

Flavour of reconstituted milk 45

Total 100

iii. Scoring Technique of Milk Powders

i) Method of Reconstitution: Generally the dry milks are reconstituted to thecomposition of their native liquid form for examining odour, taste and presenceof undissolved particles (sediments). The required quantities of WMP (13 g)and SMP (10g) are dissolved in warm water (40-45oC) to make the final volumeto 100 ml and left for about 30 min before judging.

ii) Sequence of Observations

a) First of all observe the external condition of the package for cleanliness,neatness etc.

b) Open the package and immediately inhale the aroma. Take a small amount ofpowder in to mouth for taste and tactual perceptions.

c) Simultaneously observe the appearance of powder for colour, lack of lumps/cakes and free flowing properties.

d) Then start judging the reconstituted milk adopting the same technique asdiscussed easier for fluid milk.

e) Try to correlate the flavour perceived in dry form with that noted in reconstitutedform.

f) Record all observations along with intensity of defect, if any, in the scoresheet.


1) Write the desirable attributes of khoa and paneer.

……………………………..…………………………………………......

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……………………………..…………………………………………......

……………………………..…………………………………………......

……………………………..…………………………………………......

2) Write the sequence of observations for judging paneer.

……………………………..…………………………………………......

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……………………………..…………………………………………......

……………………………..…………………………………………......

3) What should be the flavour and texture attributes of a good quality dahi? Writethe score card for dahi.

……………………………..…………………………………………......

……………………………..…………………………………………......

……………………………..…………………………………………......

……………………………..…………………………………………......

4) Why reconstitution of SMP and WMP is essential for their proper judging?Which flavour and structure defects are commonly encountered in these powders.

……………………………..…………………………………………......

……………………………..…………………………………………......

……………………………..…………………………………………......

……………………………..…………………………………………......

11.12 LET US SUM UP

Processed milk and all dairy products should be evaluated for sensory qualitybefore packaging and marketing so that the consumers are supplied good qualityproducts. The quality of raw materials and processing and storage conditions areresponsible for adversely affecting sensory properties of dairy products. So at allcritical stages a trained/semi-trained sensory panel must judge the products. Thegeneral step-wise approach that should be used for judging of milk and dairyproduct is i) temper the products to a most appropriate temperature; ii) observethe package/container for cleanness, fullness, sealing and attractiveness; iii) securea representative sample from the bulk package in such a way that textural attributesare not changed; iv) inhale the aroma of product immediately after opening thepackage/withdrawal of sample; v) note the body and texture attributes first whilewithdrawing sample/cutting a piece with a butter or cheese trier, spoon, knife, etc.and later while masticating and manipulating in the mouth; vi) take a sufficientquantity of product into mouth and observe the taste reactions and finally theoverall flavour; vii) rinse your mouth with a suitable medium to cleanse the carryover affect of previous sample. In certain products some additional steps, suchas melting behaviour in ice cream, reconstitution of powders, etc are also adoptedfor complete judging of dairy product.

60

Sensory Evaluation The sensory panel members should be thoroughly acquainted with the desirableand undesirable attributes of dairy products, score cards and scoring techniques.The judging of milk, ghee, table butter, cheese, ice cream, khoa, paneer, dahi andmilk powders have been discussed.

11.13 KEY WORDS

Aged/Stored/Stale : Refers to flavours and other sensory properties thatdevelop in foods as a result of time and conditions ofstorage.

Aroma : Sensations perceived by the nose when a substance issniffed.

Aromatic : Possessing a fragrant, slightly pungent, usually pleasantaroma.

Astringent : Quality perceived due to the complex sensation causedby shrinking, drawing, or puckering of the skin surfacesof the mouth; dry feeling in the mouth.

Bland flat : Having no distinctive taste or odour property.

Briny : A taste sensation consisting of a complex saltiness andsourness.

Brittle : Texture property characterized by breaking easily andleaving sharp edges.

Cardboardy : Having a flavour reminiscent of cardboard.

Caramelized : Colour and flavour produced when sugars are heatedor heat interacted with proteins.

Chalky : A textural property characterized by a dry, powdery,oral sensation.

Characteristic : Typical, distinctive quality of a food product.

Coarse : Composed of large particle or food that contain harsherunpleasant flavour.

Cohesiveness : A textural property perceived by the tongue and teethrelated to the internal strength of the food.

Corky : Textural property similar to the tough, elastic corticaltissue of the cork oak.

Crumbly : Textural property characterized by ease with which asubstance may be separated into smaller particles.

Fibrous : Stringy textural property.

Firm : Solid, compact textural property.

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Firmness/hardness : Force required to compares a substance between molarteeth (for solids) or between tongue and palate (forsemi solids)

Foamy : Textural property consisting of a mass of bubbles formedon liquids, or in the mouth by agitation or byfermentation frothy.

Foreign flavour : Containing a flavour not normally associated with theproduct.

Greasy : Textural property suggesting a covering of oil or fat.

Harsh/sharp : Lacking harmony or smoothness; rasping, coarse, rough,grating, discordant, astringent.

Homogenous : Of uniform structure or composition throughout.

Mottled : Areas with varying intensities of shades of colour.

Putrid : Unpleasant flavour and odour associated with proteolyticspoilage.

Rubbery : Having an odour, flavour or texture similar to rubber.

Scorched : Intensified cooked generally unpleasant flavour anddiscolouration due to burnt particles.

Slimy : A sensation imparted by material that is thick, coats themouth, is not readily diluted by saliva, and is difficult toswallow.

Smooth : Having an even surface or consistency; devoid ofroughness in taste and flavour.

Soggy : Saturated with moisture; heavy and wet; sudden orsoaked.

Sour : The taste sensation caused by acids.

Springiness/ : Degree to which a product returns to its originalSponginess shape once it has been compressed between the teeth;

spongy, elastic.

11.14 SOME USEFUL BOOKS

Nelson, J.A. and Troat, G.M. (1964). Judging of Dairy Products, AVI Publ. Co.,New York.

Bodyfelt, F.W., Bobias, J. and Trout, G.M. (1988). The Sensory Evaluation ofDairy Products, AVI Publ. Co., New York.

IS: 5126 (Part 1). 1969. Glossary of general terms for sensory evaluation of foods.Part I. Methodology, BIS, Manak Bhavan, New Delhi.

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Sensory Evaluation IS:5126 (Part II). 1969. Glossary of general terms for sensory evaluation offoods. Part II. Quality characteristics, BIS, Manak Bhavan, New Delhi.

IS: 7768 (1975). Method for sensory evaluation of milk, BIS, Manak Bhavan,New Delhi.

IS: 7769 (1975). Method for sensory evaluation of table butter

IS:7770 (1975). Method for sensory evaluation of ghee.

IS:10030 (1981). Method for sensory evaluation of milk powders. BIS, ManakBhavan, New Delhi.

11.15 ANSWERS TO CHECK YOURPROGRESS

Your answer should include the following points


1) i. Aroma is sensation perceived by the nose and flavour is composed of thosesensations perceived by nose, mouth, tongue and throat i.e. flavour is totalperception.

ii. The most important attribute, to which maximum score is allowed, is flavour.The flavour of fresh milk should be pleasantly sweet having no after taste oroff flavour.

2) i. Different flavours in ghee are preferred in different regions of the countrythat is called regional preferences.

ii. Good ghee should have pleasant, nutty and slightly cooked or acidic flavour.The grains in ghee should be well developed and uniformly dispersed in theentire mass. Colour should be attractive.

iii. Aroma of ghee is best perceived at about 40oC whereas the granulationis judged at the crystallization temperature of butterfat (25-30oC for cowghee and 30-35oC for buffalo ghee)

3) Your answer should include the following points:

Steps that should be followed for judging of table butter are:

l tempering of butter at about 10oC

l sampling with a butter trier

l inhalation of aroma

l observation of colour

l examination of body & texture by pressing the plug with thumb and observingpresence of water beads

63


l place into mouth and note various sensations, i.e. taste, grit, adherence topalate, etc.

l Overall quality

4) The important body and texture defects of table butter from consumers’ pointof view are:

l Crumby/brittle: Consumers cannot apply such butter to bread.

l Gummy: Sticks to the palate and cannot be easily swallowed when eating

l Sticky: Stick to the knife/spoon, inconvenience in handling

l Weak: Starts melting immediately after taken from refrigerator.

l Gritty: Perception of undissolved salt granules.


1) l Ice cream is judged at –15o to -12.2oC

l Ice cream of desirable melting quality should show little resistance to meltingwhen exposed to room temperature. The melt (liquid) should be uniformand homogenous.

l If ice cream melts either too fast or does not melt at all the consumers getsuspicious of the quality. Particularly the ice cream that melts very fast cannotbe enjoyed by the consumers.

2) l Gummy ice cream curl behind the spoon when simple is taken and alsosticks to the roof of mouth (palate) when eaten.

l Soggy ice cream is very difficult to cut and gives feeling of too much coldness.

l Sandy ice cream imparts feeling of small grains/particles, which do not melts/dissolve easily in mouth.

l Fluffy ice cream is noted by the presence of large air cells and lightness.When melts lots of foam appears on the surface.

3) l Sampling of cheddar cheese for its sensory evaluation is done with acheese trier.

l The evaluator should stand in front of a large cheese block, insert the trier inthe centre of block, rotate 180o and withdraw alongwith plug.

l Plug is observed for aroma by smelling, surface colour, openness, bendingand breaking behaviors to ascertain the body and texture characteristics.

4) l Bend the cheese plug into a semicircle by holding its two ends by forefingersand the thumb, and observe how much resistance plug shows to the bends,how much it bends when it breaks and the nature of break.

l Work a broken piece between thumb and finger.

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Sensory Evaluation l Spread the mass thinly over the palm.

l Note the behaviour of cheese while biting, masticating and chewing in mouth.


1) l Good quality khoa should have uniform yellowish or creamy white colour,surface should be slightly greasy/oily, flavour mildly cooked & sweet andtexture depending on variety of khoa.

l Pindi khoa should be homogenous, compact with fine grains; texture ofDhap khoa in loose with grains of slightly large size than Pindi, and of Danedarkhoa very large grains.

l Paneer of good quality should have creamy white colour, uniform throughoutthe mass; compact, smooth, slight spongy and velvety texture, and pleasant,mildly acidic, sweet and nutty flavour.

2) Temper at 15oC; observe the package; withdraw a sample; smell for aroma;observe surface for colour and presence of burnt particles; cut with a knife;observe for resistance, compactness, smoothness; press and rub betweenforefinger and thumb for sponginess and grains; place a piece into mouth; chewand masticate; observe taste & textural attributes; expectorate sample andobserve after taste reactions.

3) l Dahi of good quality should have pleasant, sweetish diacetyl aroma andmild clean acid taste. Body should be firm, homogenous, free from gasholes and have clean cut with no wheying off.

l 100 points score card is used for sensory evaluation of dahi and thedistribution of scores for various attributes is: flavour, 45; body & texture,30; acidity, 10; colour & appearance, 10 and package, 5.

4) l On reconstitution of SMP and WMP to the composition of their respectiveliquid forms, the off flavours can be perceived more easily. Also the extentof sediment and undissolved particles observed in reconstitution form canbe correlated with other defects.

l The most common flavour defect of WMP is oxidized and of SMP isstale.

l Cake formation is more common in SMP and lumps are normally foundin WMP.

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