Sensory Perception of Fat in Milk

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Sensory perception of fat in milkMichael Bom Frøst*, Garmt Dijksterhuis, Magni Martens

Sensory Science Group, Department of Dairy and Food Science, Royal Veterinary and Agricultural University, Rolighedsvej 305,DK-1958 Frederiksberg C, Denmark

Received 15 September 2000; received in revised form 4 December 2000; accepted 22 December 2000

Abstract

The sensory properties of fat in milk were examined by sensory descriptive analysis. To date, no single food additive has beencompletely successful in mimicking the sensory properties of fat in milk. This experiment investigated the effects of various factorsand combinations thereof on sensory properties and perceived fattiness of milk, and compared them to the actual fat content (0.1;1.3 and 3.5% fat milk was used). The other factors studied were the addition of thickener, whitener, cream aroma and homo-genisation. Multivariate data analytical methods (Partial Least Squares Regression) were applied for analysis of the data. The threeformer additional factors contributed signicantly to perceived fattiness of the milk, and homogenisation had a small but not sig-nicant effect. It was shown that a combination of thickener, whitener and cream aroma in 0.1% fat milk was approximately suc-cessful in mimicking sensory properties of 1.3% fat milk. # 2001 Elsevier Science Ltd. All rights reserved.

Keywords: Milk; Fats; Lipids; Sensory analysis; Multivariate data analysis; Partial least square regression (PLSR); Fattiness perception; Fat sub-stitutes; Thickening agent; Whitening agent; Cream aroma; Homogenisation

1. Introduction

The sensory properties of milk are inuenced by thefat content in milk (Phillips, McGiff, Barbano, & Law-less, 1995a; Tuorila, 1986). In order to produce milkand milk-based drinks with salient sensory properties, itis necessary to understand how the different sensorymodalities are affected by the fat content. This also willlead to a better understanding of what the perceivedfattiness in milk is comprised of. Previous research hasshown that much of the sensory differences betweennon-fat and other types of milk are mainly in foundappearance, texture and mouthfeel (Phillips et al.,1995a; Tuorila, 1986). Various food additives have beenexamined as a substitute of fat in milk. Phillips, McGiff,Barbano, and Lawless (1995b) observed some effect of protein content on the sensory properties. The additionof 2% non-fat dry milk to skimmed milk gave a similareffect on the relative physical viscosity (measured bycapillary viscometer) as addition of 2% fat. Still, the perceived texture (Thickness, Mouthcoating and Residual

mouthfeel) did not change as much as with an increasein the actual fat content. Also, there was a signicantincrease in cooked avour and both the perceived andphysically measured (by MacBeth Colour-Eye spectro-photometer) colour of the milk with added non-fat drymilk were not the same as that of milk with 2% fat. Thisresult suggests that a fat substitute in milk, to be suc-cessful, should change the appearance characteristics of the milk more than the texture properties.

Other food additives have been examined as well.Phillips and Barbano (1997) tested a series of foodadditives by sensory descriptive analysis with trainedpanellists. They found that a combination of sodiumcaseinate and titanium dioxide in skimmed milk wasbest at mimicking the colour of 2% fat milk. However,the combination did not fully succeed in improving theperceived texture. Some of the other visual attributes,like the one descriptor ‘‘visual hang up’’, a measure of how much milk is clinging to the inner surface afterswirling of the glass, was still much lower than 2% fatmilk.

Other experiments substituted the addition of non-fatdry milk with a protein standardisation by ultraltra-tion (Quinones, Barbano, & Phillips, 1997, 1998). Bymixing retentate and permeate from ultraltration they

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* Corresponding author. Fax: +45-35-28-31-90.E-mail address: [email protected] (M.B. Frøst).



produced milks with a true protein content in the rangeof 0.9–4.8%. The normal range for American milk is3.13–3.38% (Quinones et al., 1998). In the experiments,the milks varied in fat content from 0.13 to 3.3%. Theirresults showed that the sensory texture and appearancedescriptors were affected by the protein standardisation

(as well as by the fat content), where increase in proteincontent gave a whiter appearance and texture propertieslike Thickness, Mouthcoating and Residual mouth-coating increased with a higher protein content. Largerdifferences in sensory properties between low and highprotein content were observed in samples with low fatcontent. The main objective of those two studies was tosee the effect of a decrease in protein content. The eco-nomical value of milk protein as a separate food addi-tive has increased substantially over recent decades(Quinones et al., 1998), thus, there would be an increasein outcome if part of the protein in milk could beseparated and sold for other purposes.

Tepper and Kuang (1996) examined the effect of a-vour addition in milk model systems by multi-dimensional scaling. They showed that products withhigh levels of added aroma compounds were perceivedsimilar to products with a higher fat content, which thenindicates an effect of avour on perception of fattiness.However, in their experiment they operated with arather large concentration range of aroma compounds(0, 0.5 and 1% w/v powdered cream avour) and a largespan of fat content (0, 5 and 10% w/v added blandvegetable oil). Still, the authors claim that their pilotstudies conrm that the chosen concentrations provided

small but distinguishable differences between samples.Richardson, Booth, and Stanley (1993) have theorisedthat the fat particle size distribution makes an essentialcontribution to perceived creaminess in milk, but onlyin the presence of adequate viscosity. They suggestedthat in order for a uid dairy product to be perceivedlike dairy cream, it should provide a smooth but viscousuid layer between the tongue and the palate. Homo-genisation of the milk only had an effect on perceivedcreaminess when the milk was also thickened to theviscosity of double cream (47.5% fat). They used a non-fat thickener (1 part 3% w/v of sodium carboxy-methylcellulose solution to nine parts of milk).

All of the mentioned experiments show an effect of different factors on the sensory properties of milk.However, none of these experiments examined morethan two factors simultaneously in relation to perceivedfattiness of milk. Also, some of the experiments usedstimuli that are extreme compared to the range of milknormally consumed in western countries. Thus, theobjectives of the present experiment was to examine theeffect of numerous factors related to perception of fat-tiness in milk within a realistic product range. In thisstudy a meta-descriptor ‘Total fattiness’ was introducedto the sensory panel, to evaluate the perceived fattiness

in milk. By doing so it was possible to see how the othersensory descriptors correlated with perceived fattiness.

2. Materials and methods

2.1. Milks

Standard Danish milk with three different levels of fatwere used (0.1, 1.3 and 3.5%). Organically producedmilk was chosen, since this is commercially available asnon-homogenised milk in Denmark, and it thus allowedfor testing of homogenisation without interference withthe production method (conventionally produced milkis only sold homogenised in Denmark). On the basis of previous literature in the eld, it was decided to test fourfactors in a reduced design. The factors varied in theexperiment are listed in Table 1.

In pilot studies, a series of four thickeners were testedin selected concentrations within the range recom-mended by the producer. Some other thickeners wereconsidered for the experiment, but for these, pasteur-isation was necessary before it was fully dissolved.Those were avoided since the additional heat treatmentmight have an unwanted effect on the sensory properties(Nursten, 1997). Three different cream avours weretested in several concentrations, and the one agreedupon by the experimenters as most similar to real creamaroma (13% fat cream) was selected. Finally, titaniumdioxide was tested in a range of concentrations and theconcentration in Table 1 was selected. The authors’

philosophy of the addition of food additives was that itshould have a perceivable effect, but not too much of aneffect i.e. keeping it within a realistic product range. Inorder to suspend the whitener in the milk, it was neces-sary to homogenise the samples. Likewise it was neces-sary to homogenise samples with thickener in order toavoid lumps of thickener in the milk. This resulted insome restrictions on the design, so that whitener andthickener could not be tested independently of homo-genisation. So, the full design of 48 samples was reducedto 30 possible combinations. From these, 16 were selec-ted for descriptive analysis (listed in Table 3, togetherwith results from the descriptive analysis). The selectioncriteria for the samples for sensory evaluation werebased on three basic considerations: (1) achieving alarge sensory space (from 0.1% fat without any addi-tives to 3.5% fat with all additives); (2) obtaining arepresentation of all combinations of additions; (3)combinations of additions that were expected to havelarge effects on sensory properties.

2.2. Descriptive analysis

Sensory descriptive analysis was performed undernormal light with milk, (approximaley 100 ml) in clear

328 M.B. Frøst et al. / Food Quality and Preference 12 (2001) 327–336



glasses, in the sensory laboratory at the University. Apanel consisting of seven external paid panellists wasused for the evaluation. All panellists had much experi-ence with sensory evaluation. In ve training sessionspanellists were trained on the products, and descriptorswere chosen after suggestions from the panel leader on

the basis of consensus among the panellists. Each train-ing session had a duration of approximately 1 1/2 h. (Inthe fth training session panellists evaluated a subset of the samples for sensory evaluation in the sensory eva-luation booths, this session took only approximately 50min). A total of 15 descriptors were used for thedescriptive analysis. Those are listed in Table 2, togetherwith their denitions and original Danish words. A

reference sample (1.3% fat, +thickener, +whitener,+aroma, +homogenisation), was chosen and theintensity of this reference sample was scored by thepanellists in the training sessions. The reference samplewas presented to the panellists and tasted prior to eachevaluation, alongside with a score card marked with the

average scores for the panel for this sample. Referencesfor descriptors ‘‘creamy smell’’ and ‘‘boiled milk smell’’were also presented and smelled by the panellists priorto evaluation. For reference materials were used 13%fat cream and boiled skimmed milk respectively. For thelatter reference material, skimmed milk was brought toboiling point and cooled down again prior to sessions.All samples and references were kept at 12 C for 1 h

Table 1Factors varied in the experiment; levels and origin of material used

Experimental factor Value of levels Origin of material or processequipment

Fat content 0.1% (w/w) Organically produced non-homogenised milk (MD-Foods, Slagelse, Denmark)1.3% (w/w)3.5% (w/w)

Thickener 0 Alginate FD 155 (Danisco Cultor, A ˚rhus, Denmark)1 g/l

Whitener 0 Titanium(IV)dioxide reagent grade (Lancaster, Eastgate, UK)1 g/l

Aroma 0 Cream Flavouring U33162 (Danisco Cultor, A ˚rhus, Denmark)0.75 g/l

Homogenisation 0 Pilot Scale homogeniser (Rannie, Denmark)150 bar

Table 2

Sensory descriptors, their denitions and original words in Danish

Descriptors Denition (reference material) Original words in Danish

Aroma LugtCreamy aroma Intensity of raw cream aroma (13% fat cream) Flødeagtig lugtBoiled milk aroma Intensity of boiled milk aroma (boiled skim milk) Kogt mælk lugt

Appearance/colour UdseendeWhiteness Degree of intensity of the colour white in the centre of the glass HvidhedYellowness Degree of intensity of the colour yellow in the centre of the glass GullighedBlueness Degree of intensity of the colour blue in the centre of the glass Bla l̊ighedTransparency Degree of transparency of the sample at the edge of the glass tilted approximately 30 GennemsigtighedGlass coating Amount of milk clinging to the inner surface of the serving glass after swirling the sample GlasvedhæftningThickness visual Degree of thickness measured during swirling of glass Tykhed/viskositet

Flavour/Taste a SmagCreamy avour Intensity of cream avour Flødeagtig smagBoiled milk avour Intensity of boiled milk avour Kogt mælk smagSweet taste Intensity of sweet taste Sød smag

Texture/Mouthfeel KonsistensThickness oral Perceived thickness of the sample evaluated in the mouth Tykhed/viskositetCreaminess oral Perceived creaminess of the sample evaluated in the mouth CremethedResidual mouth ll Degree of residual mouth coating after expectoration of the sample Eftermundfylde

Meta descriptorTotal fattiness Overall perception of fat content in the sample Samlet fedhed

a In Danish, no word for avour exists. Flavour is expressed through the Danish term for taste, ‘‘smag’’.

M.B. Frøst et al. / Food Quality and Preference 12 (2001) 327–336 329



before sessions. Only one sample at a time was served topanellists and were taken out 1–2 min before serving.For all evaluation sessions a computerised score collec-tion software (FIZZ, Biosystemes, France) was used. Ahorizontal 15-cm unstructured line scale anchored at theleft end with ‘‘a little’’ or ‘‘none’’ (in Danish: ‘‘lidt’’ or

‘‘ingen’’) and at the right end with ‘‘a lot’’ or ‘‘veryintense’’ (Danish: ‘‘meget’’ or ‘‘meget intens’’) was used.Sensory analysis of the 16 products was carried out intriplicate, and in randomised order within each repli-cate. In each session, only eight products were eval-uated, so a total of six sessions were necessary tocomplete the experiment.

2.3. Data analysis

Data analysis was performed using descriptive uni-variate analyses (mean and ANOVA for each descrip-tor). ANOVAs for the individual descriptors were per-formed using panellists as a random factor.Multivariate data analysis (Partial Least SquaresRegression [PLSR]) was applied to investigate relation-ships between sensory data and the experimental design.Initially, data were analysed to correct for irrelevantdifferences between panellists by PLSR, and level cor-rected data were used for analysis of effects of differenttreatments (cf. Martens, Wedøe, Bredie, & Martens,1999). After level correction, data was averaged overpanellists, and those data were used for analysis. For allthe multivariate analyses, cross validation was per-formed, leaving each replicate out at a time (Martens &

Naes, 1989). The analyses were performed in standardstatistical software packages (SPSS 9.0.0, SPSS Inc.Chicago, IL, USA, for univariate statistics andUnscrambler 7.51a, Camo ASA, Trondheim, Norway,for multivariate data analysis).

3. Results and discussion

The results from ANOVA showed signicant differ-ences among the samples with regard to all sensorydescriptors. Mean values and least signicant differ-ences at 5% level for all samples over all panellists andreplicates are presented in Table 3. It shows that theexperimental design used produced differences in allsensory modalities (aroma, appearance, avour/tasteand texture/mouthfeel).

3.1. Sensory descriptors and effect of experimental factors

After pre-processing of the data (level correction toaccount for panellists’ different use of scale), ANOVA-PLSR (APLSR) was performed (design as X -variablesand sensory data as Y -variable). Figs. 1a and 2a show

correlation loading plots from four signicant dimen-sions (explaining in average 60, 15, 4.2 and 4.1% of thevariation in sensory data, respectively). The observedeffects become much more apparent when looking atscore plots for the four dimensions, when the differentfactors are labelled separately and products are grouped

by factors or combinations thereof. These are shown inFigs. 1b,c and 2b,c, and are referred to along with theexplanations in the text. All other combinations of dimensions were explored during data analysis, but thecombinations shown, 1–2 and 3–4, proved sufficient forinterpretation of the data.

In dimension 1, two major clusters of descriptors areseen. One group consisting of Boiled milk smell andavour, Transparency and Blueness relates to 0.1% fatmilk. At the opposite end of the rst dimension is agroup of descriptors all relating to 3.5% fat milk, con-sisting of Sweet taste, Creamy smell and avour,Thickness visual and oral, Glass coating, Creaminess,Residual mouth ll, Total fattiness and Yellowness.This indicates a clear fat-level-direction in the results(Fig. 1b). The distances between groups with differentfat levels show that there is a much larger difference infattiness between 0.1 fat and 1.3% fat than there isbetween 1.3 and 3.5%. This indicates that perceivedfattiness is not a linear function of actual fat content inthe range spanned by the milk in our experiment,which is the range of milk fat content normally sold inDenmark.

The combined effects of thickener, whitener andhomogenisation result in a direction orthogonal to that

of fat level (Fig. 1c). This direction is mainly a differencein perceived whiteness. Samples with the addition of those three factors mainly score higher in whiteness,whereas those without, score lower. In Fig. 1c the fac-tors are grouped, so the effect of the individual factorscan be seen. From this, it is evident that whitener andthickener contribute to fattiness. There seems to be asmall effect of homogenisation as well. Signicant dif-ferences in a few sensory descriptors were observed.Homogenisation gives an increase in Creamy avourand a decrease in Blueness, both of these differenceswere only observed in 1.3% fat milk (Table 3). Theeffect of whitener and thickener is an increased per-ceived whiteness of the milk, as well as some increase inthe group of high fat related descriptors. In this direc-tion, no separation of thickener and whitener is seen,this subject will be returned to in dimension 4 below.

The third dimension spans the variation betweensamples with and without added aroma compounds, sothis is a avour dimension (Fig. 2b). Samples withadded aroma compounds have a higher intensity of Creamy smell and avour. Notice also that sweet tastecorrelates with the creamy descriptors (Fig. 2a). How-ever, the absolute differences in sweetness are smallerthan the differences in creamy smell and avour (cf.




Table 3Mean values (over panellists and replicates), Least Signicant Differences (LSD) values ( P <0.05) for all products and descriptors, product specications and

Product names Product description Sensory descriptors

Aroma AppearanceFat level (%) Thickener Whitener Aroma Homogenisation

Creamy smell Boiled mi lk smel l Whi teness Yellowness B lueness

LSD (5%) 1.12 0.97 0.78 0.85 0.76

0twah 0.1 3.56 6.20 6.02 4.27 6.45 1twah 1.3 5.24 5.79 6.39 5.84 4.18 3twah 3.5 6.11 4.43 6.27 8.05 2.69

0twAh 0.1 + 5.58 5.88 6.02 4.79 6.04 0tWaH 0.1 + + 4.19 6.05 8.26 4.16 4.09 0TwaH 0.1 + + 3.76 6.38 5.75 4.18 6.96 10tWAH 0.1 + + + 6.53 5.34 7.64 5.12 3.86 80TWAH 0.1 + + + + 6.42 5.50 7.73 4.89 4.14 71twaH 1.3 + 6.16 4.86 6.36 6.17 3.37 1twAh 1.3 + 7.89 4.42 6.34 6.56 3.65 1tWAH 1.3 + + + 8.44 3.86 7.43 6.41 2.96 61TwAH 1.3 + + + 8.36 4.35 6.71 6.68 3.09 1TWaH 1.3 + + + 6.36 3.91 8.13 5.72 2.68 53twaH 3.5 + 7.21 4.14 6.38 7.67 3.04 3TwaH 3.5 + + 7.04 4.47 6.89 7.47 2.54 3TWAH 3.5 + + + + 9.07 3.59 7.63 6.64 2.47 3

Product description Sensory descriptors

Flavour/Taste Texture/Mouthfeel

Fat level (%) Thickener Whitener Aroma Homogenisation Creamy avour Boiled milk avour Sweet taste Thickness oral Creaminess oral Residual

LSD (5%) 1.08 1.01 0.72 0.88 0.99

0twah 0.1 3.46 7.06 5.04 3.23 3.14 1twah 1.3 5.21 6.08 5.91 6.43 6.14 3twah 3.5 8.05 5.07 6.47 8.81 8.85

0twAh 0.1 + 5.73 6.58 6.85 4.09 4.89 0tWaH 0.1 + + 4.58 6.49 5.53 5.04 4.50 0TwaH 0.1 + + 3.36 7.05 4.97 3.41 3.18 0tWAH 0.1 + + + 6.12 6.09 6.38 5.04 4.90 50TWAH 0.1 + + + + 6.61 6.25 6.31 5.90 6.51 51twaH 1.3 + 6.86 5.34 6.41 6.57 6.77 1twAh 1.3 + 8.14 4.67 7.39 6.56 7.30 1tWAH 1.3 + + + 8.60 4.80 7.14 8.08 8.47 81TwAH 1.3 + + + 8.86 4.58 7.46 7.87 8.81 1TwaH 1.3 + + + 7.56 4.74 6.39 8.27 8.11 3twaH 3.5 + 8.20 4.53 6.89 8.59 8.66 3TwaH 3.5 + + 8.93 4.19 7.22 9.62 9.76 3TWAH 3.5 + + + + 10.05 3.57 8.07 9.56 10.39 9.

a Product abbreviations refer to the levels of the factors (0.1 and 3, 0.1, 1.3 and 3.5% fat, respectively; t and T, none and addition of thickener; w and W, none and addition of whitener; a compounds; h and H, no homogenisation and homogenisation).



Table 3). Still, there is some transference of scoring theattribute creamy to the scoring of sweetness. This can beconcluded since the latter did not change with the dif-ferent factors in the experiment. Samples with addedaroma score higher in Total Fattiness, indicating that anaroma component contributes to perceived fattiness in

the milks.Finally the fourth dimension shows the sensory dif-ferences between samples with added whitener versusthose with added thickener (Fig. 2c). At the 0.1% fatlevel, the sample with only added whitener scores higherin Whiteness, Glass coating, Thickness visual and oral,

Creaminess, Residual mouth ll and Total fattiness(Table 3). At the same fat level the sample with onlyadded thickener has a higher blueness and transparency.At the 1.3% fat level, the sample with only addedthickener still scores signicantly higher in transpar-ency, compared to the sample with only added whitener

(Table 3). The signicant differences in sensory descrip-tors indicate that the addition of whitener has a higherimpact on sensory properties than addition of thickenerhas. However, the chosen levels of additions for the twofactors inuence this conclusion. The grouping of thedescriptors in Fig. 2a indicates that Glass coating and

Fig. 1. (a) APLSR correlation loadings for the two rst dimensions showing differences among the 16 products. ~ Sensory Descriptors, & Factorsand * Products. For clarity of this gure product names are not shown. The inner and outer circles represent 50 and 100% explained variance,respectively. (b) Score plot from APLSR. Dimension I and 2. Indicating differences in fat levels (0=0.1%, 1=1.3% and 3=3.5%), and showing fatlevel direction based on the loadings. (c) Score plot from APLSR. Dimension I and 2. Indicating differences in addition of thickener (t/T), whitener(w/W) and homogenisation (h/H). Capital letters indicate addition of the factor. Showing whitener and thickener level direction and homogenisationlevel direction based on the loadings.




Thickness visual/oral may relate more to the colour of the milk, than to the actual thickness (Fig. 2a). Sampleswith only added whitener have higher intensities in thesedescriptors, compared to samples with only addedthickener.

3.2. Total fattiness

To evaluate the perception of fat in the products, thepanel used the meta-descriptor ‘‘Total fattiness’’. It canbe seen conceptually as a projection of all sensorydescriptors onto a ‘‘fattiness’’ percept. However, to rate

this meta-descriptor may be a task of high cognitivecharacter, and can be inuenced by the panellists’interpretations of how the individual descriptors con-tribute to perceived fattiness. So, what is then reallyinvestigated is how the different sensory attributes con-tribute to believed perceived fattiness as a result from

the previous scoring of all other attributes. From thecorrelation loadings plot for rst and second dimension(Fig. 1a) it can be seen that there is a whole group of descriptors that are highly positively correlated withTotal fattiness, (Creaminess oral, Creamy smell andavour, Sweet taste, Thickness visual and oral, Glass

Fig. 2. (a) APLSR correlation loadings for components 3 and 4 showing differences among the 16 products. ~ Sensory Descriptors, & Factors and* Products. For clarity of this gure product names are not shown, and only relevant descriptor names are shown. The inner and outer circlesrepresent 50% and 100% explained variance, respectively. (b) Score plot from APLSR. Dimension 3 and 4. Indicating addition of aroma com-pounds (a/A). Capital letters indicate addition of the factor, and showing aroma level direction based on the loadings. (c) Score plot from APLSR.Dimension 3 and 4. Indicating differences in addition of thickener (t/T) and whitener (w/W). Capital letters indicate addition of the factor.




coating and Residual mouth ll). Yellowness is alsocorrelated to Total fattiness, but not as highly as the restof this group. Further Fig. 1a shows that Whiteness isnot correlated to Total fattiness, and that the group of descriptors in the opposite end of the rst dimension isnegatively correlated to Total fattiness. Closer exam-

ination of the grouping of the fattiness related descrip-tors in the subsequent dimensions show that indimension 3 and 4 (Fig. 2a) Total fattiness is still closelygrouped with Residual mouth ll and Creaminess, indi-cating that these two descriptors are most fully reect-ing perceived fattiness in milk. However, there is notmuch Total fattiness left to explain in these two dimen-sions, since it lies relatively close to the origin in Fig. 2a.The conclusion that Creaminess and Residual mouth llmost fully reect perceived fattiness in milk was con-rmed by a PLSR-analysis with Total fattiness as the Y -variable and all other sensory descriptors as the X -vari-ables. Variation in Creaminess and Residual mouth llcontributed the most to explained variance in Totalfattiness (both of them higher than 96%).

3.3. Differences between products

Cobweb-plots can be used to focus on the differencesbetween a few products. Fig. 3 shows the sensory prop-erties of the three different fat levels. The gure shows

the same differences that were apparent from the corre-lation loading plots (Fig. 1a) and the score plot withlabels for fat content (Fig. 1b). A rather large group of descriptors is positively correlated with fattiness (Resi-dual mouth ll, Creaminess, Thickness visual/oral,Creamy smell and avour, Glass coating and Yellow-

ness). Another group of descriptors is inversely corre-lated with a high fat content (Boiled milk smell andavour, Blueness and Transparency). All of thesedescriptors vary signicantly ( P <0.05) across the threeproducts. Whiteness is not affected signicantly by thechanges in fat content. It is also, as shown in APLSR,evident that the sensory differences between 0.1 and1.3% fat are larger than between 1.3 and 3.5% fat. Thisis conrmed by the signicant differences between pro-ducts observed by ANOVA. Fig. 4 shows the sensoryprole of 0.1% fat with all added additives and 1.3%fat, homogenised. There are only signicant differencesin two descriptors. The 0.1% fat milk with additionshave a higher Whiteness, but a lower Glass coating. TheTotal fattiness is the same, so the sensory properties of 1.3% fat have been mimicked quite successfully by theaddition of all the food additives used in the experiment.This was not the case with only one food additive added(Fig. 5). Addition of whitener and aroma were not suf-cient either to mimic the increase in true fat contentfrom 0.1 to 1.3%, since there is a signicant difference

Fig. 3. Cobweb plot of sensory proles from the three different fat levels.




Fig. 4. Cobweb plot of sensory proles from 1.3% fat, homogenised and 0.1% fat added all additives.

Fig. 5. Cobweb plot of sensory proles from 1.3% fat, homogenised and 0.1% fat added only one of the food ingredients.




in Total fattiness. Nor were combinations of two foodadditives in 1.3% fat milk completely capable of mimicking the increase from 1.3% fat to 3.5% fat. Butthere were no signicant differences in Total fattiness(Table 3). The conclusions from this experiment mightnot have a high relevance with regard to milk for con-

sumption, since there (in the European Union) is a veryrestrictive legislation about food additives. However,for other milk-based beverages, where there is moreroom for improvements by adding food additives, theconclusions about how to imitate fattiness are valuable.

4. Conclusions

The results from the experiment show that the sensoryproperties of fat in milk are comprised of texture/mouthfeel, appearance and avour attributes. Analysisof the contribution of the individual sensory descriptorsto perceived fattiness in milk shows that Creaminessand Residual mouth ll most accurately reect fattinessof milk in this fat range. It is unknown to what extentthe results about perceived fattiness from a sensorypanel can be extended to the general population. How-ever, the assessment of fattiness obtained from a trainedsensory panel gives a very detailed picture of humansensory perception of fattiness. The sensory differencesbetween 0.1% fat milk with added thickener, whitenerand aroma are very small as compared to those inhomogenised 1.3% fat milk. They only differ sig-

nicantly in two descriptors: Whiteness and Glass coat-ing. It was not the case when only using one foodadditive, or combinations of two. This clearly showsthat the sensory properties of fat in milk are not easilysubstituted with food additives seeking to imitate thesensory properties of fat. The experiment showed thatthere are larger sensory differences between milk with0.1% and 1.3% fat, than there are between 1.3% and3.5% fat. This shows that the fat does not affect thesensory properties of milk in a linear fashion. It is verylikely that sensory properties of 0.1% fat milk can bechanged drastically by adding only a little extra fat tothe milk.

Acknowledgements

This work is part of the FØTEK programme sup-ported by the Danish Dairy Research Foundation(Danish Dairy Board) and the Danish Government.Nina Ahn, Judith Henning and Anne Marie Laustsen

are thanked for technical assistance. Ditte Marie Folk-enberg is acknowledged for inspiring the rst author tousing the meta-descriptor ‘‘Total fattiness’’. The dona-tion of food additives from Danisco Cultor is highlyappreciated.

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Sensory Perception of Fat in Milk

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