Journal of the Science of Food and Agriculture J Sci Food Agric 79 :707–712 (1999)

Sensory and compositional attributes ofmelting- and non-melting-flesh peaches for thefresh marketErnes to A Brovelli,1 Jeffrey K Brecht,1 Wayne B Sherman,1 Charles A Sims 2*and Jay M Harris on31 Horticultural Sciences Department , IFAS,Univers ity of Florida,Gaines ville , FL 32611-0690, USA

2 Food Science and Human Nutrition Department , IFAS,Univers ity of Florida,Gaines ville , FL 32611-0370, USA

3 Department of Statis tics , IFAS,Univers ity of Florida,Gaines ville , FL 32611-0560, USA

Abstract : A study was conducted to determine diþ erences in sensory and compositional character-

istics of melting-ýesh (MF) and non-melting ýesh (NMF) fresh market peach genotypes. Sensory

results showed that the NMF fruit (‘Oro A’ and FL 86-28C) were ‘harder’, less ‘juicy’ and more

‘rubbery’ than their MF (FL 90-20 and ‘TropicBeauty’) counterparts. A principal component analysis

of the sensory data showed a clear distinction between the textural aspects of MF and NMF fruit, but

not between their ýavour aspects. Likewise, chemical analysis showed that while diþ erences in pH,

titratable acidity, and soluble solids were detected among the four genotypes, no consistent grouping

could be made based on the MF/NMF nature of the fruit.

1999 Society of Chemical Industry(

Keywords: non-melting-ýesh peaches ; sensory evaluation; principal component analysis

INTRODUCTION

The heterogeneous genetic base of the peach, Prunuspersica (L), is displayed in the great phenotypicvariability exhibited by the fruit. According toappearance and sensory characteristics, peach fruitcan be classiüed as : round, ýat or beaked; pubescentor smooth-skinned; freestone or clingstone; white,yellow or red ýeshed; sweet, sour or astringent ; andmelting-ýeshed (MF) or non-melting-ýeshed(NMF).1

The main distinction between MF and NMF fruitis that the latter lack the rapid loss of ürmness,known as ‘melting of the ýesh’, characteristic of theünal stages of ripening of MF fruit.2 When MFpeaches, which are usually grown for the freshmarket, are left to ripen on the tree in order toachieve maximum quality, they show a propensity tomechanical damage and decay during shipping andhandling.3 Unlike MF peaches, NMF cultivars aretraditionally grown for canning purposes since thefruit maintain their integrity after undergoing heatprocessing. These NMF cultivars, however, lack thered coloration, acidity and aroma of commonlygrown dessert-type MF fruit.4 An important goal forcurrent breeding programmes is to develop NMFpeach cultivars that have sensory characteristicsappropriate for the fresh market. The objective is toproduce fruit that are able to attain maximum

ýavour on the tree, yet maintain sufficient ürmnessto allow distribution under normal marketing chan-nels.4

While the compositional aspects of diþerent peachgenotypes have been widely studied,5h7 the sensorycharacteristics of the fruit have received less atten-tion, especially in recently-developed fresh marketNMF genotypes. Descriptive sensory evaluationaddresses the complexity of food systems by takinginto account as many of a food’s attributes or notesas possible.8 The interpretation of descriptivesensory evaluation is often simpliüed with the assist-ance of multivariate statistical procedures, such asprincipal component analysis.8h11 The use of prin-cipal component analysis allows for the transform-ation of a set of variables, such as the sensory notes,into a substantially smaller set of uncorrelated vari-ables, namely principal components.9,12 Besidesaiding in data interpretation, principal componentanalysis is able to reduce the magnitude of the erroror noise that is often associated with descriptivesensory evaluation.13

The objective of the following study was to char-acterise MF and NMF cultivars based on their com-positional as well as on their sensory attributes inorder to identify diþerences between the two typeswhen harvested at a range of maturities from mini-mally mature to fully ripe.

* Corres pondence to : A Food Science and HumanCharles Sims ,

Nutrition Department, IFAS, Univers ity of Florida, Gaines ville, FL

32611-0370, USA

(Received 17 November 1997; revis ed vers ion received 21 April

1998 ; accepted 3 September 1998)

( 1999 Society of Chemical Industry. J Sci Food Agric 0022-5142/99/$17.50 707

EA Brovelli et al

EXPERIMENTAL

Plant material

This study was initiated in 1994 and was repeated,with modiücations, in 1995. The plant material con-sisted of two genotypes of MF fruit, FL 90-20 and‘TropicBeauty’, and two of NMF fruit, ‘Oro A’ andFL 86-28C. Fruit from all four genotypes wereobtained from the Teaching Orchard, HorticulturalSciences Department, University of Florida, Gaines-ville. Each NMF genotype was paired with a MFgenotype of comparable maturity date. The geno-types were unrelated by inbreeding coefficients butwere selections from the University of Florida breed-ing programme representing a rather narrow geneticbase. Thus, they represent many similarities exceptfor the major gene (recessive for NMF) diþerenceson which they were paired for comparison of MFand NMF.

Fruit classification and compositional analysis

In 1994, fruit were harvested on three dates at inter-vals of 7 days. On each date, harvesting was selectivefor those fruit whose skin ground (ie background)colour was representative of the average groundcolour for each genotype. The fruit collected in eachharvest were considered to represent a distinct matu-rity category. In the last harvest of the NMF geno-type FL 86-28C, when the ease of detachmentallowed for a clear distinction between fruit with andwithout a well-developed abscission zone, fruit weredivided into two additional maturity categories basedon that characteristic. In each case, all of the fruitthat represented the desired maturity category wereharvested from four trees and the fruit were random-ized.

After each harvest, 30 fruit per genotype were ran-domly selected. Each lot was stored at 0¡C for 14days in order to simulate shipping/marketing condi-tions and subsequently allowed to ripen at 20¡C.During ripening, ethylene production was moni-tored, and when the ethylene peak was observed, thefruit were removed from storage and divided intotwo groups for sensory evaluation and chemicalanalysis. One group of 15 fruit was used for sensoryevaluation. The group for compositional analysisconsisted of 15 fruit that were stored at [20¡C untilanalysed. For analysis, peaches were thawed, peeled,sliced, pitted and pureed in a Waring Blender for1min. The slurry was centrifuged (20min,17600] g ; 6¡C) and the ýuid fraction was used forthe determination of soluble solids by refractometry,titratable acidity by titration with 0.1M NaOH andpH.

In 1995, fruit were harvested on two dates at inter-vals of 7 days. Unlike 1994, in which harvesting wasselective for fruit at the average stage of maturity,harvesting in 1995 was non-selective and all fruit ontwo trees per harvest were collected. Once in thelaboratory, the fruit were separated into six classesbased on a diameter scale that progressed in 0.16cm

increments. Owing to the fact that FL 90-20, FL86-28C and ‘TropicBeauty’ have fruit innately largerthan those of ‘Oro A’, the initial class was 2.70 to2.86cm for the ürst three genotypes and 2.06 to2.22cm for ‘Oro A’. The classiücation scheme intro-duced in 1995 was used to increase the number offruit categories and expand the range of maturitylevels. Fruit diameter was chosen for this purposebased on evidence from the 1994 harvests that indi-cated a high correlation between diameter and matu-ration in these genotypes.14 Ground colour was notused for classiücation of the fruit because of theextensive red blush on three of the four genotypes,which made accurate measurement of the groundcolour of all the fruit with a colorimeter impossible.After classiücation by size, lots of 12 fruit from eachdiameter class were reserved for sensory evaluationand were stored at 0¡C for 1 week and subsequentlyallowed to ripen for 2 days at 20¡C. This modiü-cation from the ýexible ripening schedule of 1994,where ethylene production determined the timing ofremoval of the fruit, was done so that the sensoryevaluation of each MF/NMF pair could be con-ducted side by side, rather than on diþerent rates.The shortening of the storage time from 2 weeks in1994 to 1 week in 1995 was done in order to accom-modate fruit of more advanced maturity, which wereincluded as a result of the classiücation schemeimplemented in 1995.

Sensory evaluation

Ten panellists (4 female, 6 male, 25–48 years of age)were selected to participate based on participation inprevious descriptive sensory panels, interest, andavailability for the entire study. All panellists weregraduate students or staþ in the Food Science andHuman Nutrition Department. Panellists partici-pated in three 1-hour training sessions the weekbefore the evaluations. During the ürst trainingsession, panellists were presented with a wide rangeof both MF and NMF fresh peaches, ranging inmaturity from underripe to overripe. Genotypesused for training were harvested at the various stagesof maturity except overripe, which were allowed tofurther ripen after harvest to a point deemed to beoverripe. Several fruit of each genotype/maturitywere peeled, slice into approximately 1cm widewedges, mixed in a bowl and presented to the panel-lists. Panellists were asked to note all terms thatshould be used to describe the samples. Panellistswere provided with a list of potential descriptors thathad been used in other sensory studies on freshpeaches, but were also encouraged to develop theirown terms. Panellists then discussed the terms, andcame to an agreement on the terms needed todescribe all samples : hardness ; rubberiness ; juici-ness ; sweetness ; sourness ; bitterness ; green; peachand overripe peach.

In the second training session the following day,panellists were presented with the same samples and

708 J Sci Food Agric 79 :707–712 (1999)

Sensory evaluation of peaches

brieýy reviewed all the terms selected in the previoussession. Panellists then identiüed samples that wouldserve as ‘standards’ for each attribute. Samples thatwere chosen to represent each attribute included:‘Oro A’ (beginning to ripen) for high hardness, highrubberiness, low juiciness, low sweetness, high sour-ness, low peach, low to medium green, low bitternessand low overripe peach ; FL 90-20 (fully ripe) forlow hardness, low rubberiness, high juiciness, highsweetness, low sourness, low green and high peach ;and overripe FL 90-20 for high overripe peach.

In the third session the same day, panellists prac-tised rating some of the same samples using theagreed upon terms and ‘standards’. A ballot wasdeveloped using a 1–15 point discrete scale, with1\ low and 15\ high. Samples were assigned a3-digit random number and presented in randomorder. Panellists discussed their results afterwardsand were in general agreement on the terms to useand values assigned to the ‘standards’. The sametraining process was used in both years.

For evaluation of the treatments in 1994, 10–12peaches of each treatment (genotype, harvest date)were peeled, sliced into about 1cm wide wedges, andmixed thoroughly in a bowl. Since not all genotypesripened at the same rate, each treatment was evalu-ated separately at a session over a 2-week period.Samples (2–3 slices) of each treatment were assigneda 3-digit random number, placed in plastic cups, andpresented to panellists. Panellists evaluated thesamples on the 1–15 scale (as described above) inprivate booths, and were provided with water andunsalted crackers.

In 1995, panellists evaluated the 5–6 treatments(diameters) of each genotype at a session. ‘Oro A’treatments were evaluated at the same session as FL92-20 (a 5min break between genotypes), and‘Tropic Beauty’ and FL 86-28C were evaluated atthe same session in the same manner. This processwas repeated for the second harvest. Procedures wereotherwise identical to those in 1994.

Statistical analysis

The statistical design addressed the fact that not allof the genotypes had an equal number of maturityclasses and that diameter classes identiüed with thesame number did not necessarily coincide in theirharvest dates. Sensory evaluation results from 1994were analysed according to a randomized completeblock design, with panellist as a random block eþect,üxed genotype eþects, and üxed harvest date eþectsnested within the genotype eþects. Panellists wereconsidered a random eþect because there was nointent to compare panellists to each other. Thus, theresults of the sensory evaluation are more gener-alised, since individual responses are not likely to bereproducible while the variance of the panel as awhole would be. Chemical analysis results wereanalysed according to a two-stage nested design, withüxed genotype eþects and üxed harvest eþects

nested within the genotype eþects. Means wereseparated by pairwise t-tests with a Bonferroni cor-rection at an experimentwise type I error rate ofa \ 0.05.15

In order to compare MF and NMF fruit, resultsfrom the sensory analyses were consolidated intomeaningful variables by means of principal com-ponent analysis.12 The correlation matrix was usedin the principal component analysis in order toexamine relationships among groups of factors and inorder to minimise any extreme variances of individ-ual factors. Signiücant principal components wereidentiüed by the Kaiser criterion as those with eigen-values greater than 1.0. In 1994, results from allmaturity classes were analysed jointly, thus increas-ing the number of data points. In 1995, when fruitfrom the two harvests were separated into diameterclasses, results were further analysed based onharvest and diameter class.

RESULTS AND DISCUSSION

The sensory ratings for the diþerent MF and NMFgenotypes in 1994 are shown in Table 1. Clear dif-ferences in the textual aspects of the fruit weredetected between the two types of genotypes, withthe NMF fruit being ‘harder’, less ‘juicy’ and more‘rubbery’ than their MF counterparts. Diþerencesbetween genotypes with the same type of ýesh indi-cate that, within MF or NMF types, some variabilityin the textual aspects can be anticipated. No group-ing of the genotypes in any of the ýavour notes couldbe established based on their ýesh type (MF/NMF).

The ürst three principal components (PC)resulting from the principal component analysis ofthe 1994 sensory data explained 64% of the totalvariability (Table 2), and all three principal com-ponents had eigenvalues greater than 1.0. The factorloadings shown in Table 2 give an indication of theimportance of each sensory note within each of theprincipal components. It is apparent that all of thetextural notes, ‘hardness’, ‘juiciness’, and ‘rubberi-ness’, had large impacts on the sensory assessmentdescribed by PC1. It is also evident that a contrastbetween negative and positive factor loadings can beestablished with PC1, with ‘sweetness’, ‘peach char-acter’, and ‘overripe’, being opposed to the othersensory notes. It could be argued that this contrastrepresents the diþerence between attributes associ-ated with early stages of fruit development(‘hardness’, ‘sourness’, ‘green character’ etc) andthose associated with more advanced phases of ripen-ing (‘sweetness’, ‘peach character’, and ‘overripe’).

In a plot of PC1 versus PC2 for the 1994 sensorydata (Fig 1), the points are distributed in two bandsalong the PC1 axis, indicating that PC1 was eþectiveat explaining total variation. The plot also reveals aclear distinction between the overall sensory assess-ments for MF and NMF fruit. Based on the impor-tance of the textual notes in PC1, separate principal

J Sci Food Agric 79 :707–712 (1999) 709

EA Brovelli et al

Table 1. Sens ory ratings * for ripe MF and NMF fruit (1994)

Genotypes Sens ory note

Hardnes s Juicines s Rubberines s Sweetnes s Sournes s Bitternes s Green Peach Overripe

character character

Melting fles h

FL 90-20 4.0 c¹ 10.3 b 3.6 c 7.6 a 5.2 a 2.2 a 1.8 ab 9.2 a 2.3 b

Tropic Beauty 1.3 d 11.8 a 0.4 d 6.5 ab 3.8 d 1.7 a 1.3 b 6.0 c 5.9 a

Non-melting fles h

Oro A 9.0 b 7.1 c 8.3 a 7.5 a 4.7 b 2.8 a 2.4 ab 8.1 ab 1.2 b

FL 86-28C 10.1 a 6.3 c 5.7 b 5.8 b 4.1 c 2.3 a 2.9 a 7.0 bc 1.9 b

* Rating s cale ranges from 1 (low intens ity) to 15 (high intens ity)¹ Mean s eparation in columns by pairwis e t -tes ts with Bonferroni correction at experimentwis e a \ 0.05

component analyses were conducted for the texturaland ýavour notes. In the case of the textual principalcomponents, PC1 explained 70% of the total varia-bility and was the only principal component to showan eigenvalue greater than 1.0. A plot of texturalPC1 versus textural PC2 also revealed a clear separa-tion of MF and NMF fruit (Fig. 2). In the case ofthe ýavour principal components, however, it wasmore difficult for a single principal component toexplain a large proportion of the variation; but thecumulative proportion of the variation explained byPC1 and PC2, both with eigenvalues greater than 1,was 58%. A striking aspect of the plot of ýavour PC1versus ýavour PC2 was that the data points for MF

Table 2. Factor loadings for principal component analys is of

s ens ory data (1994)

Sens ory note PC1 PC2 PC3

Hardnes s 0.521 0.143 [0.223Juicines s 0.482 0.113 [0.196Rubberines s 0.410 0.017 [0.283Sweetnes s [0.046 0.507 0.186

Sournes s 0.169 [0.076 0.738

Bitternes s 0.133 0.433 0.319

Green character 0.251 0.358 0.216

Peach character [0.204 0.518 [0.288Overripe [0.414 0.342 [0.132% cumulative variance 28 50 64

Figure 1. Overall s ens ory PC1 vers us overall s ens ory PC2 for

1994 harves ts of genotypes FL 90-20 (MF), TropicBeauty (TB; MF),

Oro A (NMF) and FL 86-28C (NMF).

and NMF fruit were intermingled in the scatter plot(Fig 3). These results suggests that, even whenpanellists were able to make an overall distinctionbetween the two types of fruit (Fig 1), it was thetexture rather than the ýavour attributes thataccounted for that distinction. Likewise, the chemi-cal analysis revealed that although diþerences in pH,titratable acidity and soluble solids were detectedamong the four genotypes analysed (Table 3), noconsistent grouping could be made based on theMF/NMF nature of the fruit.

In 1995, a high proportion (40%) of the totalvariation in the sensory data was explained by thefruit principal component (Table 4). An analysis of

Figure 2. Textural PCl vers us textural PC2 for 1994 harves t of

genotypes FL 90-20 (MF), TropicBeauty (TB; MF), Oro A (NMF)

and FL 86-28C (NMF).

Figure 3. Flavour PCl vers us flavour PC2 for 1994 harves ts of

genotypes FL 90-20 (MF), TropicBeauty (TB; MF), Oro A (NMF)

and FL 86-28C (NMF).

710 J Sci Food Agric 79 :707–712 (1999)

Sensory evaluation of peaches

Genotype pH Soluble s olids Titratable acidity SS : TA

(¡Brix) (%malic acid) (¡Brix : %malic acid)

Melting fles h

FL 90-20 3.93 ab* 10.2 b 1.50 bc 7.17 b

TropicBeauty 3.86 ab 10.5 b 2.06 a 6.00 c

Non-melting fles h

Oro A 3.97 a 12.0 a 1.68 b 7.59 b

FL 86-28C 3.84 b 11.9 a 1.39 c 9.26 a

* Mean s eparation in columns by pairwis e t -tes ts with Bonferroni correction at experimentwis ea \ 0.05

Table 3. Chemical attributes of

ripe MF and NMF peaches (1994)

the factor loadings of PC1 revealed that the mostpronounced contrast occurred between the ‘overripe’trait and the rest of the notes. This indicates anopposing behaviour of the ‘overripe’ note and therest of the notes in the deünition of PC1. In PC2,which explained an additional 14% of the total varia-tion, a constrast can be established between ‘hard-ness’, ‘rubberiness’, ‘sourness’ and ‘green character’(notes associated with early stages of maturation) andthe rest of the sensory notes.

Separate principal component analyses of the tex-tural and ýavour notes in 1995 showed the sametrends observed in 1994. For the textural analysis,PC1 explained 60% of the variability, and, with PC2and PC3 included, 100% of the variability wasexplained. As in 1994, the larger number of notesinvolved in the deünition of the ýavour principalcomponents made it difficult for a single principalcomponent to explain a large proportion of the varia-bility. Flavour PC1 explained 40% of the variability,and, with the inclusion of PC2 and PC3, 75% of thetotal variability was explained.

As in 1994, the principal component analysis ofthe 1995 sensory data showed a clear distinctionbetween the textural aspects of MF and NMF fruit,but not between their ýavour aspects (data notshown). Unlike 1994, however, a greater dispersionin the 1995 principal components could be observed.This dispersion could be due to the fact that in 1995

Table 4. Factor loadings for principal component analys is of

s ens ory data (1995)

Sens ory note PC1 PC2 PC3

Hardnes s 0.423 [0.237 0.141

Juicines s 0.461 0.026 0.072

Rubberines s [0.021 [0.355 0.832

Sweetnes s 0.428 0.245 [0.050Sournes s 0.371 [ 0.151 [0.977Bitternes s 0.072 0.452 0.443

Green character 0.367 [0.141 1.032

Peach character 0.287 0.560 0.019

Overripe [0.249 0.441 0.268

% cumulative variance 40 54 66

the sensory evaluation included twelve fruit cate-gories (resulting from two harvests and six diameterclasses), rather than three (resulting from threeharvests) as in 1994. When the 1995 sensory resultswere sorted by diameter rather than by genotype, theprincipal component analysis showed a tendency forthe diameter classes to cluster along the PC1 axes inan ascending order (ie the smallest diameter classcloser to the origin and the largest father away fromit ; data not shown), especially for the ürst harvest.This suggests that some of the smaller fruit may havestill been in the growth phase of development at thetime of harvest.

The lack of separation in the ýavour aspects ofMF and NMF fruit in both years substantiates theconcept that the main diþerence between the twotypes of fruit lies in the texture rather than in theýavour aspects. This observation is signiücant sincecertain clingstone (NMF) genotypes have beenreported to develop unpleasant oþ-ýavours duringstorage and ripening.16 This tendency to oþ-ýavourdevelopment in ripe fruit, if found to be linked to theNMF trait, would make these genotypes unsuitablefor the fresh market.

The importance of textural attributes in the assess-ment of peach fruit sensory quality has beenaddressed by other authors. In a descriptive sensorystudy of maturation and ripening of ‘Cresthaven’peaches, Lyon et al10 noted that it was primarilytexture and not aroma attributes that explained dif-ferences due to maturity or ripening of the fruit. Asurvey of consumer perception of peach character-istics ranked texture among the most importantfactors that determine the quality of the fruit.17 It isnot yet known if the texture of NMF peaches willünd favour in the fresh market.

CONCLUSION

Based on the results of this study, it is concludedthat inclusion of the NMF trait does not compromisefruit ýavour in the peach genotypes studied, thusvalidating the breeding objective. The study alsoemphasises the usefulness of descriptive sensoryevaluation and principal component analysis inevaluating the sensory quality of new breeding rel-eases.

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ACKNOWLEDGEMENTS

Paper No R-05794 of the Florida AgriculturalExperiment Station Journal Series.

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