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The impact of maturity, storage temperature and storage duration on sensory quality and consumer satisfaction of ‘Big Top®’ nectarines
Scientia Horticulturae 190 (2015) 179–186
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The impact of maturity, storage temperature and storage duration on sensory quality and consumer satisfaction of ‘Big Top® ’ nectarines G. Echeverría a,∗,1 , C.M. Cantín a,1 , A. Ortiz b,2 , M.L. López a,b , I. Lara b , J. Graell b a b
IRTA, XaRTA-Postharvest, Parc Científic i Tecnològic de Gardeny, Fruitcentre, 25003 Lleida, Spain Universitat de Lleida, XaRTA-Postharvest, Av. Alcalde Rovira Roure, 191, 25198 Lleida, Spain
a r t i c l e
i n f o
Article history: Received 29 January 2015 Received in revised form 1 April 2015 Accepted 14 April 2015 Available online 15 May 2015 Keywords: Consumer satisfaction Fruit quality Prunus persica Sensory attributes Storage temperature
a b s t r a c t This research focuses on the effect of maturity stage and storage conditions on quality and consumer satisfaction of ‘Big Top® ’ nectarines. At harvest time, fruit were graded in three categories according to the IAD index (index of absorbance difference = A670 − A720 ) based on Vis spectroscopy. Physicochemical parameters (soluble solids concentration, titratable acidity and flesh firmness) were measured for the three maturity categories at harvest time and after up to 49 days of storage at 20, 10, 4 or −1 ◦ C. Consumer satisfaction and sensory attributes were also measured on fruit from all three categories at harvest time, as well as on fruit from the intermediate maturity class after storage at the different tested temperatures for up to 49 days. At harvest time, consumer’s satisfaction increased significantly with maturity stage at harvest, mainly due to an upper sweetness and flavour perception and higher SSC value detected in the most mature class. For short storage periods, ‘Big Top® ’ nectarines kept at 20 ◦ C received the highest scores for peach flavour intensity and overall acceptance. For longer storage periods, no significant differences among temperatures were observed on sensory quality or consumer satisfaction, except for fruit stored for the longest period (7 weeks), for which higher consumer acceptance was found for fruit stored at −1 ◦ C than at 4 ◦ C. Results also suggested that higher acceptance scores were associated mainly to more intense perception of flavour. © 2015 Elsevier B.V. All rights reserved.
1. Introduction European production of peach and nectarine in 2013 was about 3 million tonnes, 51% of which were nectarines. An important increase in the proportion of nectarine production has been observed in the last years at most peach production areas. ‘Big Top® ’ is nowadays considered the reference nectarine cultivar in Europe for fresh consumption, known as a slow-softening rate cultivar and appreciated for its early colouration resulting in greatly coloured fruit, optimum fruit size, high sweetness, juiciness and flavour (Cano-Salazar et al., 2013a,b). Moreover, recent studies have shown that it is a particularly suitable cultivar for fresh-cut production (Cefola et al., 2014; Giné Bordonaba et al., 2014). ‘Big Top® ’ nectarine is the most widely cultivated nectarine cultivar in Europe. To withstand handling in the packing house and
∗ Corresponding author. Tel.: +34 973 702648; fax: +34 973 238301. E-mail address: [email protected] (G. Echeverría). 1 Both authors contributed equally to this work. 2 Present address: UPSP GRAPPE, Groupe ESA, SFR QUASAV 4207, 55 rue Rabelais, BP 30748, 49007 Angers Cedex 01, France. http://dx.doi.org/10.1016/j.scienta.2015.04.022 0304-4238/© 2015 Elsevier B.V. All rights reserved.
marketing operations (transport, storage and retail display) these fruit have to be firm enough. Hence, they are frequently harvested before full ripeness, but such fruit often fail to develop desirable sensory attributes, and are consequently not perceived as sufficiently satisfactory by the consumer. Moreover, it has been largely documented that nectarine fruit subjected to long cold storage are prone to suffer serious quality decay, detected at the consumer level, due to the development of chilling injury symptoms, evident as mealiness, internal browning and lack of peach flavour (Crisosto et al., 1999; Lurie and Crisosto, 2005). The poor eating quality of fresh peach and nectarine transported to distant markets is one of the main current problems of the growing peach industry. Nectarine quality has always been measured in terms of the traits of the fruit, mainly through evaluation of the physical and chemical properties that best describe the progress of maturation and ripening. Flesh firmness, superficial and ground colour, soluble solids content (SSC), and titratable acidity (TA) are the parameters used generally for defining fruit quality because they provide a common language among researchers, producers and handlers (Abbott, 1999). However, when quality is measured from the consumers’ perspective, these parameters do not always match what consumers consider for deciding whether produce quality is
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acceptable (Shewfelt, 1999). Consumers often buy the first time based on fruit appearance, but repeated purchases are driven by expected quality factors mainly determined by flavour compounds and texture (Crisosto et al., 2006). In general, consumers are willing to pay more for fruit with a higher hedonic score (Delgado et al., 2013), which sheds light on why harvesting at the optimum ripening stage, and storing the fruit at the optimum temperature and duration is crucial. However, there is scarce literature where the effect of storage conditions on the consumer perception had been studied through consumer tests. Thus, it is important to define quality on the basis of consumer expectations (Predieri et al., 2006). The consumers’ judgement in the food marketplace has become crucial over the recent years (Asp, 1999). The demand for high quality fruit, including excellent taste, high nutritional value and nutraceutical value, highlights the need of monitoring the effect of the postharvest chain on sensory attributes, and subsequently on consumer satisfaction. To the best of our knowledge, no previous studies have examined the relationships between storage duration and temperature of nectarines harvested at different ripening stages and consumer perception. In the present work, ‘Big Top® ’ nectarines from different maturity stages were exposed to different temperature and periods of storage with the objective of characterising their effect on standard quality parameters, sensory attributes and consumer satisfaction. 2. Materials and methods 2.1. Fruit material Yellow-fleshed nectarines (Prunus persica L. Batsch var. nucipersica cv. ‘Big Top® ’) were harvested at 109 days after full bloom (DAFB) in 2008 at a commercial orchard located in Massalcoreig (Catalonia, NE Spain) and selected for uniformity of size and absence of defects. The IAD index (index of absorbance difference = A670 − A720 ) at harvest was used to pre-sort nectarine non-destructively by Vis spectroscopy (Ziosi et al., 2008). In this work the IAD index was measured using a commercial equipment (C2005d, Minolta, Valencia, Spain), while Ziosi et al. (2008) used a commercial spectrometer (S-2000, Ocean Optics, Dunedin, USA). Following sorting, fruit were classified into three different categories by decreasing values of the IAD (M1: IAD 0.17–0.15; M2: IAD 0.14–0.12; M3: IAD 0.11–0.09) and stored at 20, 10, 4 or −1 ◦ C for up to 49 days depending on storage temperature. Out of 3750 fruit assessed in total, 898 were graded as M1, 1278 as M2, and 759 as M3. At harvest, for each maturity class, 15 and 20 fruits were used for physicochemical measurements and consumer evaluation, respectively. After each storage period, 15 fruits were also used for physicochemical measurements per temperature and maturity class (total ∼ 500 fruits). In addition, for M2 class 15 fruits more were used after each storage period and temperature for consumer evaluation (total ∼ 500 fruits). Physicochemical parameters (flesh firmness, SSC and TA) were measured for fruit from the three classes at harvest and periodically throughout storage, while consumer satisfaction and sensory attributes described by a consumer panel were scored for fruit from the three categories at harvest time, but only for fruit from M2 class during storage.
removed from the storage chamber and not assessed sensorially. Flesh firmness was measured on opposite sides of each fruit with a penetrometer (Effegi, Milan, Italy) fitted with an 8-mm diameter plunger tip; results were expressed in N. SSC and TA were measured in juice pressed from the whole fruit. SSC was determined with a hand-held refractometer (Atago, Tokyo, Japan), and results were expressed as %. TA was determined by titrating 10 mL of juice with 0.1 N NaOH to pH 8.1 using a pH-metre (GLP 21, Crison); results were given as g malic acid/L. 2.3. Consumer satisfaction and sensory attributes assessment Fruit samples from each maturity stage were scored by consumers immediately after harvest. However, after storage only fruit from M2 class was sensorially analysed. After each storage temperature and period, fruit was kept for 3–4 h at room temperature in order to allow fruit to reach 20 ◦ C before consumer’s assessment. Fifteen nectarines per combination of factors (storage temperature × storage period) were used for sensory analysis. Sensory evaluations were conducted as elsewhere described (Echeverría et al., 2008). Each consumer, from a panel of 81 consumers, was asked to indicate his/her degree of liking/disliking using a ninepoint hedonic scale (1, dislike extremely; 9, like extremely). In addition, consumers were asked to score how they perceived the intensity of sweetness, sourness, firmness, juiciness and flavour according to a five-point hedonic scale (1, very low intensity; 5, very high intensity). Consumers were volunteers from the staff working at the University of Lleida and IRTA (Institut de Recerca i Tecnologia Agroalimentàries), and students from the University of Lleida. The samples could be re-tasted as often as desired. All evaluations were conducted in individual booths under white illumination and at room temperature. 2.4. Statistical and multivariate analysis A multifactorial design with storage period and temperature as factors was used to statistically analyse the results. All data were tested by analysis of variance (GLM-ANOVA procedure) with the SAS/STAT 9.1 procedures (SAS Institute Inc., 2004). Mean comparisons were performed using Tukey’s LSD test at P ≤ 0.05. Correlations between experimental variables were made using Spear-man’s rank correlations and, if required, presented as Spearman’s correlations coefficient (r) and P value based on a two-tailed test. Unless otherwise stated, significant differences were P < 0.05. Unscrambler version 9.1.2 software (CAMO, 2004) was used to develop two partial least square regression models (PLSR). The first PLSR was used as a predictive method to relate consumer’s satisfaction (Y) to a set of explanatory variables (X) which contains physicochemical measures and sensory attributes. It was performed considering samples from the first week of storage. The second one was developed using samples preserved for two or more weeks of storage and its aim was to identify the variables that better can predict consumer’s satisfaction. Two PLSR analyses were performed separately since during the first week we had samples Table 1 Flesh firmness, soluble solids content (SSC) and titratable acidity (TA) of ‘Big Top® ’ nectarines at harvest. M1, M2 and M3 represent fruit classes according to IAD values.
2.2. Physicochemical analyses Fifteen nectarines at harvest and per combination of factors (storage temperature × storage period) were used individually for the analysis of flesh firmness, SSC and TA. If at removal the fruit was of low quality (firmness ≤ 5 N and presence of fungal decay) the experiment was over for that temperature. In that case, fruit were
Flesh firmness (N) SSC (%) TA (g/L malic acid)
M1
M2
M3
56.34 a 11.54 b 7.96 a
47.45 b 12.03 b 6.37 b
40.65 b 13.49 a 6.51 b
Values represent means of 15 replicates. Means within each row followed by different letters are significantly different at P ≤ 0.05 (Tukey’s LSD test). M1: IAD 0.17–0.15; M2: IAD 0.14–0.12; M3: IAD 0.11–0.09.
70
70
60
60
50
50 Firmness (N)
Firmness (N)
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40 30 20
M1 M2 M3
40 30 20
M1 M2 M3
10
181
10
0
0 0
10
20
30
40
50
0
10
20
Days at -1 ºC
40
50
Days at 4 ºC 70
70 60
60
M1 M2 M3
40 30
M1 M2 M3
50 Firmness (N)
50 Firmness (N)
30
40 30
20
20
10
10 0
0 0
5
10
15
20
25
0
2
4
6
8
10
12
Days at 20 ºC
Days at 10 ºC
Fig. 1. Flesh firmness evolution during storage of ‘Big Top® ’ nectarine at four different temperatures. Values represent means of 15 replicates. Vertical bars represent standard deviation. M1: IAD 0.17–0.15; M2: IAD 0.14–0.12; M3: IAD 0.11–0.09.
from all temperature treatments and therefore we could observe the biggest differences in fruit firmness. As a pre-treatment, data were centred and weighted using the inverse of the standard deviation of each variable in order to avoid the influence of the different scales used for the variables (Martens and Naes, 1989). Full crossvalidation was run as a validation procedure. 3. Results 3.1. Physicochemical parameters, consumer satisfaction and sensory attributes at harvest At harvest, ‘Big Top® ’ nectarines graded according to IAD (M1, M2 and M3) showed significant differences in flesh firmness, SSC and TA (Table 1). Fruit with higher instrumental firmness and TA were found in the M1 group, compared to M2 and M3 groups. Contrary, fruit with higher SSC were found in the M3 group, compared to the other two groups. Differences between maturity classes of fruit at harvest were also detected by consumers. Consumer’s satisfaction improved significantly with maturity stage at harvest. Fruit from the third class (M3) obtained the highest acceptability score (Table 2), being statistically different from the scores obtained for M1 fruit. Otherwise, it is important to point out that all the classes obtained consumer acceptability scores higher than 5, therefore meaning that all the fruit was well accepted. Consumers also detected differences in sweetness, hardness, juiciness and flavour. Fruit from the M1
Table 2 Consumer overall liking degree and sensory attributes of ‘Big Top® ’ nectarine at harvest. M1, M2 and M3 represent fruit with classes according to IAD values.
Consumer satisfaction Sweetness Sourness Hardness Juiciness Nectarine flavour
M1
M2
M3
5.97b 2.32b 3.06a 4.00a 2.44b 2.52b
6.47ab 2.91a 3.03a 3.41b 3.35a 3.00ab
6.91a 3.15a 2.50a 3.12b 3.35a 3.38a
Values represent means of 81 replicates. Means within each row followed by different letters are significantly different at P ≤ 0.05 (Tukey’s LSD test). M1: IAD 0.17–0.15; M2: IAD 0.14–0.12; M3: IAD 0.11–0.09.
maturity group was perceived as less sweet, harder and less juicy than fruit from M2 and M3 groups. On the other hand, no significant differences were appreciated by the consumers on the sourness perception among the three maturity groups. Consumers detected a stronger nectarine flavour on the M3 fruit than on the M1 fruit. 3.2. Physicochemical parameters, consumer satisfaction and sensory attributes during storage As expected, ‘Big Top® ’ nectarines softening rate during storage was more pronounced at higher temperatures (Fig. 1). Fruit stored at −1 ◦ C did not soften at all throughout the storage period, although they eventually decayed by fungal infection. In general,
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-1 ºC 4 ºC 10 ºC 20 ºC
Consumer satisfaction (9-point hedonic scale)
8
6
4
2
4
7
14
21
28
35
42
49
Storage days Fig. 2. Consumer satisfaction scores of fruit from M2 (based on IAD ) during up to 49 days of storage of ‘Big Top® ’ nectarine at four different temperatures. Bars represent means of 81 replicates. Vertical bar represents LSD value P ≤ 0.05 (Tukey’s LSD test) for the interaction storage time × temperature.
the firmness loss rates were not significantly different among different maturity classes. Except for fruit classified as M3 (more mature) and stored at 20 ◦ C which softened faster compared to less mature fruit (M1 and M2). There was also a clear difference on the length of the period with acceptable firmness (higher than 5 N) of the fruit depending on the storage temperature (ranging from 7 days at 20 ◦ C to 45 days at 4 ◦ C). SSC and TA were not significantly different among maturity classes during storage (data not shown). SSC did not change significantly during storage at any of the four storage temperatures, whereas TA decreased slightly. Since M2 fruit at harvest was firmer and showed similar consumer acceptability than M3 fruit, this maturity stage (M2) was selected to carry out the consumer tests.
Overall consumer’s satisfaction was significantly higher for fruit stored at higher temperatures (Fig. 2), although it remained acceptable (>5) regardless of temperature. After 21 days of storage, fruit stored at −1 ◦ C obtained significantly lower scores than fruit stored at 4 ◦ C and 10 ◦ C. After 28 and 35 days of storage, no significant differences were observed on overall consumer’s satisfaction in the remaining fruit stored at −1 ◦ C and 4 ◦ C. Concomitantly, higher sweetness, flavour and juiciness scores, together with lower hardness were perceived by consumers after 4 and 7 days of storage at 20 ◦ C than for the rest of storage temperatures (Table 3). Respecting the perception of sourness, fruit stored at −1 ◦ C were described as sourer after 4 days of storage, while after 7 days of storage, fruit stored at 10 ◦ C were perceived as the
Table 3 Changes in sensory attributes scores for fruit from M2 (based on IAD ) during storage of ‘Big Top® ’ nectarine at four different constant temperatures. Sensory attributes
Storage temperatures
Storage days 4
7
14
21
28
35
42
49
Sweetness
−1 ◦ C 4 ◦C 10 ◦ C 20 ◦ C
2.57 bcAB 3.00 abBC 2.46 cB 3.33 aA
3.00 bA 2.72 bcB 2.50 cB 3.72 aA
2.65 bAB 2.61 bC 3.13 aA n.m.
2.52 bAB 3.41 aAB 3.39 aA n.m.
2.64 aAB 3.00 aBC n.m. n.m.
2.49 aB 2.89 aBC n.m. n.m.
2.43 bB 3.20 aAB n.m. n.m.
2.79 bAB 3.50 aA n.m. n.m.
Sourness
−1 ◦ C 4 ◦C 10 ◦ C 20 ◦ C
3.39 aA 2.50 bAB 2.89 bB 2.86 bA
2.41 bC 2.88 bA 3.41 aA 2.56 bA
3.16 aA 2.71 aAB 2.93 aB n.m.
3.2 aA 2.33 bBC 2.73 abB n.m.
3.26 aA 2.72 bAB n.m. n.m.
2.62 aBC 2.68 aAB n.m. n.m.
3.13 aA 2.30 bBC n.m. n.m.
2.92 aAB 2.13 bC n.m. n.m.
Hardness
−1 ◦ C 4 ◦C 10 ◦ C 20 ◦ C
3.59 aB 3.44 aA 3.78 aA 2.63 bA
3.59 aB 3.44 aA 3.75 aB 1.38 bB
3.84 aB 3.47 aA 2.34 bC n.m.
4.36 aA 2.80 bB 1.64 cD n.m.
3.97 aAB n.m. n.m. n.m.
4.26 aA n.m. n.m. n.m.
3.77 aB n.m. n.m. n.m.
3.79 aB n.m. n.m. n.m.
Juiciness
−1 ◦ C 4 ◦C 10 ◦ C 20 ◦ C
2.67 bA 2.96 bBCD 2.63 bC 3.78 aB
2.38 cAB 2.88 bCD 2.63 bcC 4.44 aA
2.76 bA 2.75 bD 3.63 aB n.m.
2.07 cB 3.20 bABCD 4.20 aA n.m.
2.44 bAB 3.23 aABC n.m. n.m.
2.13 bB 3.45 aA n.m. n.m.
2.17 bB 3.37 aAB n.m. n.m.
2.67 bA 3.50 aA n.m. n.m.
Flavour
−1 ◦ C 4 ◦C 10 ◦ C 20 ◦ C
2.81 bA 2.59 bA 2.52 bB 3.41 aB
2.66 bA 3.00 bA 2.66 bB 3.94 aA
2.89 aA 2.84 aA 3.31 aA n.m.
2.69 bA 2.93 abA 3.36 aA n.m.
3.00 aA 2.74 aA n.m. n.m.
2.53 aA 2.62 aA n.m. n.m.
2.67 aA 2.83 aA n.m. n.m.
2.83 aA 2.71 aA n.m. n.m.
Values represent means of 81 replicates. Means for a given sensory parameter within the same column followed by different small letters and within the same row followed by different capital letters are significantly different at P ≤ 0.05 (Tukey’s LSD test). n.m., non-measured.
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Fig. 3. Partial least squares regression model of consumer’s satisfaction (Y-variable) vs. physicochemical parameters and sensory attributes (X-variables) during up to 1 week of storage. Panels show the corresponding scores (top) and loadings (bottom) plots.
sourest. After 14 and 21 days of storage, samples kept at 10 ◦ C were described as sweeter, less hard and juicier than nectarines stored at lower temperatures. After 21 days of storage, fruit stored at 4 ◦ C was perceived as less sour than fruit stored at −1 ◦ C. No significant differences were perceived respect to the peach flavour attribute after 14 days of storage. After 28 and 35 days of storage, fruit stored at 4 ◦ C was perceived as less hard and juicier than fruit stored at −1 ◦ C, while no significant differences were observed in the perception of sweetness and peach flavour. After 42 and 49 days of storage, fruit stored at 4 ◦ C was perceived as less sour, less hard,
juicier and sweeter than fruit stored at −1 ◦ C, while no significant differences were observed in the perception of nectarine flavour. In general, for each storage temperature, juiciness and flavour scores were higher after longer storage periods, except for fruit stored at −1 ◦ C. Sweetness increased with storage time in the fruit stored at 10 and 20 ◦ C. On the contrary, hardness perception decreased with storage time, except for the fruit stored at −1 ◦ C. Storage period did not have any effect on sensory attributes of fruit stored at −1 ◦ C, except for the perception of sourness which decreased with longer storage time.
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Fig. 4. Partial least squares regression model of consumer’s satisfaction (Y-variable) vs. physicochemical parameters and sensory attributes (X-variables) after 14–49 days of storage. Panels show the corresponding scores (top) and loadings (bottom) plots.
3.3. Relationship between consumer’s satisfaction and physicochemical parameters and sensory attributes In order to assess the influence of the physicochemical parameters and sensory attributes (X variables) on consumer’s satisfaction (Y variable), two partial least square regression models (PLSR) were performed. The first PLSR was run with the data obtained considering only samples from the first week of storage under the four tested temperatures. This model revealed that 80% of variability in consumer’s satisfaction could be attributed to some physicochemical parameters and sensory attributes (Fig. 3). The corresponding loadings plot (Fig. 3B) shows that fruit samples stored at 20 ◦ C were
more appreciated by consumers, possibly due to the positive relationship between consumer’s satisfaction with higher intensity of flavour, juiciness and sweetness. These samples were situated on the right side of the PC1 axis, which explained 75% of total variance, and separated along PC1 from those stored under the rest of evaluated temperatures. The variables showing most weight for differentiation along PC1 were flavour, juiciness and sweetness (positively related) and sensory and instrumental firmness (negatively related). After 1 week of storage, a clear separation of the fruit according to storage temperature can be detected. A second PLSR model was built up using the data obtained from the samples stored for 2 weeks or more (Fig. 4). The validation
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step indicated that two PLS factors were relevant in the model. The percentage of explained variance was 42%. This low explained variance could indicate the existence of a non-negligible correlation amongst the used variables; in other words, that the variables contained repeated information. Biological variability associated with fruit is also a factor affecting the identification of statistical significant differences. However, although this percentage is not very high, the degree of variance encountered was sufficient for the qualitative purpose of this plot. The analysis separated three well-distinguished groups. One group (to the right side of the plot) corresponded to samples stored at 20 ◦ C. The group of samples stored at 4 ◦ C located in the middle of the plot and samples stored at −1 ◦ C were positioned on the left side of the plot (Fig. 4A). The separation of the samples according to storage temperature was clearly maintained, but consumer’s satisfaction was mainly associated with perception of flavour (Fig. 4B). Contrary to what was expected, a negative relationship was found between consumer’s satisfaction and SSC (Fig. 4B), probably due to interference with the acidity or to the similar SSC values presented by the samples used in this PLSR model.
4. Discussion It is well known that selection of an appropriate maturity at harvest is a key factor to determine fruit quality and consumer acceptability. In this work, the IAD non-destructive Vis spectroscopy technique resulted in a useful tool to separate categories of fruit based on a different maturity stage (according to firmness, SSC and TA parameters). In a previous work with ‘Big Top® ’ cultivar, the maturity classes determined by IAD showed significantly different ethylene production levels (Giné Bordonaba et al., 2014). However, this technique has not always shown a good reliability on classifying other cultivars of peach fruit according to maturity stage (Giné Bordonaba et al., 2014; Pérez-Marín et al., 2009; Reig et al., 2012). In agreement with what was previously described by Giné Bordonaba et al. (2014), riper ‘Big Top® ’ fruit at harvest obtained better consumer overall liking degree than those harvested in earlier stages of maturity. Although harvesting at a slightly unripe stage might render fruit more resistant to postharvest handling, this practice might have a negative effect on the sensory quality of the fruit. The favourable effects of maturation and ripening on ␥- and ␦lactones, responsible for the fruity flavours in peach and nectarine (Engel et al., 1988), have been previously reported (Robertson et al., 1990; Rizzolo et al., 2006; Zhang et al., 2010). On the other hand, the positive relation between sweetness and overall liking shown by consumers in this study has been already previously demonstrated. Indeed, Delgado et al. (2013) reported that sweetness perception was the main driver of liking for most peach and nectarine consumers. However, in peaches, other fruit quality characteristics also affect liking as firmness, colour and aroma (Bruhn, 1995). In general, the range of consumer acceptability scores of ‘Big Top® ’ fruit encountered in this work was in agreement with previous studies dealing with the consumer perception of this cultivar (Giné Bordonaba et al., 2014). However, mainly due to the high cost of consumer tests, there are few studies where degree of liking of a specific cultivar harvested at different maturity stages has been evaluated. Nevertheless, it has been proven that they are more effective in predicting consumer behaviour than models based on instrumental measurements (Harker et al., 2008; Saftner et al., 2008). At the same time, the influence of storage temperature on the quality and organoleptic attributes of peach fruit is extensively recognised. Cold storage is the foremost method to inhibit fruit decay and extend shelf life of most fruits. However, some peach and nectarine cultivars are sensitive to low temperature and might
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exhibit chilling injury (CI) after long periods of cold storage, especially at a particular range of temperatures, between 2.2 and 7.6 ◦ C (Cantín et al., 2010). In this study, no CI symptoms were perceived by consumers throughout the storage period in any of the tested temperatures. This disorder, together with the lack of flavour associated with unripe fruit (Gómez and Ledbetter, 1997), negatively affects the quality of the fruit, and therefore the consumer satisfaction (Infante et al., 2008a; Lurie and Crisosto, 2005). The decrease in consumer acceptance of ‘Big Top® ’ fruit over time observed in this study at low temperatures confirms that postharvest storage life of peaches is limited by quality loss, as observed for other peach and nectarine cultivars (Crisosto et al., 1999; Infante et al., 2008a,b). It has also been proven that cold storage alters flavour volatiles and partially inhibits ester synthesis, largely due to substrate deficiencies caused by suppressed oxidation mechanisms in the peach fruit during storage (Ortiz et al., 2009; Raffo et al., 2008; Robertson et al., 1990). In accordance with our results, previous studies have demonstrated that perception of flavour in peaches decreased and ‘off flavours’ increased during cold storage as a consequence of CI incidence (Crisosto and Labavitch, 2002; Infante et al., 2009). These results suggest that long storage at low temperatures should be used only when strictly necessary due to target markets. For direct consumption, and when possible, to avoid cold storage would provide fruit with a higher consumer satisfaction and display a more characteristic peach flavour. 5. Conclusions To determine the storage potential of ‘Big Top’ nectarines at different maturity stages, from a sensorial point of view, is essential to attain a high quality product able to satisfy consumer. The selection of an appropriate maturity at harvest is a key factor to determine fruit quality and consumer acceptability. In this sense, it is important to differentiate that fruit for direct consumption from that which will be consumed after a storage period. The results demonstrate the importance of ripening stage at harvest and postharvest storage temperature and duration in the perception of organoleptic attributes and overall satisfaction of the final consumer. Sweetness and flavour perception should be incorporated in peaches/nectarines postharvest studies in order to predict their effects in consumer acceptance. On the other hand, this work also outlines the importance of considering quality physicochemical parameters not as goals, but as tools to monitor the optimum quality demanded by the consumers. Acknowledgements This work was supported by the European Comission (ISAFRUIT project; contract no. FP6-FOOD-CT-2006-016279), the Generalitat de Catalunya, Spain (BP-DGR 2013; C.M. Cantín grant), and the Ministerio de Ciencia e Innovación (MICINN), Spain (FPU AP200701923; A. Ortiz grant). The authors are indebted to Mrs. A. Latorre ˜ for technical assistance. and Mrs. P. Sopena References Abbott, J.A., 1999. Quality measurement of fruits and vegetables. Postharvest Biol. Technol. 15 (3), 207–225. Asp, E.H., 1999. Factors affecting food decisions made by individual consumers. Food Policy 24 (2–3), 287–294. Bruhn, C.M., 1995. Consumer and retailer satisfaction with the quality and size of Californian peaches and nectarines. J. Food Qual. 18 (3), 241–256. CAMO ASA, 2004. Unscrambler Users Guide, ver. 9.1.2. Programme Package for Multivariate Calibration. Trondheim, Norway. Cano-Salazar, J., López, M.L., Crisosto, C.H., Echeverría, G., 2013a. Volatile compound emissions and sensory attributes of ‘Big Top’ nectarine and ‘Early Rich’ peach fruit in response to a pre-storage treatment before cold storage and subsequent shelf-life. Postharvest Biol. Technol. 76, 152–162.
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Cano-Salazar, J., López, M.L., Echeverría, G., 2013b. Relationships between the instrumental and sensory characteristics of four peach and nectarine cultivars stored under air and CA atmospheres. Postharvest Biol. Technol. 75, 58–67. Cantín, C.M., Crisosto, C.H., Ogundiwin, E.A., Gradziel, T., Torrents, J., Moreno, M.A., Gogorcena, Y., 2010. Chilling injury susceptibility in an intra-specific peach [Prunus persica (L.) Batsch] progeny. Postharvest Biol. Technol. 58 (2), 79–87. Cefola, M., Pace, B., Sergio, L., Baruzzi, F., Gatto, M.A., Carito, A., Linsalata, V., Cascarano, N.A., Di Venere, D., 2014. Postharvest performance of fresh-cut ‘Big Top’ nectarine as affected by dipping in chemical preservatives and packaging in modified atmosphere. Int. J. Food Sci. Technol. 49 (4), 1184–1195. Crisosto, C.H., Mitchell, F.G., Ju, Z.G., 1999. Susceptibility to chilling injury of peach, nectarine, and plum cultivars grown in California. HortScience 34 (6), 1116–1118. Crisosto, C.H., Labavitch, J.M., 2002. Developing a quantitative method to evaluate peach Prunus persica flesh mealiness. Postharvest Biol. Technol. 25 (2), 151–158. Crisosto, C.H., Crisosto, G.M., Neri, F., 2006. Understanding tree fruit quality based on consumer acceptance. Acta Hortic. 712, 183–189. Delgado, C., Crisosto, G.M., Heymann, H., Crisosto, C.H., 2013. Determining the primary drivers of liking to predict consumers’ acceptance of fresh nectarines and peaches. J. Food Sci. 78 (4), S605–S614. Echeverría, G., Graell, J., Lara, I., López, M.L., 2008. Physicochemical measurements in ‘Mondial Gala® ’ apples stored at different atmospheres: influence on consumer acceptability. Postharvest Biol. Technol. 50 (2–3), 135–144. Engel, K.H., Ramming, D.W., Flath, R.A., Teranishi, R., 1988. Investigation of volatile constituents in nectarines. 2. Changes in aroma composition during nectarine maduration. J. Agric. Food Chem. 36 (5), 1003–1006. Giné Bordonaba, J., Cantin, C.M., Larrigaudière, C., López, L., López, R., Echeverría, G., 2014. Suitability of nectarine cultivars for minimal processing: the role of genotype, harvest season and maturity at harvest on quality and sensory attributes. Postharvest Biol. Technol. 93, 49–60. Gómez, E., Ledbetter, C.A., 1997. Development of volatile compounds during fruit maturation: characterization of apricot and plum × apricot hybrids. J. Sci. Food Agric. 74 (4), 541–546. Harker, F.R., Kupferman, E.M., Marín, A.B., Gunson, F.A., Triggs, C.M., 2008. Eating quality standards for apples based on consumer preferences. Postharvest Biol. Technol. 50 (1), 70–78. Infante, R., Farcuh, M., Meneses, C., 2008a. Monitoring the sensorial quality and aroma through an electronic nose in peaches during cold storage. J. Sci. Food Agric. 88 (12), 2073–2078. Infante, R., Meneses, C., Predieri, S., 2008b. Sensory quality performance of two nectarine flesh typologies exposed to distant market conditions. J. Food Qual. 31 (4), 526–535.
Infante, R., Meneses, C., Crisosto, C.H., 2009. Preconditioning treatment maintains taste characteristic perception of ripe ‘September Sun’ peach following cold storage. Int. J. Food Sci. Technol. 44 (5), 1011–1016. Lurie, S., Crisosto, C.H., 2005. Chilling injury in peach and nectarine. Postharvest Biol. Technol. 37 (3), 195–208. Martens, H., Naes, T., 1989. Partial least squares regression. In: Multivariate Calibration. Wiley, Chichester, UK, pp. 116–165. Ortiz, A., Echeverría, G., Graell, J., Lara, I., 2009. Overall quality of ‘Rich Lady’ peach fruit after air- or CA storage. The importance of volatile emission. LWT-Food Sci. Technol. 42 (9), 1520–1529. Pérez-Marín, D., Sánchez, M.T., Paz, P., Soriano, M.A., Guerrero, J.E., Garrido-Varo, A., 2009. Non-destructive determination of quality parameters in nectarines during on-tree ripening and postharvest storage. Postharvest Biol. Technol. 52 (2), 180–188. Predieri, S., Ragazzini, P., Rondelli, R., 2006. Sensory evaluation and peach fruit quality. In: Infante, R. (Ed.), Proceedings of the VIth International Peach Symposium. , pp. 429–434. Raffo, A., Nardo, N., Tabilio, M.R., Paoletti, F., 2008. Effects of cold storage on aroma compounds of white- and yellow-fleshed peaches. Eur. Food Res. Technol. 226 (6), 1503–1512. Reig, G., Alegre, S., Iglesias, I., Echeverría, G., Roure, A.R., 2012. Fruit quality, colour development and Index of absorbance difference (IAD ) of different nectarine cultivars at different harvest dates. Acta Hortic. 934, 1117–1126. Rizzolo, A., Zerbini, P.E., Grassi, M., Cambiaghi, P., Bianchi, G., 2006. Effect of 1methylcyclopropene on aroma compounds in Big Top nectarines after shelf life. J. Food Qual. 29 (2), 184–202. Robertson, J.A., Meredith, F.I., Horvat, R.J., Senter, S.D., 1990. Effect of cold-storage and maturity on the physical and chemical characteristics and volatile constituents of peaches (cv Cresthaven). J. Agric. Food Chem. 38 (3), 620–624. Saftner, R., Polashock, J., Ehlenfeldt, M., Vinyard, B., 2008. Instrumental and sensory quality characteristics of blueberry fruit from twelve cultivars. Postharvest Biol. Technol. 49 (1), 19–26. SAS Institute, Inc., 2004. SAS/STAT© 9.1 User’s Guide. SAS Institute, Inc., Cary, NC. Shewfelt, R.L., 1999. What is quality? Postharvest Biol. Technol. 15 (3), 197–200. Zhang, B., Shen, J.Y., Wei, W.W., Xi, W.P., Xu, C.J., Ferguson, I., Chen, K., 2010. Expression of genes associated with aroma formation derived from the fatty acid pathway during peach fruit ripening. J. Agric. Food Chem. 58 (10), 6157–6165. Ziosi, V., Noferini, M., Fiori, G., Tadiello, A., Trainotti, L., Casadoro, G., Costa, G., 2008. A new index based on Vis spectroscopy to characterize the progression of ripening in peach fruit. Postharvest Biol. Technol. 49 (3), 319–329.
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Scientia Horticulturae journal homepage: www.elsevier.com/locate/scihorti
The impact of maturity, storage temperature and storage duration on sensory quality and consumer satisfaction of ‘Big Top® ’ nectarines G. Echeverría a,∗,1 , C.M. Cantín a,1 , A. Ortiz b,2 , M.L. López a,b , I. Lara b , J. Graell b a b
IRTA, XaRTA-Postharvest, Parc Científic i Tecnològic de Gardeny, Fruitcentre, 25003 Lleida, Spain Universitat de Lleida, XaRTA-Postharvest, Av. Alcalde Rovira Roure, 191, 25198 Lleida, Spain
a r t i c l e
i n f o
Article history: Received 29 January 2015 Received in revised form 1 April 2015 Accepted 14 April 2015 Available online 15 May 2015 Keywords: Consumer satisfaction Fruit quality Prunus persica Sensory attributes Storage temperature
a b s t r a c t This research focuses on the effect of maturity stage and storage conditions on quality and consumer satisfaction of ‘Big Top® ’ nectarines. At harvest time, fruit were graded in three categories according to the IAD index (index of absorbance difference = A670 − A720 ) based on Vis spectroscopy. Physicochemical parameters (soluble solids concentration, titratable acidity and flesh firmness) were measured for the three maturity categories at harvest time and after up to 49 days of storage at 20, 10, 4 or −1 ◦ C. Consumer satisfaction and sensory attributes were also measured on fruit from all three categories at harvest time, as well as on fruit from the intermediate maturity class after storage at the different tested temperatures for up to 49 days. At harvest time, consumer’s satisfaction increased significantly with maturity stage at harvest, mainly due to an upper sweetness and flavour perception and higher SSC value detected in the most mature class. For short storage periods, ‘Big Top® ’ nectarines kept at 20 ◦ C received the highest scores for peach flavour intensity and overall acceptance. For longer storage periods, no significant differences among temperatures were observed on sensory quality or consumer satisfaction, except for fruit stored for the longest period (7 weeks), for which higher consumer acceptance was found for fruit stored at −1 ◦ C than at 4 ◦ C. Results also suggested that higher acceptance scores were associated mainly to more intense perception of flavour. © 2015 Elsevier B.V. All rights reserved.
1. Introduction European production of peach and nectarine in 2013 was about 3 million tonnes, 51% of which were nectarines. An important increase in the proportion of nectarine production has been observed in the last years at most peach production areas. ‘Big Top® ’ is nowadays considered the reference nectarine cultivar in Europe for fresh consumption, known as a slow-softening rate cultivar and appreciated for its early colouration resulting in greatly coloured fruit, optimum fruit size, high sweetness, juiciness and flavour (Cano-Salazar et al., 2013a,b). Moreover, recent studies have shown that it is a particularly suitable cultivar for fresh-cut production (Cefola et al., 2014; Giné Bordonaba et al., 2014). ‘Big Top® ’ nectarine is the most widely cultivated nectarine cultivar in Europe. To withstand handling in the packing house and
∗ Corresponding author. Tel.: +34 973 702648; fax: +34 973 238301. E-mail address: [email protected] (G. Echeverría). 1 Both authors contributed equally to this work. 2 Present address: UPSP GRAPPE, Groupe ESA, SFR QUASAV 4207, 55 rue Rabelais, BP 30748, 49007 Angers Cedex 01, France. http://dx.doi.org/10.1016/j.scienta.2015.04.022 0304-4238/© 2015 Elsevier B.V. All rights reserved.
marketing operations (transport, storage and retail display) these fruit have to be firm enough. Hence, they are frequently harvested before full ripeness, but such fruit often fail to develop desirable sensory attributes, and are consequently not perceived as sufficiently satisfactory by the consumer. Moreover, it has been largely documented that nectarine fruit subjected to long cold storage are prone to suffer serious quality decay, detected at the consumer level, due to the development of chilling injury symptoms, evident as mealiness, internal browning and lack of peach flavour (Crisosto et al., 1999; Lurie and Crisosto, 2005). The poor eating quality of fresh peach and nectarine transported to distant markets is one of the main current problems of the growing peach industry. Nectarine quality has always been measured in terms of the traits of the fruit, mainly through evaluation of the physical and chemical properties that best describe the progress of maturation and ripening. Flesh firmness, superficial and ground colour, soluble solids content (SSC), and titratable acidity (TA) are the parameters used generally for defining fruit quality because they provide a common language among researchers, producers and handlers (Abbott, 1999). However, when quality is measured from the consumers’ perspective, these parameters do not always match what consumers consider for deciding whether produce quality is
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acceptable (Shewfelt, 1999). Consumers often buy the first time based on fruit appearance, but repeated purchases are driven by expected quality factors mainly determined by flavour compounds and texture (Crisosto et al., 2006). In general, consumers are willing to pay more for fruit with a higher hedonic score (Delgado et al., 2013), which sheds light on why harvesting at the optimum ripening stage, and storing the fruit at the optimum temperature and duration is crucial. However, there is scarce literature where the effect of storage conditions on the consumer perception had been studied through consumer tests. Thus, it is important to define quality on the basis of consumer expectations (Predieri et al., 2006). The consumers’ judgement in the food marketplace has become crucial over the recent years (Asp, 1999). The demand for high quality fruit, including excellent taste, high nutritional value and nutraceutical value, highlights the need of monitoring the effect of the postharvest chain on sensory attributes, and subsequently on consumer satisfaction. To the best of our knowledge, no previous studies have examined the relationships between storage duration and temperature of nectarines harvested at different ripening stages and consumer perception. In the present work, ‘Big Top® ’ nectarines from different maturity stages were exposed to different temperature and periods of storage with the objective of characterising their effect on standard quality parameters, sensory attributes and consumer satisfaction. 2. Materials and methods 2.1. Fruit material Yellow-fleshed nectarines (Prunus persica L. Batsch var. nucipersica cv. ‘Big Top® ’) were harvested at 109 days after full bloom (DAFB) in 2008 at a commercial orchard located in Massalcoreig (Catalonia, NE Spain) and selected for uniformity of size and absence of defects. The IAD index (index of absorbance difference = A670 − A720 ) at harvest was used to pre-sort nectarine non-destructively by Vis spectroscopy (Ziosi et al., 2008). In this work the IAD index was measured using a commercial equipment (C2005d, Minolta, Valencia, Spain), while Ziosi et al. (2008) used a commercial spectrometer (S-2000, Ocean Optics, Dunedin, USA). Following sorting, fruit were classified into three different categories by decreasing values of the IAD (M1: IAD 0.17–0.15; M2: IAD 0.14–0.12; M3: IAD 0.11–0.09) and stored at 20, 10, 4 or −1 ◦ C for up to 49 days depending on storage temperature. Out of 3750 fruit assessed in total, 898 were graded as M1, 1278 as M2, and 759 as M3. At harvest, for each maturity class, 15 and 20 fruits were used for physicochemical measurements and consumer evaluation, respectively. After each storage period, 15 fruits were also used for physicochemical measurements per temperature and maturity class (total ∼ 500 fruits). In addition, for M2 class 15 fruits more were used after each storage period and temperature for consumer evaluation (total ∼ 500 fruits). Physicochemical parameters (flesh firmness, SSC and TA) were measured for fruit from the three classes at harvest and periodically throughout storage, while consumer satisfaction and sensory attributes described by a consumer panel were scored for fruit from the three categories at harvest time, but only for fruit from M2 class during storage.
removed from the storage chamber and not assessed sensorially. Flesh firmness was measured on opposite sides of each fruit with a penetrometer (Effegi, Milan, Italy) fitted with an 8-mm diameter plunger tip; results were expressed in N. SSC and TA were measured in juice pressed from the whole fruit. SSC was determined with a hand-held refractometer (Atago, Tokyo, Japan), and results were expressed as %. TA was determined by titrating 10 mL of juice with 0.1 N NaOH to pH 8.1 using a pH-metre (GLP 21, Crison); results were given as g malic acid/L. 2.3. Consumer satisfaction and sensory attributes assessment Fruit samples from each maturity stage were scored by consumers immediately after harvest. However, after storage only fruit from M2 class was sensorially analysed. After each storage temperature and period, fruit was kept for 3–4 h at room temperature in order to allow fruit to reach 20 ◦ C before consumer’s assessment. Fifteen nectarines per combination of factors (storage temperature × storage period) were used for sensory analysis. Sensory evaluations were conducted as elsewhere described (Echeverría et al., 2008). Each consumer, from a panel of 81 consumers, was asked to indicate his/her degree of liking/disliking using a ninepoint hedonic scale (1, dislike extremely; 9, like extremely). In addition, consumers were asked to score how they perceived the intensity of sweetness, sourness, firmness, juiciness and flavour according to a five-point hedonic scale (1, very low intensity; 5, very high intensity). Consumers were volunteers from the staff working at the University of Lleida and IRTA (Institut de Recerca i Tecnologia Agroalimentàries), and students from the University of Lleida. The samples could be re-tasted as often as desired. All evaluations were conducted in individual booths under white illumination and at room temperature. 2.4. Statistical and multivariate analysis A multifactorial design with storage period and temperature as factors was used to statistically analyse the results. All data were tested by analysis of variance (GLM-ANOVA procedure) with the SAS/STAT 9.1 procedures (SAS Institute Inc., 2004). Mean comparisons were performed using Tukey’s LSD test at P ≤ 0.05. Correlations between experimental variables were made using Spear-man’s rank correlations and, if required, presented as Spearman’s correlations coefficient (r) and P value based on a two-tailed test. Unless otherwise stated, significant differences were P < 0.05. Unscrambler version 9.1.2 software (CAMO, 2004) was used to develop two partial least square regression models (PLSR). The first PLSR was used as a predictive method to relate consumer’s satisfaction (Y) to a set of explanatory variables (X) which contains physicochemical measures and sensory attributes. It was performed considering samples from the first week of storage. The second one was developed using samples preserved for two or more weeks of storage and its aim was to identify the variables that better can predict consumer’s satisfaction. Two PLSR analyses were performed separately since during the first week we had samples Table 1 Flesh firmness, soluble solids content (SSC) and titratable acidity (TA) of ‘Big Top® ’ nectarines at harvest. M1, M2 and M3 represent fruit classes according to IAD values.
2.2. Physicochemical analyses Fifteen nectarines at harvest and per combination of factors (storage temperature × storage period) were used individually for the analysis of flesh firmness, SSC and TA. If at removal the fruit was of low quality (firmness ≤ 5 N and presence of fungal decay) the experiment was over for that temperature. In that case, fruit were
Flesh firmness (N) SSC (%) TA (g/L malic acid)
M1
M2
M3
56.34 a 11.54 b 7.96 a
47.45 b 12.03 b 6.37 b
40.65 b 13.49 a 6.51 b
Values represent means of 15 replicates. Means within each row followed by different letters are significantly different at P ≤ 0.05 (Tukey’s LSD test). M1: IAD 0.17–0.15; M2: IAD 0.14–0.12; M3: IAD 0.11–0.09.
70
70
60
60
50
50 Firmness (N)
Firmness (N)
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40 30 20
M1 M2 M3
40 30 20
M1 M2 M3
10
181
10
0
0 0
10
20
30
40
50
0
10
20
Days at -1 ºC
40
50
Days at 4 ºC 70
70 60
60
M1 M2 M3
40 30
M1 M2 M3
50 Firmness (N)
50 Firmness (N)
30
40 30
20
20
10
10 0
0 0
5
10
15
20
25
0
2
4
6
8
10
12
Days at 20 ºC
Days at 10 ºC
Fig. 1. Flesh firmness evolution during storage of ‘Big Top® ’ nectarine at four different temperatures. Values represent means of 15 replicates. Vertical bars represent standard deviation. M1: IAD 0.17–0.15; M2: IAD 0.14–0.12; M3: IAD 0.11–0.09.
from all temperature treatments and therefore we could observe the biggest differences in fruit firmness. As a pre-treatment, data were centred and weighted using the inverse of the standard deviation of each variable in order to avoid the influence of the different scales used for the variables (Martens and Naes, 1989). Full crossvalidation was run as a validation procedure. 3. Results 3.1. Physicochemical parameters, consumer satisfaction and sensory attributes at harvest At harvest, ‘Big Top® ’ nectarines graded according to IAD (M1, M2 and M3) showed significant differences in flesh firmness, SSC and TA (Table 1). Fruit with higher instrumental firmness and TA were found in the M1 group, compared to M2 and M3 groups. Contrary, fruit with higher SSC were found in the M3 group, compared to the other two groups. Differences between maturity classes of fruit at harvest were also detected by consumers. Consumer’s satisfaction improved significantly with maturity stage at harvest. Fruit from the third class (M3) obtained the highest acceptability score (Table 2), being statistically different from the scores obtained for M1 fruit. Otherwise, it is important to point out that all the classes obtained consumer acceptability scores higher than 5, therefore meaning that all the fruit was well accepted. Consumers also detected differences in sweetness, hardness, juiciness and flavour. Fruit from the M1
Table 2 Consumer overall liking degree and sensory attributes of ‘Big Top® ’ nectarine at harvest. M1, M2 and M3 represent fruit with classes according to IAD values.
Consumer satisfaction Sweetness Sourness Hardness Juiciness Nectarine flavour
M1
M2
M3
5.97b 2.32b 3.06a 4.00a 2.44b 2.52b
6.47ab 2.91a 3.03a 3.41b 3.35a 3.00ab
6.91a 3.15a 2.50a 3.12b 3.35a 3.38a
Values represent means of 81 replicates. Means within each row followed by different letters are significantly different at P ≤ 0.05 (Tukey’s LSD test). M1: IAD 0.17–0.15; M2: IAD 0.14–0.12; M3: IAD 0.11–0.09.
maturity group was perceived as less sweet, harder and less juicy than fruit from M2 and M3 groups. On the other hand, no significant differences were appreciated by the consumers on the sourness perception among the three maturity groups. Consumers detected a stronger nectarine flavour on the M3 fruit than on the M1 fruit. 3.2. Physicochemical parameters, consumer satisfaction and sensory attributes during storage As expected, ‘Big Top® ’ nectarines softening rate during storage was more pronounced at higher temperatures (Fig. 1). Fruit stored at −1 ◦ C did not soften at all throughout the storage period, although they eventually decayed by fungal infection. In general,
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-1 ºC 4 ºC 10 ºC 20 ºC
Consumer satisfaction (9-point hedonic scale)
8
6
4
2
4
7
14
21
28
35
42
49
Storage days Fig. 2. Consumer satisfaction scores of fruit from M2 (based on IAD ) during up to 49 days of storage of ‘Big Top® ’ nectarine at four different temperatures. Bars represent means of 81 replicates. Vertical bar represents LSD value P ≤ 0.05 (Tukey’s LSD test) for the interaction storage time × temperature.
the firmness loss rates were not significantly different among different maturity classes. Except for fruit classified as M3 (more mature) and stored at 20 ◦ C which softened faster compared to less mature fruit (M1 and M2). There was also a clear difference on the length of the period with acceptable firmness (higher than 5 N) of the fruit depending on the storage temperature (ranging from 7 days at 20 ◦ C to 45 days at 4 ◦ C). SSC and TA were not significantly different among maturity classes during storage (data not shown). SSC did not change significantly during storage at any of the four storage temperatures, whereas TA decreased slightly. Since M2 fruit at harvest was firmer and showed similar consumer acceptability than M3 fruit, this maturity stage (M2) was selected to carry out the consumer tests.
Overall consumer’s satisfaction was significantly higher for fruit stored at higher temperatures (Fig. 2), although it remained acceptable (>5) regardless of temperature. After 21 days of storage, fruit stored at −1 ◦ C obtained significantly lower scores than fruit stored at 4 ◦ C and 10 ◦ C. After 28 and 35 days of storage, no significant differences were observed on overall consumer’s satisfaction in the remaining fruit stored at −1 ◦ C and 4 ◦ C. Concomitantly, higher sweetness, flavour and juiciness scores, together with lower hardness were perceived by consumers after 4 and 7 days of storage at 20 ◦ C than for the rest of storage temperatures (Table 3). Respecting the perception of sourness, fruit stored at −1 ◦ C were described as sourer after 4 days of storage, while after 7 days of storage, fruit stored at 10 ◦ C were perceived as the
Table 3 Changes in sensory attributes scores for fruit from M2 (based on IAD ) during storage of ‘Big Top® ’ nectarine at four different constant temperatures. Sensory attributes
Storage temperatures
Storage days 4
7
14
21
28
35
42
49
Sweetness
−1 ◦ C 4 ◦C 10 ◦ C 20 ◦ C
2.57 bcAB 3.00 abBC 2.46 cB 3.33 aA
3.00 bA 2.72 bcB 2.50 cB 3.72 aA
2.65 bAB 2.61 bC 3.13 aA n.m.
2.52 bAB 3.41 aAB 3.39 aA n.m.
2.64 aAB 3.00 aBC n.m. n.m.
2.49 aB 2.89 aBC n.m. n.m.
2.43 bB 3.20 aAB n.m. n.m.
2.79 bAB 3.50 aA n.m. n.m.
Sourness
−1 ◦ C 4 ◦C 10 ◦ C 20 ◦ C
3.39 aA 2.50 bAB 2.89 bB 2.86 bA
2.41 bC 2.88 bA 3.41 aA 2.56 bA
3.16 aA 2.71 aAB 2.93 aB n.m.
3.2 aA 2.33 bBC 2.73 abB n.m.
3.26 aA 2.72 bAB n.m. n.m.
2.62 aBC 2.68 aAB n.m. n.m.
3.13 aA 2.30 bBC n.m. n.m.
2.92 aAB 2.13 bC n.m. n.m.
Hardness
−1 ◦ C 4 ◦C 10 ◦ C 20 ◦ C
3.59 aB 3.44 aA 3.78 aA 2.63 bA
3.59 aB 3.44 aA 3.75 aB 1.38 bB
3.84 aB 3.47 aA 2.34 bC n.m.
4.36 aA 2.80 bB 1.64 cD n.m.
3.97 aAB n.m. n.m. n.m.
4.26 aA n.m. n.m. n.m.
3.77 aB n.m. n.m. n.m.
3.79 aB n.m. n.m. n.m.
Juiciness
−1 ◦ C 4 ◦C 10 ◦ C 20 ◦ C
2.67 bA 2.96 bBCD 2.63 bC 3.78 aB
2.38 cAB 2.88 bCD 2.63 bcC 4.44 aA
2.76 bA 2.75 bD 3.63 aB n.m.
2.07 cB 3.20 bABCD 4.20 aA n.m.
2.44 bAB 3.23 aABC n.m. n.m.
2.13 bB 3.45 aA n.m. n.m.
2.17 bB 3.37 aAB n.m. n.m.
2.67 bA 3.50 aA n.m. n.m.
Flavour
−1 ◦ C 4 ◦C 10 ◦ C 20 ◦ C
2.81 bA 2.59 bA 2.52 bB 3.41 aB
2.66 bA 3.00 bA 2.66 bB 3.94 aA
2.89 aA 2.84 aA 3.31 aA n.m.
2.69 bA 2.93 abA 3.36 aA n.m.
3.00 aA 2.74 aA n.m. n.m.
2.53 aA 2.62 aA n.m. n.m.
2.67 aA 2.83 aA n.m. n.m.
2.83 aA 2.71 aA n.m. n.m.
Values represent means of 81 replicates. Means for a given sensory parameter within the same column followed by different small letters and within the same row followed by different capital letters are significantly different at P ≤ 0.05 (Tukey’s LSD test). n.m., non-measured.
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Fig. 3. Partial least squares regression model of consumer’s satisfaction (Y-variable) vs. physicochemical parameters and sensory attributes (X-variables) during up to 1 week of storage. Panels show the corresponding scores (top) and loadings (bottom) plots.
sourest. After 14 and 21 days of storage, samples kept at 10 ◦ C were described as sweeter, less hard and juicier than nectarines stored at lower temperatures. After 21 days of storage, fruit stored at 4 ◦ C was perceived as less sour than fruit stored at −1 ◦ C. No significant differences were perceived respect to the peach flavour attribute after 14 days of storage. After 28 and 35 days of storage, fruit stored at 4 ◦ C was perceived as less hard and juicier than fruit stored at −1 ◦ C, while no significant differences were observed in the perception of sweetness and peach flavour. After 42 and 49 days of storage, fruit stored at 4 ◦ C was perceived as less sour, less hard,
juicier and sweeter than fruit stored at −1 ◦ C, while no significant differences were observed in the perception of nectarine flavour. In general, for each storage temperature, juiciness and flavour scores were higher after longer storage periods, except for fruit stored at −1 ◦ C. Sweetness increased with storage time in the fruit stored at 10 and 20 ◦ C. On the contrary, hardness perception decreased with storage time, except for the fruit stored at −1 ◦ C. Storage period did not have any effect on sensory attributes of fruit stored at −1 ◦ C, except for the perception of sourness which decreased with longer storage time.
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Fig. 4. Partial least squares regression model of consumer’s satisfaction (Y-variable) vs. physicochemical parameters and sensory attributes (X-variables) after 14–49 days of storage. Panels show the corresponding scores (top) and loadings (bottom) plots.
3.3. Relationship between consumer’s satisfaction and physicochemical parameters and sensory attributes In order to assess the influence of the physicochemical parameters and sensory attributes (X variables) on consumer’s satisfaction (Y variable), two partial least square regression models (PLSR) were performed. The first PLSR was run with the data obtained considering only samples from the first week of storage under the four tested temperatures. This model revealed that 80% of variability in consumer’s satisfaction could be attributed to some physicochemical parameters and sensory attributes (Fig. 3). The corresponding loadings plot (Fig. 3B) shows that fruit samples stored at 20 ◦ C were
more appreciated by consumers, possibly due to the positive relationship between consumer’s satisfaction with higher intensity of flavour, juiciness and sweetness. These samples were situated on the right side of the PC1 axis, which explained 75% of total variance, and separated along PC1 from those stored under the rest of evaluated temperatures. The variables showing most weight for differentiation along PC1 were flavour, juiciness and sweetness (positively related) and sensory and instrumental firmness (negatively related). After 1 week of storage, a clear separation of the fruit according to storage temperature can be detected. A second PLSR model was built up using the data obtained from the samples stored for 2 weeks or more (Fig. 4). The validation
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step indicated that two PLS factors were relevant in the model. The percentage of explained variance was 42%. This low explained variance could indicate the existence of a non-negligible correlation amongst the used variables; in other words, that the variables contained repeated information. Biological variability associated with fruit is also a factor affecting the identification of statistical significant differences. However, although this percentage is not very high, the degree of variance encountered was sufficient for the qualitative purpose of this plot. The analysis separated three well-distinguished groups. One group (to the right side of the plot) corresponded to samples stored at 20 ◦ C. The group of samples stored at 4 ◦ C located in the middle of the plot and samples stored at −1 ◦ C were positioned on the left side of the plot (Fig. 4A). The separation of the samples according to storage temperature was clearly maintained, but consumer’s satisfaction was mainly associated with perception of flavour (Fig. 4B). Contrary to what was expected, a negative relationship was found between consumer’s satisfaction and SSC (Fig. 4B), probably due to interference with the acidity or to the similar SSC values presented by the samples used in this PLSR model.
4. Discussion It is well known that selection of an appropriate maturity at harvest is a key factor to determine fruit quality and consumer acceptability. In this work, the IAD non-destructive Vis spectroscopy technique resulted in a useful tool to separate categories of fruit based on a different maturity stage (according to firmness, SSC and TA parameters). In a previous work with ‘Big Top® ’ cultivar, the maturity classes determined by IAD showed significantly different ethylene production levels (Giné Bordonaba et al., 2014). However, this technique has not always shown a good reliability on classifying other cultivars of peach fruit according to maturity stage (Giné Bordonaba et al., 2014; Pérez-Marín et al., 2009; Reig et al., 2012). In agreement with what was previously described by Giné Bordonaba et al. (2014), riper ‘Big Top® ’ fruit at harvest obtained better consumer overall liking degree than those harvested in earlier stages of maturity. Although harvesting at a slightly unripe stage might render fruit more resistant to postharvest handling, this practice might have a negative effect on the sensory quality of the fruit. The favourable effects of maturation and ripening on ␥- and ␦lactones, responsible for the fruity flavours in peach and nectarine (Engel et al., 1988), have been previously reported (Robertson et al., 1990; Rizzolo et al., 2006; Zhang et al., 2010). On the other hand, the positive relation between sweetness and overall liking shown by consumers in this study has been already previously demonstrated. Indeed, Delgado et al. (2013) reported that sweetness perception was the main driver of liking for most peach and nectarine consumers. However, in peaches, other fruit quality characteristics also affect liking as firmness, colour and aroma (Bruhn, 1995). In general, the range of consumer acceptability scores of ‘Big Top® ’ fruit encountered in this work was in agreement with previous studies dealing with the consumer perception of this cultivar (Giné Bordonaba et al., 2014). However, mainly due to the high cost of consumer tests, there are few studies where degree of liking of a specific cultivar harvested at different maturity stages has been evaluated. Nevertheless, it has been proven that they are more effective in predicting consumer behaviour than models based on instrumental measurements (Harker et al., 2008; Saftner et al., 2008). At the same time, the influence of storage temperature on the quality and organoleptic attributes of peach fruit is extensively recognised. Cold storage is the foremost method to inhibit fruit decay and extend shelf life of most fruits. However, some peach and nectarine cultivars are sensitive to low temperature and might
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exhibit chilling injury (CI) after long periods of cold storage, especially at a particular range of temperatures, between 2.2 and 7.6 ◦ C (Cantín et al., 2010). In this study, no CI symptoms were perceived by consumers throughout the storage period in any of the tested temperatures. This disorder, together with the lack of flavour associated with unripe fruit (Gómez and Ledbetter, 1997), negatively affects the quality of the fruit, and therefore the consumer satisfaction (Infante et al., 2008a; Lurie and Crisosto, 2005). The decrease in consumer acceptance of ‘Big Top® ’ fruit over time observed in this study at low temperatures confirms that postharvest storage life of peaches is limited by quality loss, as observed for other peach and nectarine cultivars (Crisosto et al., 1999; Infante et al., 2008a,b). It has also been proven that cold storage alters flavour volatiles and partially inhibits ester synthesis, largely due to substrate deficiencies caused by suppressed oxidation mechanisms in the peach fruit during storage (Ortiz et al., 2009; Raffo et al., 2008; Robertson et al., 1990). In accordance with our results, previous studies have demonstrated that perception of flavour in peaches decreased and ‘off flavours’ increased during cold storage as a consequence of CI incidence (Crisosto and Labavitch, 2002; Infante et al., 2009). These results suggest that long storage at low temperatures should be used only when strictly necessary due to target markets. For direct consumption, and when possible, to avoid cold storage would provide fruit with a higher consumer satisfaction and display a more characteristic peach flavour. 5. Conclusions To determine the storage potential of ‘Big Top’ nectarines at different maturity stages, from a sensorial point of view, is essential to attain a high quality product able to satisfy consumer. The selection of an appropriate maturity at harvest is a key factor to determine fruit quality and consumer acceptability. In this sense, it is important to differentiate that fruit for direct consumption from that which will be consumed after a storage period. The results demonstrate the importance of ripening stage at harvest and postharvest storage temperature and duration in the perception of organoleptic attributes and overall satisfaction of the final consumer. Sweetness and flavour perception should be incorporated in peaches/nectarines postharvest studies in order to predict their effects in consumer acceptance. On the other hand, this work also outlines the importance of considering quality physicochemical parameters not as goals, but as tools to monitor the optimum quality demanded by the consumers. Acknowledgements This work was supported by the European Comission (ISAFRUIT project; contract no. FP6-FOOD-CT-2006-016279), the Generalitat de Catalunya, Spain (BP-DGR 2013; C.M. Cantín grant), and the Ministerio de Ciencia e Innovación (MICINN), Spain (FPU AP200701923; A. Ortiz grant). The authors are indebted to Mrs. A. Latorre ˜ for technical assistance. and Mrs. P. Sopena References Abbott, J.A., 1999. Quality measurement of fruits and vegetables. Postharvest Biol. Technol. 15 (3), 207–225. Asp, E.H., 1999. Factors affecting food decisions made by individual consumers. Food Policy 24 (2–3), 287–294. Bruhn, C.M., 1995. Consumer and retailer satisfaction with the quality and size of Californian peaches and nectarines. J. Food Qual. 18 (3), 241–256. CAMO ASA, 2004. Unscrambler Users Guide, ver. 9.1.2. Programme Package for Multivariate Calibration. Trondheim, Norway. Cano-Salazar, J., López, M.L., Crisosto, C.H., Echeverría, G., 2013a. Volatile compound emissions and sensory attributes of ‘Big Top’ nectarine and ‘Early Rich’ peach fruit in response to a pre-storage treatment before cold storage and subsequent shelf-life. Postharvest Biol. Technol. 76, 152–162.
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