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Effect of Drying on the Textural Attributes of BellPepper and PumpkinRaquel P. F. Guiné a & Maria João Barroca ba CI&DETS, Department of Food Industry, ESAV, Polytechnic Institute of Viseu, Viseu, Portugalb CERNAS-ESAV-IPC/Department of Chemical en Biological Engineering, ISEC-IPC, Coimbra,PortugalPublished online: 04 Oct 2011.

To cite this article: Raquel P. F. Guiné & Maria João Barroca (2011) Effect of Drying on the Textural Attributes of Bell Pepperand Pumpkin, Drying Technology: An International Journal, 29:16, 1911-1919, DOI: 10.1080/07373937.2011.596297

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Effect of Drying on the Textural Attributes of Bell Pepperand Pumpkin

Raquel P. F. Guine1 and Maria Joao Barroca21CI&DETS, Department of Food Industry, ESAV, Polytechnic Institute of Viseu, Viseu, Portugal2CERNAS-ESAV-IPC=Department of Chemical en Biological Engineering, ISEC-IPC, Coimbra,Portugal

The present work evaluates the effect of different drying treat-ments on the textural attributes of bell peppers (green and red)and of pumpkins (C. maxima and C. moschata), which were driedusing different methods: freeze-drying and air drying at differenttemperatures.

From the results obtained it is possible to conclude that withrespect to pumpkin no dependence was found between the fiberorientation and the hardness of the fresh vegetable, but a significantdependence was observed on the location of the sample, with thosesamples situated closer to the skin showing higher values of hard-ness. As to the bell peppers, the hardness is higher for those mea-surements made from the external side when compared to thosemade from the internal side.

As to the effect of drying on the texture of the vegetables, it wasfound that the increase in air drying temperature drastically reducesthe hardness of all vegetables and that freeze drying has an inter-mediate effect between the vegetables dried at 30�C and 70�C.Moreover, the springiness tends to be higher in dried bell peppersbut no significant effect was observed on this attribute in the caseof pumpkins. With respect to cohesiveness, the results are similarto those for springiness, so that it is slightly higher in the dried bellpeppers, but in the case of pumpkins no differences were found.Finally, the trends observed for chewiness follow those for hardnessin all cases at study.

Keywords Air drying; Bell pepper; Freeze drying; Green pepper;Hardness; Pumpkin; Red pepper; Texture; TPA

INTRODUCTION

Drying operations are important steps in the chemicaland food processing industries, being one of the mostwidely used primary methods of food preservation.[1,2]

The basic objective, when drying food products, is toremove water from the product up to a level that drasti-cally minimizes microbial spoilage and deterioration reac-tions.[1] Thus, the dried products can be stored for alonger period,[2–5] apart from other advantages, suchas need of smaller space for storage, lighter weight for

transportation and storage under ambient temperatures,with important economic savings.[2,5] Different dryingmethods are used for fruits and vegetables, with hot airdrying currently as the most widely used method inpost-harvest technology of agricultural products. However,during drying many changes take place inside the foods,and these structural and physical-chemical modificationsaffect the final product quality, particularly when com-pared to the fresh products.[5] In fact, the high tempera-tures in the hot air drying lead to an important loss ofproduct quality, namely in relation to composition andthe nutritional value as well as physical properties, density,porosity, mechanical properties, and organoleptic qualityof the products.[3] Understanding how these changes hap-pen enables food scientists to design processes and equip-ment that preserve the desirable characteristics andminimize or eliminate the undesirable effects.[6] Freeze dry-ing, on the other hand, tends to better preserve the pro-duct’s original characteristics, giving place to driedproducts of higher quality.[7] However, the complexity ofthe phenomena that affect biological materials in generaland food products in particular complicates any attemptto exactly define their quality.[8]

Pumpkin is a seasonal crop of importance for humanconsumption, having numerous culinary uses, either as avegetable or as an ingredient in food preparations like pies,soups, stews, or breads.[2] It is a good source of carotene,water-soluble vitamins, and amino acids, being relativelylow in total solids, usually ranging between 7% and10%.[3,9] This chemical composition, rich in antioxidantsand vitamins, gives pumpkin an important health-protecting effect. In fact, the range of values of lipophilicsubstances as carotenoids present in pumpkin varietiescan contribute significantly to the uptake of provitaminA and especially lutein, a carotenoid with special physio-logical functions.[10] The yellow to orange color of thepumpkin flesh arises from this group of substances.Additionally, the good performance of the pumpkin-fiberproducts in relation to water and glucose highlights the

Correspondence: Raquel P. F. Guine, CI&DETS, Departmentof Food Industry, ESAV, Polytechnic Institute of Viseu, Quintada Alagoa, Ranhados, 3500 606 Viseu, Portugal; E-mail:raquelguine@esav.ipv.pt

Drying Technology, 29: 1911–1919, 2011

Copyright # 2011 Taylor & Francis Group, LLC

ISSN: 0737-3937 print=1532-2300 online

DOI: 10.1080/07373937.2011.596297

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possibility of their use as food ingredients.[11] However,fresh pumpkins are very sensitive to microbial spoilage,even when refrigerated, as it is necessary to freeze or drythem in order to extend their life.[2] Drying is a storagemethod which has the capability of extending the consump-tion period of pumpkins, allowing one to maintain many oftheir nutritive properties.[3]

The fruit of Capsicum plants can have a variety of namesdepending on place and type, and they are commonlycalled chilli pepper, red or green pepper, or just pepper.The bell pepper (Capsicum annuum) refers to the actualfruit of the capsicum plant as the term used in NorthAmerica, while in Britain it is simply referred to as pepper.In Portugal, ‘‘Pimento’’ or ‘‘pimentao’’ are the wordsfor bell pepper, independent of the color.[12] Bell peppersare heart-shaped and measure from 7 to 10 cm long andfrom 5 to 7 cm wide (medium, elongate). They are eatengreen or ripe and are used for salads, soups, stews, relishes,and pickling.[12] Their color can be green, red, yellow andorange or, more rarely, white, purple, blue, black, andbrown. Green peppers are unripe bell peppers, while theothers are all ripe, with the color variation based on culti-var selection.[13] Because they are unripe, green peppers areless sweet and slightly more bitter than yellow, orange, orred peppers, which all have a rather similar hot taste. Bellpeppers present different nutritional compositions, depend-ing on the variety and stage of maturity, but are naturallyrich in ascorbic acid and provitamin A carotenoids, spe-cially the red ripe ones.[13–16] These two vitamins arepowerful antioxidants that help reduce the risk of manydiseases.[17–20] Bell peppers are also a source of manyminerals and their attributed medicinal properties are quitediverse. Bell peppers are used worldwide either as a food oras a condiment. However, like other vegetables they arequite perishable, originating high losses due to storageproblems, marketing, and inappropriate processing tech-nologies.[21,22] In the work by Pal et al.,[23] thin-layer dryingexperiments under controlled conditions were conductedfor green sweet pepper in a heat pump dryer at tempera-tures ranging from 30�C to 45�C and also in a hot air dryerat 45�C, with relative humidities ranging from 19 to 55%.They observed that the retention of total chlorophyll con-tent and ascorbic acid content was higher in the heat pumpdried samples with higher rehydration ratios and sensoryscores. Furthermore, the quality parameters showed adeclining trend with increase in drying air temperaturefrom 30�C to 45�C.[23]

Both pumpkin and bell pepper are very popular in Por-tugal and are used to prepare a wide variety of dishes apartfrom the consumption in their fresh form. Nevertheless, it’svery difficult to find these vegetables in the market in theirprocessed form, which brings complexity to their use.Therefore, drying assumes a pivotal role in the processingof these vegetables, allowing a wider usage owing to the

ease of handling and storing when compared to the freshproducts.

Apart from the perceived primary characteristics, tex-ture also plays an important role in the acceptability offoods by consumers. In a sensory point of view, textureis generally defined as the overall feeling that a food givesin the mouth and is therefore comprised of properties thatcan be evaluated by touch.[24] However, in a more specificway, texture is composed of several textural propertieswhich involve different types of characteristics: mechan-ical (hardness, chewiness, and viscosity), geometrical (par-ticle size and shape), and chemical (moisture and fatcontent).[25] Texture results from complex interactionsamong food components at a microstructural level as wellas at higher structural levels such as, for instance, thestructure of the tissue (cellular orientation, porosity) andthe different types of tissues or organs that constitute foodmaterials.[26,27] Therefore, it is crucial to determine andcontrol the texture of the processed foods.[28–30] Severalauthors have studied the changes of the mechanicalproperties of food during convective drying and, in gen-eral, they found that a soft product (fresh) is transformedinto a rigid product (dried). Alternatively it changedfrom a predominantly plastic behavior to a more elasticbehavior.[31]

Instrumental measurements of texture have becomebasilar for the management of quality in the food indus-try.[32] Instrumental texture profile analysis (TPA) is oneof the methods to determine the texture by simulating orimitating the repeated biting or chewing of a food.

The present work aimed to study the effect of freezedrying and air drying at different temperatures on thetexture of pumpkin and bell pepper. For that, texturalattributes (hardness, springiness, cohesiveness, andchewiness) were estimated from the TPAs obtained witha texturometer.

MATERIALS AND METHODS

Pumpkins (Cucurbita moschata and Cucurbita maxima)were purchased in a local market. After the removal ofthe skin, the pulp was cut into samples of 20mm diameterand 5mm thick, which were then dried under different con-ditions (Figure 1(a)). Bell peppers (green and red) were alsopurchased in a local market, washed and cut to samples ofthe same size of pumpkin (20mm diameter and 5mmthick), and dried (Fig. 1(b)). While for the drying of pump-kin only the pulp was used, the bell pepper was dried withthe skin.

For the convective drying, an electrical FD 155 Binderdrying chamber with ventilation was used. The stove wasoperated at constant temperatures of 30�C, 50�C, and70�C, and the air flow was 0.5m=s. For the freeze drying,the samples were frozen in a conventional kitchen freezerfor about 24 hours at a temperature ranging from �18�C

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to �20�C, and then left in the freeze-drier (model TableTop TFD5505) for 38 hours at a temperature between�47�C and �50�C, and a pressure of 5mTorr (0,666 Pa).

To evaluate the moisture content of the products beforeand after drying, a HG53 Halogen Moisture Analyzer fromMettler Toledo was used. The temperature was set to120�C and the speed was medium (3 in a scale from1¼ very fast to 5¼ very slow), operating conditions thatwere found to be optimum for this kind of product.[10,33,34]

To determine the textural properties of pumpkins, tex-ture profile analysis was carried out on cylindrical samplestaken at 10, 30, and 40mm from the skin and on axial andradial directions as illustrated in Figure 2. Measurementsto the fresh bell peppers were done on both sides ofthe pepper tissue, from the skin (external) and the flesh(internal).

Texture profile analysis (TPA) to all the samples wasperformed using a Texture Analyser (model TA.XT.Plusfrom Stable Micro Systems). The texture profile analysiswas carried out by two compression cycles between parallelplates performed on cylindrical samples (diameter 10mm,height 3mm) using a flat 75-mm-diameter plunger, with a5-second period of time between cycles. The parametersthat have been used were the following: 5 kg force load celland 0.5mm=s test speed. The textural properties (hardness,springiness, cohesiveness, and chewiness) were calculated

after equations (1) to (4) (see Figure 3):[35]

Hardness ðNÞ ¼ F1 ð1Þ

Springiness ð%Þ ¼ ðt2=t1Þ � 100 ð2Þ

Cohesiveness ðdimensionlessÞ ¼ A2=A1 ð3Þ

Chewiness ðNÞ ¼ ðF1Þ � ðt2=t1Þ � ðA2=A1Þ ð4Þ

FIG. 1. Sample preparation for drying: (a) pumpkin; (b) bell pepper.

FIG. 2. Sample preparation in pumpkin for texture analysis: (a) schematic representation; (b) cutting devices.

FIG. 3. Illustration of a texture profile analysis and variable definition.

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DISCUSSION OF RESULTS

Table 1 resumes the values of the moisture content ofthe different products in the fresh state and Table 2 showsfor those products which have been submitted to differentdryings the values of the corresponding moisture content atthe end of the drying treatment. Regarding the moisturecontent measurements, they were done for each type ofproduct and each situation (fresh or dried) in six samples,and the medium values and standard deviations were thencalculated. The results in Table 1 show that the values ofthe moisture content of the fresh bell peppers are very simi-lar independent of variety (94.13% for green bell pepperand 91.87% for red bell pepper), and the same wasobserved for the pumpkin (91.87% for C. maxima and90.25% for C. moschata). From Table 2 it can be seen thatthe increase in the air-drying temperature diminishes theoperating time, from 44 hours at 30�C to 11 hours at70�C, to obtain products with a moisture content under20%. The freeze-drying treatment allows us to obtain theproducts with the lower moisture content, between 6.47%for the red bell pepper and 8.73 for the C. moschata. Thislast drying method allows us to reach a lower moisture con-tent with minimal changes in volume, contrary to the airdrying, in which to reach the same level of dehydration

much more intense changes would occur in the product.In fact, in the freeze-drying the moisture is frozen insidethe food and is then removed by sublimation, thus givingplace to highly porous materials. In the air drying, themoisture is removed from the food by diffusion from theinterior to the surface and then evaporation, and in thisprocess a high degree of shrinking occurs.[36]

The results of firmness (hardness) for the fresh bell pep-per are illustrated in Figure 4, for both varieties studied.This parameter can be related to the force performed bymastication that takes part during eating. It was found thatrupture of the skin from the flesh side required a lowerforce when compared with the same action from the skinside. The values for hardness obtained from the externalside were 13.8N and 11.8N, whereas those obtained fromthe internal side were 10.9N and 8.7N, respectively, for thegreen and red bell peppers. Therefore the external side isharder than the internal for both varieties of pepper stu-dies. This phenomenon is related to the constitution ofthe biological material that constitutes the skin, and parti-cularly the cell-wall polysaccharides, which aim at giving ahigher mechanical resistance, thus enabling a barrier forprotection of the fruit. Furthermore, it can be seen thatthe green bell pepper is harder when compared to the redone, which is expected taking into consideration the factthat the red bell pepper corresponds to the same fruit asgreen bell pepper, but in a more advanced state of ripeness.

Regarding the other vegetable analyzed in the presentstudy, Figure 5 shows the hardness of the two varieties offresh pumpkin, measured on the axial and radial direc-tions, and at different locations. In every case 6 analyseswere performed and 6 TPAs were obtained. At each pos-ition analyzed, 1, 3, and 4 cm measured from the skin,the results show small differences between both directions,both in the C. maxima and in the C. moschata. This meansthat there is no dependence of hardness on the fiber orien-tation; the maximum force needed for the first bite isapproximately the same independently of the orientationof the bite. However, the results also show that hardnessis very dependent on the distance from the skin. This can

TABLE 1Values of the moisture content for the different products in

the fresh state

ProductNumber ofanalyses

Medium valueof moisture

content (% wb)Standarddeviation

Green bell pepper 6 94.13 0.60Red bell pepper 6 95.47 0.56Pumpkin(C. maxima)

6 91.87 0.50

Pumpkin(C. moschata)

6 90.25 0.61

TABLE 2Values of the moisture content for the different products analyzed after the end of the drying processes

Moisture content (% wd.)� (standard deviation)

ProductAir dried

(30�C=44 hrs)Air dried

(50�C=22 hrs)Air dried

(70�C=11 hrs) Freeze dried (22 hrs)

Green bell pepper 18.49� (1.42) 19.57� (1.95) 12.14� (1.57) 7.12� (0.88)Red bell pepper 14.42� (0.88) 13.67� (1.27) 11.52� (1.66) 6.47� (0.91)Pumpkin (C. maxima) 18.47� (0.98) 17.52� (1.70) 12.74� (1.64) 8.08� (1.31)Pumpkin(C. moschata)

17.73� (0.72) 17.54� (1.47) 14.69� (1.60) 8.73� (1.05)

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be attributed to the heterogeneous composition of the fleshof the pumpkin from skin to seeds. In fact, the flesh of thepumpkin is considerably harder than the pulp near the cen-ter, which results, as mentioned above for the peppers,from the constitution of the cell-wall polysaccharides ofthe skin cells, providing a higher resistance and protectiveeffect. The medium values of hardness (calculated consider-ing both, the axial and radial measurements) for the fresh

C. maxima were 12.4N, 20.0N, and 32.6N at 4, 3, and1 cm of the skin, respectively. For the C. moschata, themedium values were 12.8N, 20.4N, and 37.5N in the samelocations.

Figure 6 shows the results obtained for the texture para-meters (hardness, cohesiveness, springiness, and chewi-ness), calculated from the compression TPA curves forthe bell pepper through equations (1) to (4). In everycase 6 analyses were performed and 6 TPAs were obtained.The results are relative to both varieties of bell peppers, inthe fresh state and after the different drying treatmentstested (air drying at different temperatures �30�C, 50�C,70�C, and freeze-drying), and correspond to the measure-ments made from the internal side. The results in Fig. 6(a)show that in the first bite the fresh bell peppers require amuch higher energy than the dried vegetables, which meansthat drying makes the products softer. For example, com-paring the fresh peppers with those dried at 30�C, the firm-ness decreases from 10.9N to 1.7N in the green variety andfrom 8.9N to 1.5N in the red variety, which are extremechanges, corresponding to decreases of 84% and 83%,respectively. This behavior could be expected, as long asthe temperatures involved were not extremely high. In fact,with drying a high quantity of water is lost and the concen-tration of the sugars present increases considerably.[37]

These sugars give the product a softer and more elasticconsistency. Moreover, the increase in temperature forthe air drying of the bell pepper also produces a pro-nounced effect on firmness with a decrease from 1.7N at30�C to 1.3N at 70�C, corresponding to 24% reductionover a 40�C interval for the green pepper. For the red pep-per the decrease from 1.5N to 1.1N represents 27% overthe same temperature range. However, this trend isobserved because relatively low temperatures were used,up to 70�C. In fact, if very high temperatures were used,around 100�C or over, the sugars present would undergocaramelization processes, thus originating a harder pro-duct, and a reverse trend would then be expected. Finally,the freeze-drying treatment also induces a pronouncedsoftening of the peppers compared to the fresh vegetables,although not so intense as the air drying does. In fact, thefreeze-dried peppers show a hardness of 2.6N and 2.4N forthe green and red varieties, respectively, representingdecreases of 76% and 73% relative to the correspondingfresh products, but higher than the samples dried by con-vection, regardless of temperature. These differences aremainly related to the different structural changes that hap-pen during these two methods of drying. As previously sta-ted, in freeze drying the water is lost by sublimation, thusoriginating a highly porous structure, while in the air dry-ing the degree of shrinking is very intense. As a result, thesugars’ concentration is higher in the air-dried products ascompared to the freeze-dried, thus conferring on them asofter nature.

FIG. 5. Hardness of pumpkin in the fresh state: (a) C. maxima; (b)

C. moschata.

FIG. 4. Hardness of bell pepper in the fresh state.

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From the results presented in Fig. 6(b), it can beobserved that, in general, the drying treatments (air con-vection at different temperatures and freeze drying) of bellpeppers originate an increase on cohesiveness. This texturalparameter accounts for the internal bonds in the food, andtherefore refers to the force that keeps the sample cohesive.The increase in cohesiveness observed with drying indicatesthat the bell peppers acquire a more cohesive structure,which is a consequence of the loss of great amounts ofwater. With respect to the green bell pepper the valuesincrease 4%, 5%, and 12% for the air drying and 12% forthe freeze drying, compared to the cohesiveness of the freshproduct. For the red bell pepper the increases are higher,ranging from 30% for the air drying at 30�C to 55% at50�C, being 41% for the freeze drying. The results inFig. 6(c) show the values for springiness, which is a mea-sure of the recovery after the compression during the mas-tication; that is to say, the speed of return to the originalstate after removal of the force which deformed the pro-duct. The results indicate that both varieties present verysimilar values for springiness and this variable is slightlyhigher for the bell peppers dried at higher temperatures(50�C and 70�C). This behavior is attributed, as stated pre-viously, to the increase in the sugars concentration, thusgiving way to a more elastic product. As to chewiness(Fig. 6(d)), which represents the energy needed to disinte-grate a solid food to swallow it, the results show an intensedecrease from the fresh state to the dried forms, being thevalues for the different air-drying temperatures quite simi-lar and lower that the value for the freeze drying. For the

green bell pepper, chewiness decreases 84% in the productdried at 30�C and 70% in the freeze-dried product com-pared to the fresh one. In the red pepper, the decreasewas 79% and 59% for the same drying treatments. Thistrend in quite similar to that observed for the variationsof hardness, which would be expected taking into consider-ation the dependence of chewiness from hardness, asexpressed in equation (4). Generally, comparing the twodrying methods tested, the results show a trend for textureof bell peppers to be more sensitive to air-convective dry-ing, and particularly at the highest temperature, than thefreeze drying. This is, as explained earlier, a consequenceof the different structural changes that take place underthe different drying conditions.

Since the values for the hardness of bell peppers in thefresh state show relatively high values of the standarddeviations, a statistical test was performed in order to per-ceive if these corresponded to statistically different sam-ples. In that way a t-test was made with softwareStatistica version 6.0 from Statsoft. The t-test is the mostcommonly used method to evaluate the differences inmeans between two groups. In the t-test analysis, compar-isons of means and measures of variation in the two groupscan be visualized in box and whisker plots. Figure 7(a)shows the box and whisker plot for the hardness of thefresh peppers, for the measurements in the green and redgroups. In fact, the results show that although the meanvalues are different, they are not statistically different, asthe graph shows. Figure 7(b) shows the box and whiskerplot for the hardness of the green peppers, in fresh and

FIG. 6. Texture attributes for fresh and dried bell peppers: (a) hardness; (b) cohesiveness; (c) springiness; (d) chewiness.

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after the different dryings. Also, in this case there aregroups that are not significantly different, like the air-driedpeppers at different temperatures. However, the differencebetween the fresh and the dried groups becomes evident.

Figure 8 illustrates the results obtained for the textureparameters for both varieties of pumpkin in the fresh stateand after the different dryings. Also, in this case 6 analyseswere made, and the TPAs correspond to the samples takenon the axial direction and at 3 cm of the skin. The results inFig. 8(a) show that the fresh pumpkins have a much higherhardness (19.4N and 19.7N for the C. maxima and C.moschata) when compared to the dried samples (varyingfrom 6.6N to 5.5N at 30�C and from 0.3N to 1.1N at70�C, respectively). For example, the reductions in hard-ness from the fresh pumpkins to those dried at 30�C are66% and 72%, while the decreases from 30�C to 50�C are67% and 43%, and from 50�C to 70�C are greater, 87%and 65%, respectively, for C. maxima and C. moschata,thus indicating that higher temperatures have a more pro-nounced effect on the softening of the pumpkin pulp. Also,in the case of pumpkins, this trend is attributed to the lossof water and consequent shrinking, with the increase in thesugars’ concentration and elasticity. Furthermore, thefreeze-drying treatment produces pumpkins with firmnessequal to 1.6N and 2.4N, higher than the samples driedat 70�C, but smaller than the samples dried at 50�C.Finally, the freeze-drying treatment also induces a pro-nounced softening of the pumpkins, representing adecrease of around 90% relative to the fresh product.

The results in the graph of Fig. 8(b) show that the cohes-iveness of pumpkin remains approximately constant after

FIG. 7. Box and whisker plots: (a) hardness of the fresh peppers; (b)

hardness of green peppers fresh and after drying. FD is freeze dried and

the temperatures 30, 50, and 70�C correspond to the air-dried peppers.

FIG. 8. Texture attributes for fresh and dried pumpkin: (a) hardness; (b) cohesiveness; (c) springiness; (d) chewiness.

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drying, except for the freeze-dried C. moschata, whichshows some increase. These results mean that fresh anddried pumpkins have similar strengths of internal bonding.Based on the values found for springiness (Fig. 8(c)), it isalso possible to conclude that drying (convective air dryingand freeze drying) do not significantly alter the capacity ofthe pumpkin to return to its original shape after defor-mation. An exception was observed for the C. maximadried at 30�C, which showed a lower value for springinessthan those of all other cases. With respect to the differencesbetween both varieties studied, springiness is higher for theC. moschata, meaning that this variety is more elastic thanthe other variety at study. Furthermore, the drying signifi-cantly reduces the chewiness of the pumpkins (Fig. 8(d)),once again due to the intense diminishing in the hardness,as observed earlier (Fig 6(a)). Finally, comparingthe freeze-dried pumpkins with those dried by convection,it is possible to see that the values encountered for thedifferent texture parameters closer to those of thesamples dried at 50�C, which is the intermediate tempera-ture tested.

CONCLUSIONS

The present work evaluated the effect of different dryingtreatments on the textural attributes of green and red bellpeppers and pumpkins of the varieties C. maxima and C.moschata, which were dried using two different methods,freeze-drying and air drying, with this last at differenttemperatures.

From the results obtained in the present study it is poss-ible to conclude that for the bell peppers hardness is higherwhen the measurements are taken from the external side ascompared to the internal, and that the green bell pepper isharder when compared to the red one. As to the pumpkins,the results show small differences between the hardnessmeasured in both directions (radial and axial), and this istrue for both varieties studied. However, the results alsoshow that hardness is very dependent on the distance fromthe skin, and the values are higher when the samples movefrom the inside to the outside, closer to the skin.

As to the effect of drying, it was found that whenincreasing the air-drying temperature the hardness of allvegetables studied is drastically reduced, and the freezedrying has an intermediate effect between the air dryingsat 30�C and 70�C.

Regarding cohesiveness, it is higher in dried bell peppersas compared to the fresh peppers, although no significanteffect was observed for the case of pumpkins, where thisproperty is approximately constant regardless of the case.

With respect to springiness, in the bell peppers the sam-ples dried at 30�C are similar to the fresh, with the samplesdried at 50�C the ones that presented the higher values forthis property related to the elasticity of the material. In thecase of pumpkins, the samples dried at 30�C present

slightly lower values than the fresh and the other driedsamples, which are all very similar.

As to chewiness, the trends observed for all vegetablesstudied are similar to those of hardness, as expected.

ACKNOWLEDGMENTS

The authors thank CI&DETS and CERNAS forfinancial support.

REFERENCES

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