PaPer Ital. J. Food Sci., vol. 28 - 2016 73 - Keywords: fruit leather, antioxidant activity, phenolic content, sensory evaluation - Evaluation of fruit lEathEr madE from two cultivars of papaya Zuhair radhi addai*1,2, aminah abdullah1, sahilah abd. mutalib1 and Khalid hamid musa1 1School of Chemical Science and Food Technology, Faculty of Science and Technology, University Kebangsaan Malaysia, 43600 Bangi Selangor, Malaysia 2Department of Biology, Faculty of Education for Pure Science, Thi-Qar University *Corresponding author: zuhair_2003@yahoo.com AbstrAct two papaya cultivars were used to manufacture fruit leather. the objective of this study was to formulate papaya leather from locally grown papaya using natural ingredients like pectin, hon- ey and citric acid. the fresh fruits were pureed and mix with natural ingredients, and dried in an oven at 60°c for 12 hours. the physicochemical properties and antioxidant activity were deter- mined. the results showed that fruit leather made from Hongkong cultivar is significantly (P<0.05) higher in sensory parameters as well as physicochemical properties and antioxidant activity. the phenolics content and antioxidant activity increased by process of drying the fruit leather com- pared to fresh fruits in both papaya cultivars. therefore, the consumer requirements for healthy and safe food products were respected. http://zuhair_2003%40yahoo.com 74 Ital. J. Food Sci., vol. 28 - 2016 IntroductIon Like numerous fruits and vegetables, pa- paya is a rich source of antioxidants. Antioxi- dants have a neutralising effect on free radicals, which are unstable molecules that can trigger a range of diseases, including cancers, cardio- vascular and neurodegenerative diseases (PrI- or et al., 1998). naturally occurring antioxi- dants have been examined by (PrAkAsH, 2010), who discerned that disease risk is reduced by such antioxidants as vitamin c, vitamin E, car- otene, phenolic acids, phytate and phytoestro- gens. similarly, epidemiological research has emphasised the important role of antioxidants derived from fruits and vegetables in preventing degenerative processes (AmEs et al., 1993). Pa- paya fruit can be eaten fresh or as part of differ- ent processed foods, including baked products, beverages, cereals, confectionery, dairy snacks and sauces (usHbc, 2010). the demand for pa- paya as dried fruit is also high, alongside sul- tanas, peaches and apricots (LoHAcHoomPoL, 2007). Healthy products with dried papaya in- clude breakfast cereals, energy bars and fruit snacks. In addition, there is a range of other papaya-based products, such as jam, jelly, pa- paya toffee, papaya bar, papaya squash, papa- ya soft drinks, papaya pulp powder, and oth- ers swAmy and PrEmnAtH (2010). Fresh papa- ya is a seasonal fruit with a shelf life between one and two weeks. to respond to consumer de- mand, with fresh substitute is necessary to en- sure year-round availability and drying is the most commonly used preservation method. As explained by (tEsHomE, 2010), the drying pro- cess entails eliminating as much water as pos- sible from the fresh fruit in order to inhibit en- zyme and bacterial activity, thus halting decom- position. there are various types of drying pro- cesses, including sun drying, oven drying, cabi- net drying, dehydrator drying and freeze drying. based on food type, from 2 to 30% of water is left in the dried foods. In addition to prolonging product shelf life, water content reduction en- sures that the product is stable from a microbi- ological perspective and minimises deteriorating chemical reactions. Fruit leathers are referred to the dried sheets of fruit pulp that taste sweet and have a soft, rubbery texture. their produc- tion involves the dehydration of fruit puree to a leathery sheet (rAAb and oEHLEr, 1999). In this regard, the study had two goals: (a) to use local- ly grown papaya to make fruit leathers based by using on natural ingredients like pectin, honey and citric acid, as well as to determine the cul- tivar most suitable for the production of papaya fruit leather; (b) to analyse the extent to which the drying process affects fresh and processed papaya in terms of antioxidant content, phys- ic-chemical properties and sensory evaluation. mAtErIALs And mEtHods Samples collection and preparation Papaya (Carica papaya L. cv. Hongkong and Ek- sotika) fruits at the mature stage of ripening were collected from Pusat Flora cheras, Jabatan Per- tanian, and Hulu Langat semenyih in selangor, malaysia. the fruits were selected to ensure uni- formity in size (800 g to 1000 g) and color as well as to ensure freedom from diseases and infection. the selected fruits were transferred on the same day to the university kebangsaan malaysia food laboratory, bangi. the other three major ingredi- ents used in the trials were honey (Polleney honey, chaina), pectin (Germany) and citric acid (usA). Procedure for making papaya fruit leather For each cultivar, frozen papaya cultivars were thawed at 40c overnight in the fridge. six hundred grams of thawed papaya cultivars were weighed. Honey 10% (v/v), 2% (v/v) of citric acid and % 6 (v/v) of pectin were weighed and mixed with papaya fruits. A cascade blender model cE071br (Japan) was used to mix all these ingredients for 2 minutes to make a pu- ree. cooking oil was lightly sprayed over trays made of stainless steel before 200 g of puree was spread uniformly over the trays with a met- al spreader. the drying of the leather was done in the middle section of the cabinet dryer, which had been preheated to 60° ± 2°c. throughout the drying interval, the dryness of the leather was closely monitored. two batches were made for every cultivar each of them has three trays. the trays were dried for 12 hours for both pa- paya cultivars. A process flow chart of papaya leather production. ripe Papaya ↓ washing ↓ Pulping ↓ Addition of honey + citric acid + pectin ↓ mixing ↓ cooking ↓ spreading on trays ↓ drying ↓ cutting into slabs ↓ Packing ↓ Labeling Ital. J. Food Sci., vol. 28 - 2016 75 Physiochemical properties of papaya fruits moisture content was measured by drying sample at 105°c overnight in memmert oven (Germany). titratable acidity (tA) was deter- mined from 10 ml of sample diluted with 50 mL of water, titrated with 0.1 n naoH and calcu- lated as percent citric acid. total soluble solids (tss) were measured with an abbe refractom- eter at 20°c and pH was determined using pH meter using juice extracted directly from pulp. Humidity content the moisture content was determined by dry- ing samples of approximately 1 g at 105°c in an forced air oven (watson Victor Ltd, nZ) for 24 hours. the textural of papaya leather were con- ducted with a stable micro system tA-EZtest/ AGs-H- Japan). Texture analyzer the procedures for operating the texture ana- lyzer were stated in the standard operating Pro- cedure (soP). the following parameters were de- termined: hardness (g/f). the pulp color was lon- gitudinally determined on four points of each flat side of the fruit using a minolta cr-300 colorim- eter. the (L*) value represented the luminosity of the fruit, where 0 = black and 100 = white but the (a*) value ranged from the negative (green) to the positive (red) scale and the (b*) value ranged from negative (blue) to positive (yellow), (AoAc 1998). Antioxidants extraction Papaya were peeled, cut into 1 cm slices and crushed in a food processor to produce uniform slurries. the mixture was prepared fresh to pre- serve the extracted antioxidant compounds. In the extraction process, about 1 g of papaya slurries were weighed in universal bottles and 10 ml solvent was added. solvents used were 50% aqueous methanol; samples (papaya slur- ries with solvents) were then homogenized using homogenizer (t 250, IkA, Germany) at 24,000 rpm for 1 min. All extracted samples were cen- trifuged by using tabletop centrifuge (mLX 210, thermo-line, china) at 4750 g for 10 min. the supernatants were collected for further analysis. Total phenol content (TPC) Antioxidant activity was determined using tPc based on the method of (musA et al. 2011). Approximately 0.4 mL distilled water and 0.5 mL diluted Folin-ciocalteu reagent were added to 100 μL papaya extracts. the samples (papaya extracts with Folin-ciocalteu reagent) were set aside for 5 min before 1 mL 7.5% sodium car- bonate (w/v) was added. the absorbances were taken at 765 nm wave length using a spectro- photometer after 2 h. the calibration curve of gallic acid (GA) was used for the estimation of sample activity capacity. the result was record- ed in terms of mg of GA equivalents per 100 g of fresh sample (mg GA/100 g of Fw). Total flavonoid content (TFC) the tF content was determined by the colori- metric method as described by (Abu bAkAr et al., 2009). A total 0.5 mL of the extract was mixed with 2.25 mL of distilled water in a test tube, followed by the addition of 0.15 mL of 5% (w/v) nano 2 solu- tion. After 6 min, 0.3 ml of a 10% Alcl 3 ·6H 2 o solu- tion was added, and the reaction was allowed to stand for another 5 min before 1.0 ml of 1 m naoH was added. the mixture was mixed well by vortex- ing, and the absorbance was measured immedi- ately at 510 nm using a spectrophotometer (Ep- och, biotek, usA). the results were expressed as milligrams of quercetin equivalents (QE) per 100 g of fresh sample (mg QE/100 g of Fw). Ferric reducing antioxidant power (FRAP) First, 300 mm acetate buffer FrAP reagent was prepared fresh as follows: pH 3.6 (3.1 g sodium acetate trihydrate plus 16 mL glacial acid made up to 1:1 with distilled water); 10 mm 2,4,6-tris (2-pyridyl)-s-triazine (tPtZ) in 40 mm Hcl; and 20 mm Fecl3·6H2o in the ratio of 10:1:1 to pro- vide the working reagent. In addition, approxi- mately 1 mL FrAP reagent was added to 100 μL papaya extracts, and the absorbances were taken at 595 nm wavelength using a spectrophotome- ter after 30 min. the calibration curve of trolox was established to approximate sample activity capacity. the result was recorded as mg of trolox equivalents (tEs) per 100 g of fresh sample mg (tE/100 g of Fw) (musA et al., 2011). DPPH Radical scavenging activity based on the method of (musa et al. 2011) the antioxidant activity was assessed using a 2,2-di- phenyl-1-picrylhydrazyl (dPPH) scavenging sys- tem. the stock solution was obtained by dissolv- ing 40 mg dPPH in 100 mL methanol, which was stored at -20°c until further use. Approximately 350 mL stock solution was mixed with 350 mL methanol to obtain the absorbance of 0.70±0.01 unit at 516 nm wavelength by using a spectro- photometer (Epoch, biotek, usA). In the dark, approximately 100 μL papaya extracts with 1 mL prepared methanolic dPPH solution was stored overnight for scavenging reaction. the percent- age of dPPH scavenging activity was determined based on the following equation: dPPH scavenging activity (%) = [(A blank –A sample ) / A blank ] × 100, where A is the absorbance. 76 Ital. J. Food Sci., vol. 28 - 2016 ABTS assay the Abts radical cation (2,2-azino-bis-3-eth- ylbenzothiazoline-6-sulfonic acid) was gener- ated by the interaction of Abts (250 µm) and k 2 s 2 o 8 (40 µm). After the addition of 990 µL of Abts solution to 10 ml of fruit extract, the ab- sorbance at 734 nm was monitored. the per- centage decrease of the absorbance was calcu- lated and plotted as a function of the concen- tration of the extracts and trolox for the stan- dard reference data (Özgen et al. 2006). the fol- lowing formula was used: Percentage (%) of reduction power = [(A blank –A sample ) / A blank ] × 100, where A is the absorbance. Oxygen radical absorbance capacity (ORAC) the orAc assay was conducted according to (HuAnG et al., 2002). the orAc assay was car- ried out on a fluorescence microplate reader (FLuostar omega, bmG LAbtEcH, multi-de- tection microplate reader, Germany). Perox- yl radicals were generated by AAPH, and fluo- rescence microplate reader was used at an ex- citation wavelength of 485 nm and an emission wavelength of 525 nm. trolox was used as stan- dard (50, 25, 12.5, 6.25, 3.12 mm). Proper dilu- tions of papaya extracts were made with orAc buffer (potassium phosphate buffer, pH 7.4). For each orAc run, a micro plate was prepared containing 25uµ of trolox standards, buffer control, and sample dilutions, as well as 150ul of fluorescein (FL) solution. All orAc analyses were performed at 370c with a 20 min incuba- tion and 60 min run time. After the incubation, 25ul of AAPH was added to each well for a final volume of 200 uL. the results were calculated using the differences of areas under the FL de- cay curves between the blank and a sample and were expressed as micromole trolox Equivalents per gram of sample (µmol tE/g). Sensory evaluation A consumer acceptability sensory trial was con- ducted at university kebangsaan malaysia in the sensory evaluation laboratory. Panellists com- prised 30 volunteers who were staff or students at the university. Each panellist was asked to taste two samples, one from both cultivar (2 x 2 cm square). Attributes selected for the papaya fruit leather were colour, sweetness, sourness, flavour, texture and overall appearance. In this study, the hedonic scale was implemented; on a scale of 1 to 7 there were tabulations of scores, where 1 in- dicates “extremely dislike” and 7 represents “ex- tremely like” (AmInAH, 2004). For reliability pur- poses, distilled water was given to the panelists for them to rinse the mouths between evaluations. Statistical analysis data were expressed as the means val- ues ± standard deviation. mean of minimum three measurements were compared by analy- sis of variance (AnoVA). significant differenc- es between means were determined by duncan (P<0.05). correlation analysis was performed using Pearson’s. the software used was sPss ver.19. (brymAn and crAmEr, 2012). rEsuLts And dIscussIon Physicochemical properties of papaya the pH, titratable acidity and tss for the two papaya cultivars are shown in table 1. the culti- vars exhibited considerable differences in terms of pH (P<0.05). the Hongkong cultivar had a higher level of pH (5.47), while the Eksotika cul- tivar had a lower pH (5.34). In comparison to fresh fruit, drying caused a substantial decline in the pH of all fruit leathers (P<0.05). Further- more, there were significant discrepancies be- tween the average pH of the Hongkong cultivar (3.93) and that of the Eksotika cultivar (3.82). Likewise, (HArsImrAt, 1998) demonstrated that acidity has a positive effect on shelf life. by con- trast, (bAbALoLA et al., 2002) found that papa- ya leather stored in a cool environment for 30 days had a higher pH compared to other sam- ples. similar findings were obtained in the case of pineapple leather (PHImPHArIAn et al. 2011), mango leather (AZErEdo et al., 2006) papa- ya and guava leathers (bAbALoLA et al., 2006). the present study revealed that the titratable acidity differed substantially between the cul- table 1 - Effect of processing on pH, tA and tss of two papaya cultivars. result showed mean ± standard deviation. Cultivars pH TA TSS Fresh Leather Fresh Leather Fresh Leather Hongkong 5.47±0.02a 3.93±0.01b 0.15±0.01b 1.63±0.02a 11.74±0.52b 68.50±0.57a Eksotika 5.34±0.03a 3.82±0.01b 0.17±0.02b 1.48±0.03a 12.46±0.14b 70.50±0.60a a-b Mean with different letters within each raw are significantly different (P< 0.05). Ital. J. Food Sci., vol. 28 - 2016 77 tivars of both fresh and dried papaya. Hong- kong and Eksotika had the highest average to- tal acid content in fresh fruit, with 0.15% and 0.17%, respectively, of citric acid (reference). In the case of all fruit leathers, drying determines a considerable increase in the titratable acidity. As shown in table 1, the highest acidity among fruit leathers was shown by the cultivar Hong- kong (1.63%), while the lowest was exhibited by Eksotika (1.48%). In keeping with bEAudry et al. (1992), the results of this study indicated that the titratable acidity (tA) of fresh papaya is be- tween 0.3 ± 0.1 to 0.7 ± 0.1% of citric acid equiv- alent. the addition of 4% of citric acid to the fruit leather puree increased the tA of the two papa- ya leather cultivars. In addition, drying contrib- utes to concentration in the fruit’s natural acidi- ty, leading to a significant increase in the acidity of the fruit leather. Among all cultivars, Eksoti- ka displayed the highest levels of titratable acid (0.17%). However, after drying, tA was highest in leathers with concentrations between 1.48 and 1.63 %. the high levels of acidity in fruit leather not only inhibit bacterial growth, but also pro- tect the colour and flavour of the fruit. Hence, in terms of processing or manufacturing, papa- ya cultivars with high acidity should be used. this study also found that Hongkong cultivars is most appropriate for fruit leather production. VAIdyA et al., (2007) reported the acidity of fruit leather made from kiwifruit which was found to be 3.8% but the reason for the high acidity was not discussed. Vega Galvez et al. (2009) report- ed an acidity of 2.2 ± 0.12% (monohydrated cit- ric acid), pH of 2.7 ± 0.09, and soluble solids of 15.0 ± 0.07 °brix in dried o’neil blueberries. the two cultivars also differed greatly with regard to tss (P<0.05). the tss of Hongkong cultivar fresh fruit was 11.74 while Eksotika fruit culti- var was 12.46. Although there is a substantial increase in the °brix of all fruit leathers after dry- ing, with a tss of 68.50 and 70.50 respectively for both papaya cultivars (Hongkong and Ekso- tika). the two cultivars did not display notice- able discrepancies. All processed papaya leath- ers had higher tss than fresh fruit. the high- er levels of °brix in fruit leathers compared to fresh fruit, particularly sweet fruit, had already been noted in earlier research. For example, the addition of ingredients, such as pectin, glucose, syrup, and sugar, to raw pineapple puree in- creased the tss of the latter between 66.4 and 75.3 °brix. the pineapple fruit leather had a fi- nal tss of between 82.4 and 86.9 after drying (PHImPHArIAn et al., 2011). In the case of kiwi fruit, (VAIdyA et al., 2007) observed that the ad- dition of 15% sugar increased its °brix, which became even higher (68 °brix) after the fruit was dried in a cabinet drier for 15 hours at a tem- perature of 45° ± 2° c. the present study used honey as an added sweetener. In this research, creamed honey (83 °brix) was added as a sweet- ener. the °brix found in creamed honey was sim- Fig. 1 - Effect of processing on moisture of two papaya cul- tivars. a-b mean with different letters are significantly different (P < 0.05). ilar to that found by AnuPAmA et al. (2003). the °brix of blueberry fruit leathers increased due to the addition of 15% of honey. the high °brix of blended papaya leather was explained by (ku- mAr et al., 2008) in terms of a high carbohy- drate content, making it a good energy source. Humidity content of fresh fruit As illustrated in Fig. 1, the moisture content of two papaya leathers were 14.31% and 15.42%, (Hongkong and Eksotika) respectively. the fruit leathers from different cultivars exhibited dis- crepancies with respect to moisture content lev- els (P<0.05). In this study, given the relative re- duced moisture content (22%-24%), all cultivar leathers can be classified as concentrated or in- termediate moisture foods. Although the prod- uct thickness may be one of the reasons for high moisture content in this product. nevertheless, the final product thickness was decreased from 4 mm to 1 mm. based on their research on hot air drying of grape leather, mAskAn et al. (2002) argued that drying of the product surface oc- curs rapidly at high temperatures, particular- ly in the case of thinner samples. the moisture content of jackfruit leather, papaya leather and blended papaya leather was determined to be 11-17% (cHE mAn et al., 1992), 12-13% (cHAn and cAVALEtto, 1978) and 20.80% (kumAr et al., 2008), respectively. However, IrwAndI et al. (1998) emphasized that, despite suppress- ing bacterial development and extending shelf life, a low moisture content of fruit leathers may have an adverse effect on texture quality. HuAnG and HsEIH (2005) found that increasing the pec- tin concentration (from 1 to 1.5%) affected the hardness of the sample and decreased moisture content and aw of pineapple fruit leathers had an a w value of < 0.55. similarly, PHImPHArIAn et 78 Ital. J. Food Sci., vol. 28 - 2016 al. (2011) reported that both moisture content and water activity were influenced by the pec- tin concentration. what is more, the pectin con- centration also affected aw on pear fruit leather. Texture of papaya leather the papaya leather cultivars in Hongkong and Eksotika had a range texture (Fig. 2) of 490.48 - 483.60 respectively. A possible cause for the high texture was the pectin, which gen- erated a firm gel structure followed by a tough texture. the high texture due to the 6% pec- tin concentration used in this study was com- bined with the reduced moisture content of the papaya leather. reduced moisture content and harder texture are the outcome of high- er temperatures and extended drying periods (cHE mAn, 1995) and (okILyA et al., 2010). A comparison was difficult to achieve due not only to the different genetic structure of this fruit (bAbALoLA et al., 2002), but also to extra ingredients that influenced the texture qual- ity. GuJrAL and kHAnnA (2002) found that (2005), the values obtained in this study were considerably lower. Colour measurements the final fruit leather product (table 2) was lighter in colour (L* mean value of 32.10 and 30.70) less than the fresh fruit (L* mean value of 48.52 and 45.43). All cultivars decreased in brightness (L*) indicating that fresh papaya had a lighter colour compared to the fruit leathers. this was expected as the drying and addition of pectin, honey and citric acid to papaya pu- ree can have significant effects on the colour of the papaya fruit. For example, citric acid is a strong acid and the addition of citric acid in the papaya puree may have impacted the stability of the anthocyanins. Anthocyanins are highly unstable and very susceptible to degradation. Anthocyanins are oxidised in the absence of ox- idase enzymes and subsequent condensation reactions can lead to brown pigment formation (singleton, 1987). this reaction may have led to colour changes in the papaya fruit leather but the addition of citric acid was necessary in the production of papaya fruit leather as it protect- ed the natural colour and helped destroy bacte- ria during drying. Pectin concentration has also been found to affect the colour of the product as the absorbance intensity was decreased in the production of jam, which suggested a rela- tionship between pectin and anthocyanin deg- radation (dErVIsI et al., 2001). significant in- creases in L* values after drying were also ob- served by yAnG and AtALLAH (1985). the au- thors suggested that in both forced air and mi- cro-convection dried papaya increased L* val- ues indicated a higher loss of anthocyanin from thermal degradation. However, for a* values a significant decrease was found in both papaya cultivars after drying, which may be due to an- thocyanin oxidation as well as heat degradation during dehydration. In this study, papaya fruit leather also showed lower a* (13. 21 and 11.61) than fresh fruit (from 27.24 and 20.34) for two papaya cultivars Hongkong and Eksotika re- spectively. the b* values in c. papaya (Hong- kong) were higher (10.25) compared to c. papa- ya (Eksotika). the extra added ingredients and the drying process had an effect on the b* value. the leather cultivars in Hongkong and Eksoti- ka had an average b* value of 10.25 and 8.84 respectively. similar results were also observed in previous studies with jackfruit leather (cHE mAn and sIn, 1997; okILyA et al., 2010) and blended papaya leather (kumAr et al., 2010). After drying, these fruit leathers became darker. this was especially prevalent in light coloured fruit leather (rAAb and oEHLEr, 1999). other factors that can also affect papaya anthocya- nins are: pH, storage, temperature, light, light, oxygen, concentration and structure of antho- cyanins, other flavonoids, protein and miner- Fig. 2 - Effect of processing on texture of two papaya cul- tivars. a-b mean with different letters are significantly different (P < 0.05). the tensile force in the mango leather was re- duced by increased levels of sucrose (ranging from 4.5% to 9%). the texture decreased even more when skim milk powder was added, in comparison to soy protein concentrate. In this study, it is probable that the texture or exten- sibility of papaya leathers was affected by the pectin, honey and citric acid that were added. HuAnG and HsIEH (2005) obtained a hardness value for pear fruit leathers of between 4420 and 13200 g (18 formulations with various wa- ter, pectin and corn syrup ratios). there were also differences in terms of ingredients, while the texture of the leathers may have been in- fluenced by water absorption and the protein content of the fruit (bAbALoLA et al., 2002). by contrast to the results of HuAnG and HsIEH Ital. J. Food Sci., vol. 28 - 2016 79 oxidant activity (FrAP, dPPH, Abts and orAc) were illustrated in tables 3 and.4. the fresh fruit showed different trends with regard to to- tal phenolic content and total flavonoid content. the tPc and tFc were higher in Eksotika (62.59 mg GAE/100g dw and 45.40 mg QE/100g dw, respectively) than in Hongkong (49.61 mg GAE/100 g dw and 40.01 mg QE/100g dw, re- spectively). Also an antioxidant activity (FrAP, ddPH, Abts and orAc) was higher in Eksoti- ka (197.41 mg tE/100g dw, 71.48%, 73.89% and 13.62 µmol tE/g dw, respectively) than in Hongkong (127.74 mg tE/100g dw, 49.62%, 61.84% and 11.50 µmol tE/g dw, respectively). Antioxidant capacity and phenolic concentra- tion were found to differ according to the types of papaya cultivars. the reason for this may be differences in regions, climate, as well as in the solvents employed for extraction. Furthermore, antioxidant activity may also be affected by li- pid composition, antioxidant concentration, tem- perature, pH, oxygen, and water. compared to earlier research carried out by (connor et al., 2002), (EHLEnFELdt and PrIor, 2001) and (PrI- or et al., 1998), this study reported higher lev- els of antioxidant activity. Although dried fruit leathers showed comparable trends, fruit leath- er had higher tPc, tFc and antioxidant activ- ity (FrAP, dPPH, Abts, and orAc) than fresh fruit. drying determines increase in the levels of antioxidant activity and phenolics in both culti- vars. However, Eksotika exhibited a greater in- crease in antioxidant activity than Hongkong. the fruit leathers showed different trends with regard to total phenolic content and total flavo- noid content. tPc and tFc were higher in Ek- sotika (121.41 mg GAE/100g dw and 108.78 table 3 - the effect of processing on the total phenolics con- tent and total flavonoids content of two papaya cultivars. result showed mean ± standard deviation. Phenolics Fresh Leather Hongkong Eksotika Hongkong Eksotika TPC 49.61±1.03 a 62.59±1.09 b 104.71±2.50 b 121.4±1.79 a TFC 40.01±1.26b 45.40±0.82 a 91.43±1.54 b 108.78±1.77 a a-d Mean with different letters within each raw are significantly dif- ferent (P< 0.05). table 2 - Effect of processing on colour of two papaya cultivars. result showed mean ± standard deviation. Cultivars L* a* b* Fresh Leather Fresh Leather Fresh Leather Hongkong 48.52±1.02a 32.1±0.71b 27.24±0.51a 13.21±0.20b 31.71±0.50a 10.25±0.41b Eksotika 45.42±1.13a 30.7±1.01b 20.34±0.42a 11.61±0.18b 29.41±0.15a 8.84±0.65b a-b Mean with different letters within each raw are significantly different (P< 0.05). table 4 - the effect of processing on antioxidant activity (FrAP, dPPH, Abts and orAc) of two papaya cultivars. result showed mean ± standard deviation. Antioxidant activity Fresh Leather Hongkong Eksotika Hongkong Eksotika FRAP 127.74±1.88b 197.41±2.50a 231.51±3.87b 284.32±1.10a DPPH 49.62±108b 71.48±0.87a 76.11±0.13b 89.47±102a ABTS 61.84±0.86b 73.89±1.79a 84.97±0.60b 92.12±1.52a ORAC 11.50±0.72b 13.62±0.96a 29.54±0.24b 34.40±1.91a a-d Mean with different letters within each raw are significantly different (P< 0.05). als. these factors were associated with colour changes in papaya fruit. In this study, during the development of fruit leather the interactions between heat and the food ingredients may have significantly affected the anthocyanins’ stabil- ity and this could have resulted in the colour change of the fruit. Ingredients such as honey contain antioxidants as well as hydrogen per- oxide, which may cause degradation of antho- cyanins by oxidation mechanism or by indirect oxidation (LoHAcHoomPoL, 2007). Also, it is noted that under high concentrations of oxygen and ascorbic acid increased pigmentation loss occurred which resulted in change to the col- our of papaya. other major factors mentioned by IrwAndI et al. (1998) that influenced the col- our of fruit leathers were: processing condition, storage time and temperature. Phenolics content and antioxidant activity A comparison between fresh fruit and fruit leathers in terms of the total phenolic content (tPc), total flavonoid content (tFc), and anti- 80 Ital. J. Food Sci., vol. 28 - 2016 mg QE/100g dw, respectively) than in Hong- kong (104.71 mg GAE/100 g dw and 91.43 mg QE/100g dw, respectively). Also, an antioxi- dant activity (FrAP, ddPH, Abts and orAc) was higher in Eksotika (284.32 mg tE/100g dw, 89.47%, 92.12% and 34.40 µmol tE/g dw, respectively) than in Hongkong (231.51mg tE/100g dw, 76.11%, 84.97% and 29,54 µmol tE/g dw, respectively). As previously shown, in both cultivars, drying causes increase in phenolics and antioxidant ac- tivity within the range of 50% to 53%. this in- crease is due to loss of moisture from the sam- ples and thus reflected in the weight, leading to an increased concentration, as well the addition of honey and lemon contributed to the increase in phenols and antioxidants. total phenolic contents assay is known to overestimate the content of phenolic compounds, because other agents present in food, such as carotenoids, amino acids, sugars and vitamin c, can interfere (bAHorun et al., 2004; LuXImon- rAmmA et al., 2003). Furthermore there may be a contribution of millard reaction products to the total phenolic and antioxidant activity (ZHuAnG and sun, 2011). oxidation produces free rad- icals which are taken up by the vitamins and polyphenols. reports that the antioxidant ac- tivity of partially oxidised polyphenols is higher compared to that of non-oxidised phenols have prompted further research. As highlighted by GArAu et al. (2007), there are other factors that may contribute to a reduced antioxidant activi- ty; these include extended drying intervals. de- spite the use of identical cultivars, it is difficult to generate a comparison between the antioxidant activity results of this study and those of earlier ones, due to differences in the assays, extraction techniques and standards (tE, GAE) employed. moreover, apart from fruit quality, antioxidant activity is also influenced by factors such as ge- ography, environment, climate and harvesting practices. the analysis of the impact of drying on total phenolic content revealed that, in con- trast to fresh fruit cultivars, there was a reduc- tion in total phenolic content. thermal deterio- ration is the likely cause for the increase in the total phenolic content of the two cultivars. Fur- thermore, dI scALA et al. (2011) specified that the total phenolic content may also decline due to dehydration, during which polyphenols bind to other compounds, such as proteins, or their chemical structure undergoes changes that ex- table 5 - correlation coefficients of antioxidants activities of different papaya cultivars. Correlation coefficient (R2) FRAP DPPH ABTS ORAC TPC 0.95 0.80 0.87 0.98 TFC 0.92 0.86 0.85 0.98 Fig. 3 - the effect of processing on texture of two papaya cultivars. a-b mean with different letters are significantly different (P < 0.05) isting techniques are unable to extract or iden- tify. In the present study, although the increase was significant, papaya fruit leathers exhibited higher antioxidant activity and phenolics con- tent than fresh fruit. Correlation of TPC and TFC with FRAP, DPPH, ABTS and ORAC assays A correlation analysis among phenolic com- pounds (tPc and tFc) assays, and antioxidant activity (FrAP, dPPH and Abts) was performed regardless of the extraction cultivars. A high cor- relation (table 5) was found between tPc, tFc and antioxidant activity (FPAP, dPPH Abts and orAc) for both cultivars (Hongkong and Eksoti- ka). thus, it can reasonably be concluded that in the extract, antioxidant activity is related to the active component. Findings of researches of correlation analyses among tPc, tFc, and antioxidant activities (FrAP, dPPH, and Abts) are high (mAHAttAnAtAwEE et al., 2006). there have been significant effects on the antioxidant activities of papaya fruit. Sensory evaluation the statistical analysis of the sensory evalua- tion was conducted on the basis of 30 respons- es. the average scores for six properties of all fruit leathers are presented in Fig. 3. A score of 1 signified ‘dislike extremely’, while a score of 7 signified ‘like extremely’. the cultivars differed significantly (P<0.05) in terms of colour, sweet- ness, sourness, flavour, texture, and general product acceptance. of the two types of culti- vars, Eksotika achieved the lowest acceptabili- ty scores of colour. this implied the importance attributed to the visual appearance of the prod- uct. there was a greater preference for the pa- paya leather cultivar Hongkong, due to its red- dish colour, than for the dark coloured Eksotika. surprisingly, the results for fresh papaya were different. In a study undertaken by (sAFtnEr et al., 2008), the highest scores among all cultivars Ital. J. Food Sci., vol. 28 - 2016 81 were obtained by the Highbush cultivars coville and Hannah’s choice for the intense blue col- our, acceptable appearance, colour, fruit size, sweet/tart balance, flavour and overall eating quality. In a different study, GuJrAL and kHAn- nA (2002) increased the sucrose level in order to enhance the colour, flavour and texture of man- go leather. such approaches should be applied in the case of blueberry fruit leathers as well, to improve the darker colour of certain varieties of blueberry. similarly, the colour of the papaya leather could be enhanced by adding other col- ourless fruit (dErVIsI et al., 2001). the fruit leathers obtained an average sweet- ness score of 6.00. this meant that the panelist ‘liked’ the product sweetness and thus it was necessary to add honey. However, as warned by kumAr et al. (2008), the overall taste rat- ing may decline due to an excessive increase in the amount of sugar. the sourness of the papa- ya leather was ‘moderately liked’ by a panelist, with an average score of 5.6. moisture content and duration of drying have an impact on the texture of fruit leather. the moisture content is reduced and the texture is hardened by high- er temperatures and extended drying intervals (okILyA et al., 2010). Furthermore, the texture quality of the end-product may also be affected by the addition of flavour and colour-enhancing ingredients like pectin, honey, sugars, nuts, salt and other fruits (rAAb and oEHLEr, 1999). Ek- sotika cultivars obtained a lower flavour score (5.2) than Hongkong (6.0). okILyA et al. (2010) explained that the amount of sugar within the fresh pulp affects how the fruit leather tastes. the taste of papaya fruit leather was enhanced in this study by adding honey and citric acid. similarly, kumAr et al. (2008) noted that papa- ya and guava fruit leather were affected by the addition of extra ingredients. compared to indi- vidual scoring, the overall score for sensory at- tributes was considerably improved by the ad- dition of 60% papaya and 40% guava, the nu- tritional and textural quality of the fruit leather remained unaffected. It was necessary to make this addition in order to enhance the low scent of the papaya fruit, which constituted a major obstacle to the commercial use of this fruit. As specified by (raab and oehler 1999), the taste of fruit leather could also be improved by using additional ingredients like leaf oregano and gar- lic salt. the blueberry fruit leather achieved an average overall score of 5.0, indicating that the panelists ‘moderately liked’ it. theoretically, the overall reception of all sensory attributes of the papaya fruit leather was the reason for its over- all acceptability. the Hongkong cultivar obtained an overall acceptable score of 6.00 making it the best liked fruit leather. the colour, appearance, sweetness, sourness, texture and flavour of the cultivar determined the preference of the pan- elists for it. Furthermore, Hongkong received an overall acceptability score of 6 out of 7. on the other hand, Eksotika obtained the lowest score, being ‘moderately liked’ by the panelists for its colour, general appearance and flavor. concLusIons Fruit leather was successfully developed from two different papaya cultivars using three addi- tional ingredients - honey, pectin and citric acid. this processed product was intended to preserve or enhance the nutritional value and sensory quality of the papaya fruit. the moisture con- tent of the fruit leather derived from the two cul- tivars was reduced (14.31% and 15.42%), signi- fying that they were safe from a bacterial view- point and could be classified as an intermediate moisture food. the phenolics content and antiox- idant activity were increased using the process of drying the fruit leather. substantial discrep- ancies in colour, sweetness, sourness, texture, flavour and overall acceptability were reflected in the consumer sensory assessment. ‘Like moder- ately’ was the average overall acceptability score. 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