Development and quality evaluation of Pitaya berry (Hylocereus polyrhizus) pulp and peel jam

Introduction

Dragon fruit (Hylocereus polyrhizus), belongs to the family Cactaceae, is native to Mexico, Central America and Northern South America. It is commonly known as pitaya or nightblooming cactus and is a fast-growing, evergreen climbing cactus. Vietnam is one of the leading exporters of dragon fruit, while its cultivation has expanded in several Indian states, including Karnataka, Kerala, Tamil Nadu, Maharashtra, Gujarat, Odisha, West Bengal and Andhra Pradesh (Karunakaran et al., 2019) [6] . In India, red-skinned fruits with white pulp (H. undatus) and red-skinned fruits with red pulp (H. polyrhizus) are predominantly cultivated (Kakade et al., 2020) [4] . Dragon fruit is valued for its nutritional and functional properties. The edible portion contains considerable amounts of moisture, protein, minerals, vitamin C, carbohydrates and dietary fibre (Le Bellec et al., 2006). The fruit also possesses antioxidant and antimicrobial properties, while its peel and seeds are potential sources of micronutrients and bioactive compounds (Gunasena et al., 2007). The red-fleshed species H. polyrhizus has also been reported to contain higher phenolic and antioxidant potential than white-fleshed dragon fruit. The peel, which may constitute nearly one-third of the total fruit weight, is generally considered a by-product of fruit processing but is rich in phenolic compounds, antioxidants, fibre and polysaccharides (Vaillant et al., 2005) [23] . It therefore has considerable potential for value addition and can be utilized as a source of natural colour and functional ingredients. However, dragon fruit is highly perishable because of its high moisture content, delicate peel, rapid respiration and susceptibility to water loss and microbial deterioration. Consequently, processing is essential to reduce post-harvest losses and extend its availability beyond the short harvesting season. Food processing provides an effective means of converting seasonal dragon fruit into value-added products such as jam, jelly, juice, nectar, squash and beverages. Dragon fruit contains approximately 0.20-1.04% pectin, which makes it suitable for jam and jelly preparation. Processing surplus fruit into jam can improve fruit utilization, reduce postharvest losses and provide additional economic opportunities for growers and processors. Furthermore, incorporation of the nutrient-rich peel into jam can facilitate better utilization of the whole fruit and convert a processing by-product into a value-added food ingredient.

Materials and Methods

The experiment was conducted during 2025-2026 at Horticulture Processing Laboratory, Department of Fruit Science, College of Agriculture, Indira Gandhi Krishi Vishwavidyalaya, and Raipur (C.G.). Fresh, healthy and damage free pitaya berries were selected and washed thoroughly with clean water to remove dirt and other adhering impurities. The fruits were peeled carefully and the pulp and peel were separated. The pulp and peel were cut into small pieces and separately blended using a mixer grinder to obtain a uniform consistency. The pulp and peel were then mixed according to the different treatment combinations. For the preparation of pitaya berry pulp and peel jam, the pulp and peel mixture was heated with continuous stirring. Sugar was added as per the treatment details, and the mixture was cooked with continuous stirring. Citric acid and pectin were added at the appropriate stage of cooking. The jam was cooked until the desired total soluble solids level of 66°, 68°, or 70 °Brix, depending on the treatment, was attained. The prepared jam was filled hot into pre-sterilized glass jars, sealed immediately with airtight lids and allowed to cool. The pulp juice of Pitaya berry fruits was extracted separately by passing it through a muslin cloth. The Total Soluble Solids (TSS) content of the pulp was determined using an ERMA hand refractometer (58-90 °Brix) at room temperature, and the values were expressed as °Brix.

Titratable acidity of pitaya berry pulp was determined according to the method described by Ranganna (1986) [18] . The prepared sample was titrated against 0.1 N NaOH using phenolphthalein as an indicator until a persistent faint pink end point was obtained. The acidity was expressed as percentage (%) and calculated using the following formula: Titre × Normality of alkali x Vol. made up× Eq. wt. of acid × 100 Acidity (%) = Vol. of sample taken for estimation × Wt. of sample taken × 1000

Ascorbic acid (mg/100g) Ascorbic acid content of Pitaya berry pulp was determined according to the method described by Ranganna (1986) [18] using 2,6-dichlorophenol-indophenol dye. The pulp extract was prepared in 3% metaphosphoric acid and titrated against the standard dye solution until a light pink end point was obtained. The ascorbic acid content was expressed as mg per 100g of pulp and calculated using the following formula:

Titre value x Dye factor x Volume made up x 100 Ascorbic acid (mg/100g) = Aliquot of extraction taken x volume of sample

Reducing sugar content of Pitaya berry pulp was estimated by titration against Fehling's solution. For analysis, 25 ml of filtered pitaya berry pulp extract was transferred to a volumetric flask and diluted with distilled water. The sample was neutralized with an alkali solution, followed by the addition of 2 ml lead acetate solution. After thorough mixing and allowing the solution to stand, 2 ml potassium oxalate solution was added to clarify the extract. Equal volumes (5 ml each) of Fehling's solution A and B were transferred into a conical flask and heated. The clarified pitaya berry extract was gradually added from a burette, followed by the addition of 1-2 drops of methylene blue indicator. The solution was heated intermittently while continuing the titration until a brick-red colour appeared, which indicated the endpoint. The reducing sugar content was expressed as percentage and calculated using the following formula:

Invert sugar (mg) × dilution × 100 Reducing sugar (%) = Titre × wt. or volume of the sample × 1000

The total sugar content of Pitaya berry pulp was determined by the Lane and Eynon (1923) [11] method. About 50 ml of the pulp extract was taken in a 100 ml volumetric flask, followed by the addition of 5 ml concentrated HCl, and the solution was allowed to stand at room temperature for 24 hours for inversion of sugars. The hydrolysed solution was neutralized with NaOH using phenolphthalein as an indicator and the volume was adjusted to 100 ml with distilled water. The resulting solution was titrated against Fehling's solution A and B mixed in equal proportions, using methylene blue as the indicator. The endpoint was indicated by the development of a brick-red colour. The total sugar content was expressed as percentage and calculated using the following formula:

Invert sugar (mg) × Dilution × 100 Total sugars (%) = Titre × wt. or volume of the sample × 1000

The non-reducing sugar content of pitaya berry pulp was calculated from the values obtained for total sugar and reducing sugar. It was determined by deducting the reducing sugar percentage from the corresponding total sugar percentage. The results were expressed as percentage (%). Non-reducing sugar (%) = Total sugar (%) -Reducing sugar (%)

TSS:acid ratio

The TSS:acid ratio of Pitaya berry pulp was determined by dividing the total soluble solids (TSS) content by the titratable acidity, following the method described by Ranganna (1986) [18] . The results were expressed as a ratio.

Total soluble solids (°Brix) TSS:acid ratio = Titratable acidity (%)

Sugar:acid ratio

The Sugar:acid ratio of Pitaya berry pulp was determined according to the method described by Ranganna (1986) [18] by dividing the total sugar content by the titratable acidity. The results were expressed as a ratio.

Total sugar (%) Sugar: acid ratio = Titratable acidity (%)

Results and Discussion

A) Quality parameters of Pitaya berry pulp and peel jam The quality parameters of Pitaya berry pulp and peel jam was evaluated with respect to total soluble solids (°Brix), titratable acidity (%), ascorbic acid (mg/100g), total sugar (%), reducing sugar (%), non-reducing sugar (%), TSS:acid ratio and Sugar:acid ratio. The results obtained for these parameters are presented in Tables 2 (a

Total Soluble Solids (°Brix)

The total soluble solids (TSS) of freshly prepared pitaya berry pulp and peel jam were maintained according to the treatment specifications at 70, 68 and 66 °Brix. Statistical analysis indicated that the treatments had a non-significant effect on TSS, suggesting that the desired TSS levels were successfully achieved during jam preparation irrespective of the pulp and peel proportions.

A significant variation of titratable acidity content of Pitaya berry pulp and peel jam was observed among the treatments. At the time of preparation (0 day), T5 (80% pulp + 20% peel + 68 °Brix TSS) exhibited the minimum titratable acidity (0.57%), which was found statistically at par with T2 and T1, having acidity percentage of 0.59 and 0.60%, respectively. However, the maximum titratable acidity (0.88%) was recorded under the treatment T12 (40% pulp + 60% peel + 66 °Brix TSS). The treatments containing higher proportions of peel exhibited comparatively higher acidity than those containing a greater proportion of pulp. This trend may be attributed to the naturally higher organic acid content present in the peel, which contributed to the overall acidity of the jam. Similar observations were reported by Gaur et al. (2005) [2] in ber jam.

The ascorbic acid content was significantly influenced by the different treatments evaluated under the present investigation. The maximum ascorbic acid content (3.01 mg/100g) of pitaya berry pulp and peel jam was observed under the treatment T5 (80% pulp + 20% peel + 68 °Brix TSS), which showed non-significant differences with the treatments T2 and T3 having the respective ascorbic acid content of 2.97 and 2.93 mg/100g. The minimum ascorbic acid content (1.76 mg/100g) was registered under the treatment T12 (40% pulp + 60% peel + 66 °Brix TSS). A gradual decline in ascorbic acid content was noticed with the increase in peel proportion. This reduction may be due to the comparatively lower vitamin C content in the peel and the susceptibility of ascorbic acid to oxidation during thermal processing. Similar findings have been reported by Kanwal et al. (2017) [5] in guava jam and Kiranmai et al (2017) [7] in tamarind and mango blended jam.

The total sugar content of freshly prepared pitaya berry pulp and peel jam differed significantly among the treatments. the maximum total sugar content (68.94%) was recorded under the treatment T5 (80% pulp + 20% peel + 68 °Brix TSS), which was statistically non-significant with the treatments T1, T4, T3 and T2 having the total sugar content of 66.93, 67.48, 67.92 and 68.41%, respectively. The minimum total sugar content (63.61%) was observed under the treatment T12 (40% pulp + 60% peel + 66 °Brix TSS). In general, total sugar content decreased as the proportion of peel increased. This may be due to the lower concentration of natural sugars in the peel compared to the pulp, resulting in reduced overall sugar content in the final product. Similar observations were reported by Safdar et al. (2012) [19] in mango jam and Nisa et al. (2018) [13] in Pitaya berry jam.

The reducing sugar content of freshly prepared Pitaya berry pulp and peel jam varied significantly among the treatments. The maximum reducing sugar content (29.97%) was recorded under the treatment T5 (80% pulp + 20% peel + 68 °Brix TSS), which was found at par with the treatment T3 and T2 having the respective reducing sugar content of 29.16 and 29.54%. The minimum reducing sugar content (25.67%) was recorded under T12 (40% pulp + 60% peel + 66 °Brix TSS) under the present study. In general, reducing sugar content decreased with an increase in peel proportion, indicating that pulp contributed more readily available sugars than peel. Similar findings were reported by also Krishna et al. (2023) [9] in guava papaya mixed jam and Rafique et al. (2023) [16] in karonda jam.

Non-reducing sugar content of freshly prepared Pitaya berry pulp and peel jam ranged from 37.94% to 38.56% and was found to be non-significant among the treatments. The maximum non-reducing sugar content (38.97%) was recorded under the superiority of treatment T5 (80% pulp + 20% peel + 68 °Brix TSS). followed by T2, T3, T4, T1, T6, T7, T8, T9, T10 and T11 having the respective non-reducing sugar content of 38.87, 38.76, 38.65, 38.56, 38.49, 38.42, 38.34, 38.25, 38.14 and 38.06. The minimum non-reducing sugar content (37.94%) was observed under the treatment T12 (40% pulp + 60% peel + 66 °Brix TSS). The higher nonreducing sugar content observed in T5 might be due to comparatively lower inversion of sucrose into reducing sugars during processing. In fruit jam, prolonged heating in the presence of organic acids promotes hydrolysis of sucrose into glucose and fructose, resulting in a decrease in nonreducing sugar content. Similar findings were reported by Koli (2004) [8] in sapota jam and Sawant et al. (2009) [21] in kokum pineapple blended jam.

TSS:acid ratio

The TSS:acid ratio differed significantly among the treatments. The maximum TSS:acid ratio (119.30) was recorded in T5 (80% pulp + 20% peel + 68 °Brix TSS), which was found non-significant with T1 having the TSS:acid ratio of 116.67. In contrast the minimum TSS:acid ratio (75.00) was observed in T₁₂ (40% pulp + 60% peel + 66 °Brix TSS). The ratio gradually decreased as the peel content increased because of the corresponding increase in titratable acidity. The higher value in T5 may be due to the optimum combination of pulp proportion and TSS level, which increased the concentration of total soluble solids, while reducing titratable acidity during processing. Similar observations were reported by Saravanan et al. (2004) [20] in papaya jam.

Sugar:acid ratio

A significant variation in Sugar:acid ratio were observed among the treatments. The maximum Sugar:acid ratio (120.95) was recorded under the supremacy of treatment T5 (80% pulp + 20% peel + 68 °Brix TSS), which was found to be significantly superior from rest of the other treatments, while the minimum value (72.28) was recorded in T₁₂ (40% pulp + 60% peel + 66 °Brix TSS). Treatments containing higher pulp proportions recorded higher Sugar:acid ratios, whereas increasing the peel proportion reduced the ratio due to higher acidity and lower sugar content. Similar findings were reported by Pavlova et al. (2013) [15] in raspberry and peach jam and Khan et al. (2012) [10] in strawberry jam.

B) Sensory parameters of Pitaya berry pulp and peel jam

The organoleptic evaluation was carried out for all the sensory parameters such as colour and appearance, taste, texture, flavour and overall acceptability of Pitaya berry pulp and peel jam and the results are presented in Table 3 and illustrated graphically in Fig. 2.

Colour and appearance

The data for colour and appearance scores of Pitaya berry pulp and peel jam were significantly influenced by different recipe treatments. The maximum colour and appearance score (9.10) was recorded under the superiority of treatment T5 (80% pulp + 20% peel + 68 °Brix TSS), which showed non-significant difference with the treatment T2 having the colour and appearance score of 8.90, whereas the minimum score (7.86) was observed in T10 (40% pulp + 60% peel + 70 °Brix TSS). The variation in colour and appearance may be attributed to the combined effect of peel incorporation and TSS on the visual quality of the jam. Treatment T5 obtained the highest score, indicating that incorporation of 20% peel improved the appearance and retained the desirable natural colour of the product. Similar findings were reported by Relekar et al. (2011) in sapota jam and Vidya and Narain (2011) [24] in woodapple jam.

Taste

The taste scores of Pitaya berry pulp and peel jam varied significantly under various recipe treatments. The maximum taste score (9.05) was recorded under the treatment T5 (80% pulp + 20% peel + 68 °Brix TSS), which was found nonsignificant with the treatments T2, T3, T6, T4, T1, T8, T11, T7 and T9, having the taste scores of 8.87, 8.85, 8.84, 8.83, 8.82, 8.81, 8.75, 8.70 and 8.68, respectively. The minimum taste score (7.76) was observed in T10 (40% pulp + 60% peel + 70 °Brix TSS). The superior taste score in T5 may be attributed to the optimum balance of pulp, peel, sweetness and acidity, resulting in better sensory acceptability. Similar findings were reported by Patel et al. (2015) [14] in pineapple and banana blended jam and Kanwal et al. (2017) [5] in guava jam.

Texture

The data revealed significant variation in the texture scores of Pitaya berry pulp and peel jam among different recipe treatments at 0 day of storage. The maximum texture score (9.15) was recorded under the excellency of treatment T5 (80% pulp + 20% peel + 68 °Brix TSS), which was found significant differences with the treatments T2, T3, T6, T4, T1, T8, T11, T7, T9 and T12, having the texture scores of 8.67, 8.65, 8.57, 8.52, 8.50, 8.45, 8.43, 8.35, 8.32 and 8.25, respectively, under the present investigation. However, the minimum texture score (7.65) was observed under treatment T10 (40% pulp + 60% peel + 70 °Brix TSS), which was significantly inferior to all the other treatments under the study. The superior texture in T5 may be attributed to the optimum incorporation of peel, which contributed natural pectin and dietary fibre, thereby improving gel formation and consistency. In contrast, higher peel incorporation may have increased fibre content and resulted in a coarse texture with lower acceptability. Similar findings were reported by Panchal et al. (2018) in Pitaya berry pulp and peel jam and Souad (2012) [22] in watermelon rind jam.

Flavour

The flavour scores of Pitaya berry pulp and peel jam varied significantly among different recipe treatments. The maximum flavour score (9.45) was recorded in T5 (80% pulp + 20% peel + 68 °Brix TSS), which was significantly superior to the other treatments, while the minimum score (7.65) was observed in T10 (40% pulp + 60% peel + 70 °Brix TSS). The higher flavour score in T5 may be attributed to the optimum balance of sweetness, acidity and natural fruit flavour, along with the contribution of desirable flavour compounds from moderate peel incorporation. Similar findings were reported by Khan et al. (2012) [10] in strawberry jam and Gaur et al. (2005) [2] in ber jam.

Overall acceptability

The significant variation in the overall acceptability of Pitaya berry pulp and peel jam was observed among different recipe treatments at 0 day of storage. The maximum overall acceptability score (9.02) was recorded in T5 (80% pulp + 20% peel + 68 °Brix TSS), whereas the minimum score (7.36) was observed in T10 (40% pulp + 60% peel + 70 °Brix TSS). The higher acceptability of T5 may be attributed to the optimum balance of sweetness, flavour, colour and consistency achieved through moderate peel incorporation. Similar findings were reported by Teixeira et al. (2020) in orange peel-incorporated orange jam and Afoakwa et al. (2006) [1] in pineapple. The superscript letters signifies that the treatment means with similar letters are at par at 5% level of significance, while the means with different letters are significantly different at 5% level of significance. These letters have been affixed based on CD-value comparison of treatment means

Conclusion

The present investigation on the standardization of recipe and quality evaluation of Pitaya berry pulp and peel jam revealed that incorporation of peel had a significant influence on the quality and sensory parameters of the product. Among the different recipe treatments, T5 (80% pulp + 20% peel + 68 °Brix TSS) emerged as the most promising treatment, recording the maximum ascorbic acid (3.01 mg/100g), total sugar (68.94%), reducing sugar (29.97%), non-reducing sugar (38.97%), TSS:acid ratio (119.30) and sugar:acid ratio (120.95). It also exhibited the maximum sensory scores for colour and appearance (9.10), taste (9.05), texture (9.15), flavour (9.45) and overall acceptability (9.02), indicating superior consumer acceptability. Therefore, the use of 80% pitaya pulp and 20% peel at 68 °Brix TSS can be considered the most suitable recipe for preparation of good-quality, acceptable and value-added pitaya berry pulp and peel jam. The utilization of peel further contributes to the effective conversion of a processing by-product into a value-added food product, thereby offering potential for commercial fruit processing and entrepreneurship.

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